Proposed mechanism for depression of maximal rate of left ventricular pressure fall (peak negative dP/dt) during regional myocardial ischemia.
To investigate the mechanism of the depression of left ventricular (LV) peak negative dP/dt during acute regional ischemia, studies were performed in seven open-chest anesthetized dogs. Regional LV wall thickness was measured with ultrasonic crystals in both an ischemic and a normally perfused segment. Ischemia was produced by complete occlusion of the left anterior descending coronary artery for 30 seconds. Within 10 seconds of ischemia, premature thinning of the ischemic wall developed, which preceded thinning of the normal LV wall by 100 +/- 20 msec. Premature thinning of the ischemic segment was associated with 29% reduction of peak negative dP/dt, a 29% prolongation of LV isovolumic relaxation time, and a 15% reduction of the LV systolic ejection period. We offer the following explanation for the depression of LV peak negative dP/dt. 1. Peak negative dP/dt is depressed as a result of a prolongation of the isovolumic relaxation time. 2. The isovolumic relaxation time is prolonged as a result of shortening of the systolic ejection period. 3. Shortening of the systolic ejection period is mediated by an early fall of LV systolic pressure caused by inability of the LV to sustain systolic pressure. 4. Inability of the LV to sustain systolic pressure is caused by premature thinning of the ischemic region during late systole.
D000818:Animals; D001011:Aorta / Q000503:physiopathology; D001794:Blood Pressure; D003326:Coronary Circulation; D003327:Coronary Disease / Q000503:physiopathology*; D004285:Dogs; D004562:Electrocardiography; D006352:Heart Ventricles / Q000503:physiopathology; D006439:Hemodynamics; D009200:Myocardial Contraction