Defective wires made by St. Jude Medical Inc. to connect heart-shocking defibrillators caused at least 20 patient deaths due to short circuiting, according to an article published in a leading cardiology journal.
Dr. Robert Hauser analyzed a database of reported device malfunctions, linking St. Jude's Riata and Riata ST wires to 22 deaths. St. Jude stopped selling the devices in December 2010 due to safety concerns, but more than 79,000 people in the U.S. and 49,000 abroad still have the implants.
St. Paul, Minn.-based St. Jude challenged the accuracy of the analysis, including the number of patient deaths.
Defibrillators are lifesaving devices implanted in the chest to correct dangerous heart rhythms that can be fatal. The defibrillator itself is attached to the heart with thin wires, known as leads, which monitor the heart for irregular beats, occasionally triggering electrical shocks that correct the problem.
Hauser searched the Food and Drug Administration's database of device malfunctions for reports of death with St. Jude's defibrillators. He recorded 9.7 deaths caused by Riata leads for every 100,000 devices implanted. He says the figure could be even higher since many reports do not give enough detail to determine the cause of the malfunction.
"For the tens of thousands of patients worldwide who have Riata and Riata ST leads, there is an urgent need for test methods that are capable of identifying life-threatening defects," writes Hauser, in Monday's issue of the journal Heart Rhythm. Hauser is a practicing cardiologist at the Minneapolis Heart Institute.
St. Paul, Minn.-based St. Jude challenged several of Hauser's points, including the total tally of deaths linked to its devices. The company's chief medical officer, Mark Carlson said two reported deaths were the result of duplicative paperwork, reducing the actual number to 20. The company also disagrees with the alleged cause of the malfunction.
The company stopped selling Riata leads because of evidence the coating over the wires could wear and break down over time. The company said the issue has been corrected in its currently sold Durata leads, which are insulated with polyurethane, instead of silicone.
But Hauser blames the deaths on a short-circuiting problem which is tougher to detect than thinning insulation.
"Electrical shorts are particularly lethal because they may occur abruptly during shock delivery, and thus failure to defibrillate may be the first and only sign of lead failure," Hauser writes.
In December, St. Jude launched its own 500-patient study to determine the failure rate for Riata leads and track them over time.
"The evidence we have at the moment indicates very few have electrical abnormalities and that they continue to perform normally," Carlson said in an interview. "But physicians and patients need to know whether that will continue to be the case."
St. Jude and the FDA do not recommend having the leads removed because surgery is often more likely to trigger a malfunction than leaving the wires alone. Instead, physicians should regularly monitor patients.
Leads have long been the biggest safety issue associated with implantable pacemakers and heart defibrillators. In 2010, Medtronic paid $268 million to settle lawsuits brought by patients who received defective leads, which could crack over time. The company estimated at least 13 patients died because of the problem, which it first reported in 2007.