Background: Left atrial volume index (LAVI) is well proven to be a reliable method of determining left atrial size, which has prognostic implications in cardiovascular diseases. Studies demonstrate that increased LAVI is a predictor of mortality in myocardial infarction, but its association with other major adverse cardiovascular events (MACEs) among patients post acute coronary syndrome (ACS) has not been adequately evaluated.Methods: We calculated the baseline LAVI for all patients who were admitted with ACS between December 2010 and August 2011. The patients were stratified into 2 arms: normal LAVI and increased LAVI, with a cutoff value of 28 mL/m(2). All patients were prospectively followed up during 6 months for development of MACEs.Results: Of the 75 patients who completed the study, 32 had increased LAVI, and 43 had normal LAVI. More than half (55%) of the patients were diagnosed with unstable angina. During the follow-up period of 6 months, 30 patients (93.8%) in the increased-LAVI arm and 23 patients (53.5%) in the normal-LAVI arm developed at least a single MACE. Patients with increased LAVI had significantly more MACEs (P = 0.021). The occurrence of MACE remained significantly higher in the increased-LAVI group even when atrial fibrillation was excluded (P = 0.016). After adjusting for confounding variables by multivariate analysis, LAVI was found to have a significant association with MACEs (P = 0.030, odds ratio = 1.229 (95% confidence interval, 1.020-1.481).Conclusion: LAVI is a useful tool for prognostication and an independent predictor of MACEs post ACS.