Global cardiac remodeling after acute myocardial infarction: a study in the rat model

Infarct expansion, regional dilation and thinning of the infarct zone, occurs within 1 day after myocardial infarction. Whether the early change in regional shape of infarct expansion affects the architecture of remote normal regions is unknown. To study this question, 45 rats with a transmural infarct were killed at 1, 2 and 3 days after infarction and their hearts were examined for infarct size and extent of expansion. Wall thickness and radius of curvature were measured within, adjacent to and remote from the infarct zone. Equivalent regions were analyzed in eight control hearts. The extent of disproportionate wall thinning and increased radius of curvature within the infarct zone of hearts with expansion was not dependent on infarct size. Significant wall thinning and increased regional radius of curvature were also seen in adjacent and remote regions of the hearts with expansion (p less than 0.001). These structural changes outside of the infarct occurred independent of infarct age and size, and were not seen in hearts without infarct expansion. Thus, when disproportionate thinning and dilation occur in the infarct region, they are accompanied by a distortion in shape of the entire heart including remote normal myocardium. This remote remodeling of noninfarcted myocardium correlates with extent of expansion, but not with age or size of the infarct.