The Hamilton County (Tenn.) medical examiner has ruled that teenage distance runner John Bruner of Dalton, who collapsed on Aug. 4 near the end of the Missionary Ridge Road Race in Chattanooga and later died, had a rare “coronary artery anomaly.”

Medical examiner Dr. James Metcalfe described Bruner’s condition as an anomalous origin of the left coronary artery, which occurs in 0.01 to 0.05 percent of the population, according to Dr. Brad DeLay of Dalton Family Practice. Delay is a friend of Greg and Margie Bruner, John’s parents.

“I’ve never had a patient with this anomaly and know of just two, John being one of them,” DeLay said Thursday morning at his office on Professional Boulevard. “The other was in 1990 when I was running in my first marathon, the Marine Corps Marathon in Washington, D.C. Lisa B. Christensen, a 19-year-old midshipman in the Boston University Naval ROTC, collapsed a little more than two miles from the finish and died at Arlington Hospital. She had the same condition that John Bruner had.”

Bruner, The Daily Citizen’s Co-Male Cross Country Runner of the Year in 2005, was also 19. He was about to begin his sophomore year at Georgia College and State University in Milledgeville, where he was a member of the school’s cross country and track teams.

“This condition is not a disease but just a variation of normal anatomy of the coronary arteries,” DeLay said in a prepared release. “It is the cause of 12-20 percent of the U.S. high school athletic cardiac deaths per year, or about one to two high school athletes per year. It is not an inherited disease.”

Statistics, DeLay pointed out, indicate the more life-threatening forms occur in 0.01 to 0.05 percent of the population. More than half will die before the age of 20, usually during exercise. Death is caused by the disruption of blood flow to the heart through the abnormal coronary artery.

Bruner was nearing the end of the 4.7-mile road race when he collapsed. He was given assistance on the course around 8:45 a.m. by three medical professionals — an American Red Cross volunteer nurse and two doctors — who used a defibrillator to restore a heartbeat. Bruner died later that morning at Erlanger Medical Center in Chattanooga.

Dr. Bates Bailey, a local cardiologist who spoke with Metcalfe before and during his autopsy of Bruner, said, “The theory is that with more demands on the body, with an increase of blood flow, the artery swells and causes a pinching of the artery.”

In a prepared statement, the Bruners said, “John Bruner loved to run and compete. He would not want speculation or fear about the cause of his untimely death to dampen the competitive spirit of the sport. We also want to provide peace of mind to the immediate responders that came to John’s aid. The entire family is grateful for their attempt to save his life.

“The cause of death was determined by the medical examiner that performed the autopsy. John was an organ donor and more than 60 individual’s lives are improved as a result.”

DeLay said an anomalous left coronary artery condition occurs when the left main coronary artery comes off the right side of the aorta, instead of the normal left side. To get back to the left side, the left coronary artery must travel between the two large vessels, the pulmonary artery and the aorta.

“This,” DeLay said, “also shows how in rare circumstances a heart attack can occur when, during exercise, pressure from the aorta and pulmonary arteries may pinch the left coronary artery, cutting off blood flow to the heart, or deform the ostium (opening) of the left main coronary artery. This cuts blood supply to the heart causing a myocardial infarction (heart attack).”

DeLay used the analogy of a backyard garden hose being pinched, stopping the water flow.

Bailey said there may always be questions about Bruner’s physical condition and that answers are never easy to come by.

“This was a fluke. And sometimes answers only yield more questions,” he said. “I don’t have all the answers. I’ll never have all the answers.”