Influence of site and size of the area at risk in acute ischemic mitral regurgitation

Abstract

Background In order to examine the influence of ischemic zone site and size on mitral regurgitation, we performed transesophageal two-dimensional echo and color flow Doppler in nine closed-chest anesthetized dogs. Methods The left anterior descending (LAD) and left circumflex (LCX) coronary arteries were each occluded for 3 minutes in random order, with 60 minutes of reperfusion between the two occlusions. Areas at risk were 25.7% ± 7.1% and 30.9% ± 8.1% of the left ventricle for LAD and LCX occlusions, respectively (P is not significant), as assessed by postmortem staining of the perfusion bed. Results The size of the temporally averaged mitral regurgitant color flow area was larger after LCX and LAD occlusion (1.1 ± 2.6 cm2 versus 0.5 ± 0.2 cm2; P<0.05). These differences could not be explained by differences in left atrial or ventricular dimensions or pressures. Linear regression analysis failed to reveal a significant relation between the size of the area at risk and color flow area for either LAD or LCX occlusion. Conclusions Thus, in this canine model of coronary occlusion, the magnitude of acute mitral regurgitation is dependent on the ischemic zone site but not on the size of the ischemic area at risk.