The U.S. Food and Drug Administration has recalled St. Jude Medical's Riata defibrillator lead over potential risks of injury or death.

Riata, which the Little Canada-based company took off the market last year, has been linked to incidents in which wires that run from the device to the heart may poke through the outer coating of their cable. That could result in the device failing to deliver a shock or, conversely, shocking patients unnecessarily.

The FDA classified the recall Class I, the most serious category. However, a St. Jude spokeswoman said the designation has no practical effect because Riata is no longer on the market.

St. Jude had sent doctors a voluntary medical device advisory letter on Nov. 28 regarding the Riata defibrillator lead. In the letter, St. Jude said a flaw with the wires on the Riata defibrillator is more prevalent than previously thought.

In addition, the letter said that the medical device maker is continuing to study incidents. Last year, St. Jude said the rate of abrasion was 0.47 percent nine years after the original implant, with 0.047 percent demonstrating "externalized cables." But in its most recent letter to physicians, St. Jude increased the abrasion rate to 0.63 percent.

A study of 212 patients in Ireland who received St. Jude's Riata defibrillator lead found that 15 percent had suffered such an "insulation breach," which could interfere with the device's lifesaving therapy.

St. Jude recommended that doctors continue monitoring their patients' implanted defibrillator systems and use X-rays or fluoroscopy if there is evidence of a lead electrical failure. That recommendation continues in the wake of the FDA's action, St. Jude said.

St. Jude said it is conducting a study to further evaluate the incidence and long-term performance of leads whose wires come through the outer coating. Enrollment in that study is expected to begin in December.

James Walsh • 612-673-7428