Alternative Blood Supply to the Lungs in Complex Congenital Heart Disease Introduction Major Aortopulmonary Collateral Arteries — MAPCAs — are abnormal congenital blood vessels that arise from the aorta or one of its major branches and supply blood to the pulmonary circulation. They are most strongly associated with congenital heart defects in which normal blood … Continue reading Major Aortopulmonary Collateral Arteries — MAPCAs