Issues with St. Jude Medical's Riata heart defibrillator have prompted the Food and Drug Administration to recommend that patients with the device get X-rays to check for abnormalities.

Defibrillators are stopwatch-sized devices that shock an errantly beating heart back into rhythm. Implanted in the upper chest, they are connected to the heart by leads, or insulated wires.

Little Canada-based St. Jude pulled its popular Riata leads off the market in December 2010, and the FDA issued a recall of the device in late 2011, after St. Jude sent a letter to physicians telling them about a possible problem related to the device.

Reports had surfaced of premature erosion of the insulation around some of the leads, which could cause the device to malfunction, possibly leading to inappropriate shock therapy to the heart and potentially life-threatening abnormal heart rhythms.

As of 2011, 79,000 Riata leads remained implanted in patients.

In a statement, St. Jude said, "We understand the FDA's decision to recommend fluoroscopic or X-ray screening of all patients with a Riata lead, in order to establish a baseline of understanding about the incidence rate of externalized conductors."

Jeffrey Shuren, director of the FDA's Center for Devices and Radiological Health, said in a statement that the majority of Riata leads "continue to function normally and provide life-saving support for patients.

"However," he said, "the agency does not have enough information to determine the frequency and timing of insulation failure in these leads."

Therefore, X-rays or other imaging alternatives will help patients and doctors get the information they need, he said.

The FDA is also requiring that St. Jude conduct three-year, post-market surveillance studies to collect clinical data related to insulation failure in Riata leads. St. Jude said it supports post-market lead surveillance programs, and is conducting its own Riata lead research.

Early results released last month were consistent with the performance found in other published studies, the company has said.

St. Jude's stock closed at $36.87 Thursday, down $1.69 a share, or 4.4 percent.

Piper Jaffray medical technology analyst Thomas Gunderson said problems with the Riata lead are "yesterday's news" as far as Wall Street is concerned.

The big question, he said, is the performance of St. Jude's second-generation Durata lead. Barring any hard safety data about the performance of Durata, "you just have sentiment now, and it seems negative about St. Jude's leads. But, again, that's already built into the stock."

Morgan Stanley analyst David Lewis said in a note to investors Thursday that the FDA is playing catch-up. The agency's "actions offer limited new information," he wrote.

Staff writer Janet Moore contributed to this report. Mike Hughlett • 612-673-7003