We assessed the effect of impaired myocardial blush after primary coronary intervention (PCI) on left ventricular remodeling in patients with ST-segment elevation myocardial infarction (STEMI). The study population consisted of 145 patients with first anterior STEMI that was treated successfully (Thrombolysis In Myocardial Infarction grade 3 flow) with PCI. Left ventricular remodeling was defined as an increase of > or =20% in end-diastolic volume based on repeated echocardiographic measurements in patients. The study population was divided into 2 groups according to the presence (myocardial blush grade [MBG] 2 to 3, n = 86) or absence (MBG 0 to 1, n = 59) of myocardial reperfusion. Left ventricular remodeling appeared in 21% of the entire study group. Poor myocardial blush after PCI was associated with an increased rate of remodeling compared with good myocardial reperfusion (32% vs 14%, hazard ratio 2.308, 95% confidence interval [CI] 1.21 to 4.39, p=0.014). Symptoms of heart failure were observed significantly more often in patients with MBG 0 to 1 (35.6% vs 18.6%, p = 0.032) than in patients with MBG 2 to 3. In multivariate analysis, only age (odds ratio 0.96, 95% CI 0.92 to 0.99, p = 0.02) and MBG 0 to 1 (odds ratio 3.15, 95% CI 1.35 to 7.31, p = 0.008) were associated with left ventricular dilation. In conclusion, impaired microvascular reperfusion is associated with left ventricular remodeling and development of congestive heart failure in patients with anterior STEMI that is treated with primary coronary angioplasty.