Left ventricular aneurysm (LVA) after myocardial infarction often results in serious complications. So far, when the LVA happened is unclear. Furthermore, it is a question whether percutaneous coronary intervention (PCI) can change or reverse the formation of LVA? And the report about the long term follow-up was rare. So this study was to evaluate the time sequence of the formation of LVA through left ventriculography in large scale of consecutive acute myocardial infarction (AMI) patients and evaluate the influence of PCI at different time after AMI on the change of systolic synchrony through phase analysis of equilibrium radionuclide angiography. The change of serum brain natriuretic peptide (BNP) was also measured to investigate its association with LVA. And follow up to 3 years to record the major adverse cardiac events. Total of 326 consecutive patients of anterior AMI with LVA were enrolled into this study. All patients were divided into four groups according to the time 'onset to balloon': group A (<3 h), group B (> or =3 and < or =6 h), group C (>6 and < or =12 h) and group D (>1 week). The paradox volume image as well as the parameters of left ventricular function and systolic synchrony were measured by equilibrium radionuclide angiography at 1 week and 6th month after AMI. Plasma BNP was measured in different time after AMI. The major adverse cardiac events were recorded up to 3 years. At the 6th month after AMI, left ventricular ejection fraction, peak ejection rate and peak filling rate in group A, B and C were significantly increased than those in group D while phase shift and peak phase standard deviation were decreased significantly (P < 0.05, respectively). At 6th month after AMI, the paradox volume index in group A was lowered than that in group B, C, and D (P < 0.05, respectively). In 18th hour, 5th day and 24th week after AMI, the values of BNP in group D were higher than those in group A, B and C (P < 0.05, respectively). There was not significantly different between group B and group C. Within the 3rd year follow-up, the incidences of angina post-AMI and mortality in group A, B, and C were significantly lowered than those in group D (P < 0.05, respectively). The LVA can formate shortly after the AMI. The early, fully and permanently patency of infraction related artery can effectively inhibit the left ventricular remodeling process, prevent LVA formation, improve its function and prognosis.