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The beat goes on. (Neighborhood Heart Watch).

Heart failure affects three to five million people in the United States, the vast majority over age 65. Up to 50 percent of individuals with advanced heart failure develop abnormalities of the heart's electrical impulses which control the heart's contractions, so cardiac function is severely compromised. When the heart fails and becomes weaker, it doesn't squeeze and pump blood normally. And the way the heart muscle squeezes down may become unsynchronized, which can worsen symptoms -- including shortness of breath, fatigue, and swelling of the feet and ankles.

Fortunately, an innovative new therapy employing advanced pacemaker technology, called cardiac resynchronization therapy (CRT), helps relieve the symptoms of heart failure and improve quality of life. That's good news for the estimated one million people in the United States with the diagnosis of severe heart failure, who could potentially benefit from this therapy.

In CRT, researchers use an implanted device to deliver tiny electrical impulses that stimulate the right and left lower chambers of the heart to beat in a synchronized fashion to help supply more oxygen-rich blood to meet the body's needs.

To learn more about the benefits of CRT, Medical Update interviewed one of the principal researchers in the Multicenter InSync Randomized Clinical Evaluation (MIRACLE) trial, Dr. James B. Young from the Cleveland Clinic Foundation.

"CRT improves heart function in several ways," says Dr. Young, who presented data from the trial at the American College of Cardiology's recent annual scientific meeting. "First, it increases the efficiency of contraction, so it resynchronizes the ventricle. Second, it improves the way the blood flows into the heart by resynchronizing the contraction and relaxation patterns of the heart. Blood flows into the heart more efficiently, so it improves something called diastolic dysfunction. It also decreases mitral regurgitation on balance when we look at all the biventricular patient studies, so it decreases the inefficiencies that are created by leaking valves. Finally, there are likely other mechanisms that we can't quite clarify that relate to energy transmission, the heart's metabolism, and response to the stress of heart failure."

In CRT, a device is implanted without major surgery to help coordinate the cardiac muscle function in patients with heart failure.

"The InSync ICD device, in fact, is two devices in one," adds Dr. Young, head of cardiac transplant medicine at the Cleveland Clinic Foundation. "It is a cardioverting device and a biventricular pacing system. Patients who are at risk for sudden cardiac death, who would benefit from an ICD (implantable cardioverter defibrillator), and who have significant congestive heart failure with dysynchrony (chaotic contractile patterns), were studied in the InSync ICD trial. We found that these patients were significantly improved with respect to symptoms and quality of life. They were able to exercise more on maximal stress tests. The heart was contracting more efficiently. Finally, having a biventricular resynchronization pacing system in place did not adversely affect the ICD, and the ICD could, in fact, detect potentially malignant arrhythmias. ICDs fired just fine. It confirmed the hypothesis that this combined therapy in appropriate patients was safe and effective."

Ongoing clinical trials are scheduled to further determine the benefits of CRT for patients with severe heart failure.
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Title Annotation:cardiac resynchronization therapy
Publication:Medical Update
Article Type:Brief Article
Geographic Code:1USA
Date:Mar 1, 2002
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