We have recently developed an animal model of gradual occlusive coronary artery disease instrumented to allow quantitative evaluation of extent of ischemia in terms of regional mechanical function. We propose to extend this model to include measurement of coronary artery flow and regional myocardial perfusion during gradual occlusion. With this model we propose to (a) test the hypothesis that repeated episodes of reversible ischemia prompt collateralization, (b) determine the relationship between duration of ischemia and infarct development under partial perfusion conditions, and (c) characterize the nature of ischemic episodes occurring spontaneous activities (simulated angina pectoris). These studies will provide new knowledge regarding the pathophysiological natural history of gradual coronary artery occlusion and will provide a firm basis for experimental evaluation of interventions thought to modify the development and reversibility of myocardial ischemia.