Coronary hemodynamics during isometric handgrip and atrial pacing in patients with angina pectoris compared to...

The responses in coronary blood flow and the relative myocardial extraction 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 healthy men. The myocardial extraction of oxygen and coronary sinus flow were measured by catheterizing the coronary sinus, using a catheter with thermistors for the measurement of flow by thermodilution and electrodes for atrial pacing. In the healthy men the increase in the consumption of oxygen was covered entirely by an increased coronary blood flow during both provocations, with no change in the arteriovenous oxygen difference during handgrip and a decrease during pacing. There was no significant difference in the reaction between younger and older men. In the patients with angina the increased consumption of oxygen during pacing was covered by an increased coronary blood flow with an unaltered 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 relative extraction of oxygen to cover an increase in the requirement for oxygen. This may be due to a higher intramyocardial pressure. Patients with coronary heart disease are more dependent than healthy men on an increase in the relative myocardial extraction of oxygen. This may be related to a lower effective perfusion pressure because of the coronary arterial obstructions or to an increased intramyocardial pressure and a relatively shorter duration of diastole because of the impaired cardiac function.