An unusual coronary artery origin in a patient with anomalous left coronary artery.

In the typical patient with anomalous left coronary artery (ALCA) arising from the pulmonary artery, the left coronary artery arises from within the left or posterior pulmonary sinus. We report a case of ALCA in which the left coronary arose medially from the pulmonary artery above the commissure separating the right and posterior pulmonary sinuses. This unusual origin highlighted some of the problems with the noninvasive diagnosis of ALCA.