Implantable cardiac defibrillator use significantly lowers heart failure mortality
NEW ORLEANS -- The use of an implantable cardiac defibrillator (ICD) can provide a significant reduction in mortality in heart failure patients, according to a study coordinated by researchers from the Duke Clinical Research Institute.
"Treatment using conventional therapy plus an implantable cardiac defibrillator showed a statistically significant reduction in total mortality when compared to standard treatment with a placebo and standard treatment with amiodarone, an anti-arrhythmia drug," said Kerry L. Lee, Ph.D., an associate professor of biostatistics at Duke and principal investigator of the data coordinating center of the trial.
Results of the trial, called SCD-HeFT (Sudden Cardiac Death in Heart Failure Trial), were presented today (March 8, 2004) at the American College of Cardiology scientific sessions. The trial was sponsored by the National Heart, Lung and Blood Institute (NHLBI). Medtronic, Inc., Minneapolis, supplied the ICDs and Wyeth Pharmaceuticals, Madison, N.J., supplied the amiodarone and placebo pills. Lee has no financial interests in either company.
Currently, more than 5 million Americans suffer from congestive heart failure (CHF), with more than 400,000 new cases diagnosed annually. CHF is a condition of decreased or impaired function of the heart muscle resulting in an inability to pump sufficient blood through the body. Patients with CHF also have a higher risk of abnormal heart rhythm, known as arrhythmia, which often leads to sudden cardiac death. About half of all CHF patients who die do so from sudden cardiac death.
"With the population growing older, chronic heart failure will become a much more significant problem in the United States," Lee noted.
Traditionally, CHF is treated with ACE inhibitors, beta blockers, diuretics, statins and aspirin to improve the heart's efficiency. This study's goal was to determine whether adding a cardiac defibrillator or anti-arrhythmia medication to standard therapies could reduce the risk of sudden cardiac death. An ICD is a small device implanted beneath the skin which corrects abnormal heart rhythms when they occur by providing a controlled electrical impulse to the heart.
In the study, 2,521 patients were enrolled in 148 centers, including Duke, in the United States, Canada and New Zealand. All participants had been diagnosed with moderate to severe CHF, otherwise known as Class II and Class III, according to the New York Heart Association classification system for heart failure. Seventy-seven percent of participants were men, with minorities making up 23 percent of the total. Study participants ranged in age from 19 to 90, with the median age being 60.
Most participants were receiving multiple drugs to treat their CHF. 85 percent were receiving ACE inhibitors; 70 percent digoxin; 69 percent beta blockers; 56 percent aspirin; 38 percent statins; 34 percent warfarin; and 14 percent angiotensin II receptor blocker (ARB).
Participants were randomly entered into three study arms in equal proportions: conventional therapy plus a placebo; conventional therapy plus amiodarone; and conventional therapy plus ICD. The drug arms of the trial were double-blinded so that neither the patient nor the medical providers knew who were receiving placebo or amiodarone. Patients were enrolled from September 1997 through July 2001 and were followed until October 2003.
"What we found was that patients with the ICD had a three-year mortality rate of 17.1 percent compared to 22.3 percent for those receiving placebo and 24 percent for those receiving amiodarone," Lee said. "After five years, the mortality for the ICD patients was 28.9 percent while the amiodarone patients had a 34.1 percent mortality rate and the placebo patients 35.8 percent.
"It is a significant achievement any time you can find a reduction in mortality of that amount," Lee continued.
When the study ended, 666 participants had died: 182 (22 percent) in the ICD group, 240 (28 percent) in the amiodarone group and 244 (29 percent) in the placebo group.
Lee noted that Class II CHF patients achieved the most significant reduction in mortality from the ICD therapy as compared to the Class III patients.
"It seemed that the more severe the case of heart failure, the more likely the patient died from causes other than arrhythmias which aren't helped by an ICD," Lee explained.
Lee also noted that the ICD reduced deaths equally for patients whose CHF resulted from heart attack, or ischemia, (52 percent of patients in the trial)and for those patients whose heart failure was due to non-ischemic causes, such as hypertension or a virus.
Duke served as the data-coordinating center for the trial. The study director was Gust H. Bardy, M.D., of the Seattle Institute for Cardiac Research, which served as the clinical coordinating center. Other study leaders were Daniel B. Mark, M.D., from Duke; and Robin Boineau, M.D., and Michael Domanski, M.D., of the NHLBI.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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