Four pulmonary veins carrying oxygenated blood drain into the left atrium via 4 pulmonary ostia, 2 on either side. Variations in the number of pulmonary veins and their drainage pattern are seen in 36% of normal population, and have gained importance recently, because the ectopic beats that originate in the pulmonary ostia, act as triggers for cardiac arrhythmias. This happens due to the fact that the pulmonary veins receive extensions of myocardial sleeves from the left atrium. Atrial fibrillation is the commonest cardiac arrhythmia and is controlled by drugs, but in cases where medicaments fail, radiofrequency ablation is the treatment of choice, for which a thorough knowledge of number of pulmonary veins and their openings is essential. Hence this study was undertaken to evaluate the variations in number of pulmonary veins and their drainage pattern, and comparing the same with previous studies. We studied 60 formalin fixed hearts and found variations in 13 hearts, out of which 5 hearts showed bilateral variations. The commonest variation in drainage pattern on the right side was 3 pulmonary veins with 3 pulmonary ostia seen in 10 cases and on the left side it was 1 pulmonary vein with 1 pulmonary ostium seen in 13 cases. These variations are congenital and are due to the complex development of the venous system. The knowledge of these variations is of immense importance to radiologists and cardio-thoracic surgeons for various diagnostic and therapeutic methods in the treatment of atrial fibrillation.

Keywords: Pulmonary Vein; Pulmonary Ostia; Left Atrium; Atrial Fibrillation.