Progressive left ventricular remodeling and apoptosis late after myocardial infarction in mouse heart

We tested the hypothesis that left ventricular (LV) remodeling late after myocardial infarction (MI) is associated with myocyte apoptosis in myocardium remote from the infarcted area and is related temporally to LV dilation and contractile dysfunction. One, four, and six months after MI caused by coronary artery ligation, LV volume and contractile function were determined using an isovolumic balloon-in-LV Langendorff technique. Apoptosis and nuclear morphology were determined by terminal deoxynucleotidyl transferase-mediated nick end-labeling (TUNEL) and Hoechst 33258 staining. Progressive LV dilation 1-6 mo post-MI was associated with reduced peak LV developed pressure (LVDP). In myocardium remote from the infarct, there was increased wall thickness and expression of atrial natriuretic peptide mRNA consistent with reactive hypertrophy. There was a progressive increase in the number of TUNEL-positive myocytes from 1 to 6 mo post-MI (2.9-fold increase at 6 mo; P< 0.001 vs. sham). Thus LV remodeling late post-MI is associated with increased apoptosis in myocardium remote from the area of ischemic injury. The frequency of apoptosis is related to the severity of LV dysfunction.