Replacing recalled implantable cardioverter defibrillators led to an 8 percent rate of complications in Canadian patients -- more than four times higher than the previously estimated rate, according to a study done last fall at University of Western Ontario.

Meanwhile, the overall malfunction rate of defibrillators has decreased to 1 percent from 3 percent in the past few years, according to a separate analysis of malfunction data by William Maisel, a researcher at Harvard University.

Balancing Risks

While Maisel's reliability study might boost confidence in the Twin Cities-dominated cardiac rhythm management industry, the replacement complications study could give doctors another reason to hesitate in recommending the implants.

The $10 billion-a-year industry was battered by recalls in 2005, and saw its 20 percent annual sales growth slip to barely half that late last year and early this year. The big three in the industry are Fridley-based Medtronic Inc., Boston Scientific Corp., which bought No. 2 Guidant Corp. and its Arden Hills operations last week, and Little Canada-based St. Jude Medical Inc.

And while it appears riskier to remove recalled devices from patients, it seems to be less risky to leave them in, according to the two studies. What's more, an earlier study by Cleveland Clinic concluded that patients with recalled devices do not have higher death rates than those whose devices were not recalled.

"These studies should help doctors and patients better balance the risks of malfunction with the risks of replacement," said Thomas Gunderson, a securities analyst with Piper Jaffray Cos.

Doctors May Have Overreacted

Of the 2,915 Canadian patients who had recalled devices, nearly one in five -- 533 patients -- underwent replacement. Nearly 6 percent of the patients whose devices were replaced suffered major complications, the study found. Two died.

"Not nearly as many replacements would have been done in the last year if this information had been available," said Dr. Andrew Krahn of the London Health Sciences Center in Ontario, co-author of the replacement complications study.

Krahn hopes his study will have an impact on new guidelines about when, how and what to report about potential device failures.

Even before the study, critics such as Dr. Bruce Wilkoff, a cardiologist and professor at Case Western University in Cleveland, contended that doctors overreacted to the recent recall notices from the U.S. Food and Drug Administration. For instance, in the recall involving the low risk of sudden battery failure in 87,000 Medtronic defibrillators, more than 19,000 devices were replaced. At least one patient -- a California man -- died from post-surgical complications after his device was replaced.

Given that replacing a defibrillator is a relatively minor procedure -- it's typically done in an hour using a local anesthetic on the patient, who often returns home the same day -- the rate of major complications will surprise doctors, Krahn said. He believes the higher-than-anticipated rate could be because such patients are older and sicker than the general population.

Another reason the complication rate is higher for replacements is that scar tissue often forms over the device, thus making the area more susceptible to infection when the device is replaced. Infection can sometimes result in the device's wire lead attached to the heart having to the replaced. In fact, Krahn said, about one in four cases involving complications require the lead to be replaced. Replacing the lead is an invasive, aggressive and risky procedure that can result in major complications in one in 50 patients, and death in one in 200 patients, Krahn said.

Sudden Cardiac Death

"I think this study emphasizes the importance of device reliability," said Dr. Robert Hauser, who along with two of his colleagues at the Minneapolis Heart Institute went public last May when Guidant refused to disclose a defect in one of its defibrillator models that was linked to a patient's death. Since then, Guidant has been hit by a series of safety alerts, recalls, investigations and lawsuits.

The higher complication rate could give pause to doctors recommending defibrillators to patients who are not clear candidates for the device, Hauser said. After all, the devices have to be replaced about once every five years or so, often because of battery depletion. Hauser argues that the replacement complications study underscores the importance of developing defibrillators with batteries that last longer or are rechargeable, he said.

"When we perceive a problem, we have the urge to act on it," Krahn said.

"But there are risks in acting, and patients must be prepared to manage them."

Gunderson agrees that doctors whose patients are borderline candidates might hesitate before recommending a defibrillator, at least until there's more definitive information on whether they need it or not.

"Unfortunately, doctors may be more reluctant to refer patients on for the devices," Hauser said.

But one industry official argues that the risk of complications from replacement is low and should not deter anyone who needs a defibrillator from getting one.

"The much greater risk lies with the many people who are at proven risk for sudden cardiac death and do not have an ICD," said Paul Donovan, a spokesman with Boston Scientific, which last week bought Guidant.