BackgroundThe purpose of this investigation was to compare the magnitude of change in myocardial perfusion and function during exercise with that obtained during total coronary artery occlusion. Radionuclide studies are widely used for the diagnosis and determination of prognosis in patients with suspected or known coronary artery disease. These studies are based on the premise that the relative deficit of coronary blood flow, which is induced by exercise and recognized as increased demand, relates to the jeopardy experienced by the decrease or sudden absolute interruption of coronary blood flow that is recognized as decreased supply and is associated with coronary stenosis or total coronary artery occlusion. The magnitude of exercise-induced perfusion and function abnormalities compared with those induced by total coronary artery occlusion in humans has not been previously reported.Methods and ResultsWe prospectively studied 20 patients with ≥50% diameter stenosis documented by quantitative coronary angiography in at least one vessel. A same-day rest/exercise sestamibi myocardial function and perfusion study was performed within 24 hours before percutaneous transluminal coronary angioplasty. At 1 minute after balloon inflation, while the vessel was occluded, sestamibi was injected, and a myocardial perfusion and function study was performed. Perfusion defect size was greater during occlusion (28±3%) than during exercise (13±2%) (P< .01). Ejection fraction was greater during exercise (53±3%) compared with values measured during occlusion (41±2%) (P< .01).ConclusionsPhysiological abnormalities induced by coronary occlusion are greater than those that occur during exercise, thereby indicating that stress-induced ischemia may not reflect the total potential myocardium in jeopardy from a stenotic lesion, if sudden occlusion occurs.