Exercise-training is used widely in the rehabilitation of patients with ischemic heart disease (ISCHD). However, it is not clear whether myocardial blood supply (as opposed to a peripherally mediated decrease in the work load and O2 requirement of the heart) can be improved by exercise-training in patients with ISCHD. The objective of our research is to determine whether 12 months of exercise-training of progressively increasing duration, intensity and frequency can improve blood supply to underperfused regions of myocardium in patients with ISCHD. The most important of the methodological approaches we are using to achieve this goal are: a) Radionuclide ventriculography with technetium-99m. To evaluate the effect of training on myocardial blood supply, we use radionuclide ventriculography to determine the responses of the ejection fraction to dynamic and isometric exercise tests. Exercise in the tests performed after 12 mo. of training is adjusted to result in the same, or higher, heart rate x systolic blood pressure (RPP) as was attained prior to training. We interpret a significant improvement in the response of ejection fraction to exercise that elicits the same RPP, and a decrease or normalization of exercise-induced wall motion abnormalities as evidence for an improvement in myocardial blood supply. b) Exercise electrocardiography. In our electrocardiographic evaluation of the effect of exercise-training on myocardial oxygenation, we are determining the RPP threshold for ST depression. c) Myocardial perfusion imaging with thallium-201. Our approach is to obtain exercise and resting 201T1 scans before and after 12 mo. of exercise-training. We interpret the absence, or clear cut reduction in size, after training, of an exercise-induced perfusion defect that was present before training as evidence of an improved myocardial blood supply (but only if there are concomitant improvements in work capacity, VO2max and exercise electrocardiogram). d) plasma catecholamine concentrations at RPP threshold for ST depression and at maximum exercise. Higher catecholamine levels together with a higher RPP are being interpreted as evidence for an increased myocardial O2 requirement, e) 24 hr. Holter monitoring to evaluate the frequency of ventricular arrhythmias.
