BACKGROUND: The aim of this study was to evaluate the mid-term changes in cardiac function by transthoracic echocardiogram (TTE) in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI) according to valsartan dose. METHODS: Between April 2006 and February 2009, 78 subjects (mean age: 57 +/- 12 years, M : F = 74 : 4) with STEMI who underwent primary PCI were enrolled. Fifty three patients received low dose valsartan (40 or 80 mg) and 25 patients received high dose valsartan (160 or 320 mg). Follow-up TTE was done approximately 2 years later. We evaluated the changes in left ventricular (LV) function between initial and final TTE after primary PCI and compared the changes between low and high dose valsartan group. RESULTS: The mean follow-up TTE duration was 24 +/- 8 months. Deceleration time (188.6 +/- 56.3 msec vs. 221.5 +/- 71.3 msec, p = 0.01), E/e' (12.24 +/- 5.2 vs. 10.1 +/- 4.9, p = 0.002), ejection fraction (52.7 +/- 8% vs. 55.2 +/- 8.4%, p < 0.01), and wall motion score index (1.45 +/- 0.30 vs. 1.33 +/- 0.32, p < 0.01) showed significant changes during the follow-up period. Wall motion improvement in injured myocardial segments was more frequently observed in the high-dose valsartan group compared to the low-dose group [18/25 (72%) vs. 24/53 (43.7%), p = 0.03]. There was no significant difference in the changes in cardiac dimensions and function between the low and high dose valsartan group. CONCLUSION: In patients with STEMI who undergoing primary PCI, high-dose valsartan treatment may be more helpful than low-dose in improving wall motion in the injured myocardium.