Defibrillators may improve survival in non-ischemic cardiomyopathy

Main Category: Public Health
Article Date: 12 Nov 2003 - 0:00 PDT

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Contact: Elizabeth Crown
e-crown@northwestern.edu
312-503-8928
Northwestern University

Research from Northwestern University suggests that implantable cardioverter defibrillators (ICDs) can improve the survival rate of people who have a weakened heart muscle caused by factors unrelated to coronary artery disease - a condition known as non-ischemic cardiomyopathy.

Previous studies showed that people whose heart muscle had been weakened as a result of coronary artery disease (ischemic cardiomyopathy) could benefit from ICDs. This research is among the first to indicate that the approximately 200,000 other Americans who suffer from this condition may also benefit.

An ICD is a small device implanted under the skin near the collarbone and connected to the heart with insulated wires called leads. ICDs deliver shocks and other electrical therapies to the ventricles to stop ventricular tachyarrhythmias (abnormally fast heart rhythms originating in the heart's lower chambers).

Initial results from the DEFINITE (Defibrillators in Non-Ischemic Cardiomyopathy Treatment Evaluation) ICD were presented today at the American Heart Association's Scientific Sessions 2003 conference in Orlando, Florida by principal investigator Alan Kadish, M.D., Chester D. and Deborah M. Cooley Professor of Medicine from Feinberg School of Medicine at Northwestern University in Chicago.

The DEFINITE study, initiated in May 1998, followed 458 participants at 48 medical centers in the United States and Israel. Participants were randomized into two groups -- one receiving standard heart failure drug therapy (control group) and the other receiving drug therapy plus an implant of a St. Jude Medical ICD. The goal was to evaluate whether the ICDs offered an overall survival benefit to those who received them.

During the study, overall mortality at two years was 13.8 percent in the standard therapy (control) group versus 8.1 percentin the ICD group. Though these results did not reach the level of statistical significance defined in the study protocol, they do show a strong trend toward reduction of overall mortality.

The research did show a statistically significant reduction in the rate of arrhythmic death. Of the 56 total deaths, 11 people in the control group, while only three people in the ICD group, died from cardiac arrest.

'The DEFINITE study showed that ICDs can reduce the risk of sudden cardiac death in non-ischemic cardiomyopathy patients and tend to reduce all-cause mortality,' Kadish said. 'This finding was especially dramatic in Class III heart failure subjects, consistent with previous studies on preventive use of ICDs in this category of patients.'

In cardiomyopathy, a patient's heart is typically enlarged and gradually weakens over time, leaving the patient at risk for life-threatening ventricular tachyarrhythmias (abnormally fast heart rhythms originating in the heart's lower chambers).

These tachyarrhythmias include ventricular tachycardia (VT) and ventricular fibrillation (VF) -- common contributors to sudden cardiac arrest and the number one cause of cardiac death in the United States. Sudden cardiac arrest accounts for approximately 300,000 deaths annually.

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