Effect of oxygen breathing on pacing-induced angina pectoris and other manifestations of coronary insufficiency.

Eleven patients with arteriographically confirmed coronary artery disease and normal arterial oxygen saturation were studied. The angina threshold was determined first by successive elevation of heart rate at increments of 10 and 5 beats/min by right atrial pacing while the patients were breathing air via a close-fitting mask. The mask was then connected to an oxygen tank without the patient's knowledge. After 5 min of oxygen breathing, the heart rate was again raised to the previously determined threshold level. In nine of 11 patients angina did not recur. The absence of angina