Maximal cardiac output during upright exercise: Approximate normal standards and variations with coronary heart disease

The observed normal ranges for age- and weight-adjusted maximal oxygen uptake and age-adjusted maximal heart rate measured during the Bruce protocol are shown for 99 normal sedentary men. On the basis of observations in 10 normal men, the relation between oxygen uptake and cardiac output (measured with the direct Fick principle) was used to estimate normal limits of maximal cardiac output and stroke volume for the 99 normal sedentary men. These normal standards were then used to evaluate the results of 77 studies in patients with coronary heart disease who had various clinical and angiographic findings and who performed symptom-limited upright exercise while cardiac output was measured using the direct Fick principle. Patients with angina and infarction showed the greatest impairment of age- and weight-adjusted maximal oxygen uptake and age-adjusted maximal cardiac output, maximal heart rate and maximal stroke volume when compared with patients with angina or healed infarction alone. Arterial-mixed venous oxygen difference at maximal exercise was comparable in the three groups. The surgical cohort (studled after aortocoronary vein bypass grafting) had significantly higher maximal heart rates. Patients with an ejection fraction of less than 50 percent had significantly impaired age-adjusted maximal cardiac output and stroke volume.