Totally Anomalous Pulmonary Venous Connection Incidence and Etiology At the turn of the seventeenth century Wilson2 described a “monstrous formation of the heart in which the superior caval vein was joined by a trunk formed by two large veins coming out of the lungs.” We now know that the various forms of such totally anomalous pulmonary venous connections (TAPVCs) in the absence of isomerism of the atrial appendages or visceral heterotaxy accounted for 1 out of every 40 patients registered in the New England Regional Infant Cardiac Program.3 As such, the entity ranked 12th in frequency and occurred once in 17,000 live births In the Baltimore-Washington Infant Study, the malformation was encountered less commonly, accounting for 1.5% of all patients with a cardiovascular malformation and being seen once in 14,700 live births.4 TAPVC is known to be part of the Holt-Oram, Klippel-Feil, phocomelia, and Schachenmann syndromes.5 It is more difficult to establish the incidence of partially anomalous pulmonary venous connection, since anomalous connection of a solitary vein (Fig 28.1) may be unrecognized either in life or death Such anomalies have been reported in about 1 in 200 routine postmortems.6,7 Furthermore, in an extensive investigation based on surgical and autopsy experience, seven-tenths of all cases of anomalous pulmonary venous connection were found to be of the partial variety, although this review included patients with isomerism of the atrial appendages.8 FIG 28.1 Anomalous connection of the right upper pulmonary vein to the superior caval vein (SCV), which was discovered as an incidental finding in an otherwise normal autopsy Earlier reports on TAPVC stressed the preponderance of males in the setting of infradiaphragmatic drainage,5 with an equal mix of gender in the remaining types In those recorded in the New England Regional Infant Cardiac Program,3 however, two-thirds with supracardiac and cardiac connections were males, whereas it was the infradiaphragmatic variant that showed an equal mix of genders As with so many lesions, there are some examples of familial clustering,9 with one report10 suggesting autosomal dominant inheritance Some evidence suggesting maternal exposure during the first 3 months of pregnancy to teratogens emerged from the Baltimore-Washington Infant Study.4 Reanalysis of that dataset in 200411 found the association with maternal exposures inconclusive but identified a link between totally anomalous connection and paternal exposure to lead prior to conception Anatomy Anomalous pulmonary connections take various forms and show several important clinical features The first important feature is the proportion of the pulmonary venous drainage that is connected to sites other than the morphologically left atrium This can be a solitary pulmonary vein, all of the veins from one lung, or the entirety of the pulmonary venous drainage (Fig 28.2) Combinations are also possible when all veins do not drain anomalously, so although rare, it can be possible for all of the drainage from one lung and a solitary vein from the other lung to be connected to sites other than the morphologically left atrium Once it has been established that a pulmonary vein or pulmonary veins are draining anomalously, it is of equal importance to determine the site of drainage and whether all the veins drain to the same site It is necessary to seek stenotic areas or regions along the route of anomalous drainage It is also necessary to establish whether the anomalous pulmonary venous connection is an isolated malformation or part of a more complex anomaly and whether there are associated structural malformations of the pulmonary vasculature FIG 28.2 Possibilities for anomalous connection of the pulmonary veins Before discussing these important anatomic variables in more detail, use of