The Food and Drug Administration (FDA) issued a safety communication alerting doctors that heart valves, which are implanted in hundreds of thousands of patients, do not always open and close properly, possibly because a blood clot has formed in the heart. These clots, they warn, could travel to the brain and cause a stroke. Despite this risk, the agency stressed that the valves still seem safe and are worth the risk.
In recent years, more bioprosthetic aortic valves have been implanted. These are made from cow, pig or human tissue. They have been preferred over mechanical ones made from synthetic materials because patients with bioprosthetic aortic valves do not require lifelong blood thinners to prevent blood clots.
The safety concern arose last year following a study testing tissue valves placed through tubes in blood vessels rather than in open-heart surgery. The procedure allows more people to have heart valve replacement. However, scans on two patients who underwent this type of valve replacement procedure revealed that the valves were not working correctly. One of the patients suffered a stroke.
The researcher who led the study expanded the study to determine just how widespread the issue of the valves not working correctly was. He tested 55 patients with heart valves and found that 22 – or 40 percent – had the same problem. Another 17 patients out of 132 – or 13 percent – in two registries tracking tissue valve recipients also had the problem.
The initial testing involved a valve manufactured by St. Jude Medical; however, the problem has since been seen with other brands of heart valves, as well as in valves implanted during open-heart surgery.
Among all 187 patients involved in the study, six suffered strokes or so-called mini-strokes, and the risk was slightly higher among patients whose heart valves were not opening and closing properly. Only a handful of the participants were taking a blood thinner. The research showed these patients were at lower risk of strokes.
The study has brought up even more questions. Is the risk greater soon after the device is implanted, or does the risk continue over time? Is the risk due to blood clots, or something else? And is the problem more common with tube or surgically placed valves?
In the meantime, the FDA says heart valves save lives and should remain on the market at least until data proves otherwise. The agency also urged doctors to report any valve-related problems for tracking.