Alterations in total and regional myocardial blood flow during acute rejection of orthotopic canine cardiac allografts

Using radioactive microspheres, we studied the quantitative and sequential distribution of myocardial blood flow during acute rejection of cardiac orthotopic allografts in 15 nonimmunosuppressed dogs. During rejection mean output per kilogram decreased 49 percent from control, stroke volume per kilogram decreased 40 percent, total left ventricular flow decreased 43 percent, and the subendocardial/subepicardial flow ratio (I/O) of the left ventricular free wall decreased 21 percent. Relative subendocardial hyperfusion occurred despite an increase in the ratio of left ventricle subendocardial supply (diastolic pressure-time index) to demand (tension-time index). The data indicate that total left ventricular flow decreases severely and selective left ventricular subendocardial ischemia develops very early during acute cardiac rejection.