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When Implanted Heart Devices Fail

The Odds -- and Consequences -- of Pacemaker, ICD Breakdowns
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WebMD Health News

April 25, 2006 -- Implanted electronic heart devices can fail. When they do, bad things can happen -- even to patients whose pacemakers and ICDs are still ticking, new studies show.

Implanted pacemakers straighten out a wobbly heart rhythm. Implanted cardioverter-defibrillators (ICDs) jump-start a helplessly fluttering heart. These state-of-the-art electronic devices save lives. But they're complex machines that can -- and do -- break down.

What's the risk of this happening? And when manufacturers announce recalls of problem ICD models, what's the risk of having your implant replaced?

The new studies now open a window on this crucial information. They appear in the April 26 issue of the Journal of the American Medical Association, along with an editorial by Bruce L. Wilkoff, MD, director of cardiac pacing and tachyarrhythmia devices for The Cleveland Clinic.

"These devices have improved in reliability, but people are just now becoming aware of the fact they are not perfect," Wilkoff tells WebMD. "This is a small problem that solves a very big problem. Cardiac deaths are the most common reason people die in the U.S. today. We have an incredibly successful treatment, but there are costs both in money and in morbidity."

The Risk of Pacemaker, ICD Failure

William H. Maisel, MD, MPH, director of the pacemaker and device service at Boston's Beth Israel Deaconess Hospital in Boston, analyzed device malfunctions reported to the U.S. FDA. He also analyzed pacemaker and ICD implant patients followed in three different studies in the U.S., the U.K., and Denmark.

"We wondered whether the increasing complexity of these devices has been associated with decreased reliability," Maisel tells WebMD.

Maisel and colleagues looked at reports of pacemaker and ICD malfunctions reported to the FDA between 1990 and 2002. During this time, there were 2.2 million pacemakers in use, and more than 415,000 ICDs. There were 17,000 reports of devices that had to be replaced. Hardware problems caused most of the breakdowns.

Reassuringly, the annual rate of pacemaker replacement due to malfunction went down, suggesting these devices became more reliable," Maisel says. "ICD malfunction declined during the first part of study, from 1994-1998, then increased from 1998-2002. This suggests that ICDs became less reliable as they became more complicated."

The usual problem with FDA data is that the FDA adverse-event reporting system is voluntary. Might missing reports have skewed the data?

"Combined, the studies included patients implanted with several hundred thousand pacemakers and thousands of ICDs," Maisel says. "The results were amazingly consistent with the FDA reports. They also showed that the pacemaker malfunction rate has declined significantly. The ICD malfunction rate also declined notably from the 1980s to the mid-1990s, but again we saw an increase in the ICD malfunction rate from 1990 to 1992. The rate of malfunction for ICDs increased more than fourfold from 1998-2001."

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