Earlier this week, Motley Fool health-care bureau chief Brenton Flynn discussed Johnson & Johnson's (NYSE:JNJ) failed attempt to get its blood thinner Xarelto approved by the FDA for a lucrative new treatment area. In this video, Brenton tells us about one headwind that could potentially impact sales of blood thinners across the board. If a device coming out from Boston Scientific (NYSE:BSX) to prevent blood clots due to atrial fibrillation receives approval in the U.S., it could be worth half a billion dollars for the company, and could slightly weigh on blood thinner sales, if successful. Brenton tells us which companies could be affected by this under-the-radar trend.