MEDICINE OF THE MONTH
Left Atrium: Pulmonary Vein Variations and Their Drainage Pattern
Pulmonary veins carry oxygenated blood from the lungs to the left atrium. Variations are quite common in the number and pattern of drainage. It plays an important role in generating atrial fibrillation. During the development of left atrium, a single embryonic pulmonary vein develops as an outgrowth from its posterior wall. On further development, the pulmonary veins and its branches are incorporated into the left atrium. At the end of the embryonic period independent four pulmonary veins drain into left atrium. In the initiation and maintenance of atrial fibrillation pulmonary veins and posterior part of left atrium play a critical role. Depending upon the number of pulmonary veins they are classified into type A to type D.