Just over a year after he was recruited from a major competitor, Michael F. Mahoney formally took the reins as Boston Scientific Corp.’s chief executive Thursday, promising to revitalize the long-struggling Natick medical device maker.

“I plan to take the company back to growth,” said Mahoney, 47. “The company has a wonderful legacy, but we haven’t grown [it] for years. I hope to provide some management stability, and I see a lot of opportunity” for boosting sales.