Effect of exercise intensity and duration on regional function during and after exercise-induced ischemia.

BACKGROUNDTransient reversible myocardial dysfunction has been documented after episodes of exercise-induced ischemia. This study was undertaken to determine whether the duration or intensity of exercise affects the severity of postischemic dysfunction in this setting.METHODS AND RESULTSTen dogs were instrumented with ultrasonic microcrystals for measurement of wall thickening, with circumflex coronary artery flow probes, and with hydraulic occluders. Dogs performed low-intensity exercise, which was sufficient to increase coronary perfusion 50% above control, and high-intensity exercise, which was sufficient to double coronary blood flow. To investigate the effects of exercise intensity on postischemic dysfunction, we had dogs perform high-intensity exercise for 5 minutes in the presence of a stenosis. On the alternate day, dogs performed low-intensity exercise for 10 minutes in the presence of a stenosis. These two protocols provide equivalent coronary flow debts. Mean transmural blood flow during high-i...