The earliest description of TAPVR was given by Wilson in 1798. In 1942, Brody presented an autopsy series of patients with this anomaly. Muller at UCLA is credited with the initial attempt of surgical treatment of TAPVR in 1951. He described a closed operation consisting of a side-to-side anastomosis between the common pulmonary vein trunk and the left atrial appendage. In 1956, Lewis, Varco, and associates at the University of Minnesota Minneapolis, MN, reported the first successful total correction of TAPVR using hypothermia and inflow occlusion. The same year, Burroughs and Kirklin described their experiences with surgical correction using cardiopulmonary bypass (CPB). The introduction of deep hypothermic circulatory arrest by Barratt-Boyes and colleagues in the early 1970s was a major advance toward accomplishing surgical repair because this technique provides a bloodless operative field. Further advances in early diagnostic modalities, neonatal intensive care, including the availability of extracorporeal membrane oxygenation (ECMO), and pediatric cardiac surgical anesthesia, as well as an awareness of the merits of early surgical intervention, have contributed to the excellent results with TAPVR repair reported recently by many centers.

The respiratory system develops as an evagination from the foregut at 26 days. The venous plexus from the early lung buds drains into the anterior cardinal and umbilico vitelline veins, both of which are part of the splanchnic (systemic) venous system. The anterior cardinal veins give rise to the right and left superior vena cavae (SVC), the coronary sinus, and the azygos vein. The umbilico vitelline veins form the inferior vena cava (IVC) and the portal vein. In normal circumstances, the common pulmonary vein develops as an outpouching from the dorsal left atrial wall, eventually fusing with the pulmonary venous plexus at 28 to 30 days. Shortly thereafter, the anterior cardinal and umbilico vitelline venous channels normally undergo involution (Fig. 97.1). Failure of the common pulmonary vein to unite with the pulmonary venous plexus leads to persistence of these embryonic pulmonary venous-to-systemic venous anastomoses, yielding total anomalous pulmonary venous drainage into right atrial tributaries. In some instances, abnormal leftward displacement of the developing atrial septum results in anomalous connection of all four pulmonary venous ostia directly to the right atrium.

The common underlying anatomic defect in all cases of TAPVR involves anomalous drainage of the entire pulmonary venous circulation into the right atrium, either directly, or via the SVC, IVC, or coronary sinus. The pulmonary venous blood may drain into the systemic venous circulation through a single common channel or by multiple portals of entry. An interatrial communication, usually manifested as a patent foramen ovale (PFO) or secundum atrial septal defect (ASD), is mandatory for shunting of partially oxygenated blood to the left heart.

There are several classification schemes for TAPVR. The most commonly used system is the one described in 1957 by Darling and associates. This four-tier system is based on the site of pulmonary venous drainage into the systemic circulation. In type I, or supracardiac TAPVR, all four pulmonary veins form a horizontal common pulmonary venous confluence behind the left atrium that gives rise to a vertical vein that drains into a supracardiac systemic vein (innominate vein, SVC, or azygos vein) (Fig. 97.2). The most common configuration involves an ascending left vertical vein or persistent left SVC that drains into the innominate vein. Type II, or cardiac TAPVR, is characterized by total pulmonary venous drainage into a markedly dilated coronary sinus (Fig. 97.3) or, less commonly, directly into the right atrium. Type III, or infracardiac TAPVR, involves a more vertical pulmonary venous confluence giving rise to a descending vertical vein that travels through the esophageal hiatus to below the diaphragm, where it most often makes an anomalous connection with the portal vein, one of its branches (Fig. 97.4), or the ductus venosus. In such cases, pulmonary venous blood returns to the right atrium by way of the IVC. Type IV, or mixed TAPVR, comprises all mixed defects with connections at different levels.

According to most series, a supracardiac connection is the most common TAPVR variant (45% to 60%), whereas the cardiac and infracardiac types are encountered somewhat less frequently (15% to 30% each) and the mixed type is the rarest (5% to 10%). In general, the infracardiac variants of TAPVR are usually associated with significant obstruction of the anomalous draining vein due to the length of the venous channel and the resistance created in the hepatic portal system. Supracardiac variants are significantly obstructed approximately half of the time while cardiac variants rarely present with significant obstruction. Alternate classification systems have used the embryologic origin of the anomalous connection, the length
of the draining veins, and the degree of obstruction between the pulmonary venous and systemic venous pathways. The most complete system, proposed by Herlong and associates as part of the Congenital Heart Surgery Nomenclature and Database Project, describes the anatomic variant, the presence or absence of obstruction, and the type of obstruction (extrinsic or intrinsic compression). Whereas the majority of TAPVR cases are isolated anomalies, the lesion occasionally coexists with other cardiac and extracardiac congenital malformations. TAPVR, especially in autopsy series, has been diagnosed concomitantly with a variety of other acyanotic and cyanotic heart defects, including patent ductus arteriosus, valvular atresia and stenosis, ventricular septal defect, transposition of the great arteries, tetralogy of Fallot, double-outlet right ventricle, and common atrioventricular canal. In addition, there is a well-known association between TAPVR and the heterotaxy syndrome, which includes visceral heterotaxy, isomerism, dextrocardia, and splenic abnormalities (asplenia, polysplenia, hyposplenia). In some series, up to 30% of patients with TAPVR have heterotaxy syndrome.