Medtronic plc (NYSE: MDT) said it will buy HeartWare International Inc. (Nasdaq: HTWR) for about $1.1 billion, gaining technology to treat heart-failure patients. Medtronic will pay $58 a share, almost double HeartWare’s June 24 closing price of $29.98, the company said Monday in a statement. The boards of both companies have unanimously approved the transaction, which is expected to close during Medtronic’s second fiscal quarter ending Oct. 28. Medical devices has been fueling M&A in the middle market. Apax Partners is buying a majority share of the respiratory business of Becton, Dickinson and Co.; Stryker Corp. (NYSE: SYK) acquired the Y-Wire and Tiger Jamshidi Needle products from SafeWire; and TE Connectivity Ltd. (NYSE: TEL) agreed to buy health-care device company Creganna Medical. Buying Framingham, Massachusetts-based HeartWare will expand Medtronic’s offerings of diagnostic tools, therapies and services for patients suffering from heart failure. Medtronic estimates that the global market for ventricular-assist devices is about $800 million and will increase by a percentage in the mid-to-high single digits this year and next. Heart failure is a condition or a collection of symptoms in which the heart isn’t pumping enough blood to meet the body’s needs. Heart failure remains a leading cause of hospitalization and death in the U.S., where more than 5 million people are affected. Medtronic has been active with acquisitions. Earlier in 2016, the company bought kidney treatment company Bellco; In 2015, Medtronic acquired video laryngoscope maker Aircraft Medical and also added mitral valve manufacturer Twelve Inc. JPMorgan Chase & Co. served as financial adviser to Medtronic, which received legal advice from Ropes & Gray LLP. Perella Weinberg Partners offered financial advice to HeartWare, whose legal adviser was Shearman & Sterling LLP.   Additional Reporting By Mergers & Acquisitions' Demitri Diakantonis