Hermitage, TN-based Summit Medical Center wants to build an emergency and diagnostic medical complex in Mt. Juliet. Summit, part of HCA Corp.'s TriStar division, has presented Mt. Juliet with a letter of intent to develop and operate an "outpatient medical facility providing emergency services, diagnostic imagery, laboratory services and/or physician office space." Jeffrey Whitehorn, the hospital's chief executive, said his hospital is the emergency room of choice for about three-fifths of Mt. Juliet's residents who seek such care.