Effects of moderate coronary stenosis on myocardial flow reserve in man and in the dog.
The influence of coronary stenosis on resting blood flow (201Tl-uptake) and myocardial flow reserve (bicycle ergometry) is studied in 18 patients with coronary disease. Severe coronary stenosis of 75--90% caused a reduced 201Tl-uptake 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 of 201Tl-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.
D000328:Adult; D000787:Angina Pectoris / Q000000981:diagnostic imaging; D000818:Animals; D003326:Coronary Circulation; D003327:Coronary Disease / Q000000981:diagnostic imaging / Q000503:physiopathology*; D003331:Coronary Vessels / Q000503:physiopathology; D004176:Dipyridamole / Q000494:pharmacology; D006321:Heart / Q000000981:diagnostic imaging; D006346:Heart Septum / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D005082:Physical Exertion; D011859:Radiography; D011877:Radionuclide Imaging; D014664:Vasodilation / Q000187:drug effects
D004176:Dipyridamole