Regional left ventricular wall thickness early and late after coronary occlusion in the conscious dog

Regional wall thickness and endocardial segment lengths in normal and ischemic zones of the left ventricle were measured simultaneously with ultrasonic-dimension gauges before and after chronic circumflex artery occlusion in conscious dogs. After 3 wk, end-diastolic segment lengths (EDL) in normal zones increase 10% (P less than 0.01), shortening increased 22% (P less than 0.05), and end-diastolic wall thickness (EDWT) was reduced by 12.8% (P less than 0.01). In ischemic zones at 3 wk, EDL was reduced by 15.4% (P less than 0.01), and subendocardial shortening recovered slightly to 15% of control; EDWT increased 11% at 3 days postocclusion and thereafter remained near control values (change not significant), but systolic wall thickening improved substantially, reaching 38% of control at 3 wk. Thus, tissue loss and slight return of function occurred in the ischemic subendocardium, whereas overall wall function (as reflected by regional wall thickening) improved considerably over time. These findings suggest that recovery of function in the outer layers of the wall after myocardial infarction modifies the close correlation between regional subendocardial segment and wall thickening dynamics observed acutely.