Implanted Heart Device Prevents Death

Medically Reviewed by Gary D. Vogin, MD
From the WebMD Archives

Dec. 5, 2001 -- For those who have survived a heart attack, death can come quickly and without warning a few years later. It's called sudden cardiac death. Yet too few people realize they are at risk, doctors say.

Victims of cardiac arrest lose consciousness in seconds, and death is inevitable unless they receive an electric shock to restore the heart's rhythm within minutes of the event, says Eric Prystowsky, MD, president of the North American Society of Pacing and Electrophysiology.

Now, a landmark study finds that these deaths are highly preventable with the aid of a small device -- called an implantable cardiac defibrillator or ICD -- that in effect jump-starts a damaged heart.

After just a few years of testing, an independent review panel has decided the device's effectiveness no longer needed to be proven. The panel has called for an end to the Multi-Center Automatic Defibrillator Implantation Trial (MADIT II).

The study's preliminary results are "exciting, significant -- they showed a 30% decrease in mortality in those with the defibrillator," Prystowsky tells WebMD. He has been a lead investigator of studies involving earlier versions of the device, and is also director of electrophysiology laboratory at St. Vincent Hospital in Indianapolis.

The device could potentially save thousands of lives, he tells WebMD. "There are many, many people who need to be evaluated, to see if they should have this device."

Vice president (and heart attack survivor) Dick Cheney has an ICD in his chest because his cardiologists determined his risk of sudden cardiac death was high. The rest of America's heart attack survivors -- estimated at 7 million -- should also be talking to their doctors about getting evaluated for one, Prystowsky says.

Sudden cardiac death is a leading cause of death in the U.S., killing more people than lung cancer, breast cancer, and AIDS combined, according to statistics.

Here's how the device works: When a heart attack occurs, it damages the left ventricle, the heart's main pumping chamber. The ICD, like a pacemaker, is implanted under the skin and monitors the heart's rhythm. When a dangerous rhythm is detected, it delivers a controlled electric shock to restore the heart's normal rhythm.

Over the last few years, several studies have shown the benefits of ICDs for patients who have had heart attacks.

In those studies, patients' survival rate improved dramatically with the ICD device -- "by as much as 50%," says Prystowsky.

The current study enrolled more than 1,200 people -- all with previous history of heart attack -- who randomly received either the ICD or drug therapy for abnormal heart rhythm. The study was conducted in 71 centers in the U.S. and Europe.

In analyzing the study's early results, reviewers found that the ICD group was "doing significantly better than the other group," Prystowsky tells WebMD. The reviewers' decision means further study of the device is unnecessary.

"These studies have all shown the enormous benefits of the ICD," he says.

However, doctors estimate that fewer than 20% of people who could benefit from ICDs actually receive them.

Without an ICD device, only 1 in 20 people who experience ventricular fibrillation -- an abnormal heart rhythm -- will receive emergency care in time to save their lives, says Prystowsky.

"Ejection fraction" -- that's the key term people need to know, he says. "If you've had a heart attack, find out what your "ejection fraction" number is. This is the measure that cardiologists' use to judge how well your heart is pumping. Ask a heart attack survivor what his cholesterol is, he'll know. Very often he doesn't know anything about ejection fraction."

A normal ejection fraction is at least 50%; anything less is trouble, he tells WebMD. Think of your heart as a pump. "If it squeezes out half, that's 50% of the blood going into the system. If the heart is ineffective as a pump because of damage from a heart attack -- and that damage is severe enough to cause significant reduction -- that person is at risk for sudden death."

That person needs to talk to a cardiologist about getting an ICD, he says.

"Ask your father what his ejection fraction is," Prystowsky says. "If it's 40% or under, he needs to know he's at potential risk for sudden death and should see his doctor. Ask about it."