FIG 36.14 Series of angiograms depicting four large major aortopulmonary collateral arteries, one of which connects to the central pulmonary artery (arrow) through a connection in the right upper lobe territory (A) The other three (B–D) provide isolated supply to segments in the right (B) and left (C–D) lungs FIG 36.15 (A–B) Angiograms from a patient with major aortopulmonary collateral arteries (MAPCAs) to the right lung (B) and a ductus arteriosus to the left lung (A) As is typical for patients with tetralogy of Fallot/pulmonary atresia/MAPCAs and ductus, the left pulmonary artery arborizes normally and completely and is supplied only by the ductus Both the ductus and the MAPCA shown at the right were previously stented before referral to our center Note that the descending aorta is ipsilateral to the lung supplied by the ductus, and the arborization of the left lung's pulmonary artery system is normal, in contrast to the MAPCA-supplied right lung (C–D) Schematic of single-stage repair in the setting of a patent ductus to the left lung and two good-sized MAPCAs to the right lung (C–D, From Watanabe N, Mainwaring RD, Reddy VM, et al Early complete repair of pulmonary atresia with ventricular septal defect and major aortopulmonary collaterals Ann Thorac Surg 2014;97:909–915.) There are several points of nomenclature that we use clinically that should be clarified The number of MAPCAs is frequently reported as the number of vessels arising from the aorta, subclavian arteries, coronary arteries, or other systemic arteries From a surgical point of view, however, the number of MAPCAs should be thought of as the number of discrete vessels that must be managed (unifocalized or ligated) Because MAPCAs that originate from a major systemic artery often divide before they enter the lung or the pulmonary arteries, the number of vessels that must be managed is not always the same as the number of discrete origins from the systemic circulation Therefore our convention is to count each MAPCA or branch that must be managed separately, prior to entering the lung parenchyma or connecting with the pulmonary arteries, as a unique MAPCA The defining characteristic of a MAPCA that must be managed separately is that it is or will be obstructed (or otherwise have a fixed limitation in flow) in its native state if it is not unifocalized separately, as is most often the case, or augmented in its native configuration (see Fig 36.13) Another important term that may not be universally agreed upon is “dual supply,” which we use to connote a robust functional connection between a MAPCA or lung territory supplied by a MAPCA and lung territory that is in continuity with the central pulmonary artery system A MAPCA that connects robustly to the central pulmonary artery system or to another MAPCA, either within the lung parenchyma or prior to entering the parenchyma, is considered to provide a dual supply In this respect, “dual supply” indicates that the conduit portion of the collateral will be redundant once the central pulmonary arteries are fed by a right ventricle-to-pulmonary artery connection or a systemic-topulmonary artery shunt If lung territory supplied by a MAPCA communicates with another segment or lobe through acquired intersegmental connections or through a small connection that is inadequate to provide sufficient flow to the lung territory in question, that collateral should not be considered a dual supply MAPCA If a MAPCA does not provide dual supply, by definition it is the sole (or isolated) supply of blood to a particular region of lung By definition, a dual supply collateral does not need to be unifocalized or augmented in order for the lung territory it supplies to receive adequate flow once a central source of pulmonary blood flow is provided Both the number of MAPCAs and dual/isolated supply status can be delineated by angiography and/or computed tomography, although only the former can provide direct data on pressures and gradients