Principles of Cardiac Catheterization.
Cardiac catheterization in humans was developed more than 50 years ago and has since evolved through many phases. Today, it is one of the most common invasive procedures in the United States, with more than 1.5 million cardiac catheterizations performed each year. More than 80% of these procedures are performed to evaluate or diagnose known or suspected heart disease.[2,3]
The first cardiac catheterization reportedly was performed in 1844 in a horse. Claude Bernard inserted a mercury thermometer into the animal's carotid artery, advancing it through the aortic valve and into the left ventricle. He then advanced the thermometer by a retrograde approach through the jugular vein to the right ventricle. Bernard was studying the differences in temperature between blood returning from the lungs and blood returning from the rest of the body.[1,4]
In 1929 Werner Forssmann, a 25-year-old surgery student in Berlin, performed the first true human cardiac catheterization on himself. Forssmann passed a urologic catheter 65 cm through one of the veins in his arm into his right atrium. He used a mirror and fluoroscopic imaging for guidance. With the catheter in place, he walked upstairs to the radiology department and documented the catheter's position with a chest radiograph. (See Fig. 1.) Forssmann continued to perform catheterization studies for a few more years, with the primary purpose of finding a way to deliver drugs directly into the heart.[1,4,5]
[Figure 1 ILLUSTRATION OMITTED]
More recent milestones in the development of diagnostic and therapeutic catheterization include:
* Passage of a catheter into the right ventricle to calculate cardiac output in 1930.
* The first documented passage of a catheter into the pulmonary artery in 1947.
* Development in 1953 of a percutaneous insertion technique.
* The first trans-septal catheterization, also in 1953.
* Passage of a balloon-tipped, flow-guided catheter (the Swan-Ganz) into the heart in 1970.
* Introduction of percutaneous transluminal coronary angioplasty (PTCA) in 1977.
Since that time, interventional cardiology has grown into a dominant application of cardiac catheterization.
Today, physicians recognize the comprehensive and quantitative advantages of cardiac catheterization techniques for measuring cardiac structure and function. The therapeutic applications of cardiac catheterization also have increased, and continued improvements in equipment and technique have resulted in highly effective methods for managing patients with cardiac disease.
Overview of Heart and Great Vessel Anatomy
In about 200 AD, Galen discovered that the arteries contained blood and not air, as previously thought. However, he also believed that there were pores between the left and right sides of the heart. In the 1500s, dissections by Vesalius disproved the pore theory and Servetus first pointed to separate circulation of the right and left sides of the heart. The groundwork for modern concepts of circulation was laid by Harvey (1578-1657), who suggested that the circulation of the blood was powered by the pumping of the heart:
It has been shown by reason and experiment that blood by the beat of the ventricles flows throughout the lungs and heart and is pumped to the whole body ... the blood in the animal body moves around in a circle continuously, and ... the action or function of the heart is to accomplish this by pumping. This is the only reason for the motion and beat of the heart.
(William Harvey, Exercitatio Anatomica de Moto Cordis et Sanquinis in Animabilus, 1628)
In its simplest form, the contraction of the heart's muscle walls propels blood throughout the body, bringing nutrients to, and waste from, vital organs. However, cardiac muscle is more complex in both structure and function than skeletal muscle. The cells of cardiac muscle are constantly responsive to slight changes in the body's demands, with a complex control system that adjusts muscle action. Whereas skeletal muscle contraction is activated by nervous tissue, cardiac muscle contraction is activated by specialized cells in the muscle that produce an electrical signal. The nerves supplying the heart play more of a regulatory role. When these forces and the many anatomic components of the heart work together, the average heart beats about 42 million times a year. As many as 525 000 gallons of blood pass though the average heart annually.
The area on the anterior chest wall that overlies the heart and great vessels is the precordium; the heart structures lie in the middle third of the thoracic cage, known as the mediastinum. The heart consists of 4 pumping chambers: the right and left atria and the right and left ventricles. (See Fig. 2.) The 4 chambers are separated by valves that act as unidirectional "doors," preventing backflow of blood. The valves open and close passively in reaction to changes in flow pressure.
[Figure 2 ILLUSTRATION OMITTED]
Atrioventricular valves lie between the cavities of the atria and ventricles. Semilunar valves lie between the outflow tracts of each ventricle and the great arteries into which the respective ventricles eject blood. The heart commonly is thought of as a pump, but in reality, it is 2 pumps. The right side of the heart pumps blood to the lungs while the left side simultaneously pumps blood to the rest of the body. The septum, an impermeable wall, separates the 2 sides. Yet even with their independent actions, the 2 sides of the heart interact in both normal and diseased hearts.
The left side of the heart consists of the left atrium and the left ventricle. The atrioventricular valve that lies between these 2 chambers is called the mitral or bicuspid valve.[7,8] When the mitral valve opens, the left ventricle fills. The valve only opens when the pressure in the left ventricle is very low, as it is during diastole or the relaxation phase. The left ventricle contracts to eject blood to the body.
The right atrium receives deoxygenated blood returned by the venous system. Blood flowing into the right atrium enters through the tricuspid valve. The tricuspid valve opens when the right ventricle is in diastole and closes when the right ventricle contracts. Because the right ventricle only has to drive blood into the lungs, rather than the entire body, it is thinner and does not generate as much pressure as the left ventricle. The contraction of both ventricles is triggered by a series of electrical events that are repeated with each heartbeat.
The inner surfaces of the atria and ventricles are covered with connective tissue called the endocardium. The endocardium also extends over the valves and although previously thought to be inert tissue, it is now believed to be an important contributor to the regulation of left ventricular contraction.[7,8] The pericardium is a thin, bag-like, fibrous structure within which the heart lies. It is a double-walled sac that surrounds and protects the heart. Between the 2 layers is a small collection of fluid. The fluid serves as a lubricant, allowing for smooth, frictionless movement of the heart muscle during contraction and relaxation.[7,10]
The great vessels lie above the base of the heart. The pulmonary artery leaves the right ventricle, branches out and carries venous blood to the lungs. The pulmonary veins return newly oxygenated blood to the left side of the heart. The aorta, which ascends from the left ventricle, transports the blood to the body. The aorta has the important function of regulating abrupt decreases and increases in pressure in the left ventricle. The superior and inferior vena cava return deoxygenated blood to the right side of the heart.
Coronary artery walls are made up of 3 layers. The layers provide the strength and flexibility needed for the arteries to handle vasodilation and vasoconstriction, as well as the pressure of blood flow. The innermost layer is called the intima. It is made up of endothelial cells in a thin layer that are supported by connective tissue. The intima is semipermeable, allowing the transport of oxygen and nutrients in the arterial wall. The media is the middle, muscular layer. It consists of smooth muscle cells and collagens. (Collagens are a form of connective tissue secreted by smooth muscle cells.) The cells are covered by a thin fibrous network known as the internal and external elastic lamina.
The adventitia is the outer layer of an arterial wall. Connective tissue, some smooth muscle cells and the vasovasorum make up this layer. The vasovasorum is an arteriole network that supplies blood to the adventitia and the outer part of the media. Overall, circulation is a continuous loop and blood is kept moving by continually shifting pressure gradients.
Indications for Cardiac Catheterization
A wide array of diagnostic tests are available to evaluate patients with evident or suspected cardiac disease. Indications for cardiac catheterization may be based on the patient history and physical exam, electrocardiograms (ECGs), echocardiography, chest radiography, laboratory studies and other methods.[11,12] Because it is an invasive procedure, cardiac catheterization is considered carefully based on available diagnostic information. In general, it is recommended to confirm a clinically suspected condition, define the anatomic and physiologic severity of a known condition or determine the presence or absence of associated conditions.
Cardiac catheterization can yield useful information for determining the need for cardiac surgery or other interventions. During the past decade or so, the safety of cardiac catheterization has improved markedly, and it often can be performed as an outpatient procedure. There is some disagreement among health care professionals on the need for cardiac catheterization for every patient undergoing cardiac surgery. In general, patients undergoing some types of surgery may not benefit from cardiac catheterization. However, in other cases, the information gathered from the catheterization procedure can provide a precise road map for the cardiac surgical team prior to entering the operating room.
Information obtained from cardiac catheterization can help determine a patient's prognosis. It also can help diagnose obscure or confusing problems in heart disease. Cardiac catheterization is indicated in patients for whom an invasive therapeutic intervention is contemplated, most commonly those with coronary artery disease or valvular disease. (See Table 1.)
Table 1 Indications for Cardiac Catheterization and Angiography
Suspected Coronary Artery Disease:
* Angina, especially if it is unstable or refractory to treatment, if a stress test is strongly positive or if the patient is a young person with a positive family history.
* After acute myocardial infarction (including patients who have received thrombolytic therapy), if accompanied by angina or a positive stress test.
* In patients suspected of "silent" ischemia who have occupational hazards or a strong family history of infarction/sudden death.
* Ischemic cardiac myopathy and congestive heart failure (CHF).
* Before major noncardiac surgery in patients who are at high risk due to age, diabetes or a lipid disorder. Before cardiac surgery in patients at risk for coronary artery disease.
* Congenital heart disease or pericardial disease.
Suspected Valvular Disease:
* Aortic stenosis with angina, syncope or CHF.
* Aortic regurgitation with CHF, angina or progressive cardiac enlargement.
* Mitral stenosis with CHF refractory to digitalis and diuretics or with recurrent emboli with atrial fibrillation. (Note: surgery may be performed without catheterization if diagnosis is certain.)
* Mitral regurgitation with CHF or progressive cardiac enlargement.
* Percutaneous transluminal coronary angioplasty, electrophysiological study, biopsy, hemodynamic monitoring, balloon valvotomy.
Coronary Artery Disease
The major culprit in the high mortality rate for cardiovascular disease is coronary artery disease (CAD). It is the major killer of both men and women, and the American Heart Association estimates that nearly 14 million people in the United States have a history of classic CAD symptoms. On average, 1 in every 5 men and 1 in every 17 women at age 60 will develop coronary artery disease.
Coronary artery disease is the partial or complete occlusion of one or more coronary arteries, resulting in impairment of the blood supply to the heart. The main clinical conditions that occur as a result of CAD are myocardial infarction (heart attack) and angina pectoris (chest pain due to insufficient blood supply to the myocardium). Silent or asymptomatic ischemia is an additional form of CAD that might indicate the need for cardiac catheterization. These patients show no symptoms but have evidence of ischemia on diagnostic tests or possess extremely high risk factors for myocardial infarction. Cardiac catheterization plays a crucial role in managing CAD by confirming the disease and characterizing its extent. Angiograms are the most important product of cardiac catheterization for diagnosis and management of CAD.
The valves play a key role in the pressure pump action of the heart. The purpose of the cardiac valves is to ensure unidirectional flow of blood. A normal valve performs this function without obstruction of forward flow and without allowing reverse flow. Any of the 4 valves may become stenotic (ie, obstruct normal forward flow of blood) or regurgitant (allow backward flow of blood.) In some conditions, a valve will be both stenotic and regurgitant. Cardiac catheterization has several applications in valve disease, including hemodynamic measurement, assessment of the severity of disease and treatment.
Cardiomyopathy is a serious disorder of the heart muscle. The heart becomes inflamed and does not pump blood as it should.[18,19] The disease can be primary (ie, not attributed to a specific cause) or secondary to a specific cause or disease. There are 3 main types of cardiomyopathy: dilated, hypertrophic and restrictive.
Dilated cardiomyopathy is dilation of the ventricular chambers with decreased ability to contract and pump blood. This is the most common form of cardiomyopathy.[19,20] It also is referred to as congestive cardiomyopathy, and most patients with the condition develop congestive heart failure.[18,19]
In hypertrophic cardiomyopathy, the left ventricular muscle mass enlarges (hypertrophies). Hypertrophy of cardiac muscle can result from many cardiac diseases. However, in hypertrophic cardiomyopathy, it occurs without an obvious cause and out of proportion to the magnitude of identifiable stimuli. In more than half of all cases, it can be attributed to a genetic disorder and is most common in young adults.[18,19]
Restrictive cardiomyopathy is not as common as the hypertrophic or dilated forms. The walls of the ventricle become excessively rigid, making it difficult to fill with blood between heartbeats. Weakness, dyspnea on exertion and swollen hands and feet are common complaints. The predominant symptom is progressive exercise intolerance. Restrictive cardiomyopathy usually is caused by another systemic or heart disease.[16,19,20]
Cardiac catheterization is used in patients with cardiomyopathy to measure hemodynamic pressures, cardiac output and resistances.
Congestive Heart Failure
In the United States, 2.5 to 3 million people have congestive heart failure, and the incidence is increasing. It usually develops as a result of decreased myocardial contraction ability and is caused by a variety of conditions and diseases including CAD, scar tissue from past myocardial infarction (MI), hypertension, valvular disease, cardiomyopathy, congenital heart disease and endocarditis. Cardiac output is inadequate and blood flow to organs and tissues is compromised, particularly upon exertion. Atrial pressures also increase. As blood flow output slows, blood returning to the heart through the veins backs up, causing congestion in the tissues. Sometimes fluid collects in the lungs and interferes with breathing.
Congenital Heart Disease
Congenital heart disease is the most common category of congenital malformations in newborns, occurring in about 1% of live births. If the conditions are not treated, about one third of these children will die in the first year.[16,22] In most cases, the cause is unknown, although viral infections such as rubella can cause serious problems. The defects occur in the heart or nearby vessels and can obstruct blood flow in the heart or vessels or cause dysfunctions in the pattern of flow. There are a number of congenital heart diseases, many of which can benefit from cardiac catheterization.
Atrial septal defects are a common form of congenital heart disease, comprising about 15% of all congenital abnormalities. In this disease, there is an opening between the left atrium and the right atrium. This allows blood to return via the hole to the right atrium rather than moving through the left ventricle, out the aorta and to the body.
Ventricular septal defect is an opening between the lower chambers of the heart. Most are located just beneath the aortic valve in the membranous or muscular portion of the septum. Patients with small ventricular septal defects do not require treatment, and the only abnormal finding may be a loud murmur. If the opening is large, the patient requires open heart surgery to prevent complications such as childhood undernourishment and impaired growth.[16,22]
Other forms of congenital heart disease include patent ductus arteriosus, a connection between the pulmonary artery and the aorta that does not close off as is usual between 2 and 3 weeks after birth. It typically is diagnosed in childhood and corrected at the time of diagnosis. Premature babies are thought to have an incidence of patent ductus arteriosus as high as 40%. Congenital aortic stenosis is common in both children and adults. In this condition, the aortic valve formed incorrectly, affecting the flow of blood between the left ventricle and the aorta. The need for surgery to correct or replace the valve depends on the severity of symptoms.
Some emergencies warrant immediate cardiac catheterization. When a patient presents in the emergency department with chest pain, major life-threatening conditions must be excluded. Some of these include pulmonary embolism, aortic dissection, spontaneous tension pneumothorax and myocardial ischemia. A normal ECG may indicate life-threatening causes other than myocardial ischemia; however, a normal ECG does not always exclude ischemia as a diagnosis.
* Pulmonary embolism. Pulmonary embolism symptoms include unexplained shortness of breath, lightheadedness and chest pain. Onset of symptoms may be gradual, sudden or intermittent. Surprisingly, patients with life-threatening pulmonary embolism often have no pain. A ventilation-perfusion lung scan and a high-quality chest radiograph are the best initial imaging choices for pulmonary embolism. Patients with high-probability scans probably do not need pulmonary angiography, unless there is a strong contraindication to heparin or thrombolytic therapy. If invasive intervention is being considered, angiography may be indicated. A carefully performed right heart catheterization may provide diagnosticians with clues to alternative diagnoses that were not suspected, such as left ventricular failure.
* Aortic dissection. Aortic dissection should be considered in patients who present with sudden onset of severe, tearing back or retrosternal pain. Also called dissecting aneurysm of the aorta, it occurs mostly in patients between ages 40 and 70. Patients younger than 40 may have a congenital aortic anomaly or a condition known as Marfan syndrome, and in some patients, pregnancy is a predisposing factor for aortic dissection. Up to 40% of deaths from dissection occur within the first 48 hours. Magnetic resonance angiography (MRA) or coronary angiography may be used to confirm the diagnosis of aortic dissection.
In general, cardiac catheterization in these patients defines the extent of dissection and whether or not it involves the ascending aorta and arch. It also can show complications of dissection and any coexisting CAD. Due to the emergency nature of this condition, patients may require rapid, definitive surgical therapy. The decision to use coronary arteriography depends on the length of the delay and clinicians' level of expertise with a given diagnostic procedure.
* Aortic rupture. Penetrating injuries such as stab wounds and even nonpenetrating injuries such as automobile accidents can rupture the aorta. Rupture can occur just above the aortic valve or just distal to the left subclavian artery. Diagnosis of aortic rupture may be complicated by other injuries and lack of specific findings. Symptoms such as increased blood pressure in the arms and reduced pulses in the legs, and radiographic signs such as a widened mediastinum can indicate aortic rupture. When rupture is suspected, it should be confirmed if possible. If catheterization is chosen, angiography should be performed in at least 2 planes. The likelihood of associated injuries can be easily confirmed by abdominal aortography.
* Injury. Penetrating injuries to the chest, often caused by bullet or knife wounds, can produce other internal injuries that may be diagnosed or confirmed by emergency cardiac catheterization. Hemorrhagic pericarditis with cardiac tamponade; pneumopericardium; myocardial contusion; and damage to coronary vessels, the septum or the valves can occur. Patients may show signs of pericardial effusion, congestive heart failure, arrhythmias, valvular defects, arteriovenous fistulas or intracardiac shunts. All of these signs may be absent, and only certain ECG changes may indicate injury. Frequent ECGs are recommended even when there is nonpenetrating injury. Patients with murmurs, valvular defects or shunts should have cardiac catheterization prior to any surgical intervention.
Contraindications for Cardiac Catheterization
Relative contraindications are widely accepted, although few data exist on the inherent risks of cardiac catheterization when specific conditions are present. (See Table 2.) In many cases, the determination will be made based on the individual patient's situation, particularly because the acuteness of the medical condition may necessitate a higher-risk procedure. The decision should be based on careful consultation between the referring physician and the diagnostic team.
Table 2 Relative Contraindications To Coronary Angiography(*)
Acute renal failure Chronic renal failure secondary to diabetes Active gastrointestinal bleeding Unexplained fever, which may be due to infection Untreated active infection Acute stroke Severe anemia Severe uncontrolled hypertension Severe symptomatic electrolyte imbalance Lack of patient cooperation due to psychological or systemic illness Severe concomitant illness that drastically shortens life expectancy or increases risk of therapeutic interventions Patient refusal to consider definitive therapy such as percutaneous transluminal coronary angioplasty, coronary artery bypass surgery or valve replacement Digitalis intoxication Documented anaphylactoid reaction to angiographic contrast media Severe peripheral vascular disease limiting vascular access Decompensated congestive heart failure or acute pulmonary edema Severe coagulopathy Aortic valve endocarditis
(*) Reprinted with permission from: The American College of Cardiology and the American Heart Association Inc. ACC/AHA guidelines for coronary angiography. J Am Coll Cardiol. 1999;33:1761.
Renal insufficiency is the most extensively studied relative contraindication to coronary angiography. Between 10% and 40% of patients with renal insufficiency reportedly have worsened renal function after angiography. Diabetic patients with pre-existing renal insufficiency are especially prone to developing renal failure. Patients with known anaphylactoid reaction to contrast media, particularly those with cardiovascular disorders who are taking beta-blockers, are at risk for contrast reaction from ionic angiographic contrast. Early studies suggested that pretreatment of a reaction-prone patient with certain histamines or corticosteroids reduces risk of contrast reaction to an acceptable level when weighed against the procedure's benefits.
Other relative contraindications include patients undergoing anticoagulant therapy with warfarin sodium, which is associated with elevated prothrombin times; patients with severe, uncontrolled systemic hypertension; and patients with severe electrolyte abnormalities. Many of the relative contraindications for coronary angiography are temporary or reversible. If the procedure can be safely delayed, risks may be reduced. The American College of Cardiology and American Heart Association guidelines recommend that cardiac catheterizations for high-risk patients with relative contraindications not be performed in an outpatient setting.
Patient preparation for cardiac catheterization begins with education and informed consent. A physician should meet with the patient and family members to explain the procedure and its risks. Physicians and catheterization lab staff should be reminded to keep the explanations simple and use language the patient can understand.[13,30] If the patient feels overwhelmed by too much information or terms he or she does not understand, education may heighten anxiety. Areas that should be covered include:
* The purpose of cardiac catheterization.
* Diet and medication prior to the procedure.
* A brief description of the procedure, including requirements such as keeping arms above the head, coughing or holding the breath when instructed.
* When to expect results.
* After care and monitoring.
The physician should obtain informed consent as part of the patient education meeting and consent should be obtained prior to any premedication.
Patients preparing to undergo cardiac catheterization procedures should have a complete physical and a series of lab tests, including a complete blood count, coagulation parameters, electrolytes, renal function and other special tests applicable to the patient's specific condition. A chest radiograph and recent ECG results also should be available for preprocedure evaluation.[30,32] These tests help assess the patient's risk and candidacy for an outpatient procedure.
Dietary and Medication Instructions
Dietary restrictions prior to the procedure should be clearly outlined on an inpatient's chart on the day prior to the procedure. Outpatients should receive written instructions, and the instructions also should be entered on the patient's procedure orders. Protocol varies by institution, but most laboratories require fasting beginning at midnight the evening before the procedure or at least 6 hours prior to the procedure.[5,13]
Certain medications may be discontinued or adjusted in dosage to minimize risk or help ensure a successful study. The most common of these are anticoagulants. Warfarin (Coumadin) normally should be discontinued 2 to 3 days prior to the procedure. As an alternative, intravenous heparin can be administered to patients on chronic anticoagulation therapy, stopping about 4 hours before the procedure,[13,32] In emergency cases, cardiac catheterization still can be performed with interventions such as fresh frozen plasma or a percutaneous closure device used to reverse anticoagulation.
Other medications that may be reduced or discontinued before cardiac catheterization include coronary vasodilators, diuretics and certain drugs used to treat diabetes mellitus.[30,32] Diabetic patients may require special dietary and pharmaceutical considerations. When possible, patients with diabetes should be scheduled early in the day so that those receiving oral hypoglycemia agents can omit the morning dose. Insulin doses may be reduced. Infusions of dextrose in water solution may be started 3 to 4 hours after fasting begins, and all diabetic patients should be observed carefully for signs of hypoglycemia.
Many patients are anxious about the catheterization procedure and may request a sedative the evening before the procedure. Diazepam or diphenhydramine may be administered 30 minutes before the procedure.
At the time of the patient consultation and consent meeting, peripheral pulses and the access site should be assessed to determine whether an alternate entry point must be considered. The risks and complications of the alternate site should be explained to the patient at that time.
Just prior to the procedure, re-examination of the ECG is essential and a brief review of the patient history ensures that there have been no major changes since the last patient interview. An examination of heart sounds, breathing and carotid and peripheral pulses is essential immediately before and after catheterization. Pertinent lab data, clinical conditions and results of pervious catheterizations should be reviewed at this time as well.
During the procedure, the patient should be closely monitored for signs of hypotension, arrhythmias and angina. Changes in cardiac output require prompt treatment to prevent serious complications. To ensure a safe procedure, continuous ECG monitoring and prompt attention to problems are critical. Blood pressure and cardiac output measurements and oximetry also are performed. Monitoring a patient's comfort level and liberal use of pain medication often are recommended to help relax the patient. All patients should be observed for signs of contrast reaction.
Following cardiac catheterization, the patient should be checked regularly according to post-catheterization orders that outline any special monitoring requirements. The orders also will indicate laboratory test and medication requirements. The patient's vital signs should be stable. Other signs that should be checked include adequate urine output (to verify that contrast-induced renal failure has not occurred), and extremity coolness, which may indicate thrombus or vasoconstriction. Tachycardia with low blood pressure indicates blood loss. Arterial access areas should be checked for pain, hematoma and loss of distal pulses. The patient's legs should be kept straight for 4 hours after a diagnostic procedure with femoral access and 8 hours following a therapeutic procedure. Nursing staff should check the groin area regularly for signs of hematoma, bleeding or pseudoaneurysm.
A wide variety of equipment must be available for all types of catheterization procedures that might be performed in a given lab. The equipment generally falls into 3 categories: physiological measurement equipment, such as blood pressure and ECG monitors; imaging and image processing equipment; and support equipment, including catheters, guidewires, temporary pacemakers, sheaths and a crash cart. The equipment may be durable or disposable and should be located in a functional and convenient manner. When equipping the catheterization laboratory, both pediatric and adult procedures must be considered, as well as use of the room for both diagnostic and therapeutic procedures.
Contrast angiography is the gold standard in imaging the cardiac chambers and coronary arteries. Magnetic resonance angiography is growing in use and has some promise in diagnosing many coronary artery and cardiac diseases. However, contrast-enhanced angiography is the definitive method for diagnosis of many diseases, such as pulmonary embolism.
When filled with blood, cardiac chambers and vessels provide little contrast on images. Therefore, a radiopaque contrast agent must be injected to enhance the vessels or chambers being studied. The constant pumping movement of heart structures requires short x-ray exposures to "freeze" the motion. To study blood flow or cardiac function, rapid image sequences are necessary.
High-quality imaging is mandatory for evaluating cardiovascular structures and functions and for the safe placement of catheters and interventional devices. Diagnostic and therapeutic catheterization require fluoroscopy with a 35 mm cineangiography primary recording medium. Fluoroscopy facilitates placement of catheters while cineangiographic film permanently captures anatomic and functional details of the cardiac chambers, great vessels and coronary circulation. Although excellent images are expected for both types of procedures, interventional procedures require more highly detailed fluoroscopy. Digital angiographic systems provide an alternative to static imaging.
A typical system consists of the x-ray tube, collimator, antiscatter grid, video camera and cine film camera. (See Fig. 3.) These components usually are mounted on a C-arm, U-arm or other mounting system over the exam table. A 3-phase, 12-pulse generator with an output of 80 to 100 kW or a constant potential generator with an output of at least 100 kV is recommended by the ACC/AHA task force on cardiac catheterization. Other required equipment includes a cine film processor and projector, a method of coordinating x-ray exposure time and the cine camera function and an image intensifier. A system to acquire, process and store images is needed for digital angiography. Monitors to display AP and lateral image chains and physiologic data are located nearby.
[Figure 3 ILLUSTRATION OMITTED]
Cineangiographic imaging is best when a synchronous 35-mm camera is used. Fluoroscopic images may be saved and replayed almost immediately with video recording. When selecting a video system for cardiac catheterization, signal-to-noise ratio and image resolution are important considerations. Selection of cine film for cineangiography should be based more on the film's contrast and graininess than film speed. The areas imaged in cardiac angiography are such that the degree of x-ray attenuation varies dramatically and results in a large range of exposure.
Cardiac catheterization procedures deliver high levels of patient and operator radiation dose. Patient entrance exposure from a typical cardiac angiographic study, with 10 minutes of fluoroscopy and 1 minute of cine film studies, is equivalent to between 250 and 650 chest films. Exposure is higher in many interventional studies, such as PTCA, and care must be taken to avoid radiation dose injury to thoracic skin.
When therapeutic procedures are involved, the dose can be even higher. In one study, the highest patient skin doses were found in PTCA with stent procedures. One reason is that long fluoroscopy time and multiple cine runs with the tubes in the same irradiation geometry increase dose substantially. For cardiac catheterization in general, the critical skin location is most likely the right flank, while for catheterization with left ventricle imaging, the middle of the back probably receives the highest dose. (See Fig. 4.)
[Figure 4 ILLUSTRATION OMITTED]
The best ways to reduce total operator exposure are to minimize patient dose and resulting scatter by calibrating to national standards, use the optimum dose, reduce fluoroscopy time to the minimum required for catheter placement and use proper collimation.[34,36] Equipment to limit exposure includes an x-ray dense shield positioned between the x-ray tube and the operator. Protective aprons should be at least 0.5 mm lead equivalent. The apron should extend to the knees, have a shallow cutout to protect the sternum and be of the wraparound type. Wraparound leaded eyeglasses protect the eyes, and a thyroid shield protects the neck and thyroid. Personnel exposure is somewhat higher with C-arm mounting.
A high-pressure contrast injector is used to administer the relatively large amounts of contrast agent required for many cardiac catheterization studies. The power injector delivers contrast through intravascular catheters into the large vessels and cardiac chambers. Injectors should be able to deliver as much as 50 mL/sec, the high-end of standard injection rates for left ventricle and pulmonary artery opacification. On the other hand, low-flow rates are desired for the timed injection of therapeutic agents such as streptokinase.[12,31]
Power injectors should have volume control, a mechanical stop and pressure limit control. Flow injectors allow for selection of both volume and rate of delivery of contrast material. They are set to shut down automatically if the pressure exceeds a preset maximum. For coronary angiography, too little contrast allows intermittent entry of nonopaque blood into the coronary arteries, which produces streaming and makes interpreting lesions difficult. On the other hand, too vigorous of an injection could cause coronary dissection or other complications. A prolonged injection also may lead to complications. Considering these factors and the relatively low flow rate (3 to 8 mL) for coronary arteries, some labs favor manual injection of contrast for coronary angiography.[12,40]
Catheters and Guidewires
The characteristics of the catheter chosen for a particular procedure depend on clinical considerations. Shorter catheters are better for obtaining accurate pressure signals, but length is dictated by the specific cardiac chambers to be reached as well as the entry site. Catheter diameter should be small enough to minimize vascular trauma but large enough for contrast infusion and structural integrity. Catheter flexibility also may be a consideration.
Cardiac catheters have several parts. The catheter body generally is straight for most of its length. The bends are called curves, and the terms primary, secondary and so on are assigned to the curves, with the primary curve being the one closest to the catheter's tip. Catheter tips vary greatly and can have a number of side holes, a single end hole or a closed end. Some have tapered tips, while others, such as those designed for insertion through an arteriotomy or sheath, do not taper. (See Fig. 5.)
[Figure 5 ILLUSTRATION OMITTED]
The catheter is connected to a manifold with several stopcocks. This permits the operator to manipulate the catheter and flush it with saline. It also allows the operator to add contrast material or measure pressure without having to switch the catheter to a separate line. Angiographic catheters are sized by external and internal diameter and length. External diameter is expressed in French sizes, with 1 Fr equaling 3 mm. French sizes 4 to 8 are used most often for diagnostic angiography. Catheter lengths vary, and commonly used catheters measure about 80 to 110 cm long. (See Table 3.)
Table 3 Common Catheters Used in Cardiac Catheterization Procedures(32,42-26)
Catheter Design Judkins-type Preshaped curves, tapered tips with end holes Amplatz-type Left: preshaped half circle, tapered tip extends perpendicular to curve; right: smaller but similar hook-shaped curve Multipurpose Straighter, end hole and 2 side (Schoonmaker, King) holes at tip Pigtail Preshaped to make a full circle 1 cm in diameter, tapered tip, multiple side holes NIH Thick walled, rounded tip, closed end, 4 to 6 side holes Gensini Thin walled, open end, 6 side holes Lehman Woven core, 3 side holes, closed-end tip Sones Made of Dacron, gradually tapered tip, 2 side holes, single end hole Swan-Ganz Balloon tipped Cournand Stiffer design, end hole Trans-septal More rigid; made of Teflon; (Brockenbrough) curved, tapered tip; end hole; 2 to 6 side holes Catheter Common Uses And Approaches Judkins-type Used with femoral approach in more than 90% of coronary angiography catheterizations Amplatz-type Used when Judkins is not suited to patient's anatomy Multipurpose Left ventriculography, selective (Schoonmaker, King) coronary angiography Pigtail Primarily for high-flow contrast studies, femoral ventriculography NIH Brachial approaches for right or left ventriculography, angiography in major vessels Gensini High-flow contrast studies; brachial approach to cross the aortic valve Lehman Ventriculography Sones Brachial approach Swan-Ganz Used in most right heart catheterizations Cournand Right heart catheterization, selective blood sampling; femoral or brachial approach Trans-septal Left atrial catheterization; (Brockenbrough) designed to cross from right to left atrium through fossa ovalis Catheter Notes Judkins-type Naturally seeks the coronary orifice when advanced according to left coronary artery technique Amplatz-type Has been adapted for use in the brachial approach; requires more manipulation than Judkins type Multipurpose (Schoonmaker, King) Pigtail Design adds to stability NIH Easily maneuvered and positioned directly through a sheath or cutdown Gensini Lehman Sones More flexion in the distal portion for manipulation from the subclavian artery into the ascending aorta, forming a loop in the aortic sinus Swan-Ganz Design allows it to float through the right side of the heart easily and safely; readily measures pulmonary artery occlusion pressure Cournand Trans-septal Side holes assist with (Brockenbrough) angiography
Many catheters carry the names of those who developed them. For coronary angiography, more than 90% of catheterizations can be completed with a Judkins-type catheter and a femoral approach. With special preshaped curves and tapered end-hole tips, these catheters are advantageous in that they naturally seek the coronary orifice with very little manipulation. There are several types of Judkins catheters, including the Judkins right coronary catheter, which advances into the ascending aorta and rotates clockwise 45 [degrees] to 90 [degrees].
Amplatz-type catheters are useful in cases where the Judkins catheter is not suited to a particular patient's anatomy.[42,43] The left-Amplatz catheter is a preshaped half-circle with a tapered tip extending perpendicularly to the curve. The manipulation needed for Amplatz catheters means they generally have a higher incidence of coronary dissection than Judkins-style catheters. The right Amplatz modified catheter has a smaller but similar hook-shaped curve. It is advanced into the fight coronary cusp and rotated similarly to the right Judkins-style catheter. Amplatz catheters also have been adapted for use in the brachial approach.
Multipurpose catheters (Schoonmaker and King) generally are straighter with an end hole and 2 side holes near the tip. This type is used for left ventriculography and selective coronary angiography procedures. Special-purpose femoral artery catheters include venous bypass graft and internal mammary artery catheters. These special catheters require extensive expertise for accurate manipulation.[42,43]
The potential for catheter recoil and intramyocardial contrast injection necessitates that ventriculographic catheters contain multiple side holes, never a single end hole. The pigtail catheter often is used in femoral-approach ventriculography. It has a tapered tip preshaped to make a circle 1 cm in diameter. The curled tip design and multiple side holes help the catheter achieve stability, and it is used primarily for high-flow contrast studies. The pigtail catheter is advanced to the aortic valve to enter the left ventricle.[42,43]
The NIH catheter is thick walled and has a rounded tip and closed end. There are 4 to 6 side holes at the tip. It can be maneuvered easily and positioned directly through a sheath or cutdown. The NIH catheter frequently is used in brachial approaches for right or left ventriculography and angiography in major vessels.
A thin-walled catheter called the Gensini catheter has an open end and 6 side holes. It is well-suited to high-flow contrast studies and for crossing the aortic valve from the brachial approach. Another catheter used for ventriculography is the Lehman catheter, which has a woven core, 4 side holes and a closed-end tip.
The Sones catheter is made of Dacron and has a gradually tapered tip with 2 side holes and a single end hole. Tapering allows more flexion in the distal portion of the catheter. As a result, the catheter can be manipulated from the subclavian artery into the ascending aorta, forming a loop in the left aortic sinus.[32,43]
If patients are undergoing left heart catheterization, the same site usually is used for right heart entry. If right heart catheterization is performed alone, the access site depends on whether or not the catheter can remain in place for monitoring. The majority of right heart catheterizations are performed with a Swan-Ganz balloon-tipped flotation catheter. Swan and Ganz developed the balloon-tipped catheter for clinical use in 1970. The balloon tip design usually allows the catheter to float through the right side of the heart safely and easily, so that pulmonary artery occlusion pressure can be measured readily.
The Cournand catheter is a stiffer catheter designed specifically for right heart catheterization, with an end hole that may be used to obtain a truer wedge pressure.[42,44] It also can be used for selective blood sampling and can be introduced through the femoral or brachial veins. Other right heart catheters include the Goodale-Lubin, which is similar to the Cournand but has 2 closely located side holes, and the Zucker, which has electrodes near the tip for optional cardiac pacing or simultaneous measurement of intracardiac pressures.[42,43]
The trans-septal catheter was developed specifically to cross from the right to left atrium through the fossa ovalis. Brockenbrough-type trans-septal catheters advance over a Brockenbrough-type needle for left atrial catheterization.[42,46] They are made of Teflon and are more rigid than conventional catheters, having a curved, tapered tip with an end hole and 2 to 6 side holes. The side holes assist with angiography, while the curved tip helps the catheter advance from the left atrium to the ventricle. A design modification to the sheath facilitates insertion of different catheters into the left atrium or ventricle.
After venous access is obtained with a needle, a guidewire is threaded through the needle and into the vessel. Sometimes called a spring guide, leader or guide, the basic construction consists of a thin strand of round wire wrapped around a metal rod or tube.[42,43] Many are made of stainless steel and Teflon coated to reduce friction between the wire and the needle, sheath or catheter. There are many sizes and types of wires, with 3 general categories. Short wires (15 to 30 cm) are used to place sheaths. Wires 12.5 to 150 cm long generally are used to thread a catheter to the central aorta or great vein. Wires 250 to 300 cm long are used to exchange catheters without moving the wire tip. A guidewire should be at least 20 cm longer than the catheter with which it will be used.
The proximal tip is the end of the wire that extends outside the patient's body. The distal tip is the end that enters the patient and must be especially smooth and flexible. Guidewires are available in various designs, lengths, diameters and tip configurations, and the selection depends on the particular procedure.
Most catheterizations today are performed with the assistance of a sheath, or a tube with a rubber diaphragm on the distal end, and a side arm through which pressure can be measured or drugs infused. The diaphragms are designed to prevent blood or air from leaking into the sheath. They are typically about 20 to 35 cm long and about 5 to 8 Fr in diameter. The sheath's features have made cardiac catheterization easier for the physician and patient. Sheaths allow for more rapid catheter changes and reduce both arterial trauma and bleeding into subcutaneous tissues during the procedure.
The Cardiac Catheterization Team
Composition of the catheterization laboratory team varies among facilities. At a minimum, the team should include a physician, assisting physician or nurse, a nurse circulator or recording technician assigned to the laboratory and a nurse outside the lab, ready to assist. Every lab also should have staff with technical knowledge of laboratory and radiologic equipment and procedures. One person may possess a cross section of skills, depending on the lab's size and volume. Each member of the team performs a crucial role.
In some states, registered radiologic technologists are required in cath labs and most labs have at least one registered technologist on staff. The radiologic technologist dedicated to cardiac catheterization should have experience in the proper use of generators, cine pulse systems, automatic film processing and image intensification. In cooperation with electronic or radiology service engineers, the technologist usually is responsible for routine maintenance and troubleshooting of imaging-related equipment. At least one technologist in the lab must be familiar with darkroom technique. The radiologic technologist, in cooperation with a radiation physicist, usually is responsible for monitoring radiation safety protocols for staff and patients.
Accessing the Cardiovascular System
Cardiac catheterization has become increasingly complex, and the techniques used for these procedures vary.[5,30] Once the specific procedure is chosen, the physician must select a site to introduce the catheter.
To plan the access site, physicians take into account the patient's history, physical exam and the anticipated diagnosis or indication for the procedure. Initial access to the cardiovascular system is the most commonly reported problem in catheterization, and catheter entry into the circulatory system usually is the only painful part of the procedure. Each method of access has advantages and disadvantages, depending on the patient and circumstances.
Also called the direct approach, this technique accesses the artery through a surgical cut. It most often is used to access the brachial artery, which is in the arm, through a cut in front of the elbow. Cutdown also may be used to access the femoral artery, but normally only in special circumstances, such as in small children.[5,48] Use of this technique has diminished during the past 25 years. The brachial approach is selected in patients who have severe peripheral vascular disease that involves abdominal, femoral or other arteries. Patients who are very obese may require this technique because the femoral approach may be technically difficult in those patients and bleeding more difficult to control. Severe hypertension, aortic regurgitation and wide pulse pressure are additional indications for this approach.[5,13]
The disadvantages of the brachial approach are the need to repair the artery and risk of incomplete repair, which could result in hemorrhage or embolism. Another disadvantage is the small size of the vessels, which limits the choice of catheters.
In the cutdown approach, the patient receives local anesthesia, and the arm is placed on a board and taped at the wrist. A towel may be placed under the elbow to straighten the arm and fix landmarks.[47,49] After palpation of the brachial artery, the physician makes a transverse incision with a surgical blade. If right heart catheterization alone is planned, the incision is narrow and over a medial vein. For right and left heart catheterization, the incision is wider and over the brachial artery. The length of the incision is based on the need for good exposure to the venous structures. Care should be taken to avoid the nearby medial nerve. Tissues are separated, and an appropriate vein is brought to the surface, separated from adjacent nerves and fascia, and then tagged. The same technique can be used to bring the brachial artery to the surface.
Removing overlying tissue is important, as this allows easier arterial repair following the procedure. The physician applies clamps to prevent backbleeding, and a small transverse incision is made in the artery with a scalpel. This incision should be large enough to admit only the tip of the catheter. With small angled forceps, the physician opens the artery and advances the catheter, intubating the artery. The catheter then is aspirated, flushed with heparinized solution and connected to the manifold. Next, the catheter can be advanced to either the right or left side of the heart.[47,49]
Catheter control and flexibility are best maintained if the catheter is advanced as soon as possible after introduction into the vascular system. The right heart catheter is advanced under fluoroscopy to the superior vena cava. From there, the catheter can be advanced to the pulmonary artery, passing from the right atrium to the right ventricle. To measure wedge pressure, the catheter can be advanced to the wedge position, with help from the patient in breathing deeply and then coughing.
After the right heart catheter is advanced to the pulmonary artery or wedge position, a left heart catheter can be advanced through the brachial artery. It will travel to the ascending aorta just above the aortic valve. Once there, central aortic pressure and arterial pressure can be measured. Then the left heart catheter is advanced into the left ventricle, and critical pressure measurements can be made. After pressure measurement is completed, most of these procedures continue with left ventriculography and coronary angiography. When the procedure is complete, vascular clamps are placed to control bleeding at the access site. The cut is sutured and inspected for additional bleeding.
The percutaneous approach, also called the Seldinger technique or the percutaneous femoral approach, does not involve cutdown or arterial repair. Instead, a needle and guidewire are introduced into the femoral artery and vein.[5,46] It is clearly the preferred technique for cardiac catheterization. Because there is no need for arterial cutdown and repair, certain complications are less likely, and the procedure can be performed repeatedly in the same patient at intervals. Infection and thrombophlebitis at the entry site rarely occur and surgical closure is unnecessary. In addition, this approach is more readily adaptable to a variety of other entry vessels, such as the internal jugular vein, axillary artery and radial artery. In this technique, the catheters may be left in place for easy interventional access to the coronary arteries. The Seldinger approach is quicker and easier to perform because the large blood vessels of the groin are less likely to suffer catheter damage and are easier to locate.
Disadvantages of the percutaneous femoral approach are decreased catheter control and the need for bed rest following the procedure while the arterial wall heals and bleeding is stopped.
The physician locates the preferred entry vessel through palpation or landmark identification. The inguinal skin crease provides a good landmark for locating a puncture site. After locating the puncture site, the skin surrounding the area is anesthetized. The puncture should be made in the inguinal ligament for easier entry to the femoral artery and vein and to minimize vascular complications. Skin nicks help with marking and needle entry of palpable sites. (See Fig. 6.)
[Figure 6 ILLUSTRATION OMITTED]
The vessel is entered through the skin with a needle, the type and size of which depend on the patient and the guidewire to be used. Aspiration of the needle often is necessary to ensure vigorous blood return. Once blood is flowing vigorously, a guidewire is inserted into the vessel through the needle. The guidewire remains in the vessel while the needle is withdrawn. In most percutaneous procedures, a sheath is placed over the guidewire and the catheter is advanced through the sheath. Using a sheath reduces patient discomfort and repetitive local arterial trauma as catheters are exchanged, but it increases the size of the puncture slightly.
Fluoroscopy should be used to observe movement of the guidewire tip, particularly if any resistance is felt. The catheter is inserted when the wire tip reaches the level of the diaphragm of the ascending aorta. To accomplish this, the protruding wire is wiped with a moistened gauze pad and its free end is threaded into a sheath and dilator combination. When the sheath is in place, the wire and dilator are removed, and the sheath is flushed by withdrawing blood and administering heparinized saline solution. The catheter is advanced to the superior vena cava for a blood sample to compare oxygen saturations. Most right heart catheterizations are performed with an 8-Fr multilumen balloon-tipped flotation catheter with thermodilution cardiac output capability (the Swan-Ganz type). The choice of catheter depends on its function, and manipulation should be adjusted depending on the catheter type.
For right heart catheterization, the catheter can be advanced from the femoral vein to the pulmonary artery by positioning the tip of the catheter in the lower portion of the right atrium. With the proper rotation and guidance, the catheter passes over the tricuspid orifice and into the right ventricle, where pressure can be recorded. Next, the catheter tip crosses the pulmonic valve to a wedge position for pressure recording. Careful attention to protocol and entry guidelines helps the physician continue advancing the catheter into the pulmonary artery. In general, catheters advanced from the leg are more likely to find the left pulmonary artery naturally, while those advanced from above tend to find the right pulmonary artery. Either artery can be catheterized with careful use of a curved J guidewire.
Once in either pulmonary artery, another blood sample for oxygen saturation can be obtained and pulmonary arterial pressure measured. The right heart catheter remains in the pulmonary artery for the duration of the procedure, continuously monitoring pulmonary artery diastolic pressure.
Left heart catheterization from the femoral artery requires use of an appropriate size vascular sheath equipped with a backbleed valve and sidearm tubing. In most cases, the initial left heart catheter used is a pigtail catheter with multiple side holes. Left heart catheterization normally is performed retrograde through the aortic valve from the femoral approach. After the catheter is flushed, it is advanced to the ascending aorta for pressure measurement. With a pigtail catheter, the tip can be advanced to a position just above the aortic valve and rotated so that the tail is oriented toward the left coronary cusp.
Guidewires often are used in crossing the aortic valve. After completion of left heart catheterization and associated angiography, heparin is reversed with protamine. Careful sheath and catheter removal with firm manual pressure to the femoral artery helps minimize complications. Right and left heart catheterization can be performed in the same procedure, and this combination is the preferred method for evaluating cardiac chamber pressures. After the right heart catheter is advanced to the pulmonary artery wedge position and pressure recordings are taken, the catheter is withdrawn and left heart catheterization can begin.
The goal of this approach is to cross from the right atrium to the left atrium through the fossa ovalis. In most patients, mechanical puncture of the area with a needle/catheter combination is required to enter the left atrium. Formerly, the trans-septal approach often was performed because it was the best method at the time to directly measure left atrial and left ventricular pressures. However, introduction of the Swan-Ganz catheter and retrograde catheterization of the left ventricle led to a decline in the use of the trans-septal approach. In recent years, a resurgence of this approach has occurred, largely because of interventional procedures that depend on this technique.
The trans-septal catheter consists of a tapered needle designed to puncture the atrial septum and a tapered catheter. The catheter, usually a Ross or Brockenbrough type, passes over the needle to enter the left atrium.[48,50] For this procedure, the percutaneous approach is used to enter the right femoral vein. After advancing a guidewire to the inferior vena cava, the catheter and sheath are passed as a unit over the wire and the entire system is advanced to the superior vena cava. The guidewire is removed and the needle advanced through the catheter.
The physician must be careful not to let the needle move beyond the tip of the catheter until the fossa ovalis is reached. When in correct position, the needle is advanced out of the catheter across the septum and into the left atrium, with care taken to prevent too much movement and resulting damage. The primary complication of trans-septal catheterization is puncture or perforation of surrounding heart structures such as the aortic root, coronary sinus or posterior free wall of the right atrium.[46,48]
Angiography commonly is performed immediately following right and left heart catheterization to determine the presence or degree of coronary artery disease, assess complications of MI, evaluate positive stress tests and for other diagnostic purposes.[5,6] Using fluoroscopic guidance, a special catheter is guided into the aorta and the left and right coronary arteries.
In most patients, angiography can be performed by the brachial or femoral approach, although the femoral approach generally is preferred. Catheter positioning depends on the approach and the specific goals of the procedure.
Left ventriculography is indicated primarily to assess left ventricular size, shape and performance, as well as to quantify mitral regurgitation and locate ventricular left-to-right intracardiac shunts. A pigtail catheter is advanced from the femoral artery over the appropriate guidewire to the level of the diaphragm. It enters the left ventricle via the aortic valve. (See cover illustration.) The guidewire then is withdrawn and the catheter is aspirated, flushed and advanced to the aortic valve. With proper technique, it can be advanced to a mid-body position in the left ventricle, flee of the ventricle wall to minimize risk of complication. A test injection of a small amount of contrast can be used to screen for potential problems.
When the catheter is in the appropriate location, 30 to 50 mL of contrast material is power injected into the ventricular chamber at a flow rate of about 10 to 20 mL per second. Volume and rate are based on patient size, hemodynamic state and other factors.
Right ventriculography seldom is performed in the cardiac catheterization laboratory, largely because the information it reveals can be obtained or inferred from other data. However, it is considered safer than left ventriculography. Contrast injection into the vena cava, right atrium or right ventricle provides opacification. A pigtail catheter or similar type with multiple sideholes is used to inject 25 to 45 mL of contrast in adult patients, with a typical injection rate of 15 to 25 mL/sec.
Angiographic studies of the aorta are performed to measure the structure's size, detect dissections, quantify aortic regurgitation and search for congenital or acquired vascular lesions. A variety of approaches are used to introduce contrast to the aorta, with the percutaneous femoral artery approach the most widely used method. The most commonly employed catheter is the pigtail with multihole design. For ascending aortography, the catheter usually is placed 1 to 2 cm above the aortic valve to minimize the chance of interference with valve competence. After a test injection of several milliliters to ensure proper position, typical contrast injections for aortography are 30 to 50 mL over a period of about 2 seconds.
This procedure is recommended for a variety of congenital and acquired diseases, including suspected pulmonary embolism and branch pulmonary arterial stenosis.[26,43] The risks of pulmonary angiography are similar to those for right ventriculography, with an additional risk of pulmonary arterial rupture. The most commonly used catheters are pigtail and flow-directed types. Venous access can be achieved through the femoral, brachial or jugular approaches, although femoral is the most common access method.[43,45] Once the catheter is advanced to the main pulmonary artery, it then can be directed into the right or left pulmonary artery. Exact catheter positioning depends on the study indication or location of the suspected pulmonary embolism. A typical contrast injection rate of 20 to 25 mL/sec for a total volume of 40 to 50 mL is recommended, depending on specifics such as the patient's cardiac output.
The radiographic images produced during angiography demonstrate the vascular network to internal structures. Accurate coronary diagnosis requires contrast injections in multiple views. In the 1990s, this became easier with equipment mounted on a rotating U-arm or C-arm. Each study begins with a series of screening projections that are adjusted or supplemented by appropriate special projections to more completely define suspicious areas. Cine filming in either single or biplane projections at 30, 50, 60 or 90 frames/sec is the norm, with 60 frames/sec being the preferred technique.
The choice of projections for an angiographic study is based on the specific anatomy to be examined. For example, the entire left coronary artery is visible in either the anteroposterior (AP) or shallow right anterior oblique (RAO) projection, also known as the right PA oblique projection. To view the ostium and proximal portions, the shallow left anterior oblique (LAO or left PA oblique projection) with minimal cranial angulation is best.[51,55]
Biplane left ventriculography usually is performed in the RAO projection at approximately 30 [degrees] and LAO projection at 45 [degrees] to 60 [degrees]. Single-plane ventriculography usually is performed in the RAO projection, which permits functional assessment and visualization of the anterior wall, apex and inferior wall. When selecting a single projection, the RAO is best when there is a major obstruction in the left anterior descending or right coronary artery, or both. In patients with diffuse 3-vessel disease, the RAO projection is adequate for assessment of surgical risk. The LAO projection with cranial angulation demonstrates the interventricular septum, apex, lateral wall and posterior wall.
In choosing a projection, the goals are to view the ventricle approximately perpendicular to its long axis and minimize overlap with the spine. In both projections, the image intensifier should be positioned so that the entire left ventricle and a sufficient area of the left atrium can be seen.
Assessing the right ventricle requires single-plane ventriculography because of its complex shape. Biplane right ventriculography generally is done in either the posteroanterior (PA) and lateral projections or RAO and LAO projections. Between 15 [degrees] and 20 [degrees] of cranial angulation optimizes visibility of the right ventricle.
Biplane cineangiography most commonly is performed for aortography with a 30 [degrees] RAO projection and 60 [degrees] LAO projection. The LAO projection is optimized with 10 [degrees] to 20 [degrees] of cranial angulation. Large image intensifiers are used for a larger field of view, and field positioning depends on the indication. If the indication is related solely to aortic pathology, the field should be centered on the area of the suspected pathology.
Selective Coronary Angiography
Selective coronary injections may be used to aid in the diagnosis of particular diseases and conditions, such as Kawasaki disease, coronary artery fistulae and pulmonary atresia with intact ventricular septum. Special catheters have been developed to safely perform selective coronary angiography in children. Similar projections are used with a reduction in contrast. A study of selective procedures at a children's hospital examined the safety of these procedures. The most common indication in these cases was surveillance of coronary vasculopathy after heart transplantation. Complication rates were low and the study concluded that selective coronary angiography can be safely performed in patients of any age, including neonates.
A contrast agent is injected selectively into the right or left main coronary ostia. Selective coronary angiography is performed with special catheters and techniques, most commonly Judkins-type catheters. Catheters designed for selective arteriography are generally smaller because peripheral vascular complications are a main concern. Entry usually is made from the femoral approach, though the brachial approach also is used. The procedure usually is performed following a routine technique such as ventriculography. The left Judkins catheter is advanced and multiple injections are made with filming in different views. Thorough knowledge of coronary anatomy and radiographic conventions, as well as the expected configuration of a vessel in various projections, is necessary to perform selective procedures.
Intracardiac and Intravascular Pressures and Recordings
Indices of cardiovascular performance are critical to assessment of a patient's health. Pressure, flow and resistance are primary indicators of cardiovascular function. Pressure is defined as a force per unit area, or how vigorously blood presses against: the wall of the vessel. Flow is a reflection of the blood's energy associated with its movement. Cardiac output is the total amount of blood flowing through the cardiovascular system per unit of time. Resistance is the opposition to the flow of' blood throughout the system. Routine collection of right and left heart hemodynamic data, appropriate blood sampling for oxygen saturation and cardiac output measurements usually can be completed safely in less than 30 minutes.
Pressure Recording Systems
Measuring intracardiac pressures through catheters is an essential part of cardiac catheterization. The end of a fluid-filled catheter is attached to an external pressure transducer to capture pressure measurement information. A pressure wave is created by cardiac muscular contraction and then transmitted along the catheter to the transducer, converting to an electrical signal on a monitor. To graph the complex waveforms produced by pressure changes, a device must measure the physical movement or deformation of a flexible element or membrane in response to pressure changes. This can be likened to the use of a tire gauge to measure air pressure within the tire. Although no current system is perfect at measuring the intricacies of pressure (such as damping or oscillations over time), transducers are used in most catheterization laboratories.
An electrical strain gauge allows the transducer to convert mechanical energy to electrical energy. Inside the transducer is a thin but rigid metal foil called the transducer membrane that moves or bends slightly in response to the pressure wave. The pressure wave then is transmitted through a column of fluid in the catheter to the transducer, which must be balanced and calibrated for accurate measurement. Electronic equipment connects the transducers to the visual displays. The incoming signal is filtered and amplified for final display, usually on a television-type screen.
The shape and magnitude of intracardiac pressure waveforms on the screen provide diagnostic information. For example, a large V wave in the left atrial or pulmonary artery wedge pressure recording indicates mitral regurgitation. Left ventricular and aortic pressures can be measured simultaneously to assess aortic valve function. Comparing pressures in different chambers can indicate particular conditions.
Flow and Cardiac Output Measurement
There are several methods for determining cardiac output. Most are based on the Fick principle, named for the work of Adolphus Fick in 1870. Tire principle states that the rate of oxygen consumption equals the difference in oxygen content between arterial and venous blood multiplied by the total flow of blood through the circulation. The Fick method for measuring cardiac output works by determining the oxygen content in a patient's expired air during a 3-minute period. It is considered the most accurate method of cardiac output measurement. A metabolic hood or large airtight bag is used to compare the room air oxygen level against the patient's expired air to indicate oxygen consumption.
The indicator dilution method also is based on the Fick principle. The most common of these techniques is thermodilution. A pulmonary artery balloon flotation catheter of the Swan-Ganz type has a temperature sensor at the tip and a separate lumen for injecting saline. Ice-cold saline is injected through the catheter as it is positioned in the pulmonary artery, and the dip in blood temperature is measured downstream. This technique is favored because it does not require withdrawal of blood and uses a universally available indicator, iced saline.
The angiographic cardiac output method measures output as the product of stroke volume, or the amount of blood ejected by the heart on each beat, and the heart rate. Using contrast ventriculography, volumes from the end-diastolic and end-systolic frames of the cineangiogram are measured. Stroke volume is the difference between these 2 volumes.
Resistance Measurement Techniques
Resistance is never consistent; it varies with pressure and flow and is influenced by many factors. Usually, vascular resistance calculations are applied to pulmonary and systemic circulation. Measuring valve resistance provides information about valve obstruction because resistance represents opposition to the normal flow. Accurate measurement of resistance depends on cardiac output measurements. To make quantitative estimates of pulmonary and systemic vascular resistance, it is necessary to measure driving pressure across the pulmonary and systemic vascular beds and the respective blood flows through them. Therefore, pulmonary wedge pressure measurements can be combined with cardiac output data to estimate resistance.
The use of cardiac catheterization techniques for therapeutic purposes was first suggested in 1950 when Rubeo-Alvarez and Limon-Lason suggested that a catheter could be used in the treatment of pulmonic stenosis. Since that time, interventional techniques have been developed for a broad range of cardiac applications.[1,4]
For more than 15 years, primary percutaneous transluminal coronary angioplasty (PTCA) has been advocated as a treatment for acute myocardial infarction. Studies show that the procedure reduces rates of death, stroke and recurrent ischemia or infarction when compared with fibrinolytic therapy. The mortality rate from the procedure itself is generally low in low-risk patients. Approximately 30% of the more than 1 million people who undergo diagnostic cardiac catheterization each year are referred for revascularization by balloon dilatation, a figure equal to the number referred for bypass surgery. Time is critical in treating acute MI, and primary angioplasty has proven an effective means of achieving reperfusion and maintaining better mortality rates, particularly when it is performed within 2 hours of the patient's arrival.
Clinical indications for angioplasty include acute MI, mild angina pectoris with evidence of ischemia, unstable angina and asymptomatic patients with ischemia who are at high risk for MI.[64,65] Contraindications for PTCA include certain high-risk coronary anatomy and multiple PTCA restenoses.
Three basic components make up the angioplasty equipment system: catheters, guidewires and dilatation catheters. The catheter allows stable access to the coronary ostium and a route for contrast administration and dilatation equipment. The leading guidewire is passed through the catheter, across the target lesion and well into the distal coronary vasculature. In essence, it provides a rail over which therapeutic devices can be passed. The selected balloon catheter should be designed to inflate to a precisely defined diameter under inflation pressure. Inflating a balloon above its burst pressure can cause balloon rupture and possibly air embolization.
Arterial access for angioplasty is normally from the femoral, brachial or radial sites. The selection of entry site is based on the specific procedure and guiding catheter. Once the guidewire and balloon catheter are in the appropriate location, inflation is performed under fluoroscopy to confirm position. The balloon may be slowly inflated to higher pressures, if needed.
Early restoration of an infarct-related artery is the treatment goal for acute MI. Fibrinolytic drugs are available as treatment, but they fail to restore complete perfusion in about 50% of cases. Primary angioplasty produces better results but is not as widely available, and may cause delays in treatment. Recent studies indicate that angioplasty should be used more widely, with fibrinolytic drugs administered immediately and rescue angioplasty used when drug therapy fails. In one observational study, patients with acute MI underwent angiography 90 minutes after the start of fibrinolytic therapy. Rescue angioplasty was performed when drug therapy failed. Rescue angioplasty provided effective early reperfusion for patients in whom drug therapy had failed.
Following angioplasty, the patient's body begins to repair the mechanical injury caused by the procedure. Within minutes, a layer of platelets and fibrin is deposited on the lesion. Within hours to days, inflammatory cells begin to infiltrate the site, and smooth muscle cells migrate to the lumen. By about 6 months, the repair process should stabilize and lumen diameter return to normal. (See Fig. 7.) In some patients, the healing response is excessive and the gain in lumen diameter is lost. This results in the return of severe stenosis and ischemic symptoms and is known as restenosis. Debate and research continue on the use, cost effectiveness, appropriate case selection and timing of PTCA and general angioplasty procedures.[62,62,66]
[Figure 7 ILLUSTRATION OMITTED]
Stents have become a treatment of choice for revascularization. In fact, stents now are used in 60% to 70% of coronary interventions.[67,68] The coronary artery stent is a coiled apparatus, usually made of metal. It is permanently placed in the patient's plaque-filled coronary artery after plaque reduction with PTCA. Stents generally are balloon expandable.[5,65] Research has shown that coronary stenting is more effective than PTCA alone, both in the short-term, due to immediate luminal gain, and in the long-term, due to less restenosis.
Stent implantation is performed following angioplasty using a technique similar to angioplasty.[65,70] The stent should be placed to cover the entire lesion or dissection without obstructing inflow or outflow. Using either a self-guiding stent or appropriately sized balloon, the stent is expanded to hug the arterial wall with no empty spaces that could allow thrombus formation. Patients generally are premedicated with aspirin or other mild anticoagulants. Inadequate or excessive use of anticoagulants in stent implantation is a major cause of morbidity and mortality.
The use and effectiveness of stents are still under review. However, evidence suggests that they are indicated for treatment of abrupt or threatened vessel closure during angioplasty and for the reduction of restenosis caused by focal lesions in blood vessels larger than 3 mm in diameter.
It is estimated that up to 25% of PTCAs are performed for the treatment of restenosis. Stent implantation may be indicated in these patients. Several studies have addressed the issue of restenosis following PTCA and the usefulness of stents to reduce its occurrence. In one such study, stenting was associated with a lower 6-month incidence of restenosis than revascularization via surgery or repeat angioplasty. The long-term value of stenting is still under review, but early research suggests that for certain indications, the survival rate at 5 years is about 93% and long-term reduction of restenosis risk is promising.
Studies were begun in the early 1980s on the use of balloon valvuloplasty in patients with valvular stenosis, the first being performed on a child with pulmonic valve stenosis. In recent years, the procedure has been expanded to other indications.[5,71] Performed in the cath lab, this procedure consists of inserting a large catheter through the femoral artery and introducing a balloon that inflates to between 18 and 25 mm. Another technique that has proved more effective involves double balloons. Both balloons are inserted through the same septal puncture.
The Inoue antegrade technique was introduced in 1994 and now is the most widely used valvuloplasty technique. The balloon is introduced from the femoral vein trans-septally into the left atrium after dilating the interatrial septum. When inflated it resembles a segmental hourglass, which aids in positioning and inflation in the stenotic valve, reducing risk of ventricular perforation. Baseline hemodynamic measurements are obtained before the catheter crosses the aortic valve and are repeated after balloon inflation and deflation. Arterial pressure is monitored continuously and pulmonary artery oxygen saturation is measured before each inflation. When the gradient and increase in valve area measurements are satisfactory, the balloon catheter and sheaths are removed.
Also called percutaneous balloon aortic valvuloplasty (PBAV), this therapeutic technique is used mostly in pediatric patients with congenital aortic stenosis. For adult aortic stenosis, the restenosis rate was high. However, the procedure may be used as a palliative measure in adults who are not candidates for surgery. Studies have shown that the procedure works best in patients with pliable valves and a minimum of leaflet thickening, immobility, calcification and subvalvular involvement.
In CAD and other cardiac diseases, cardiac catheterization may be a diagnostic/preparatory procedure for surgical intervention or other treatment. For example, a patient with acute coronary ischemic syndrome likely has experienced rupture of plaque within a coronary artery, which leads to additional complications. In this case, the goal of cardiac catheterization is to identify the artery where the rupture occurred, restore vessel patency through PTCA and, if needed, administer intracoronary drugs. The diagnostic exam also may reveal other features, such as multivessel or severe associated valve disease, that are used in the decision to proceed with open-heart surgery.
In addition to coronary artery bypass graft surgery, valvular replacement surgery, emergency repair and other surgical interventions may follow cardiac catheterization, including surgery to repair any damage from the procedure, such as pseudoaneurysms or excessive bleeding. Complications of PTCA may lead to possible emergency bypass grafting or abrupt vessel closure.[5,65]
A major issue addressed by the ACC/AHA guidelines and still under debate is the need for on-site surgical backup during cardiac catheterization. Immediate surgical backup is critical when performing diagnostic catheterization on acutely ill, unstable or high-risk patients. Labs performing angioplasty, endomyocardial biopsy or trans-septal catheterization also should have immediate surgical backup. However, ambulatory cardiac catheterization labs are common. These labs carefully screen patients, considering the indications and possible risk of complications before selecting patients.
Medications Used In Therapeutic Procedures
A variety of medications may be used during and immediately after therapeutic catheterization procedures. Many of the same medications used in diagnostic catheterization, such as local anesthetics, are used in addition to therapeutic-specific medication.
Patients undergoing PTCA face a longer and more complicated procedure than those undergoing diagnostic catheterization. In fact, the length of therapeutic cardiac catheterization procedures varies considerably and patient comfort and anxiety are greatly affected. During the procedures, manipulation of coronary vasculature can cause episodes of ischemia with angina and hypertension. Typical preprocedure sedatives include lorazepam in conjunction with parenteral morphine, a similar preparation to that used for cardiac surgery. An initial dose of an antihistamine enhances sedation and decreases sensitivity to contrast.
Once in the cath lab, these sedatives may be supplemented with incremental doses of intravenous morphine or fentanyl. Sedative use for stent placement should follow a similar guideline.
Nitroglycerin is a powerful vasodilator that can decrease coronary vascular resistance and increase blood flow. With its administration, the luminal areas of normal coronary arteries increase by about 20%. Low-dose nitroglycerin can assist patient comfort. If blood pressure support is needed, additional IV fluid volume may be indicated.
Heparin is used widely in therapeutic and diagnostic cardiac catheterization procedures. It does not increase procedural complications as long as doses are correctly measured and introduced. After successful completion of many cardiac catheterization procedures, the anticoagulant effects of heparin are reversed through administration of protamine sulfate.
For PTCA, preprocedure administration includes aspirin to diminish platelet deposition on the lesion area and calcium channel blockers to prevent vessel spasm at the treatment site. Heparin may be continued following removal of the sheath. After PTGA, patients usually are given a calcium channel blocker for 6 weeks and aspirin indefinitely.
In stent placement, thrombosis remains a potentially critical complication. Prophylaxis against stent thrombosis usually includes a combination of antiplatelet agents such as aspirin, dextran and dipyridamole, as well as administration of heparin. Upon discharge, patients continue taking aspirin, dipyridamole and warfarin (Coumadin).
Embolism and secondary stroke are major concerns in balloon valvuloplasty. Some practitioners medicate patients with anticoagulants for up to 6 months prior to the procedure. After successfid stenting, patients are likely to receive aspirin or a combination of aspirin and Coumadin. A careful balance ensures proper anticoagulation while at the same time preventing vascular complications and major bleeding.
Complications of Cardiac Catheterization
The risks of cardiac catheterization have decreased over the years, but the challenges of managing risk still exist. One reason is that more procedures are being performed on an outpatient basis, and therefore the patient may not be in the hospital when a complication occurs. One method to control complications is careful patient referral and selection.[3,77] Examples of relatively uncommon but possible complications include MI, neurologic deficit and others. (See Table 4.)
Table 4 Risk of Complications Associated With Diagnostic Cardiac Catheterization(3)
Outcome Risk (%) Vascular disorder 0.43 Arrhythmia 0.38 Contrast reaction 0.37 Procedural hypotension 0.26 Death 0.11 Neurologic deficit 0.07 Myocardial infarction 0.05 Perforation 0.03 Other 0.28 Total 1.7
The mortality rate for cardiac catheterization has remained steady at about 0.1% during the past 15 years. Rates for particular complications also have remained relatively constant despite technological advances. These advances are most likely countered by an increase in the number of older patients undergoing catheterization. In 1980 the number of patients older than 60 undergoing catheterization was about 38%. In 1990, it had risen to 58%. Although the risk of complications is a factor in any invasive procedure, the overall risk for cardiac catheterization procedures is relatively low.
Cardiac catheterization can cause stroke or MI in some patients, especially in patients older than 60, those with severe heart failure and those with significant valvular heart disease. Strokes occur in less than 0.1% of patients during or after catheterization, but they are a possibility because of the disruption of atherosclerotic plaques within the aorta. Such strokes are almost always embolic in origin, which emphasizes the importance of avoiding air bubbles, careful catheter flushing and other precautions.
Although MI also is rare, it almost always occurs during the procedure rather than after. Ischemia is fairly common during diagnostic cardiac catheterization and routine during coronary intervention. Usually, the ischemia responds to drug therapy, such as intravenous or intracoronary nitroglycerine, or to deflation of the angioplasty balloon. The risk of MI is precipitated by patient-specific factors such as the extent of CAD, clinical indications such as unstable angina and conditions such as insulin-dependent diabetes. Patient preparation with medications mentioned earlier, proper use of heparin and careful patient monitoring during the procedure can minimize risks.
Vascular problems are the most common complications following cardiac catheterization and frequently present as external bleeding or a groin mass at the site of the femoral artery puncture. Complications at the access site are more likely to occur after the procedure. Large hematomas can form, or the site may begin rebleeding, even to the point of requiring transfusion. Pseudoaneurysm in the femoral artery, arterial occlusion and limb ischemia are other complications at the access site.[72,79]
Continued bleeding may be the result of improper use of anticoagulants, a poorly placed puncture, vessel laceration or poor technique in vessel closure or groin compression. An excellent understanding of vascular access and closure techniques can aid in recognizing and preventing these complications.
Although rare, perforation of the cardiac chambers, coronary arteries or great vessels is a possible complication in both diagnostic and interventional cardiac catheterization. If perforation of a cardiac structure occurs, it is marked by bradycardia and hypotension from vagal stimulation. Blood accumulates in the pericardium, and the normal pulsation of the heart borders may appear blunted on fluoroscopy.
Perforation of the great vessels is extremely rare, and the aorta is elastic enough to resist perforation in most cases. However, aortic puncture can occur during attempted trans-septal puncture. If the coronary artery is dissected during a procedure, it usually is related to trauma from catheter positioning. Careful attention to positioning and pressure tracings are the best ways to avoid coronary dissection. A good baseline pressure tracing recorded before entering the coronary artery provides a means of detecting subtle pressure changes. Dampening may indicate incorrect catheter positioning. Vessels used as a route for advancing the cardiac catheter also are subject to perforation.
Cardiac angiography has some risk of temporary or permanent renal dysfunction. Renal function may be affected by contrast or by a systemic cholesterol embolism. At least 5% of patients experience a significant rise in serum creatinine after the procedure. Patients who have diabetes, pre-existing renal dysfunction, multiple myeloma, volume depletion or are receiving nephrotoxic drugs are at increased risk for renal complications from contrast. The best ways to minimize risk of complications are adequate prehydration and careful attention to total contrast volume.
Cholesterol emboli are an infrequent but potentially severe complication caused by cholesterol crystals obstructing small arteries or arterioles. Renal failure due to cholesterol embolization develops slowly, over a few weeks, and is most likely to occur in patients with diffuse atherosclerosis.
Allergic and anaphylactic reactions to ionic contrast agents are the most common allergic reactions in cardiac catheterization. Reactions also can occur from local anesthetics and protamine sulfate, which is used to reverse heparin effects. Incidence of allergic reactions to anesthetics is low, except with older ester agents. Some reactions are caused by preservatives in anesthetics. Patients with a history of allergic reaction to preservatives may benefit from preservative-free anesthetics.
Reactions to protamine sulfate, which is derived from salmon eggs, can occur, most commonly in insulin-dependent patients with diabetes. If reaction to protamine sulfate is suspected, an option may be to let the effects of heparin wear off, rather than attempting to reverse them.
Ionic contrast agents carry iodine, a substance that provokes an allergic reaction in up to 1% of cardiac catheterization procedures. Release of histamine and other agents in the patient causes sneezing, hives, lip and eyelid swelling and bronchospasm. In extreme cases, shock with warm extremities can occur. Patients with other atopic disorders, or allergy to seafood or penicillin are at a higher risk of contrast allergic reaction. Premedication of patients with seafood allergies or prior reactions to prednisone, an antihistamine and H2 blocker, can reduce reactions substantially.
Cardiac catheterization is a relatively new procedure. Yet during its short history, the techniques first developed by Forssmann have formed the basis for sophisticated and highly effective diagnostic and therapeutic procedures. Even though debate about cardiac catheterization's costs and risks continues, it is an indispensable tool for a wide array of cardiac problems that would otherwise remain unresolved.
Directed Reading Continuing Education Quiz
Principles of Cardiac Catheterization
To receive Category A continuing education credit for this Directed Reading, read the preceding article and circle the correct response to each statement. Choose the answer that is most correct based on the text. Transfer your responses to the answer sheet on Page 142 and then follow the directions for submitting the answer sheet to the American Society of Radiologic Technologists. You also may take Directed Reading quizzes online at www.asrt.org.
* Your answer sheet for this Directed Reading must be received in the ASRT office on or before this date.
1. Werner Forssmann, a German medical student, performed the first human heart catheterization on himself in:
2. -- first pointed out the separate circulation of the left and right sides of the heart.
3. Cardiac muscle differs from skeletal muscle in that cardiac muscle:
1. contracts upon activation by electrical signal.
2. is more complex in structure and function.
3. has a control system that adjusts muscle action.
a. 1 and 2.
b. 1 and 3.
c. 2 and 3.
d. 1, 2 and 3.
4. The valve between the left atrium and left ventricle is called the -- valve.
5. The connective tissue that covers the inner surfaces of the atria and ventricles is called the:
6. A regurgitant heart valve:
a. ensures the unidirectional flow of blood.
b. obstructs the normal forward flow of blood.
c. allows backward flow of blood.
d. both obstructs forward flow and allows backward flow.
7. Which of the following is a serious disorder of the heart muscle?
d. rheumatic fever.
8. According to the text, which of the following statements are true of pulmonary embolism?
1. it is always a painful condition.
2. symptoms include unexplained shortness of breath and lightheadedness.
3. onset of symptoms can be gradual, sudden or intermittent.
a. 1 and 2.
b. 1 and 3.
c. 2 and 3.
d. 1, 2 and 3.
9. Among patients with renal insufficiency, what percentage reportedly experience worsened renal function following angiography?
a. 0 to 5.
b. 5 to 10.
c. 10 to 40.
d. 40 to 80.
10. Which of the following medications often are discontinued prior to cardiac catheterization because of the risk of complications?
a. 1 and 2.
b. 1 and 3.
c. 2 and 3.
d. 1, 2 and 3.
11. Cool extremities in a patient during a cardiac catheterization procedure may indicate:
1. renal failure.
a. 1 and 2.
b. 1 and 3.
c. 2 and 3.
d. 1, 2 and 3.
12. The choice of cineangiography film should be based on:
a. 1 and 2.
b. 1 and 3.
c. 2 and 3.
d. 1, 2 and 3.
13. Patient radiation exposure from a typical cardiac angiography study, including 10 minutes of fluoroscopy and 1 minute of cine film studies, is equivalent to between -- chest films.
a. 10 and 50.
b. 50 and 150.
c. 250 and 650.
d. 650 and 950.
14. According to the text, more than 90% of coronary angiography procedures are performed with which style of catheter?
15. The balloon tip design is a hallmark of which catheter?
16. For a specific procedure, the guidewire should be -- than the catheter.
a. at least 10 cm shorter.
b. at least 20 cm shorter.
c. at least 10 cm longer.
d. at least 20 cm longer.
Directed Reading Continuing Education Quiz
17. The most commonly reported problem in cardiac catheterization is:
a. initial access to the cardiovascular system.
b. guidance of the catheter through the cardiovascular system.
c. contrast reactions.
d. perforation of cardiac structures.
18. The brachial cutdown approach for cardiac catheterization is recommended most often for patients:
1. who are very obese.
2. at risk for thrombophlebitis.
3. with severe peripheral vascular disease.
a. 1 and 2.
b. 1 and 3.
c. 2 and 3.
d. 1, 2 and 3.
19. Disadvantages of the percutaneous femoral approach include:
1. decreased catheter control.
2. necessity for postprocedure bed rest.
3. need for arterial repair.
a. 1 and 2.
b. 1 and 3.
c. 2 and 3.
d. 1,2 and 3.
20. The most common access method for pulmonary angiography is the -- approach.
21. -- describes the blood's energy associated with its bulk movement.
d. Cardiac output.
22. Thermodilution is a favored technique for measuring cardiac output because it:
1. does not require blood withdrawal.
2. uses a universally available indicator.
3. compares room air to expired air.
a. 1 and 2.
b. 1 and 3.
c. 2 and 3.
d. 1, 2 and 3.
23. To estimate resistance, the following measurements are combined:
a. aortic wedge pressure and left ventricular pressure.
b. pulmonary wedge pressure and left ventricular pressure.
c. aortic wedge pressure and cardiac output.
d. pulmonary wedge pressure and cardiac output.
24. What percentage of patients who undergo diagnostic cardiac catheterization are referred for revascularization by balloon dilatation each year?
25. Research has shown that PTCA followed by stenting is more effective than PTCA alone.
26. The most widely used valvuloplasty technique today is the:
a. Swan-Ganz technique.
b. Fick method.
d. Inoue antegrade technique.
27. Percutaneous balloon valvuloplasty works best in patients with:
1. pliable valves.
2. minimal leaflet thickening.
3. minimal calcification.
a. 1 and 2.
b. 1 and 3.
c. 2 and 3.
d. 1, 2 and 3.
28. Drugs commonly given to patients following stent procedures include:
2. warfarin (Coumadin).
a. 1 and 2.
b. 1 and 3.
c. 2 and 3.
d. 1, 2 and 3.
29. The most common complication following cardiac catheterization is:
a. myocardial infarction (MI).
b. vascular disorders.
d. renal complications.
30. Which of the following can reduce risk of renal dysfunction after cardiac catheterization?
1. ensuring adequate prehydration.
2. ensuring accurate vascular access.
3. monitoring total contrast volume.
a. 1 and 2.
b. 1 and 3.
c. 2 and 3.
d. 1, 2 and 3.
[1.] Pepine CJ, Hill JA, Lambert CR. Development and application of cardiac catheterization and interventional procedures: historical background. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:3-10.
[2.] Laine C, Venditti L, Localio R, Wickenheiser L, Morris DL. Combined cardiac catheterization for uncomplicated ischemic heart disease in a Medicare population. Am J Med. 1998;105:373-379.
[3.] Warner JJ, Harrison JK, Sketch MH. Recognizing complications of cardiac catheterization. Emergency Med. 2000;32(7):12-25.
[4.] Grossman W. Historical perspective. In: Baim DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:3-8.
[5.] Ricciuti CG. Cardiac catheterization. In: Van Riper S, Van Riper J. Cardiac Diagnostic Tests: A Guide for Nurses. Philadelphia, Pa: WB Saunders Co; 1997:265-295.
[6.] Barry WH. Cardiac catheterization and angiography. In: Bennett JC, Blum F, eds. Cecil Textbook of Medicine. 20th ed. Philadelphia, Pa: WB Saunders Co; 1996:208-211.
[7.] Opie LH. The Heart: Physiology, From Cell to Circulation. 3rd ed. Philadelphia, Pa: Lippincott-Raven Publishers; 1998:1-15.
[8.] Katz AM. Physiology of the Heart. 2nd ed. New York, NY: Raven Press Ltd; 1992:1-35.
[9.] Kern MJ, ed. The Cardiac Catheterization Handbook. 2nd ed. St. Louis, Mo: Mosby-Year Book Inc; 1995:564-570.
[10.] Jarvis C. Physical Examination and Health Assessment. 3rd ed. Philadelphia, Pa: WB Saunders Co; 2000:498-501.
[11.] Smith TW. Approach to the patient with cardiovascular disease. In: Bennett JC, Blum F, eds. Cecil Textbook of Medicine. 20th ed. Philadelphia, Pa: WB Saunders Co; 1996:166-169.
[12.] Kern MJ, Roth R, Deligonul U. Introduction to the catheterization laboratory. In: Kern MJ, ed. The Cardiac Catheterization Handbook. 2nd ed. St. Louis, Mo: Mosby-Year Book Inc; 1995:1-26.
[13.] Grossman W. Current practice standards. In: Balm DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:9-16.
[14.] Bashore TM, Wang AG. Cardiac catheterization laboratory settings. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:13-30.
[15.] Smith SC. Bridging the treatment gap. Am J Card. 2000;85(12A):3E-7E.
[16.] Gazes PC. Clinical Cardiology: A Cost-Effective Approach. 4th ed. New York, NY: Chapman & Hall; 1997.
[17.] Blitz LR, Kolansky DM, Hirshfeld JW. Indications and contraindications: patient selection for coronary artery interventions. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:543-550.
[18.] Grossman W. Profiles in dilated (congestive) and hypertrophic cardiomyopathy. In: Balm DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:787-800.
[19.] American Heart Association. Cardiomyopathy. Available at: http://www.americanheart.org /Heart_and_Stroke_A_Z_Guide/cmyopa.html. Accessed September 6, 2000.
[20.] Murali S. Pulmonary hypertension, cardiac transplantation, and the cardiomyopathies. In: Uretsky BF, ed. Cardiac Catheterization: Concepts, Techniques and Applications. Malden, Mass: Blackwell Science; 1997:461-495.
[21.] American Heart Association. Congestive heart failure. Available at: http://www.americanheart.org /Heart_and_Stroke_A_Z_Guide/congest.html. Accessed September 6, 2000.
[22.] American Heart Association. Congenital cardiovascular disease. Available at: http://www.americanheart.org/Heart_and_Stroke_A_Z_Guide/conghd .html. Accessed September 6, 2000.
[23.] Beerman L. Congenital heart disease in the adult. In: Uretsky BF, ed. Cardiac Catheterization: Concepts, Techniques and Applications. Malden, Mass: Blackwell Science; 1997:496-523.
[24.] Lock JF, Perry SB, Keane JF. Profiles in congenital heart disease. In: Baim DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:823-842.
[25.] Goldhaber SZ. Profiles in pulmonary embolism. In: Baim DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:773-786.
[26.] Brinker J, Savader SJ. Noncardiac angiography. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:339-398.
[27.] Chodos AP, Jacobs AK. Invasive evaluation of cardiac artery disease. In: Uretsky BF, ed. Cardiac Catheterization: Concepts, Techniques and Applications. Malden, Mass: Blackwell Science; 1997:421-460.
[28.] Carroll JD. Aortic valve and aortic root disease. In: Uretsky BF, ed. Cardiac Catheterization: Concepts, Techniques and Applications. Malden, Mass: Blackwell Science; 1997:348-374.
[29.] Martin TD, Pepine CJ, Hill JA, Lambert CR. The patient with known or suspected disease of the aorta. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:1008-1031.
[30.] Faxon DP. The cardiac catheterization laboratory: set-up and management. In: Uretsky BF, ed. Cardiac Catheterization: Concepts, Techniques and Applications. Malden, Mass: Blackwell Science; 1997:63-93.
[31.] ACC/AHA ad hoc task report. J Am Coll Cardiol. 1991;18:1149-1182.
[32.] Panayiotou H, Lambert CR, Schectmann N, Pepine CJ, Hill JA. Evaluation and preparation of the patient for cardiac catheterization. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:77-90.
[33.] Caracciolo EA, Donohue TJ, Kern MJ, Bach RG, Tommaso C, Deligonul U. High-risk cardiac catheterization. In: Kern MJ, ed. The Cardiac Catheterization Handbook. 2nd ed. St. Louis, Mo: Mosby-Year Book Inc; 1995:444-483.
[34.] Shaw CC. Radiographic principles. In: Uretsky BF, ed. Cardiac Catheterization: Concepts, Techniques and Applications. Malden, Mass: Blackwell Science; 1997:31-62.
[35.] Thompson BT, Hales CA. Diagnostic strategies for acute pulmonary embolism. Available at: http: //www.medscape.com/UpToDate/2000/09.00/utd 0901.12.thom/utd0901.12.thom-01.html.Accessed September 9, 2000.
[36.] Baim DS. Angiography: proper utilization of cineangiographic equipment and contrast agents. In: Baim DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:39-56.
[37.] Miralbell R, Doriot P, Nouet P, Rouzaud M. X-ray dose to the skin in patients undergoing percutaneous transluminal coronary angioplasty. Cathet Cardiovasc Interv. 2000;50:300-306.
[38.] Van de Putte S, Verhaegen F, Taeymans Y, Thierens H. Correlation of patient skin doses in cardiac interventional radiology with dose-area product. Br J Radiol. 2000;73:504-513.
[39.] Hillis LD, Landau C. Cardiac ventriculography. In: Baim DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:219-232.
[40.] Baim DS, Grossman W. Coronary angiography. In: Baim DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:183-218.
[41.] Nash IS, Fifer MA. Pressure, flow and resistance. In: Uretsky BF, ed. Cardiac Catheterization: Concepts, Techniques and Applications. Malden, Mass: Blackwell Science; 1997:2-30.
[42.] MacDonald RC. Catheters, sheaths, guidewires, needles and related equipment. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:129-161.
[43.] Deligonul U, Roth R, Flynn M. Arterial and venous access. In: Kern MJ, ed. The Cardiac Catheterization Handbook. 2nd ed. St. Louis, Mo: Mosby-Year Book Inc; 1995:45-107.
[44.] Konstam MA, Patten RD, Kimmelstiel CD, Halin NJ, Namyslowski JB, Greenfield AJ. Cardiac angiography. In: Uretsky BF, ed. Cardiac Catheterization: Concepts, Techniques and Applications. Malden, Mass: Blackwell Science; 1997:150-195.
[45.] McCullough PA, Goldstein JA. Heart pressures and catheterization. In: Uretsky BF, ed. Cardiac Catheterization: Concepts, Techniques and Applications. Malden, Mass: Blackwell Science; 1997:119-149.
[46.] Baim DS. Percutaneous approach, including transseptal and apical puncture. In: Baim DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:57-82.
[47.] Denys BG, Uretsky BF, Baughman K, Schweiger MJ. Accessing vascular structures. In: Uretsky BF, ed. Cardiac Catheterization: Concepts, Techniques and Applications. Malden, Mass: Blackwell Science; 1997:94-118.
[48.] Hill JA, Lambert CR, Vlietstra RE, Pepine CJ. Review of techniques. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:106-128.
[49.] Grossman W. Brachial cutdown approach. In: Bairn DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:83-96.
[50.] Palacios IF. Transseptal heart catheterization. In: Uretsky BF, ed. Cardiac Catheterization: Concepts, Techniques and Applications. Malden, Mass: Blackwell Science; 1997:261-275.
[51.] Pepine CJ, Lambert CR, Hill JA. Coronary angiography. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:264-306.
[52.] Sheehan FH, Kennedy JW. Ventriculography. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:247-263.
[53.] Paulin S. Aortography. In: Baim DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:255-280.
[54.] Skibo LK, Wexler L. Pulmonary angiography. In: Bairn DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:233-254.
[55.] Deligonul U, Kern MJ, Roth R. In: Kern MJ, ed. The Cardiac Catheterization Handbook. 2nd ed. St. Louis, Mo: Mosby-Year Book Inc; 1995:266-370.
[56.] Keane JF, Lock JE, Perry SB. Diagnostic cardiac catheterization in infants and children. In: Bairn DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:97-108.
[57.] Vranicar M, Hirsch R, Canter CE, Baizer DT. Selective coronary angiography in pediatric patients. Pediatr Cardiol. 2000;21:285-288.
[58.] Schweiger MJ. Coronary arteriography. In: Uretsky BF, ed. Cardiac Catheterization: Concepts, Techniques and Applications. Malden, Mass: Blackwell Science; 1997:196-260.
[59.] Kern MJ, Deligonul U, Donohue TJ, Caracciolo E, Feldman T. Hemodynamic data. In: The Cardiac Catheterization Handbook. 2nd ed. St. Louis, Mo: Mosby-Year Book Inc; 1995:108-207.
[60.] Grossman W. Clinical measurement of vascular resistance and assessment of vasodilator drugs. In: Baim DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:125-142.
[61.] Wharton TP, McNamara NS, Fedele FA, Jacobs MJ, Gladstone AR, Funk FJ. Primary angioplasty for the treatment of acute myocardial infarction: experience at two community hospitals without cardiac surgery. J Am Coll Cardiol. 1999;33:1257-1263.
[62.] Baim DS. Percutaneous transluminal coronary angioplasty. In: Baim DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:537-580.
[63.] Cannon CP, Gibson CM, Lambrew CT, et al. Relationship of symptom-onset-to-balloon time and door-to-balloon time with mortality in patients undergoing angioplasty for acute myocardial infarction. JAMA. 2000;283:2941-2947.
[64.] Vetrovec GW. Introduction to coronary angioplasty. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:551-563.
[65.] Deligonul U, Kern MJ, Bach RG, et al. Interventional techniques. In: Kern MJ, ed. The Cardiac Catheterization Handbook. 2nd ed. St. Louis, Mo: Mosby-Year Book Inc; 1995:564-570.
[66.] Mukherjee R, Ellis SG. "Rescue" angioplasty after failed thrombosis. Cleveland Clinic Journal of Medicine. 2000;67:341-352.
[67.] Briguori C, Nishida T, Adamian M, et al. Coronary stenting versus balloon angioplasty in small coronary artery with complex lesions. Cathet Cardiovasc Interv. 2000;50:390-397.
[68.] Levin T, Cutlip D, Baim DS. Use of coronary stents for the prevention of restenosis. Available at: http: //www.medscape.com/UptoDate/2000/09.00/. Accessed September 19, 2000.
[69.] Dangas G, Ambrose JA, Rehmann D, et al. Balloon optimization versus stent study (BOSS): provisional stenting and early recoil after balloon angioplasty. Am J Cardiol. 2000;85:957-961.
[70.] Kutryk MJ, Serruys PW. Introduction to coronary artery stenting. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:654-709.
[71.] Herrmann HC. Balloon valvuloplasty: indications, techniques, and results. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:764-786.
[72.] Kerensky RA. Complications of cardiac catheterization and strategies to reduce risks. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:91-105.
[73.] Kixmiller JM, Schick L. Conscious sedation in cardiovascular procedures. Crit Care Nurs Clin North Am. 1997;9:301-311.
[74.] Lange RA, Hillis LD. Assessment of cardiovascular function. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:480-515.
[75.] Carrozza JP, Baim DS. Coronary stenting. In: Baim DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:617-640.
[76.] Berman AD, McKay RG, Grossman W. Balloon valvuloplasty. In: Pepine CJ, Hill JA, Lambert CR, eds. Diagnostic and Therapeutic Cardiac Catheterization. 3rd ed. Baltimore, Md: Williams & Wilkins; 1998:659-688.
[77.] Walder LA, Schaller FA. Diagnostic cardiac catheterization. When is it appropriate? Postgrad Med. 1995;97(3):37-45.
[78.] Baim DS, Grossman W. Complications of cardiac catheterization. In: Baim DS, Grossman W, eds. Cardiac Catheterization, Angiography and Intervention. 5th ed. Baltimore, Md: Williams & Wilkins; 1996:617-640.
[79.] Parson C. Evidence-based clinical outcome management in interventional cardiology. Crit Care Nurs Clin North Am. 1999;11:143-157.
Teresa Norris, B.A., is a member of the American Medical Writers Association and a nationally published author in clinical and business health care topics. Ms. Norris has more than 14 years' experience in health care communications. She has won writing awards from national and regional organizations, including the Radiology Business Management Association. Ms. Norris works in northeastern New Mexico as a freelance writer/designer for print and online publications.
|Printer friendly Cite/link Email Feedback|
|Author:||NORRIS, TERESA G.|
|Date:||Nov 1, 2000|
|Previous Article:||Seated Mammography For Older Patients.|
|Next Article:||Extracorporeal Shock Wave Lithotripsy.|