Implantable cardioverter-defibrillators have a significantly higher malfunction rate than pacemakers, but both types of devices should have their performance monitored, according to an article in the April 26 issue of the Journal of the American Medical Association.

According to background information in the article, surprisingly little is known about the reliability and malfunction rate of pacemakers and implantable cardioverter-defibrillators. Because pacemakers and implantable cardioverter-defibrillators represent “life-sustaining” therapies for many patients, the U.S. Food and Drug Administration requires manufacturers to submit annual reports detailing the number of device implants and malfunctions that have occurred.

William H. Maisel, MD, MPH., of Harvard Medical School, and his American colleagues analyzed manufacturers’ pacemaker and implantable device annual reports for the years 1990-2002 to determine the reported number, rate, and reasons for device malfunctions and to assess trends in performance.

The researchers found that from 1990 to 2002, 2.25 million pacemakers and 415,780 implantable cardioverter-defibrillators were implanted in the United States. During this period, 17,323 devices (8,834 pacemakers and 8,489 defibrillators) were explanted due to confirmed malfunction.

The average annual total device malfunction replacement rate was 6.8 per 1,000 device implants. The annual average implantable cardioverter-defibrillator malfunction replacement rate was significantly higher than the pacemaker malfunction replacement rate (20.7 vs. 4.6 replacements per 1,000 implants). Battery/capacitor abnormalities and electrical issues accounted for half of the total device failures. Sixty-one deaths (30 pacemaker patients, 31 implantable cardioverter-defibrillator patients) were attributable to device malfunction.

The annual pacemaker malfunction replacement rate decreased significantly during the study, while the implantable device malfunction replacement rate, after decreasing from 1993 to 1996, increased markedly during the latter half of the study. More than half of the reported cardioverter-defibrillator malfunctions occurred in the last three years of the study.

The researchers write that because implantable cardioverter-defibrillators are substantially more sophisticated than pacemakers, it is not surprising that they have a higher device malfunction replacement rate.

“Routine device checks at regular intervals remain the best way for physicians to monitor ongoing device performance in individual patients. Technological advances that allow for remote wireless monitoring or monitoring via the Internet may become increasingly important. Despite this newly recognized increase in implantable cardioverter-defibrillators malfunction replacement rate, implantable cardioverter-defibrillators effectively reduce mortality in specific high-risk populations. These devices have prevented innumerable sudden deaths, and they remain an important therapy for patients at high risk for sudden cardiac death,” the authors wrote.