The most common type of total anomalous pulmonary venous connection is –

Type I TAPVC with anomalous connection at the supracardiac level is the most common type accounting for about 45% of all cases. Total anomalous pulmonary venous connection Total anomalous pulmonary venous connection (TAPVC) is characterized by abnormal drainage of pulmonary veins into the right heart either by direct connection into the right atrium or into its tributaries. According to the site or level of connection of the pulmonary veins to the systemic venous system TAPVC has been classified into four types. Type 1(45%)               :                Anomalous connection at supracardiac level (Pulmonary veins drain into left irmonimate vein or SVC) Type II (25%)              :               Anomalous connection at cardiac level (Pulmonary veins joint the coronary sinus or enter right atrium directly) Tyep III (25%)              :             Anomalous connection at infracardiac level (Pulmonary veins drain into the portal vein)                                          Type IV (5%)              :                Anomalous connection at multiple levels