Abstract
Major aortopulmonary collateral arteries (MAPCAs) are atypical in patients with transposition of the great arteries, with hemoptysis being an exceedingly rare complication. We present 2 cases of neonates undergoing arterial switch operations with postoperative courses complicated by significant hemoptysis. Both were managed successfully with MAPCA occlusion via cardiac catheterization. In the setting of hemoptysis in patients with transposition of the great arteries, clinicians should consider major aortopulmonary collaterals as a contributing factor.