Providence Health Care and two Spokane-based cardiology groups announced Wednesday they will merge this fall to create a national center that could become a destination for patients seeking state-of-the-art heart care. Providence’s chief executive, Dr. Andrew Agwunobi, said Providence, Spokane Cardiology and Heart Clinics Northwest, consolidated as Providence Spokane Heart Institute, will improve the safety, quality and efficiency of care, in part as a response to changes anticipated under health care reform.