Resting arteriovenous oxygen difference and exercise cardiac output

Measurements of the cardiac output utilizing the classical Fick method were carried out in 38 cardiac patients at rest and during exercise. The predicted cardiac output during exercise was calculated by the regression equation derived by Donald et al. ( Clin. Sci. 14: 37, 1955), relating cardiac output to oxygen consumption during the steady state of exercise in normal subjects (cardiac index = 3.708 + 0.00534 x O2 consumption, ml/min m2). The resting arteriovenous oxygen difference was found to correlate much better with the calculated percentage of predicted cardiac index during exercise (γ = 0.547) than did the resting cardiac index (γ = 0.304). The finding of an arteriovenous oxygen difference greater than 5.16 ml/100 cc indicated a strong probability of subnormal cardiac index during exercise relative to the oxygen consumption. Submitted on June 18, 1962