Phenotypes of cardiogenic shock after out-of-hospital cardiac arrest: the SCAI-V classification

BACKGROUND: Classifying cardiogenic shock (CS) after out-of-hospital cardiac arrest (OHCA) is challenging, with end-organ hypoperfusion arising from mechanisms distinct to non-arrested CS. AIMS: We sought to evaluate the performance of current CS classifications and to develop the Society for Cardiovascular Angiography and Interventions (SCAI)-V classification of CS after resuscitated OHCA. METHODS: We performed a retrospective analysis of an international derivation cohort (London, United Kingdom; GdaÅsk, Poland; n=627) and external validation of the 2x2 SCAI-V construct in the TTM-2 trial cohort (n=1,781). The primary outcome was mortality; the secondary outcome was non-neurological mortality at hospital discharge (derivation cohort) or at 180 days (TTM-2 cohort). RESULTS: In the derivation cohort, the median age was 63 years (interquartile range 53-74), and 76% were male. Applying the 2022 SCAI classification (SCAI-2022), 60% of patients had discordant haemodynamic parameters and lactate levels. We developed the SCAI-V classification, grouping patients according to their SCAI grade (shock absent or present) and lactate level (<5 mmol/L or ≥5 mmol/L) into four phenotypes - non-shock, systemic ischaemia, haemodynamic shock, and haemometabolic shock - using a 2x2 factorial framework. The SCAI-V classification was associated with all-cause and non-neurological mortality (p<0.001). Survival was highest in the non-shock group (78% and 68%, in the derivation and validation cohorts, respectively), followed by haemodynamic shock (60% and 51%), then systemic ischaemia (50% and 42%), and lowest in the haemometabolic group (20% and 27%). In the derivation cohort, the SCAI-V classification displayed superior model fit, discrimination, and calibration than the 2019 and 2022 SCAI classifications. In the TTM-2 cohort, external evaluation using SCAI-V showed consistent model fit advantages and discrimination comparable to SCAI-2022. CONCLUSIONS: The SCAI-V classification enhances phenotypic profiling of CS after resuscitated OHCA and may improve patient selection for early invasive therapies in this population.