External validation of the CAST and rCAST score in patients with out-of-hospital cardiac arrest who underwent ECPR: A secondary analysis of the SAVE-J II study

Background Risk stratification is important in patients with postcardiac arrest syndrome (PCAS). The post-Cardiac Arrest Syndrome for Therapeutic hypothermia (CAST) and revised CAST (rCAST) scores have been well validated for predicting the accuracy of neurological outcomes, particularly for conventionally resuscitated PCAS patients. However, no studies have evaluated patients undergoing extracorporeal cardiopulmonary resuscitation (ECPR). Methods Adult patients with out-of-hospital cardiac arrest (OHCA) who underwent ECPR were analyzed in this retrospective observational multicenter cohort study (SAVE-J II study). We validated the accuracy of the CAST and rCAST scores for predicting favorable neurological outcomes (cerebral performance category 1 or 2) at 30 days. Moreover, we compared the predictive performance of these CAST/rCAST scores with those of the previously documented TiPS65 risk model derived from patients with OHCA who were resuscitated using ECPR. Results A total of 1135 patients were analyzed. Their median age was 60 years and males comprised 84% of the cohort. The proportion of patients with favorable neurological outcomes was 16.6% overall. In the external validation, the area under the curve (AUC) of the CAST score was numerically larger than those of the rCAST and TiPS65 scores (AUC 0.677 vs. 0.603: p < 0.001, vs. 0.633: p = 0.154, respectively). Both CAST/rCAST risk scores showed good calibration (Hosmer– Lemeshow test: p = 0.726 and 0.674, respectively). Furthermore, the CAST score showed significantly better predictability in net reclassification than did the rCAST (p < 0.001) and TiPS65 scores (p = 0.001). Conclusions CAST and rCAST scores can predict neurological outcomes in patients with OHCA who undergo ECPR. The prognostic accuracy of the CAST score was significantly better than that of other pre-existing risk prediction models. IRB information The present study was approved by the institutional review board of Kagawa University (approval number: 2018-110) Clinical trial registration https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000041577 (unique identifier: UMIN000036490)