The U.S. FDA approved four transcatheter aortic valve replacement (TAVR) devices for use in patients at low risk of poor surgical outcomes: two of the Corevalve family from Medtronic plc, of Dublin, and two of the Sapien brand from Edwards Lifesciences Corp., of Irvine, Calif. The news comes roughly eight months after both companies presented data for this patient population at a major medical conference and signals robust growth for this device type for the foreseeable future.