Studies Gauge Safety of Replacing Implanted Defibrillators

The dilemma: Balancing surgical risks against those of device failure

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By Amanda Gardner
HealthDay Reporter

THURSDAY, May 18, 2006 (HealthDay News) -- Physicians need to carefully weigh the dangers of replacing an implantable cardioverter defibrillator -- a device that delivers a shock to restart a malfunctioning heart -- against the potential risk that the current implanted device will fail.

That's the conclusion of two new studies presented Thursday at the Heart Rhythm Society annual meeting, in Boston.

"The basic issue, as is always the case, is benefit vs. risk," said Dr. Robert Myerburg, a professor of medicine and physiology at the University of Miami Miller School of Medicine. "You have to consider the risk of replacement and how likely an individual patient would need the therapy if the device fails. It's a complicated issue," he said.

Myerburg was not involved with the studies, although he did author a recent editorial in the New England Journal of Medicine addressing the issue of product recalls and advisories.

Reliability is an important issue for the hundreds of thousands of Americans walking around with implantable cardiac devices (ICDs) such as a defibrillator.

And there has been an explosion in the use of the devices. Not only are they now used in survivors of sudden cardiac arrest but also in people who may be at risk.

Along with this increased use has been an increase in the number of device-related "advisories," alerting the medical community and the public to potential problems.

These two studies were conducted to try to get a handle on actual risks and benefits. "These studies are beginning to get some data for us, because we've never had these kind of data in the past," Myerburg said.

The first study, conducted by researchers at the Mayo Clinic, looked at the complication rates from 732 ICD replacements which took place from January 2000 through November 4, 2005. Of the total replacements, 570 were expected and elective (for instance, the battery ran out) and 162 were in response to recalls or advisories.

The Mayo team found a total of nine complications leading to additional procedures and complete removal of the system.

"It was a 1.24 percent complication rate, so now that at least gives me something to put in perspective," said Dr. David L. Hayes, chairman of cardiology at the Mayo Clinic in Rochester, Minn. "If the device failure was predicted at lower than that, then it was easier to say to the patient, 'I think there is a greater risk to replacing than not.'"

"You also have to take into account individual patient issues," Hayes continued. "Are they dependent on the device or not? But this helped me figure the risk and benefit. It gave me something a little bit more objective."

The second study looked at the complication rate for ICD replacements at 17 medical centers across Canada between October 2004 and October 2005. A total of 533 ICD replacements were performed, with 43 patients (8.1 percent) experiencing complications.

The complications were minor in 12 cases and major (involving re-operation) in 31 patients, including 10 who had to have the device removed. Two people died.

According to the authors, this rate was higher than anticipated.

"I don't think the studies are powered enough in terms of numbers, but they're giving us directions at least and they certainly will call for additional studies," Myerburg said.

Ultimately, he said, these decisions have to be individualized, but the new numbers can help.

"There are no really good numbers to guide us until recently, and these are the first attempts to get at some numbers of risk vs. benefit," Myerburg stated. "It ends up being a case-by-case thing, but before you can make those case-by-case decisions, you need to have some data."

In separate data released at the same meeting, researchers from Beth Israel Deaconess Medical Center reported that more than one in five external defibrillators have been recalled for potential malfunction in the past 10 years. External defibrillators are often placed in public places to revive heart attack victims in emergencies.

More information

To view new recommendations on ICDs, visit the Heart Rhythm Society.

SOURCES: David L. Hayes, M.D., chairman, cardiology, Mayo Clinic, Rochester, Minn.; Robert J. Myerburg, M.D., professor, medicine and physiology, University of Miami School of Medicine, Miami; May 18, 2006, presentations, Heart Rhythm Society annual meeting, Boston

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