Cellular mechanisms of myocardial infarct expansion.

Abstract

Infarct expansion is acute regional dilatation and thinning of the infarct zone. There are several possibilities for the mechanism of this alteration in cardiac shape: thinning could be caused by 1) cell rupture, 2) a reduction in the intercellular space, or 3) stretching of myocytes or 4) slippage of groups of myocytes so that less cells are distributed across the wall. To determine the relative contributions of these cellular mechanisms of wall thinning and dilatation, detailed study of transverse histological sections of rat hearts with infarct expansion was performed 1, 2, and 3 days after coronary ligation. The number of cells across the wall was determined in six regions within, adjacent to, and remote from the infarct. Cell counting was performed so that the total number of cells across the wall and the number of cells per unit length (cell density) across the wall were determined. The transmural cell count and the cell density were correlated with the wall thickness in each region. Myocyte cross-s...