Abstract Background The prognostic impact on in-hospital and long-term outcomes of contrast-associated acute kidney injury (CA-AKI) in patients undergoing chronic total occlusion (CTO) percutaneous coronary intervention (PCI) has been limitedly studied. Methods We examined 2707 consecutive procedures performed in a referral CTO center between 2015 and 2019. CA-AKI was defined as an increase in serum creatinine ≥0.3 mg/dl or ≥50% within 48 h post-PCI†. Primary endpoints were major adverse cardiac and cerebrovascular events (MACCE) in-hospital (composite of all-cause death, myocardial infarction [MI], target vessel revascularization [TVR], stroke) and at 1-year of follow-up. Results The overall incidence of CA-AKI was 11.5%, respectively. Patients with CA-AKI (n=312) had more severe comorbidities in comparison with patients without CA-AKI (n=2,395). Technical success was similar across the groups (87.2% vs. 90.5%, p=0.056), whereas procedural success was lower in the CA-AKI group (84.3% vs. 89.7%, p=0.004). In-hospital MACCE was 1.3%, respectively, and were comparable in patients with and without CA-AKI (1.6% vs. 1.3%, p=0.655), however, pericardial tamponade requiring pericardiocentesis occurred more commonly in patients with renal function impairment (2.2% vs. 0.5%, p=0.001). In multivariate analysis, CA-AKI was not associated with higher risk for in-hospital MACCE (adjusted odds ratio [OR] 1.34, confidence intervals [CI] 0.45–3.19, p=0.563). At median follow-up time of 14 months (interquartile range [IQR], 11 to 35 months), the cumulative incidence of 1-year MACCE was significantly higher in patients with versus without CA-AKI (20.8% vs. 12.8%, p<0.001), and CA-AKI was independently associated with an increased risk for 1-year MACCE (adjusted hazard ratio [HR] 1.52, CI 1.05–2.15, p=0.029) following CTO PCI. Patients with CA-AKI had inferior MACCE-free (log-rank p<0.001) survival on Kaplan-Meier analysis (Figure 1), mostly driven by higher rate of target vessel failure (log-rank p<0.001), mortality (log-rank p=0.001), and myocardial infarction (log-rank p=0.042) over time. MACCE-free survivals significantly differed both in successful (Figure 2, Panel A) versus failed (Figure 2, Panel B) CTO PCI, with less favourable outcomes in patients developing CA-AKI post-PCI. Conclusions Contrast-associated acute kidney injury commonly occurs in patients undergoing CTO PCI, that may lead to an increased risk for MACCE 1-year post-PCI, but not immediately after the procedure. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only.