AbstractBackgroundThe complex high‐risk indicated percutaneous coronary intervention (CHIP) score is a tool developed using the British Cardiovascular Intervention Society (BCIS) database to define CHIP cases and predict in‐hospital major adverse cardiac or cerebrovascular events (MACCE).AimTo assess the validity of the CHIP score in chronic total occlusion (CTO) percutaneous coronary intervention (PCI).MethodsWe evaluated the performance of the CHIP score on 8341 CTO PCIs from the Prospective Global Registry for the Study of Chronic Total Occlusion Intervention (PROGRESS‐CTO) performed at 44 centers between 2012 and 2023.ResultsIn our cohort, 7.8% (n = 647) of patients had a CHIP score of 0, 50.2% (n = 4192) had a CHIP score of 1–2, 26.2% (n = 2187) had a CHIP score of 3–4, 11.7% (n = 972) had a CHIP score of 5–6, 3.3% (n = 276) had a CHIP score of 7–8, and 0.8% (n = 67) had a CHIP score of 9+. The incidence of MACCE for a CHIP score of 0 was 0.6%, reaching as high as 8.7% for a CHIP score of 9+, confirming that a higher CHIP score is associated with a higher risk of MACCE. The estimated increase in the risk of MACCE per one score unit increase was 100% (95% confidence interval [CI]: 65%–141%). The AUC of the CHIP score model for predicting MACCE in our cohort was 0.63 (95% CI: 0.58–0.67). There was a positive correlation between the CHIP score and the PROGRESS‐CTO MACE score (Spearman's correlation: 0.37; 95% CI: 0.35–0.39; p < 0.001).ConclusionsThe CHIP score has modest predictive capacity for MACCE in CTO PCI.