Diffuse subendocardial ischemia can be produced experimentally in dogs and sheep with normal coronary arteries. This ischemia occurs whenever the area between the aortic and left ventricular diastolic pressures per minute (DPTI) falls much below the area beneath the left ventricular pressure curve in systole per minute (SPTI); DPTI represents available supply of blood to the left ventricular subendocardial muscle while SPTI represents the needs of the left ventricular muscle for oxygen. When the ratio DPTI/SPTI was reduced by supravalvar aortic stenosis, tachycardia, arteriovenous fistula or isoproterenol infusion, subendocardial blood flow was reduced below subepicardial blood flow, there was a decrease in phasic diastolic coronary blood flow and ischemic changes were seen in the electrocardiogram.
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