The Influence of Changes in Blood Volume on Angina Pectoris

Angina pectoris was precipitated in 15 patients with coronary artery disease by the technic of right atrial pacing. This was accompanied by hemodynamic evidence of impaired left ventricular function. In eight patients, while pacing was continued, a phlebotomy averaging 276 ml was carried out and in all but one patient angina was relieved and ventricular function returned to normal. Phlebotomy was accompanied by a decline in cardiac index (9.6%) and left ventricular filling pressure, but no change in brachial artery mean pressure, tension-time index, or dp/dt. With reinfusion of blood, angina returned in all but one patient and there was a rise in left ventricular end-diastolic pressure but no change in cardiac index, brachial artery pressure, tension-time index, or dp/dt. In seven patients alterations of blood volume were carried out between three 9-minute periods of atrial pacing and similar observations were obtained. The observations indicate that phlebotomy exerted its beneficial effect through a reduction in left ventricular volume, and it is suggested that this may be the primary mode of action of nitroglycerin.