Study: Defibrillators iffy 10 years after implant

BLOOMBERG
05/01/2007 - One in five implanted devices used to shock hearts back into a normal rhythm fails to work properly after 10 years, a study has found.

Electrical wires that connect cardiac defibrillators to the heart were at fault, according to the research. Malfunctioning wires, called leads, sometimes caused the devices to shock the heart unnecessarily and sometimes would fail to work when the heart began beating abnormally or stopped altogether.

The result may be death, increased costs to repair or remove the device, and increased anxiety for patients, the researchers said. The leads offer a bigger risk for patients than battery failures that triggered recalls since 2005 of thousands of devices made by Medtronic Inc., Boston Scientific Corp. and St. Jude Medical Inc., the researchers said.

"These data emphasize that lead failure may become a prominent concern" in patients who survive past 10 years, said the researchers, led by Thomas Kleemann, an electrophysiologist at Herzzentrum Ludwigshafen in Germany.

The study, published today in the journal Circulation, found that the annual failure rates increased with time and occurred with all models. The risk was highest for women and healthier patients who are most likely to live for years.

Kleemann and his colleagues followed 990 consecutive patients who received their first defibrillators at the heart center in Ludwigshafen between 1992 and 2005. Patients were monitored every three months for an average of 2 1/2 years. Overall, 148 defibrillation leads, or 15 percent, failed.

The leads are used to track abnormal heart rhythms and transmit an electric shock to the heart to restore a proper beat when needed. Almost 70,000 of devices, which cost $30,000 or more, are implanted each year in the United States, according to the American Heart Association.

The most common complication, responsible for 56 percent of the lead defects, stemmed from insulation problems. Others included fractured wires, problems in the electrical circuit and sensing failures. Newer devices designed to address some of the problems linked to polyurethane insulation fared no better and in fact may have higher failure rates, the researchers said.

"The older leads used polyurethane as an insulator, and they had defect problems," Kleemann said in a statement. "It seems that the silicone-coated wires have problems even earlier."