- The Washington Times - Tuesday, April 25, 2006

Newer and more sophisticated implantable cardioverter-defibrillators have a substantially higher malfunction rate than pacemakers for patients with abnormal heart rhythms, according to two studies.

Although stressing that both devices “remain an important therapy for patients at high risk for cardiac death,” researchers at the Beth Israel Deaconess Medical Center and Harvard Medical School in Boston, who conducted the studies, concluded that both instruments need closer monitoring, especially ICDs.

Pacemakers are implantable devices that have been around for 40 years to help keep the heart beating correctly.

Hundreds of thousands of U.S. cardiac patients — including Vice President Dick Cheney — have ICDs. These instruments, approved by the U.S. Food and Drug Administration in 1985, are designed to shock a heart beating erratically back into a normal rhythm.

The two studies, published in this week’s issue of Journal of the American Medical Association, were led by Dr. William H. Maisel, director of pacemaker and device services at Beth Israel Deaconess and assistant professor of medicine at Harvard.

“There has been no prior comprehensive report comparing the reliability” of the pacemaker and the ICD, Dr. Maisel said yesterday.

In the first study, Dr. Maisel and colleagues scoured annual FDA reports to track malfunction rates for 2.25 million pacemakers and 415,780 ICDs that were implanted in the U.S. from 1990 to 2002.

Overall, more than 8,800 pacemakers and nearly 8,500 ICDs had to be removed from patients because of confirmed malfunction.

“But you have to realize a lot more patients have pacemakers than ICDs,” Dr. Maisel said.

The replacement rate for ICDs was nearly 21 per 1,000 implants, compared with a rate of less than five per 1,000 for pacemakers. More than half of the reported ICD malfunctions occurred in the last three years of the study.

The primary complications with both instruments involved battery/capacitor difficulties and electrical issues.

A second study by the same researchers analyzed data from three registries from the United Kingdom, Denmark and North America that include information on ICD and pacemaker implants from 1988 to 2004.

That data show a fourfold increase in the ICD-malfunction replacement rate from 1998 to 2002, before a sharp drop from 2002 to 2004. Pacemaker reliability “improved markedly” during the 1980s, and the malfunction rate remained low throughout the study, according to the report.

Overall, the average annual malfunction rate for ICDs was 26 percent, compared with 1 percent for pacemakers, said Dr. Maisel, noting that the findings challenge the notion that more expensive and complicated equipment is more dependable.

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