Involving more than 100 medical institutions in the United States and Canada and more than 2,500 patients with mild to moderate congestive heart failure, the study aimed to clarify how best to prevent sudden cardiac arrest in such patients -- who typically are left breathing heavily after even modest activity because their hearts are functioning at low efficiency. Cardiac arrest is especially common in such patients, often after a bout of rhythm abnormality.
It differs from a heart attack, in which the heart stops beating because of an interruption of the flow of blood to the heart.
The new study compared three therapies.
One group received standard care for congestive heart failure, including ACE inhibitor medicines and, in many cases, beta blockers and statins.
A second group got standard care plus daily doses of amiodarone (brand name Cordarone), proved to correct potentially deadly rhythm abnormalities -- or arrhythmias -- after they occur. Although the drug is widely prescribed to people with congestive heart failure, it has never been tested to see whether it can prevent, as opposed to treat, the flutters that so often kill those patients.
Patients in the third group had ICDs surgically implanted near their left shoulder. The device, about the size of a credit card but thicker, can send 750-volt shocks to a heart that has descended into an arrhythmic state known as ventricular defibrillation, the extremely rapid but useless kind of beat that is the hallmark of sudden cardiac death. The devices are already approved by the FDA for use in people who have survived such an event. But their lifesaving value in people merely at increased risk had never been proved before the study published today.
The devices were made and provided by Medtronic Inc., a major manufacturer of implantable cardiac devices, which had no role in the analysis or publication of results.
Surprisingly, after about four years of treatment, amiodarone offered no survival benefit and may have even precipitated some deaths.
"We believed putting patients on this drug was a good thing. This study proved that to be incorrect," said Richard Luceri, director of the arrhythmia center at Holy Cross Hospital in Fort Lauderdale, Fla., who implanted many of the study's ICDs.
But while 29 percent of the patients receiving standard therapy died during the study, only 22 percent of those with ICDs died. That seven-percentage-point difference amounts to a 23 percent reduction in the number of deaths. That suggests that tens of thousands of lives could be saved each year with wider use of ICDs.
The saved lives came with a cost: Because the vast majority of ICDs never needed to fire, many people underwent modest but real risks for no benefit. Infections and other significant problems appeared in 14 percent of patients who got the devices.
"The problem is, you don't know who is the one who's going to drop dead and who's not," said study leader Gust H. Bardy, director of the Seattle Institute for Cardiac Research.
The Medicare follow-up could help answer that question. The new study suggested, for example, but could not prove, that the one-third of study participants who were most severely ill were not helped by their ICDs.
At the same time, data trends in the study suggest that many of those whose ICDs never went off are likely to be saved by the devices in years to come. Although the study itself has formally ended, such hints could be confirmed or debunked with ongoing Medicare-required data collection.