With left ventricular assist device company Thoratec Corp. (THOR) off the market following its recent purchase by St. Jude Medical Inc. (STJ), M&A activity may start to circulate in the heart care device sector. While 2014 was a big year for medical device mergers, this year things have slowed down, at least for the very biggest deals. Some of last year's deals include Medtronic plc's (MDT) $43 billion merger with Covidien plc; crosstown rival Zimmer Holdings Inc. (ZMH) buying Biomet Inc. for $13.4 billion; and Becton Dickinson and Co.'s (BDX) $12.2 billion deal for CareFusion Corp. (CFN). But with Thoratec, medtech may be getting read to steal the limelight away from the pharmaceutical and health insurer sectors that have gotten all the attention -- and the flow of deal money -- this year. Especially the cardiac industry, according to Diana Lee, a senior credit officer at Moody's Investors Service. 'Cardiovascular stenting and cardiac rhythm management are mature markets with lower growth and players are spending a lot of time looking at higher growth potential, like aortic valve markets,' Lee said in an interview shortly after the Thoratec deal was announced.