Immediate regional endocardial surface expansion following coronary occlusion in the canine left ventricle: Disproportionate effects of anterior versus inferior ischemia

The exact time of onset of functional expansion after acute myocardial infarction/ischemia remains unclear in spite of its potential link to chronic pathologic infarct expansion and its potential implications for therapy. To examine this early change in ventricular morphology, 14 open-chest dogs were studied with two-dimensional echocardiography before and after occlusion (10 minutes) of the left anterior descending coronary artery (LAD, n=7) or circumflex artery (CIRC, n=7). The endocardial surface area (ESA) and the area of abnormal wall motion (AWM) were reconstructed from the echocardiographic data using a previously reported technique for quantitatively mapping the ESA and extent of AWM. For the total group (N = 14), the mean ESA before occlusion was 48.9 ± 9.8 cm², increasing to 65.7 ± 18.9 cm² at 10 minutes occlusion (p < 0.001). For the LAD subgroup, the mean ESA before occlusion was 50.7 ± 9.3 cm², increasing to 79.1 ± 14.1 cm² at 10 minutes following occlusion (p < 0.001). For the CIRC subgroup, the mean ESA before occlusion was 47.1 ± 10.8 cm², increasing to 52.3 ± 12.6 cm² at 10 minutes after occlusion (p < 0.001). The ESA increase for the LAD subgroup was significantly larger than that of the CIRC subgroup (LAD range 14.5 to 49.9 cm² versus CIRC range 1.5 to 9 cm², p < 0.0001). Coronary occlusion resulted in similarly sized regions of AWM for both subgroups (LAD, 31.3 ± 12.2 cm² versus CIRC, 25.9 ± 10.3 cm², p = n.s.). For the LAD group, the largest increase in endocardial circumference occurred within the zone of AWM at the apex (39.9 ± 12%). The endocardial surface area therefore expands immediately after coronary occlusion and the magnitude of this process is primarily related to the site (anteroapical) rather than to the extent of AWM.