Acute occlusion of left coronary ostium associated with congenital quadricuspid aortic valve.

A 10-year-old girl suffered from chest discomfort during exercise. She experienced an acute myocardial infarction accompanied by an obstruction in an orifice to the left coronary artery. An emergency operation revealed that the aortic valve was quadricuspid, and a left-sided small cusp had adhered to the aortic wall resulting in an unusual sac with a tiny slit. Resection of the sac disclosed the ostium to left coronary artery. Blood toward the left coronary artery passed through the tiny slit. The mechanisms of obstruction in the coronary artery were uncertain. She recovered well after the aortic valve replacement with resection of the aortic cusps.