Hemodynamic Predictors of Myocardial Oxygen Consumption During Static and Dynamic Exercise

Hemodynamic predictors of myocardial oxygen consumption (MVO2) during static and dynamic exercise were examined in ten normal subjects. Studies were done under the following circumstances: 1) during upright bicycle exercise at an average heart rate of 147 beats/min, 2) during static exercise with an isometric load in the left hand equal to 17% of the maximal voluntary contraction (MVC), and 3) during combined dynamic exercise (average heart rate 147 beats/min) and static exercise using 17% MVC of the left hand. Mean myocardial blood flow (MBF) was 181 ml/100 gm LV/min during dynamic exercise, 98 ml/100 gm LV/min during static exercise, and 201 ml/100 gm LV/min during combined static and dynamic exercise. Addition of a static load to the dynamic load resulted in a higher blood pressure (average 12 mm Hg), MVO2 and MBF than during dynamic exercise alone. MVO2 correlated best with products of heart rate and blood pressure regardless of whether the blood pressure was obtained by a central aortic catheter (r = 0.88) or by a blood pressure cuff (r = 0.85).When the current data were combined with previous data, 82 determinations of MVO2 and MBF in 29 normal subjects during several levels of upright exercise were available for analysis. Forty-four determinations were done during dynamic upright exercise, 18 during exercise after propranolol, ten during combined static and dynamic work, and ten during static work alone. MVO2 correlated best with the product of heart rate and blood pressure (r = 0.86). Heart rate alone correlated better with MVO2 (r = 0.82) than did the tension time index (r = 0.65) or the product of systolic blood pressure, heart rate, and ejection time (r = 0.68). The readily measured variables of heart rate and of heart rate × blood pressure correlated well with MVO2 in normal young men during exercise under a wide variety of circumstances.