Relation between aerobic capacity and extent of myocardial ischemia in patients with normal cardiac function

The relation between aerobic capacity and extent of exercise-induced myocardial ischemia has not been investigated. Fifty patients with coronary artery disease (>/=50% stenosis) without myocardial infarction underwent cardiopulmonary exercise testing followed by quantitative thallium perfusion imaging. Results were compared with those of age- and sex-matched healthy controls with a low likelihood of coronary artery disease. Patients with Q-wave infarction, pulmonary disease, and peripheral vascular disease were excluded. Cardiopulmonary exercise testing and thallium perfusion imaging parameters were correlated for extent of global ischemia, occurrence of increased pulmonary thallium uptake, and transient ventricular dilatation during exercise.

Patients with global ischemia <20% (group 1, n = 25) had normal cardiopulmonary exercise testing results, similar to the control group, except for workload and maximal predicted heart rate, which were reduced. However, patients with ischemia >/=20% (group 2, n = 25) had poor cardiopulmonary exercise testing results compared with the controls. The ventilatory anaerobic threshold showed the most significant decrease of all cardiopulmonary exercise testing parameters (48% +/- 6% vs 57% +/- 6%, P <.0001), and it was the only parameter to correlate with extent of ischemia (r = -0.5; P <.003) as well as frequency of increased pulmonary uptake and transient ventricular dilatation (r = -0.33, P =.03).

Ventilatory anaerobic threshold is significantly related to extent of myocardial ischemia and signs of heart failure during exercise. However, patients with mild to moderate exercise-induced ischemia may have normal cardiopulmonary exercise testing performance.