AbstractBackgroundThe SYNTAX score Ⅱ 2020 (SSⅡ‐2020) was created as a customized decision‐making tool for individuals diagnosed with complex coronary artery disease (CAD). Nevertheless, there has been a scarcity of research investigating the long‐term predictive significance of SSⅡ‐2020 for patients with both CAD and chronic renal insufficiency (CRI) who undergo percutaneous coronary intervention (PCI).AimsWe sought to showcase the prognostic capacity of SSII‐2020 in evaluating long‐term all‐cause mortality (ACM) within this high‐risk patient cohort.MethodsA retrospective cohort comprising 1156 individuals diagnosed with CRI and exhibiting left main CAD, three‐vessel CAD or both was included in this investigation. We categorized participants into three groups based on the optimal SSII‐2020 threshold for predicting long‐term ACM, determined using the X‐tile software.ResultsAt the median follow‐up duration of 6.3 years, the ACM rates were determined to be 10% in the low, 17% in the moderate, and 28% in the high SSII‐2020 groups (p < 0.001). Employing multivariate Cox regression analysis, it was observed that the high SSII‐2020 group exhibited a 3.289‐fold increased risk of ACM (95% confidence interval [CI]: 2.229–4.856, p < 0.001) compared with the low SSII‐2020 group, whereas the high SSII‐2020 group displayed a 1.757‐fold (95% CI: 1.190–2.597, p = 0.005) in comparison to the median SSII‐2020 groups. Compared with SSII, the SSII‐2020 had an incremental value for predicting 7‐year ACM (C‐index: 0.662 vs. 0.534, p = 0.007; IDI: 0.016, p < 0.001).ConclusionsSSII‐2020 enhances long‐term ACM prediction, facilitates improved risk stratification, and improves clinical utility for PCI patients with complex CAD and CRI.