Studies Raise Concerns Over Heart-Device Reliability Two new studies in the Journal of the American Medical Association show that devices called "implantable cardiac defibrillators" have a much higher failure rate than previously believed.
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Studies Raise Concerns Over Heart-Device Reliability

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Studies Raise Concerns Over Heart-Device Reliability

Studies Raise Concerns Over Heart-Device Reliability

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From NPR News, this is ALL THINGS CONSIDERED. I'm Melissa Block.


And I'm Robert Siegel.

Two studies in this week's Journal of the American Medical Association raise concerns about the reliability of implantable cardiac defibrillators, devices like the one that Vice President Cheney has. While these devices have saved countless lives from sudden heart attacks, researchers say they also have to be more closely monitored for possible malfunctions.

NPR's Patricia Neighmond reports.


The two studies examine the reliability of both pacemakers and implanted cardiac defibrillators. Dr. William Maisel is a cardiologist who specializes in heart rhythms.

Dr. WILLIAM MAISEL (Beth Israel Deaconess Medical Center): Both devices are about the size of a small pager. They're implanted under the skin in the chest, and are attached to wires that go into the heart.

NEIGHMOND: Both devices monitor heart rhythm and automatically intervene if there's a problem. The pacemaker looks for slow rhythms and sends electronic impulses to make the heart beat faster, if need be. In the study, pacemaker malfunction decreased over the past decade rather dramatically. But that wasn't the case for defibrillators, which are more complex. These devices look for dangerously fast heart rhythms and intervene in one of two ways. Maisel.

Dr. MAISEL: If the patient has a very fast, potentially lethal heart rhythm problem, then the device will deliver a shock to the heart muscle much like you would see on RESCUE 911 where the paramedics come and deliver an external shock. This device does it internally. It does it automatically in a matter of seconds.

NEIGHMOND: Which works 75 percent of the time, says Maisel, mostly without patients even noticing. But sometimes the devices don't work. In one study, Maisel and colleagues from Beth Israel Deaconess Medical Center and Harvard Medical School analyzed manufacturers' malfunction reports between 1990 and 2002. They looked at nearly one-half a million implanted defibrillators. They found about 8,400 problems. That's one out of every 50 implanted.

Dr. MAISEL: The most common causes of device malfunction were what we call hardware malfunctions, such as batteries, capacitors, electrical short circuits.

NEIGHMOND: Mostly nonfatal flaws but, over the course of 12 years, there were 31 deaths that resulted from the device not working. Maisel says manufacturers need to make information about potential problems more clearly and publicly available, especially for the doctors who need to know.

Dr. MAISEL: In fact, I did ask physicians about expected device reliability a couple of years ago, and the results of that suggested that physicians overestimated device reliability by about a factor, somewhere between 10 and 100, meaning that they felt the devices were 10 times more reliable than they really were.

NEIGHMOND: In another study, Canadian researchers found that taking out a faulty device carries a substantial risk. These complications include infection, pain and in rare cases death. In an editorial, heart rhythm specialist Bruce Wilkoff of the Cleveland Clinic says no medical treatment comes without risk.

Dr. BRUCE WILKOFF (Cleveland Clinic): We have a disease process, sudden cardiac death, which is the number one killer in the United States today. And we have a therapy, matter of fact, the only therapy that makes a difference in this regard, a very effective therapy, implantable defibrillators, that work extremely well. On the other hand, they don't come with zero risk.

NEIGHMOND: Wilkoff says it would be a shame if heart patients were scared of receiving these life-saving devices. As study author William Maisel points out, his study should be viewed in context. The chances of an implanted defibrillator saving a life are 1,000 times greater than the chance of its malfunctioning when needed.

Patricia Neighmond, NPR News.

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