The aetiology of non-exertional angina pectoris

The occurrence of angina pectoris while at rest, although long recognized, has not been satisfactorily explained. In the non-exertional attacks studied there was an increase in heart load, as estimated by the product of heart rate and systolic pressure. Angina occurred when the load exceeded a critical level. Recumbency was associated with 94% of non-exertional attacks; 58% followed a meal; in 54% both factors were present. It is suggested that recumbency causes an increase in heart load because of expansion of blood volume by transfer of fluid from interstitial spaces, and that a meal does so because of digestive activity.