External validation of ECPR prognostic models derived from pre-ECMO indicators in patients undergoing extracorporeal cardiopulmonary resuscitation

Objective: To externally validate previously published prognostic models developed exclusively from pre-extracorporeal cardiopulmonary resuscitation (ECPR) variables in a contemporary ECPR cohort. Methods: We conducted a bicenter retrospective external validation of four published pre-ECPR prognostic models (Lee, RESCUE-IHCA, CHIU-S1, and CHIU-S2) in adult patients treated with ECPR between January 2015 and December 2024. Model performance was evaluated for in-hospital survival and favorable neurological outcome (FNO; Cerebral Performance Category 1-2) in the overall cohort, in-hospital cardiac arrest (IHCA), and cardiac-origin cardiac arrest (Cardio_CA) subgroups. Discrimination (the area under the receiver operating characteristic curve, AUROC), calibration, overall model fit (Brier score), and decision curve analysis (DCA) were assessed. For point-based CHIU scores, validation focused on observed outcome rates across predefined risk strata. Results: Among 214 patients, 79.0% (169/214) had IHCA; survival to discharge was 45.8% and FNO occurred in 24.8%. Discrimination for survival was modest across models (overall ECPR AUROC 0.608-0.709; IHCA 0.586-0.672; Cardio_CA 0.591-0.689) but was higher for FNO (overall ECPR 0.709-0.764; IHCA 0.696-0.744; Cardio_CA 0.698-0.718). The Lee model showed poor calibration with slopes far below 1, whereas RESCUE-IHCA model underestimated survival but demonstrated better calibration (slopes close to 1), higher overall accuracy (lower Brier scores) and broader clinical utility (wider net-benefit ranges in DCA). CHIU models provided limited risk separation between adjacent strata. Conclusions: In this external validation, pre-ECPR models showed modest performance, with better discrimination for neurological outcome than for survival. RESCUE-IHCA showed the most favorable overall performance. Future studies should develop and validate more robust, transportable tools.