The number of implanted heart defibrillators that fail is increasing as they become more sophisticated, a trend that government officials said yesterday is worrisome but difficult to stop.
At a meeting with physicians and heart-device makers, the Food and Drug Administration released a study that found 4,225 defibrillators had failed between 2000 and 2003, about as many as those that failed in the previous 10 years. Overall, the failure rate of the devices was significantly higher in the second half of the period studied than in the first half.
In the FDA study released yesterday, researchers reported that malfunctioning defibrillators and pacemakers were directly responsible for 61 deaths between 1990 and 2002.
The FDA said on its Web site that the higher percentage of failures may be a result of design changes that made the devices smaller -- they are now the size of a stopwatch -- while their computer memory was increased and their power maintained.
William H. Maisel, the Harvard Medical School physician who conducted the FDA study, said the increase is significant and contrasts with a consistent decline in the rate at which pacemakers have to be removed.
Both devices use electric jolts to keep hearts beating properly, but the defibrillators are more sophisticated and have more uses.
Scott Gottlieb, the FDA's deputy commissioner for policy, said the study's results and other agency data are disturbing, although the devices remain lifesavers for several million people.
"When we looked across the annual reports we receive about these products, we have found some increasing trends for certain kinds of problems with some devices," he said at the meeting. "This happened even as these devices got smaller, more sophisticated and more robust in their lifesaving benefits."
According to the Heart Rhythm Society, the professional organization that organized yesterday's meeting, as many as 175,000 Americans are likely to get defibrillators implanted this year. Their usage has expanded even as serious questions have been raised about the dependability of some models.
One of the biggest defibrillator makers, Guidant Corp., recalled 109,000 implantable devices in June after finding they could develop an internal short circuit without warning, resulting in a failure to deliver a shock when needed.
In the recall notice, the FDA advised patients to discuss with their doctors the advisability of replacing their defibrillators. But, yesterday, a number of physicians said they do not have all the information they need to make those decisions.
"We've gotten no real guidance from industry, the FDA or the academic community about when" to take the devices out, said Eric N. Prystowsky, director of the Clinical Electrophysiology Laboratory at St. Vincent Hospital in Indianapolis. "We're told to use our judgment, but there's huge confusion."
Sen. Charles E. Grassley (R-Iowa) said in a news release last week that the FDA has not handled the defibrillator safety issue well. "Senior FDA officials acknowledged to my staff that [the Center for Devices and Radiological Health] needed to do a better job," he said. "When a regulatory agency official says 'There's a lot of stuff going on under the table,' how can Americans rest easy?"
But yesterday, the device center's director of compliance said that the agency is working on new approaches to monitoring device safety, but that its funding is limited.
"We will do what we can with the resources we have, focusing on the high-risk areas," Timothy A. Ulatowski said.