Two adult cases of congenital atresia of the left coronary ostium-comparison of a sudden death case with a long-term survival case.

We present two extremely rare autopsy cases with atresia of the left coronary ostium. Case 1 was a 34-year-old man who died of sudden cardiac causes with localized acute subendocardial infarction and Case 2 was an 82-year-old woman who died from non-cardiac causes. In both cases, a string-like small left main trunk that was located in its normal position was found; however, the orifice of the left coronary artery was absent in both cases. The collateral artery (CA), whose caliber was smaller than that of the proximal left descending artery (LAD), arose from the right coronary sinus and was anastomosed with the distal LAD. However, it was only in Case 1 that the CA showed an acute angle of take-off from the aorta, subsequently coursing between the root of the aorta and the pulmonary trunk, with possible mechanical compression by these two arteries. These two cases suggest that atresia of the left coronary ostium is developmentally and anatomically different from single coronary artery or left coronary artery arising from the opposite sinus of valsalva. Atresia of the left coronary ostium is considered to be an important differential diagnosis as a cause of sudden death, not only in the pediatric population but also in adults. The caliber and/or other anatomical features of the CA may predominantly dictate the clinical course of patients with atresia of the left coronary ostium.