Does the Extent of the Zone at Risk after Coronary Artery Occlusion Influence the Percentage of the Zone that Evolves to Infarction?

Abstract

To examine whether the extent of the zone at risk for infarction after coronary artery occlusion influences the percentage of the zone that evolves to necrosis in the absence of intervention, ^99mTc-labeled albumin microspheres were injected into the left atrium 1 min after coronary occlusion in 34 dogs. Six hours after occlusion, the left ventricle was cut into 3-mm-thick slices for triphenyltetrazolium chloride staining and autoradiography. The extent of myocardial necrosis and hypoperfused zone was measured by planimetry and expressed as a percentage of the total volume of the left ventricle. The extent of myocardial necrosis and hypoperfused zone varied widely from 8 to 40% and 14 to 43% of the left ventricle, respectively. However, there was a close correlation between infarct size (IS, percent of left ventricle) and the extent of hypoperfused zone (HZ, percent of left ventricle): IS = 0.89x (HZ) – 0.21 (r = 0.909, SEE = 3.02, p < 0.01). The ratio of infarct size to the extent of hypoperfused zone was 87.9 ± 2.3%. Dogs with large hypoperfused zones (≧ 30% of the left ventricle) had a significantly greater ratio of infarct size to the extent of the hypoperfused zone (95.3 ± 2.4%, n = 11, p < 0.05) than dogs with small hypoperfused zones ( < 30% of the left ventricle; 84.3 ± 3.0%, n = 23). Moreover, the ratio was ≧ 90% in all but one dog (91 %) with large hypoperfused zones, but in only 10 of 23 dogs (43%) with small hypoperfused zones (p < 0.05). Thus, the extent of hypoperfused zone was a major determinant of infarct size after coronary artery occlusion. The extent of the zone at risk for infarction after coronary occlusion also influenced the percentage of the zone with necrosis.