Repair of Infracardiac Total Anomalous Pulmonary Venous Return

Abstract

Total anonmlons puhnonary venous return (TAPVR) occurs when the left atrium and primordial puhnonary vein bud fail to unite with the venous plexus that surrounds the lung buds at approximately the end of the first month of gestation. The connection between the puhnonary venous plexus and the splanchhie venous system persists and usually becomes tile only route of venous drainage for tile lung after birth. In tile infracardiac type of TAPVR, the pulmonary veins join a single collector that courses directly dorsal to the left atrium, separated from the atrium by the pericardium (Fig 1). The puhnonary venous collector continues inferiorly, penetrating the diaphragm at the esophageal hiatus to join, most commonly, the portal vein and right atrium via the ductus vcnosus. Less commonly, the venous collector joins the inferior vena cava (IVC) or, rarely, tile gastric vein. In most neonates, obstruction of puhnonary venous return then occurs when the ductus venosus begins to close shortly after birth, and pulmonary venous return must pass through the hepatic parenehyma before entering tile right atrium. Because tile pulmonary veins do not connect to the left atrium, tile only inflow to tile left atrimn and ventricle must cross tllrough tile foramen ovale. Frequently in TAPVR the size (volmne) of left atrium and ventricle are at tile lower limit of normal. The left atrium is particularly hypoplastic, because a significant part of what comprises the left atrial cavity ori~nates from tile fusion of the puhnonary vein trunk to tile. atrium. The left ventricle can also appear quite small, particularly when there is puhnonary hypertension from pulmonary venous obstruction, because tile interventricular septum shifts posteriorly, decreasing the left ventricular end-diastolic volume. Because all of the inflow to tile left ventricle must cross the foramen ovale, tile snlall and poorly compliant left ventricle nmy not receive sufficient inflow to maintain normal systemic output. These infants frequently present with signs of puhnonary edema from venous obstruction, as well as low cardiac output with hypoperfnsion and metabolic acidosis.