The impact of on-site cardiac rhythm on mortality in patients supported with extracorporeal cardiopulmonary resuscitation: A retrospective cohort study

BACKGROUND Extracorporeal cardiopulmonary resuscitation (ECPR) is increasingly used in patients with out-of-hospital or in-hospital cardiac arrest in whom conventional cardiopulmonary resuscitation remains unsuccessful. The aim of this study was to analyze the impact of initial cardiac rhythm - detected on-site of the cardiac arrest - on mortality. METHODS We performed a retrospective cohort study of patients who received ECPR in our tertiary care cardiac arrest center. Patients were divided into three groups depending on their cardiac rhythm: shockable rhythm, pulseless electrical activity, and asystole. The primary endpoint was mortality within the first 7���days after ECPR deployment. Secondary endpoints were mortality within 28���days and impact of pre-ECPR potassium, serum lactate, pH and pCO2 on mortality. The association of the initial cardiac rhythm and the location of arrhythmia detection (patient monitored in hospital [category: monitored], not monitored but hospitalized [in-hospital], not monitored, not hospitalized [out-of hospital]) with the primary and secondary outcome was examined by means of univariable and multivariable logistic regression. RESULTS Sixty-five patients could be included in the final analysis. Thirty-two patients (49.2%, 95%CI 36.6% - 61.9%) died within the first 7���days. In terms of 7-day-mortality patients differed in the initial cardiac rhythm (p=0.040) and with respect of the location of arrhythmia detection (p=0.002). Shockable cardiac rhythm (crude OR 0.21; 95%CI 0.03 - 0.98) and pulseless electrical activity (0.13; 0.02 - 0.61) as the initial rhythm on-site showed better odds for survival compared to asystole. However, this association did neither persist in adjusted analysis nor in pairwise comparison. DISCUSSION The study could not demonstrate a better outcome with shockable rhythm after ECPR. More homogeneous and adequately powered cohorts are needed to better understand the impact of cardiac rhythm on patient outcome after ECPR.