Doctors have discovered a potential problem involving implanted heart valves that hundreds of thousands of people have received — they don’t always open and close properly, possibly because a blood clot has formed that could raise the risk of stroke.
Although the problem appears common, experts stressed that not enough is known about the situation to change practice now, and federal health officials say the valves still seem safe and well worth the risk.
It’s bound to be unsettling for people with bio- prosthetic aortic valves, ones made from cow, pig or human tissue. They have become more popular than mechanical ones made from synthetic materials because they don’t require lifelong use of blood thinners to prevent blood clots.
Some tissue valves also can be placed through tubes into blood vessels rather than in open-heart surgery, which has allowed far more people in recent years to have bad valves fixed.
The safety concern emerged last year in a study testing a tube-placed valve. Scans on two patients, including one who had a stroke, revealed that their valves were not working right.
Dr. Raj Makkar, the doctor at Cedars-Sinai Heart Institute in Los Angeles leading the study, wanted to know how widespread this was. In a report published Monday by the New England Journal of Medicine, he and others say the problem has now been found in 22 of 55 (40 percent) patients in the study, and in 17 of 132 (13 percent) patients in two registries tracking tissue-valve recipients.
Few valve recipients were on blood thinners, but those taking warfarin, sold as Coumadin and other brands, seemed protected from the problem, and warfarin also successfully treated it.
