Atypical pulmonary venous drainage pathway associated with infracardiac total anomalous pulmonary venous connection: report of a case.

Darling's classification for total anomalous pulmonary venous connection (TAPVC) is based only on the level of the site of drainage of the anomalous pulmonary veins (PVs) to the systemic venous circulation. Although it is a clinically useful classification, atypical course of the PVs is occasionally encountered as well. We report a case of infracardiac-type TAPVC in which the left upper PV traversed the posterior mediastinum and merged into the right PVs at the right hilum. The combined vein coursed medially and caudally, meeting the left lower PVs, and finally penetrated the diaphragm; the pulmonary venous drainage formed a shape of "C." Despite definitive diagnosis according to Darling's classification, sometimes atypical course of the PVs do exist. Echocardiography may not be adequate for atypical cases. Contrast-enhanced computed tomography may be recommended in stable patients where an atypical course is suspected.