Studies Find Implantable Defibrillators Erratic
Implantable defibrillators, which can detect abnormal heart rhythms and deliver a life-saving shock, have an erratic history of reliability, according to three studies being published today in the Journal of the American Medical Association.
The studies reveal an upsurge in the malfunction rate of implantable defibrillators in recent years after experiencing several years of relatively high reliability rates. The malfunction rate declined from 39 per 1,000 implantations in 1993 to 8 per 1,000 in 1996 but then increased to 36 in 2002.
William H. Maisel, a cardiologist at Beth Israel Deaconess Medical Center in Boston, headed two of the three studies. The FDA asked Maisel to delve further into the problems associated with implantable defibrillators after one of his studies indicated a rise in the device’s malfunction rate.
For patients who currently have an implantable defibrillator implanted in their chest, doctors warn against hasty decisions regarding defibrillator replacement surgery since replacing the device may be more risky than leaving it as is.
In the third study, a cardiologist at the University of Western Ontario, Andrew D. Krahn, examined the rate of complications in patients who had been issued advisories regarding their defibrillators’ chance of failure.
Of the 3,000 patients who received the notice, 18 percent opted for a replacement of their implantable defibrillator. Six percent of those patients suffered complications with their implantable defibrillator and two died. Only three malfunctions occurred in the group of patients who decided against a replacement and none of those resulted in serious injury or death.
Implantable defibrillators are perhaps the most popular medical devices of the past decade. Over the past six years, the number of defibrillators implanted in Americans has more than tripled and sales are increasing 15 to 18 percent annually.
Some doctors attribute the rise in malfunction rate to technological advances being made to the device. “I believe the decrease in reliability was most likely due to an increase in device complexity,” said Maisel.
“There is always a balance of speed [in getting the product to market] versus safety,” he continued. “Most patients and physicians would say they want the newest technology as soon as possible. But people need to realize that sometimes comes at the price of reliability.”
Last year, Guidant Corporation of Indianapolis, one of the five manufacturers of implantable defibrillators, recalled three models after they discovered that deteriorating insulation contributed to two deaths in 42,000 devices.