Differentiation of Interatrial

THE 4 forms of interatrial comnmunication -ostium secundum, ostium primum, common atrium, and total anomalous pulmonary venous connection-are associated with clinical symptoms and signs and radiologic, electrocardiographic, anid physiologic features that permit proper differential diagnosis in most instanees. The usual type of atrial septal defect, ostium secundum, is by far the most common form of interatrial communication, and it is one that can be repaired by several different satisfactory surgical technics. Ostium primum defects (partial form of common atrioventricular canal), total anomalous pulmonary venous coninection, and commoni atrium are examples of less common forms of communication between the atria and require open cardiotomy with the use of extracorporeal circulation for satisfactory surgical treatment. Accuracy of diagnosis is, therefore, of practical importance for selection of patients for operation.