Effects of moderate coronary stenosis on myocardial flow reserve in man and in the dog

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Abstract
Summary The influence of coronary stenosis on resting blood flow (201Tl-uptake) and myocardial flow reserve (bicycle regometry) is studied in 18 patients with coronary disease. Severe coronary stenosis of 75–90% caused a reduced201T-u[pake both at rest and peak exercise. In contrast to this group patients with a 50–60% stenosis have a normal scintigram at rest but focal defects of201Tl-uptake at peak exercise. Results are compared with experimental data obtained after acute coronary constriction and simultaneous coronary dilatation (myocardial flow reserve, MFR) in 12 dogs. 60% coronary constriction causes a 37% decrease of poststenotic MFR measured with tracer microspheres. Changes of transmural flow distribution (endo/epi ratio) are minor in the left ventricular free wall but significant in the poststenotic septum (endo/epi=.84). It is concluded that even a moderate coronary stenosis of 60% not affecting resting blood flow becomes “critical” under conditions of high flow velocities.