Helping the beat go on! (Free Course).

COURSE OBJECTIVES

After completing this course the dental professional should be able to:

* Identify the route of blood through the heart

* List the muscle parts of the heart

* Explain how the electrical system of the heart functions

* List the advantages of the Automatic External Defibrillator (AED)

OUTLINE

I. Introduction

II. The Heart

A. Blood Flow

B. Electrical System

C. Ventricular Fibrillation 

D. Ventricular Tachycardia 

III. Fatalities

IV. Automatic External Defibrillator

A. Procedure

V. Summary

VI. Bibliography

VII. Post-test

INTRODUCTION

The Automatic External Defibrillator (AED)--you've heard the name--you may have already seen one in a continuing education class. But what does it really do and why??

Simply put, it is a machine that can recognize the rhythm of your heart. It knows if the heart's electrical system is in an abnormal rhythm called ventricular fibrillation (v fib) or pulseless ventricular tachycardia (v tach). If needed, it will tell you to press a button that will send an electrical shock into the heart. This shock will stop the heart momentarily allowing the electrical system of the heart to restart in a viable rhythm.

Now--you've just read that paragraph and you are thinking to yourself "I thought she said it was simply put". First of all--what is ventricular fibrillation and why is it so bad? Let's take a step back first to understand why and how the heart works.

THE HEART

Blood Flow

The muscle of the heart is called the myocardium. It has its own network of blood supply delivered by the coronary arteries. A normal heart works in a synchronized rhythm between the top parts of the heart (the right and left atrium) and the bottom parts of the heart (the right and left ventricles). The atriums and ventricles make up the "muscle" part of the heart. The heart is divided into the right and left sides by a thin septum. The right heart is comprised of the right atrium that receives the oxygen poor blood that has circulated throughout the body and is returning to the heart via the venae cavae. There it is pumped through a one-way valve called the tricuspid valve into the right ventricle. The right ventricle then pumps this still oxygen poor blood through the pulmonic valve into the pulmonary artery (the only artery in the body which carries deoxygenated blood in the body), which allows the blood to enter the lungs where it picks up oxygen. The now oxygen rich blood travels into the pulmonary vein (this is the only vein in the body to carry oxygenated blood) and then goes into the left atrium. The right atrium pumps the blood through the mitral valve into the left ventricle. The blood continues on through yet another valve called the aortic valve into the aorta. The blood is now about to start its journey to the rest of the body.

Electrical System

All of this could not happen without the electrical system of the heart. This system is unique because it does not rely on nerves to send out an impulse to the specialized conduction tissue that has the ability to transmit electric impulses with great speed to the muscular tissue of the heart. In a normally working heart this impulse is generated by the sinoatrial node (SA node) which is located in the right atrium. When the heart beat is generated from the SA node the heart beats between 60-100 times per minute. Once these specialized conduction tissues of the SA node send out the impulse, it only takes 0.08 seconds for the impulse to travel through the atria making them contract and then the impulse goes to the next major electrical point of the heart called the atrioventricular node (AV node). The AV node then sends the impulses to the Bundle of His. The electrical impulses split here into the right and left bundles that travel through each side of the ventricles and wind up in the Purkinje Fibers which cause the ventricle to contract. When the SA node is not working properly the AV node will take over sending impulses to the heart muscles but it is not as quick as the SA node and the rate of the heart beat will be slowed to about 40-60 beats per minute.

All of the muscular activity of the heart works just because its electrical system tells it what to do! This is different than any other muscle in your body. Think about it. Your heart just works! All this work is from a muscle that is around the size of your fist and weighs approximately one pound. Your heart is responsible for pumping about five quarts of blood per minute throughout the body--that equals about 1800 gallons per day!!!

Ventricular Fibrillation

When the electrical part of the heart goes out of whack it causes the ventricles to just quiver (like shaking a bowl of Jell-O) going into a v fib rhythm that does not allow them to squeeze the blood though the body and the person can experience sudden cardiac death.

Ventricular Tachycardia

Pulseless v tach is where the heart is beating so fast that the relaxation phase of the heart is not long enough for the blood to refill the chambers of the heart. (As when you breathe in and out so fast that your lungs do not have time to fill with any air.) The heart can actually beat 180 beats per minute or higher! Imagine that is three contractions a second!!! There is no way the heart can sustain life in this type of rhythm and it very quickly converts to v fib.

FATALITIES

Approximately 350,000 people die from sudden cardiac death each year according to the National Institute of Health, Health Technology Advisory Committee in 1999. Of those only approximately 30% suffered a heart attack. Most people who suffer from sudden cardiac death do so because of an irregular fatal heart rhythm and do not have heart muscle damage since they did not have a heart attack. The most effective treatment for v fib is the AED. However, the probability of reviving someone in v fib decreases by approximately 7%-10% for every minute defibrillation is delayed. If untreated, within minutes the electrical activity of the heart will come to a total stop. This is called asystole (without rhythm) and the person has virtually no chance of resuscitation.

AUTOMATIC EXTERNAL DEFIBRILLATOR (AED)

So how does an AED work? It is important, if an AED is to be used, that the victim's chest not be covered with water or wet clothing. The water can conduct electricity between the electrode pads and result in decreased energy delivery to the heart. The victim should be moved out of the water and the chest should be dried.

Procedure

Once you come upon an unconscious patient, you should still follow the normal steps of assessment: ABC--(airway, breathing, circulation). If you determine the patient is unresponsive, has no normal breathing, and no signs of circulation (pulseless), begin CPR immediately. Have someone bring the AED, place it next to the victim's left ear and power it on. All the machines that would be used by non-emergency personnel have voice prompts. It will tell you exactly what to do.

You will place two pads on the patient, one on the upper right side of the patient's chest between the right nipple and right collarbone and one on the left side of the chest a few inches below the armpit. If the patient is wearing a medication patch or a nicotine patch it is imperative that it be removed and the area wiped free of any residue. By placing sensor pads on the patient's chest, the machine (which is a computerized device) can analyze what electrical impulses are going on in the heart. It is set to work only if it finds the heart is in ventricular fibrillation or in ventricular tachycardia with a rate of over 180 beats per minute.

The machine will tell you to stop CPR, call CLEAR, and make sure no one is touching the victim while the AED analyzes the rhythm of the heart. If it finds that the heart will require a shock it will inform you to stand away, call CLEAR, and after checking to be sure no one is touching the victim, press the shock button to shock the heart. The AED sends an electrical impulse into the heart causing the electrical activity to pause. By doing this it allows the electrical activity to be interrupted from the dangerous rhythm it is in. When the electrical activity resumes, it has a chance to go back into a normal rhythm. Often it takes more than one shock for the rhythm to convert. After the shock is delivered the AED will once again analyze the heart's electrical activity. The machine will provide up to three shocks before it tells you to resume CPR for one minute if the patient's rhythm has not converted. After three shocks, you must apply CPR for one minute before the AED will allow you to shock the heart again.

SUMMARY

As with any life-threatening situation there are no guarantees. You should still call 911 even if the use of an AED is available. EMS personnel are trained to provide oxygen and intravenous drugs and any advanced airway support that may be needed. They also have a direct line to a hospital to receive instructions when needed. Even with all this wonderful technology sometimes the patient will remain in cardiac arrest. But for those who have a chance of being saved, the AED is the most dramatic advancement in life saving tools in your hands today.

Glossary

Artery--vessel that carries the blood from the heart to body

Atria--two (2) upper chambers of the heart that receives blood from the body

Bundle of His--bundle of fibers of the impulse-conducting system of the heart

Purkinje fibers--fibers of the impulse-conducting system of the heart

V fib--abbreviation for ventricular fibrillation; ventricles quiver instead of contract

V tach--abbreviation for pulseless ventricular tachycardia; heart beating so fast it cannot go into the relaxation phase

Ventricle--two (2) lower chambers of the heart when filled with blood contracts to force blood into the arteries

Please note: There is an administrative fee of $8 to cover a portion of grading and publication costs. This fee MUST accompany the test when it is submitted for grading. Use answer sheet opposite. APPROVED FOR ONE CONTINUING EDUCATION CREDIT--ADAA Members Only

TEST QUESTIONS: Helping The Beat Go On

1. The letters AED stand for:

A. Auxiliary External Device

B. Airway Electrical Device

C. Automated Emergency Defibrillator 

D. Automated Emergency Device

2. The muscle of the heart is the:

A. Epicardium 

B. Myocardium

C. Endocardium 

D. Pericardium 

3. When the electrical part of the heart goes out of whack and causes the ventricles to quiver this condition is known as:

A.Ventricular Tachycardia

B. Ventricular Fibrillation

C. Ventricular Standstill

D. None of the above

4. In which of the following situations would you use the AED?

A. Unresponsive, shallow, rapid breathing and signs of circulation

B. Unresponsive, no normal breathing, and no signs of circulation

C. Responsive, rapid breathing, complaining of severe, crushing chest pain

D. Responsive, normal breathing, history of a heart attack or stroke

5. You have powered on the AED and attached the electrodes. What should you do next?

A. Call "CLEAR!", check to be sure no one is touching the victim, allow the AED to analyze the rhythm

B. Give 2 breaths and 15 chest compressions

C. Press the SHOCK button

D. Recheck for signs of circulation

6. Someone has collapsed at your office. One coworker has telephoned 911; another is performing CPR; you bring the AED. What should you do next?

A. Wait for the coworker to complete 2 minutes of CPR

B. Check the AED carrying case to make sure there is an extra battery

C. Tell the two coworkers to switch to 2-person CPR

D. Power on the AED and follow the voice prompts

7. You have powered on the AED, attached the electrodes to the victim, and delivered three shocks. What do you do next?

A. Remove the electrode pads

B Give 4 slow rescue breaths

C. Rapidly press the AED SHOCK button 3 times in a row

D. Resume CPR for one minute

8. If a victim is wearing a medication or nicotine patch stuck on the chest, right where you need to place the electrode pad, what should you do?

A. Place the AED electrode over the patch

B. Do not apply AED electrode; this patient can not be shocked

C. Place the AED electrode at least 4" away from patch

D. Remove the patch, wipe the skin clean, apply AED electrode where needed

9. One AED electrode should be placed on the right side of the chest, between the right nipple and right collarbone. Where should the other electrode be placed?

A. Over the center of the breastbone 

B. On top of the left nipple

C. On the left side of the chest, between the left nipple and left collarbone

D. On the left side of the chest a few inches below the armpit

10. If you have an AED, why should you still telephone 911?

A. Police responders will help secure the scene

B. EMS professionals are trained to provide oxygen and intravenous drugs and advanced airway support that may be needed

C. EMS responders can arrive within seconds, so you won't have to worry about performing CPR

D. EMS personnel are the only providers trained to give CPR or use an AED

Bibliography

Brady, Prehospital Emergency Care

Walraven, Harding, LeBlanc, Murphy, Nerney, Advanced Prehospital Care

American Heart Association, BLS for Health Providers

"Automatic External Defibrillators" National Institute of Health

Sarah L. Gresko, CDA, RDA, EMT is dental assistant/office administrator in the practice of Dr. Ignatius J. Kazella, North Hazeldon, NJ. She is also adjunct faculty for the CDA review program at Bergen Community College (NJ) and a lecturer in bloodborne pathogens, medical emergencies and health histories for PSG Associates of which she is vice president. She is presently certified in CPR and CPR Instruction as well as holding certification as an emergency medical technician, AHA CPR defibrillator instructor and holds a NJ DEP radiology license. She is District Trustee for the Second District of ADAA.