An implantable cardiac defibrillator (ICD) significantly reduces deaths in heart failure patients, according to a new study supported by the National Heart, Lung, and Blood Institute (NHLBI), one of the National Institutes of Health. The study also found that treatment with the antiarrhythmic drug amiodarone does not reduce deaths in these patients.

Preliminary results from the study -- called "Sudden Cardiac Death in Heart Failure" (SCD-HeFT) -- are being presented today at the American College of Cardiology Annual Scientific Session 2004 in New Orleans, LA.

"These findings should have a big impact on the treatment of heart failure patients," said NHLBI Acting Director Dr. Barbara Alving. "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 and President of the Seattle Institute for Cardiac Research in WA. "The results give physicians vital information for better managing the care of their heart failure patients."

Heart failure affects about 5 million Americans. It develops over time as the heart loses its ability to pump blood through the body. It can be caused by various conditions, including heart attack. Symptoms include feeling tired, having trouble breathing, and swelling (edema), usually in the legs and ankles.

It is estimated that about 50 per cent of deaths in heart failure are sudden deaths and are probably due to a ventricular tachyarrhythmia, or rapid heartbeats in one of the lower chambers. In sudden death, the heart stops abruptly.

SCD-HeFT tested whether an ICD that provides a shock without pacing impulses or an antiarrhythmic drug would help prevent sudden death in heart failure patients. An ICD is put under the skin of the chest and sends an electric signal to correct a potentially fatal arrhythmia. An antiarrhythmic drug works by preventing the occurrence of an irregular heartbeat.

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

Patient enrollment began in September 1997 and patient follow-up ended in October 2003. Participants were enrolled through 148 hospitals, clinics, and academic centers in the United States, Canada, and New Zealand. The study's Clinical Coordinating Center is at the Seattle Institute for Cardiac Research; the Data Coordinating Center is at the Duke Clinical Research Institute at Duke University in Durham, NC. The study biostatistician is Dr. Kerry Lee, Director of Biostatistics at Duke Clinical Research Institute.

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

Study participants ranged in age from 19 to 90; the median age was 60. Seventy-seven per cent were men and 23 per cent women. Seventy-seven per cent were white, 17 per cent African American, and about 6 per cent other minorities.

Fifty-two per cent had heart failure caused by heart attack (myocardial infarction) and 48 per cent had heart failure due to a different cause, such as a viral infection of the heart. Thirty per cent had diabetes and 15 per cent had had at least one episode of diagnosed atrial fibrillation when they entered the study.

At the end of the study, there were 666 deaths overall -- 182 (22 per cent) in the ICD group, 240 (28 per cent) in the amiodarone group, and 244 (29 per cent) in the placebo group.

Results showed that: -- In those with heart failure, implantable defibrillator therapy significantly reduced deaths, but amiodarone therapy did not. -- The benefit from implantable defibrillator therapy appeared to be strongest in those with moderate heart failure at enrollment. Amiodarone therapy appeared to have a detrimental effect in those with severe heart failure at enrollment. -- Implantable defibrillator therapy reduced deaths for patients whether their heart failure resulted from heart attack or a different cause.