Experimental myocardial ischemia. IV. Shape and volume changes during "isolvolumetric relaxation" in normal and ischemic ventricles.
Shape and volume changes were studied in mongrel dogs between end-systole and mitral valve opening (MVO). Biplane left ventricular cineangiograms were performed at 200 frames/sec. The dogs were studied during the control state and during regional myocardial ischemia produced by balloon occlusion of the left anterior descending coronary artery. Outward wall motion, called pre-inflow relaxation (PIR), occurred in all 10 dogs in the control state, most frequently in the apical (seven of 10) and equatorial planes (seven of 10). PIR was seen less frequently during ischemia (13 of 40 measurements vs 19 of 40 measurements during control state), usually in the basal plane (five of 10). The ventricular volume between end-systole and MVO increased in all 10 dogs during the control state (mean increment 4.4 +/- 0.7 ml). Volume increased in eight of 10 dogs during ischemia (mean increment 3.0 +/+ 1.1 ml). The characteristic patterns of wall motion occurring between end-systole and MVO are altered by regional myocardial ischemia. During ischemia PIR occurs in segments of the myocardium with normal perfusion, but usually not in ischemic segments. Biplane ventricular volume between end-systole and MVO increased in 18 of 20 measurements (mean increment 3.6 +/- 0.9 ml).
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