St. Jude Medical Inc. will stop selling its QuickSite and QuickFlex heart pacemaker connecting wires, called leads, after 39 reports of wires protruding through their outer insulation.

It is the second time in less than two years that St. Jude has pulled leads from the market after wires were found to break through their outer silicone insulation. In late 2010, St. Jude shelved Riata defibrillator leads after an Irish study showed wires came through the lead's outer coating. The U.S. Food and Drug Administration issued a recall of the Riata leads in December 2011.

It appears the problems with the QuickSite and QuickFlex pacemaker leads are much the same. As with Riata, St. Jude said that a second layer of insulation on the wires remained intact, so the leads keep working.

The affected QuickFlex and QuickSite lead -- called a left ventricular, or LV, lead -- is used to stimulate the two sides of the heart to beat efficiently and in synchronization. Left-ventricular leads are meant to improve the efficiency of the heart, but are not responsible for delivering pacing or defibrillation. If the LV lead were to fail, the other leads attached to the device would continue to deliver life-saving therapy, St. Jude said. No patients have been harmed by the damaged leads, according to the Little Canada-based company.

St. Jude now manufacturers a new generation of leads with a special, coated insulation -- Optim -- designed to prevent the problem, the company said. There have been no reports of protruding conductors in the more than 65,000 Optim-insulated leads sold since 2008, St. Jude said.

Recommendations to doctors

For patients with the older leads, St. Jude's medical advisory board recommended that physicians continue to monitor the implant. The board said X-ray or fluoroscopic imaging is not recommended for leads with normal electrical function and that "only leads that exhibit electrical anomalies and cannot be reprogrammed to deliver effective CRT pacing should be considered for replacement."

St. Jude has confirmed there were 39 reported cases of protruding wires out of the 171,000 QuickSite and QuickFlex leads sold worldwide, or about two one-hundredths of a percent. About 59,000 were sold in the United States.

The company estimates that 3 to 4 percent of the leads sold may have the flaw. It said the problem often goes unnoticed by patients and doctors because there are no outward signs the leads have been damaged.

The issue of the protruding wires was discovered when some leads were removed from patients because of infection or other medical problems unrelated to the leads themselves, said Dr. Mark Carlson, chief medical officer at St. Jude. In every case, the inner insulation was intact and the leads still were working.

St. Jude announced the problem Wednesday in a letter to physicians.

The reason for the letter to physicians is "so they know what to do. Or, more importantly, they know what not to do," Carlson said.

The Riata leads

A recent study by Dr. Robert Hauser at Abbott Northwestern Hospital's Minneapolis Heart Institute has linked problems with Riata leads to at least 20 patient deaths. Hauser said the deaths were caused by short-circuiting and not the insulation abrasion.

St. Jude disputes Hauser's findings. In December, the device manufacturer launched its own 500-patient study to determine the failure rate for Riata leads and to track them over time. Riata leads remain in about 76,000 people in the United States.

On Wednesday, in a note to investors, Kevin Strange, an analyst with Wells Fargo, said there is no evidence St. Jude's newer generation of leads will have insulation problems. But, he said, sales could be "dampened slightly."

"Given the on-going issues with Riata, we think this advisory may cause some physicians to question [St. Jude's] product quality and further diversify their risk by spreading their device usage across the three major [cardiac rhythm management] companies," Strange said.

But Rick Wise, an analyst with Leerink Swann Research, said he did not expect the problems with QuickSite and QuickFlex leads to hurt St. Jude's current generation of leads.

"Although a negative headline -- and sounding painfully similar to the ongoing Riata 'recall' -- we think this issue will be manageable for STJ. The now outdated QuickFlex and QuickSite leads comprise just 10% of the company's current LV lead mix and hence a very small proportion of overall revenues," he wrote to investors Wednesday. "This is clearly another blow to STJ's lead reputation. But given that it is again concerning older-generation lead technology and the incidence rate has been very small with no patient adverse events reported, we currently do not anticipate any material financial or market share impact for STJ."

St. Jude stock closed Wednesday at $41.67, down $2.13, or 4.9 percent.

James Walsh • 612-673-7428 Steve Alexander • 612-673-4553