Left Ventricular Remodeling is Less While Left Atrial Remodeling is Greater in Inferior Compared to Anterior Myocardial Infarction: Importance of Ischemic Mitral Regurgitation

Background. Left ventricular (LV) remodeling is greater in patients with anterior myocardial infarction (MI) compared to those with inferior MI. Left atrial (LA) remodeling is expected to have influences from both LV remodeling and mitral valve dysfunction or mitral regurgitation (MR), which is more frequent in inferior MI. Therefore, LA remodeling may not necessarily be less in inferior MI compared to anterior MI. The purpose of the study is comparison of LV and LA remodeling in patients with anteroseptal and inferior MI with or without MR.Methods. In 61 consecutive patients with prior anterior MI, 33 with prior inferior MI, and 22 normal control subjects, LV and LA volumes were measured using biplane Simpson's method, and MR fraction was quantified by Doppler echocardiography.Results. Although patients with inferior MI had significantly less LV dilatation (LV end-diastolic volume: 91±11 vs. 125±45 vs. 106±19 ml, control vs. anterior vs. inferior, p<0.01) and reduction in LV ejection fraction (63±6 vs. 44±7 vs. 49±8 %, p<0.01), their LA dilatation was significantly greater compared to those with anterior MI (51±12 vs. 64±28 vs. 78±31 ml, p<0.01). Incidence of ischemic MR (fraction>20%) was significantly higher in patients with inferior MI compared to anterior MI (7/61 vs. 12/33, p<0.01). In selected patients without significant ischemic MR, LA dilatation was comparable between inferior and anterior MI (60±28 vs. 61±16 ml, n.s.).Conclusions. Compared to patients with anterior MI, LV remodeling is significantly less but LA remodeling is significantly greater in inferior MI, suggesting the important role of ischemic MR to induce LA remodeling.