A model of acute regional myocardial ischemia and reperfusion in the rat.

Studies were conducted in 76 rats to describe and validate a new closed-chest in vivo model for acute ischemia and reperfusion of the left coronary artery. Radiolabeled microsphere distribution in six rat hearts confirmed a significant reduction in arteriolar flow at the center of the ischemic zone (93% reduction of total myocardial counts compared to nonischemic region, P less than 0.01) after 7 min of occlusion. Arteriolar flow returned to control values upon reperfusion. While hemodynamic parameters in 10 rats during 7 min of occlusion and 7 min of reperfusion were monitored, end diastolic pressures increased significantly (P less than 0.01) during occlusion. Finally, the utility of this rat model was demonstrated in a study of contrast enhanced magnetic resonance imaging (N = 4). Normal myocardium could not be differentiated from acutely ischemic myocardium on noncontrast-enhanced MR images. After 5 min of myocardial ischemia and following contrast administration (albumin-Gd-DTPA), the ischemic zone appeared less enhanced than normal myocardium. Upon release of the occluder the left ventricular free wall once again yielded a homogeneous signal similar to that of the normal myocardium.