BioEd Online

Medical implants that can restart a failing heart are causing problems for thousands of patients because of malfunctions, researchers say. This is prompting calls for manufacturers to be clearer about how often their devices go wrong.

It isn't surprising that these life-saving devices sometimes cause problems for their hosts, given that they can be quite complicated pieces of machinery. But, says William Maisel, a cardiologist at Beth Israel Deaconess Medical Center, Boston, Massachusetts, "despite literally millions of devices having been implanted worldwide, there was very little information about their reliability." Some have worried about the safety of the devices, which have become an increasingly popular solution to heart troubles (see ' Hotwire my heart').

So Maisel and colleagues trawled records at the US Food and Drug Administration (FDA) spanning the years 1990-2002 to find out exactly how many of these devices have malfunctioned. Their analysis looked at pacemakers, which provide small electrical pulses to help maintain the heart's regular rhythm, and implantable cardioverter defibrillators (ICDs), which deliver a bigger wallop to restart a stopped heart.

They found that during this time, 2.25 million pacemakers and 415,780 ICDs were implanted in patients living in the United States. Of these, 8,834 pacemakers (0.4%) and 8,489 ICDs (2%) were surgically removed due to malfunctions, which were mostly spotted during routine checkups. The survey also picked up 61 deaths caused by device malfunction¹.

Lower limits

Maisel, who also chairs the FDA's Circulatory System Medical Devices Advisory Panel, adds that the real numbers of problems could be slightly higher than this.

Malfunctions are currently logged by manufacturers before being passed on to the FDA. But this process depends on doctors returning broken devices that are still covered by the manufacturer's warranty, most of which only last for five years. In addition, if a malfunction actually caused a death it may not always be picked up during post mortem, or the device might not make it back to the manufacturer. So some problems are probably going unrecorded.

The information the FDA does have is also incomplete, Maisel adds. For example, the FDA data do not record how long each device had been fitted before it malfunctioned. "As a physician, I'd like to be able to look at different products and choose which is best for my patient," he says.

His survey shows, for example, that the launch of new, smaller ICDs in the late 1990s was followed by a four-fold rise in malfunction rates from 1998 to 2001. These devices were designed to be more comfortable for patients, with improved software to control the heart's complicated electric rhythms. But it seems that the added complexity meant there was more to go wrong, says Maisel.

Maisel would like to see manufacturers take more responsibility for knowing the fate of every ICD put into a patient. If they do not take on that task voluntarily, he says, it may be necessary for the FDA to one day force the issue.

Mirrored trends

Despite problems with the FDA records, Maisel is fairly confident that the numbers are approximately right. He compared the results with a more detailed but smaller set of data from three medical projects in Denmark, the United Kingdom and the United States. This revealed similar malfunction rates, along with the same spike in problems in the late 1990s (which died back down in 2002)². Both studies appear in this week's issue of the Journal of the American Medical Association.

In an accompanying editorial in the journal³, Bruce Wilkoff, a cardiologist at the Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Ohio, admits that in the past, the lack of good information may have hindered doctors and patients discussing all the risks associated with ICDs.

"We weren't as clear as we could have been about the ups and downs of the therapy," he says, and agrees with Maisel that manufacturers must now improve the way they report malfunctions.

However, Wilkoff stresses that patients should not be afraid of having these devices fitted, as they are ultimately life-savers. "The chance that one of these devices will save your life is about a thousand times greater than the chance that it will malfunction when you need it," agrees Maisel.

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