CORONARY HEMODYNAMICS DURING ISOMETRIC HANDGRIP AND ATRIAL-PACING IN PATIENTS WITH ANGINA-PECTORIS COMPARED TO HEALTHY-MEN

The responses in coronary blood flow and the relative myocardial extra ction of oxygen to atrial pacing (causing mainly an increase in heart rate) and isometric handgrip (causing mainly an increase in pressure) were studied in patients with angina and in young and middle-aged heal thy men. The myocardial extraction of oxygen and coronary sinus flow w ere measured by catheterizing the coronary sinus, using a catheter wit h thermistors for the measurement of flow by thermodilution and electr odes for a trial pacing. In the healthy men the increase in the consum ption of oxygen was covered entirely by an increased coronary blood fl ow during both provocations, with no change in the arteriovenous oxyge n difference during handgrip and a decrease during pacing. There was n o significant difference in the reaction between younger and older men . In the patients with angina the increased consumption of oxygen duri ng pacing was covered by an increased coronary blood flow with an unal tered arteriovenous oxygen difference, while during handgrip both the coronary blood flow and arteriovenous oxygen difference increased. It is concluded that during handgrip, compared to the artificial increase in heart rate, the myocardium is more dependent upon an increased rel ative extraction of oxygen to cover an increase in the requirement for oxygen. This may be due to a higher intramyocardial pressure. Patient s with coronary heart disease are more dependent than healthy men on a n increase in the relative myocardial extraction of oxygen. This may b e related to a lower effective perfusion pressure because of the coron ary arterial obstructions or to an increased intramyocardial pressure and a relatively shorter duration of diastole because of the impaired cardiac function.