WASHINGTON -- A leading heart valve manufacturer stopped worldwide implants of silver-coated heart valves Monday because the coating meant to reduce heart infections instead makes the valves prone to leak.
Minnesota-based St. Jude Medical Inc. recalled all hospital inventories of St. Jude's heart valves with the Silzone silver coating.
The recall affects only valves still on hospital shelves, not those already inside patients. That is because the leakage seems infrequent and occurs slowly, without creating an emergency situation, health officials said.
But 36,000 of the silver-coated valves have been implanted since 1997. Patients include 12,000 Americans, implanted since the valves began selling here in 1998.
Those patients should not panic when they hear of the recall, Food and Drug Administration medical device chief Dr. David Feigal said.
"The majority of patients who have these valves did not have this complication," he said.
The leaks seem to occur in about 2 percent of patients with silver-coated heart valves, St. Jude Medical said. That makes the valves riskier than older heart valves, of which about 1 percent eventually leak.
Such leaks develop slowly, leaving enough time for doctors to spot the problem and determine how to handle it, said Dr. James Cox, a cardiac surgeon at Georgetown University. A patient with a small leak, in fact, may only need monitoring.
"The likelihood these patients would have to have another operation is very, very small," Cox said after reading the recall information St. Jude shipped to surgeons' offices Monday afternoon.
But a patient with a larger leak or who has such symptoms as shortness of breath would need a valve replacement, doctors said.
A St. Jude spokesman declined comment about what recourse those patients would have in getting a new valve and paying for additional surgery.
While the company recommended that patients continue to have routine physician checkups unless they experience symptoms, Cox said "it would probably be a good idea" for patients to schedule echocardiograms, noninvasive scans that can spot leaks.
The recalled heart valves are identical to older St. Jude's valves except their edges, or cuffs, are coated in silver.
Silver can have antibiotic properties, so the theory was that silver-coated valves would lead to fewer heart infections, a serious risk for all recipients of artificial heart valves. The recall marks a setback in doctors' quest for infection-resistant implants.
The FDA let St. Jude sell the Silzone-coated valve before it proved the infection theory. After sales began, St. Jude began enrolling patients in a study to compare old valves with new silver-coated ones.
Last week, safety monitors spotted the leakage problem. Of 398 patients implanted with a silver-coated valve, doctors so far have removed eight leaking valves. Of 394 patients given older, uncoated valves, they have removed just one leaking valve.
No one knows why the new valves were leakier, but St. Jude stopped the trial and recalled all Silzone-coated products still on hospital shelves worldwide.
"This experience is a cautionary tale," Feigal said, noting that no previous research had suggested such a simple change could have any ill effect.
Should sale of the valves have been allowed before the company compared old valves to new?
"It's easy to say that in hindsight," but requiring long and expensive clinical trials for simple materials changes could freeze medical device development, Feigal said. "It's a question of balance."
Patients with questions are advised to contact their doctors or to check St. Jude's Internet site at www.sjm.com for more information.