Introduction: Extracorporeal cardiopulmonary resuscitation (eCPR) has emerged as therapeutic option for selected patients (pts) in refractory cardiac arrest (RCA). However, pts with non-shockable rhythm (NSR) in initial electrocardiogram (ECG) findings remain underrepresented in cohorts and its implication under investigation. We thus sought to evaluate outcomes of eCPR as stratified by initial rhythm in an all-comers real-life cohort. 

Methods and Results: A total of 301 pts (median age 59 [51-67] years, 79% male gender) consecutively treated with eCPR for RCA from 01/2016 to 05/2022 were retrospectively analysed, divided by initial ECG findings of either shockable rhythm (SR, n=152) or NSR (n=149). While prior coronary artery disease (83% vs 59%, p<0.001) and ischemic cardiomyopathy (28% vs 16%, p=0.024) were more prevalent in SR pts, other baseline characteristics distributed evenly. No differences were detected in either witness of collapse (SR 88% vs NSR 87%, p=0.93) or bystander CPR (SR 89% vs 85%, p=0.37), while mean low-flow time tended to be longer in NSR pts, yet not meeting statistic significance (84±45 min vs SR 74±29 min, p=0.16). Door-to-ECMO timing resembled in both cohorts (SR 15 [13-23] min vs NSR 17 [14-25] min), as did other intraprocedural parameters. However main causes for RCA significantly differed in between groups (p<0.001): coronary event (SR 79% vs NSR 52%), suspected primary arrhythmogenic event (SR 11% vs 7.8%), cardiogenic shock (SR 4.9% vs NSR 17%), aortic dissection (SR 0.8% vs NSR 5.8%) and pulmonary embolism (SR 2.4% vs 13%). Survival was significantly higher in SR pts (28% vs 13% in NSR, p=0.001). Favourable outcome as defined by cerebral performance category (CPC) ≤2 at discharge versus death or CPC >2 was significantly higher in SR pts (19% vs 6.9%, p=0.002). Accordingly, NSR was found to be independently predictive of mortality (HR 1.84 [1.01 – 3.33]) in multivariate analyses. Significant interactions for mortality and favourable neurological outcome according to the underlying rhythm were found for the application of suprarenine, such that its use significantly worsened prognosis in NSR but not in SR pts.  

Conclusion: Our findings depict an evident implication of initial rhythm on outcome in a large all-comers cohort of pts treated with eCPR for RCA. In spite of similar baseline and procedural characteristics, mortality and adverse neurological outcome was significantly higher in pts with initial NSR. However, rates in NSR pts still remained below those in equivalent conventional CPR cohorts, especially considering long low-flow times. Taking into account vast differences in the underlying causes of RCA, focused diagnostic algorithms preceding eCPR might enhance survival in this specific subgroup. The present analyses does not support a strict limitation of eCPR to pts with initial SR.   

Fig. 1: Logarithmic relative hazard for favourable neurological outcome - interaction of suprarenine with initial rhythm