ABSTRACT: Background:In patients with acute ST-segment elevation myocardial infarction (STEMI) who undergo primary percutaneous coronary intervention (PCI), approximately 10% are concomitant with a chronic total occlusion (CTO) in a non-culprit vessel. However, the impact of staged CTO recanalization on prognosis in this cohort remains disputable. This study aimed to compare the long-term outcomes of staged CTO recanalization versus medical therapy in patients with STEMI after primary PCI. Methods:Between January 2005 and December 2016, a total of 287 patients were treated with staged CTO-PCI (n = 91) or medical therapy (n = 196) after primary PCI in our center. The primary endpoint was major adverse cardiovascular and cerebrovascular event (MACCE), defined as a composite of all-cause death, nonfatal myocardial infarction (MI), stroke or unplanned revascularization. After propensity-score matching, 77 pairs of well-balanced patients were identified. Results:The mean follow-up period was 6.06 years. Overall, the incidence of the primary endpoint of MACCE was significantly lower in staged CTO-PCI group than that in medical therapy group in both overall population (22.0% vs. 46.9%; hazard ratio (HR) = 0.48, 95% CI: 0.29-0.77) and propensity-matched cohorts (22.1% vs. 42.9%; HR: 0.48, 95% CI: 0.27-0.86). In addition, staged CTO-PCI was also associated with reduced risk of the composite of cardiac death, nonfatal MI or stroke compared with medical therapy in both overall population (9.9% vs. 26.5%; hazard ratio (HR) = 0.39, 95% CI: 0.19-0.79) and propensity-matched cohorts (9.1% vs. 22.1%; HR: 0.40, 95% CI: 0.16-0.96). After correction of the possible confounders, staged CTO-PCI was independently associated with reduced risks of MACCE (adjusted HR: 0.46, 95% CI: 0.28-0.75), the composite of cardiac death, nonfatal MI or stroke (adjusted HR: 0.45, 95% CI: 0.22-0.94) and all-cause mortality (adjusted HR: 0.32, 95% CI: 0.13-0.83). Moreover, the results of sensitivity analysis were almost concordant with the overall analysis. Conclusions:In patients with STEMI and a concurrent CTO who undergo primary PCI, successful staged recanalization of CTO in the non-culprit vessels is associated with better clinical outcomes during long-term follow-up.