In 1951 in our laboratory in Stockholm, we successfully used our experimental pump oxygenator: the first dogs survived 40 minutes of total cardiopulmonary bypass with right ventricular cardiotomy. In the same year extracorporeal circulation was combined with hypothermia (26 degrees to 28 degrees C) to allow lower perfusion flows, thus diminishing blood trauma and the risk of perfusion complications. To avoid air emboli during cardiotomies, the heart was "arrested" with electrically induced ventricular fibrillation (1952). Our standard perfusion technique used cooling and rewarming with left ventricular bypass, the oxygenator was used only during intracardiac manipulations and when the right ventricle was unable to maintain a sufficient pulmonary circulation. Left ventricular bypass was continued until normal body temperature was reached and the heart could be weaned off the pump. In July 1954 we successfully extirpated a left atrial myxoma in our first patient undergoing open heart surgery, a 40-year-old woman, who is still alive today. Other successful applications of open heart surgery involved resection of a huge left ventricular aneurysm after infarction in 1955, correction of supracardiac total anomalous venous return in 1956, and the first hemodynamic correction of transposition of the great arteries by atrial switch method in 1958. Also in 1958, the first totally implantable pacemaker was inserted in a patient with total atrioventricular block to eliminate the infections that occurred along the percutaneous pacemaker leads. In October 1958, we also operated on a patient with severe angina pectoris with stenosis of the left anterior descending and circumflexed arteries and occluded right coronary artery. Endarterectomy of the left coronary arteries was performed, and the arteriotomies were repaired with saphenous vein patches.