Medical device maker Edwards Lifesciences (NYSE:EW) is counting on its Sapien heart valve in a big way. When the Sapien's sales grew slower than expected in the company's first quarter and Edwards lowered its full-year revenue guidance because of it, the stock dropped like a rock. Similarly, Edwards' strong second quarter renewed optimism in this medical device maker's future.

The Sapien has a lot going for it -- after all, it's the only heart valve of its type currently approved in the U.S. It added an approval in Japan, also the first of its class, back in June, giving the Sapien a critical first-mover advantage in the world's second-largest health care market. While the device's American launch has gotten off to a slow start, however, Japan could be a huge win for Edwards as it looks to fend off competitors in a growing industry.

Is the Sapien destined for new highs across the Pacific, and can Edwards' stock capitalize for your portfolio? Fool contributor Dan Carroll takes you through the big news out of Japan for Edwards -- and what medical device investors need to know going forward in a critical cardiac device battle.