St. Jude Medical on Tuesday announced regulatory approval of new heart defibrillators designed to help ease anxiety over whether the devices' wires will effectively deliver lifesaving therapy, even if damaged.

The U.S. Food and Drug Administration has approved St. Jude's next-generation Ellipse and SJM Assura implantable cardioverter defibrillators (ICDs) and cardiac resynchronization therapy defibrillators (­CRT-Ds). They are designed to lower the risk of lead abrasion and to improve the delivery of a high-voltage jolt when needed.

Leads are wires that connect a device to the heart, often snaking through veins to inside the heart itself. Leads contain several smaller wires that allow the device to sense problems with the heart's rhythm and deliver an electrical surge to correct it.

St. Jude says the new devices are more effective in a couple of ways. First, the devices feature a new algorithm that automatically adjusts shocking configurations, even if an electrical short occurs in one part of the system. Second, the new defibrillators have a special coating on the device, which St. Jude says will reduce the risk of friction. Friction caused by the lead rubbing against the device can damage the lead's insulation and contribute to lead failure.

"St. Jude Medical strives to deliver the highest levels of patient safety. The new Ellipse ICD and SJM Assura family of devices support those efforts by providing added features that ensure effective therapy delivery," said Eric Fain, M.D., president of the St. Jude Medical Implantable Electronic Systems Division.

A human heart beats approximately 40 million times a year, causing constant twisting and moving that can wear on leads. Abrasion between the lead and the device itself is the most common type of lead insulation failure.

St. Jude has been especially sensitive to market concerns about lead failure over the past few years. The Little Canada-based company pulled its Riata defibrillator leads from the market in late 2010, after doctors found that inner wires had worked their way through the lead's outer silicone insulation. The FDA recalled Riata in late 2011 because of safety concerns, although the wires remain in thousands of people.

Monitoring continues

St. Jude's newer Durata leads have shown low rates of failure, and St. Jude continues to actively monitor the performance of more than 11,000 implanted Durata leads. Still, some analysts and doctors say they remain concerned about similar problems with that lead.

The biggest issue regarding damaged leads is whether they will be able to reliably sense when the heart is in trouble and deliver needed therapy. According to St. Jude, its new defibrillators should alleviate those fears.

"This is a technology we developed to mitigate ICD lead complications and improve the reliability of defibrillation therapy," St Jude spokeswoman Amy Jo Meyer said Tuesday.

A local analyst, who asked not to be identified, said news of FDA approval of Ellipse and Assura is evidence that St. Jude continues to "look at the issue and continue to try to make improvements."

Problems with leads have been around as long as the devices themselves, the analyst said, noting that St. Jude is just the most recent company dealing with the challenge with product revisions. "It is an example of them not just burying their head in the sand on an important issue."