Ventricular remodeling after myocardial infarction.

Acute transmural myocardial infarction initiates a series of changes in left ventricular (LV) volume, regional function and geometry. This process, known as post-infarction LV remodeling, may continue for months or years following the initial ischemic event. To characterize the components of late ventricular remodeling, biplane left ventriculography was performed in 52 patients at 3 weeks and repeated at 1 year after first anterior myocardial infarction. Biplane circumference and contractile and noncontractile segment lengths were measured. Global geometry was evaluated by calculating a sphericity index and regional geometry was assessed by measurement of endocardial curvature. End-diastolic (ED) volume was increased at 3 weeks and enlarged further at one year. This late enlargement was accompanied by an increase in the length of the contractile segment and an increase in sphericity, whereas the length of the noncontractile segment decreased. Curvature analysis revealed that this late increase in sphericity resulted from flattening of regions of presumably high tension negative curvature at the infarct border zone and from less bulging of the infarcted anterior wall. Even in patients selected for late ventricular enlargement (change in ED volume > 20 ml, n = 19), this increase in volume resulted from both lengthening of the contractile segment and an increase in sphericity without a change in the noncontractile segment length. Thus, late ventricular enlargement after anterior myocardial infarction results from an increase in contractile segment length and a change in ventricular geometry and is not a result of progressive infarct expansion.