In this anomaly the function of the LMCA territory often requires extensive collateral formation from the RCA, which is often dilated. In the first month of life, physiologic pulmonary hypertension tends to preserve anterograde flow within the left coronary artery, and infants are usually asymptomatic. As pulmonary pressure drops, left-to-right shunting from the higher pressure left coronary arterial system to the lower pressure pulmonary arterial system occurs, and patients become symptomatic. Imaging findings may include markedly dilated collateral arteries and coronary veins.