Enhancement of ventricular gradient variability during acute myocardial ischemia

We evaluated the influence of local myocardial ischemia induced by experimental coronary stenosis on the ventricular gradients (VGs) and determined whether changes of VG were related to the alterations of monophasic action potentials (MAPs). The coronary flow was reduced to 50% in the left anterior descending coronary artery for 30 min in nine dogs. The VG and MAP of consecutive heartbeats over a 20-s interval were obtained from McFee and Parungao body surface leads and a suction electrode on the ischemic and non-ischemic regions. The coefficients of variation of VG and MAP parameters were calculated as indices of variability. The coefficients of variation of the VG magnitude and the MAP area in the ischemic region were greater at 5 min after partial occlusion than in the control period (P<0.05, P<0.01, respectively). There was a significant correlation between the coefficient of variation of the VG magnitude and the coefficient of variation of the MAP area in the ischemic region (r=0.707, P<0.0001) but not in the non-ischemic region. VG variability was enhanced during acute regional ischemia of the ventricular myocardium. VG variability may be caused by enhanced electrical alteration of the MAP in ischemic myocardium.