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: Shares of medical device maker Zoll Medical (Nasdaq: ZOLL) were getting jolted to life today, gaining as much as 36% in intraday trading after a favorable Medicare development.

So what: Zoll's primary business is selling resuscitation devices, and a key product in its life-saving portfolio is the LifeVest, a wearable defibrillator that's targeted at people at risk from sudden cardiac arrest. In the 10-Q filing that Zoll released in August, it warned investors that Medicare may reduce its reimbursement for this innovative, high-growth device. The announcement crushed Zoll's shares.

Today, it hit the wires that Medicare will not make any changes to its reimbursements for the LifeVest, and so it's no surprise that Zoll's shares have recovered much of their previous drop.

Now what: The potential change from Medicare was a very real risk for Zoll, so today's news is a very big relief for investors and a good reason for Mr. Market to be pushing up the stock's price. Now investors can breathe a sigh of relief and get back to focusing on the broader picture at Zoll.

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Fool contributor Matt Koppenheffer does not have a financial interest in any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or Facebook. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.