Effect of diltiazem on pacing-inducing ischemia in conscious dogs with coronary stenosis: improvement of postpacing deterioration of ischemic myocardial function.
The effects of diltiazem on regional myocardial function were examined in conscious dogs subjected to rapid cardiac pacing during coronary arterial stenosis. Ultrasonic dimension gauges were implanted within the left ventricle for measurement of the control and ischemic segment lengths. During coronary stenosis, percent shortening in the ischemic segment decreased by 18 percent. Heart rate was then suddenly increased by rapid cardiac pacing and this resulted in a further reduction of ischemic segmental shortening. On cessation of pacing, there was early potentiation of rate of increase of left ventricular pressure (dP/dt) and of control segmental shortening with subsequent exponential decay in sequential beats. In the ischemic segment, percent shortening returned to the control level in the first postpacing beat, became severely depressed at 5 seconds after pacing and gradually returned to the control level over the subsequent 5 minutes. Twenty minutes after administration of diltiazem, cardiac pacing was repeated in the same manner and there was less marked potentiation of dP/dt of the first postpacing beat. There ws no significant change in the postpacing dimension and function of the control segment; however, in the ischemic segment, although shortening of the first beat after termination of the pacing was similar, the post stimulation deterioration of shortening was significantly improved, percent shortening being augmented from 7.4 to 10.6 percent at 5 seconds (p less than 0.05). These findings indicate that diltiazem exerts protective effects on the ischemic myocardium by promoting a rapid recovery from ischemia.
D000818:Animals; D001552:Benzazepines / Q000627:therapeutic use*; D002304:Cardiac Pacing, Artificial; D003327:Coronary Disease / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D003331:Coronary Vessels / Q000503:physiopathology; D004110:Diltiazem / Q000627:therapeutic use*; D004285:Dogs; D004562:Electrocardiography; D006339:Heart Rate; D009200:Myocardial Contraction / Q000187:drug effects
D001552:Benzazepines; D004110:Diltiazem