Implanted cardiac defibrillators significantly reduce mortality in heart failure patients, but amiodarone therapy does not reduce mortality in these patients, according to a presentation at the annual meeting of the American College of Cardiology. The preliminary results come from the Sudden Cardiac Death in Heart Failure study (SCD-HeFT), which has followed over 2,500 participants for an average of almost 4 years.

"These findings should have a big impact on the treatment of heart failure patients," said Dr. Barbara Alving of the National Institutes of Health. "Until now, it was not known if implanted defibrillators would help such a wide range of heart failure patients, including those whose heart failure may not have been caused by a heart attack. The study had a relatively high percentage of women and minorities, and was larger and lasted longer than earlier trials of sudden death in heart failure patients."

"When these findings are put into practice, they will prolong the lives of many heart failure patients," said Dr. Gust Bardy, SCD-HeFT study director. "The results give physicians vital information for better managing the care of their heart failure patients."

Scientists estimate that about 50 percent of deaths in heart failure cases are sudden deaths that are probably due to a ventricular tachyarrhythmia. In the current study, investigators tested whether an implanted cardiac defibrillator that provides a shock but not pacing impulses or the antiarrhythmic agent amiodarone would help prevent sudden death in heart failure patients.

The study involved 2,521participants, who were randomly assigned to one of three treatment arms -- 847 in a placebo group, 845 in the amiodarone group, and 829 in the defibrillator group. The mean follow-up was almost 4 years.

Patient enrollment began in September 1997 and follow-up ended in October 2003. Participants were enrolled through 148 hospitals, clinics, and academic centers in the United States, Canada, and New Zealand.

All participants had moderate to severe heart failure - New York Heart Association classes II and III. Class II patients typically have trouble breathing or feel tired after exercise such as climbing stairs; class III patients have such symptoms while performing minimal activities such as walking on level ground.

Study participants ranged in age from 19 to 90 years (median, 60 years). A wide majority of patients were male (male, 77 percent; female, 23 percent) and white (white, 77 percent; African-American, 17 percent; other American minorities, 6 percent).

Slightly over half the participants (52 percent) had heart failure due to prior myocardial infarction, whereas 48 percent had heart failure due to a different cause such as viral cardiomyopathy. Of the total, roughly 30 percent had diabetes and 15 percent had had at least one episode of diagnosed atrial fibrillation when they entered the study.

At the time preliminary results were compiled, there were a total of 666 deaths: 182 (22 percent) in the defibrillator group, 240 (28 percent) in the amiodarone group, and 244 (29 percent) in the placebo group.

Analysis demonstrated three major findings. First, implantable defibrillator therapy significantly reduced deaths, but amiodarone therapy did not do so. The benefit from implantable defibrillator therapy appeared to be strongest in people with moderate baseline heart failure. Amiodarone therapy appeared to have a detrimental effect in people with severe baseline heart failure. Finally, implantable defibrillator therapy reduced deaths for patients regardless of cause of heart failure.