Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Thoratec (Nasdaq: THOR) shares fell 20% today on news of increased competition.

So what: HeartWare International said its new five-ounce implantable pump, that will compete with Thoratec's HeartMate II, has seen positive results in a study. The new device has yet to be approved in the U.S., but is half the weight of the HeartMate II.

Now what: The weight difference alone is astounding for an implanted device. It doesn't sound good for Thoratec's $230 million device unless regulators hold up the new device some surgeons are raving about. I hate to sell on a down day but the increased competition doesn't look good for Thoratec in the long run.

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Fool contributor Travis Hoium does not have a position in any company mentioned. You can follow Travis on Twitter at @FlushDrawFool, check out his personal stock holdings or follow his CAPS picks at TMFFlushDraw.

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