The chief executive officer of HighPoint Health System, of which Sumner Regional Medical Center is its flagship, announced her retirement this morning. Mary Jo Lewis, 62, was the first CEO of HighPoint, which was born after LifePoint Hospitals Inc. purchased the bankrupt Sumner Regional Health Systems in 2010. Lewis has been CEO for just 19 months. Her replacement will be the fourth CEO at the Gallatin hospital in three years. Her quick departure comes after a turbulent set of years for staff and physicians. HighPoint spokesman Rachel Lassiter said Lewis had not yet decided when her last day will be, but she has committed to staying until a new CEO is hired. A company statement said the search for a new CEO is underway.