it's bound to be unsettling for people with bioprosthetic 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. 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.
http://www.ctvnews.ca/health/doctor...problem-with-implanted-heart-valves-1.2596071