Newer Wires in ICDs May Have More Failures

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• 2007-05-01 08:05:56
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Implanted Defibrillators: Wire Trouble
Study Shows Newer Wires in ICDs May Have Higher Failure Rates Than Older Models
By Salynn Boyles, WebMD Medical News

They were supposed to be more reliable, but the wires now used in devices implanted to protect the heart actually appear to be less reliable than earlier versions.

In a newly reported German study, the annual defect rate was as high as 20% after 10 years of use for wire leads used in implantable cardioverter defibrillators (ICDs).

When researchers compared the failure rate of newer silicone wire leads to older polyurethane-coated leads, the older wires lasted longer. Roughly 93% of the polyurethane-insulated leads survived five years vs. 80% of the silicone leads.

In a statement, researcher Thomas Kleemann, MD, characterizes the findings as "somewhat surprising."

"It seems that the silicone-coated wires have problems even earlier [than the polyurethane-coated wires]," he says.

No Wire-Related Deaths
Roughly 68,000 ICDs were implanted in the U.S. in 2004, the last year for which figures are available, according to the American Heart Association. Vice President Dick Cheney, who has a long history of heart disease, has had one since 2001.

The devices are designed to continuously monitor heart rhythms and shock the heart back into its normal rhythm when an arrhythmia occurs or the heart stops beating altogether.

The wire leads that connect the defibrillator to the heart are threaded through the blood vessels.

Silicone-insulated leads replaced polyurethane ones in 1997. The hope was that the newer leads would have fewer problems, the researchers wrote.

To find out if this is the case, Kleemann and colleagues examined the annual lead defect rate among 990 patients who received the implantable devices at a heart clinic in Ludwigshafen, Germany, between 1992 and May 2005.

A total of 148 (15%) experienced a lead defect during follow-up, and the average time to failure was 4.7 years. A lead defect was a severe lead failure that would need surgery to fix the problem.

Lead defects were found to occur in both newer and older ICD models, and they occurred more often in younger patients, female patients, and those with better pumping function of the heart.

That is because these were the patients who tended to live long enough to experience the lead defects.

A total of 207 patients died during the follow-up, but the researchers did not determine that any of the deaths were caused by lead defects. The majority of deaths (55%) were due to congestive heart failure.

Close Monitoring Critical
Patients with old or newer ICDs should not be overly concerned by the new findings, but they should remain vigilant about having the devices monitored frequently, cardiologist and ICD expert Kenneth Ellenbogen, MD, tells WebMD.

Implantable defibrillators should be checked by a doctor every three to six months, he says. Studies suggest that most problems can be detected during these routine visits to the doctor. In this study, the researchers report that 65% of the lead defects were found during routine evaluation of the devices.

Ellenbogen is the director of electrophysiology and pacing and vice chairman of cardiology at Virginia Commonwealth University Health Systems. He is also a spokesman for the American Heart Association.

He says ICDs have been getting better and more reliable over time. Leads have gotten smaller and patients are increasingly getting multiple leads.

"Patients should have the attitude that when they get an implantable device -- an ICD or pacemaker -- it is like buying a brand new car," he says. "It should run well, but that doesn’t mean you are never going to have to have it fixed."