Objective:To assess the effect of intra-aortic balloon pump (IABP) on in-hospital mortality in patients with cardiac arrest undergoing extracorporeal cardiopulmonary resuscitation (ECPR).Methods:A retrospective study was performed on 696 patients with intra-hospital cardiac arrest undergoing ECPR from Samsung Medical Center in Korea between January 2004 and December 2013. According to whether IABP was used, the patients were divided into ECPR group and ECPR+IABP group. Cox regression and propensity score matching (PSM) were used to examine the correlation between IABP usage and in-hospital mortality, and standardized mean difference ( SMD) was used to check the degree of PSM. Survival analysis of in-hospital mortality was performed by the Kaplan-Meier method, and further analyzed by the Log-Rank test. Using the propensity score as weights, multiple regression model and inverse probability weighting (IPW) model were used for sensitivity analysis. In-hospital mortality, extracorporeal membrane oxygenation (ECMO) withdrawal success rate and neurological function prognosis were compared between the two groups. Results:A total of 199 patients with cardiac arrest undergoing ECPR were included, including 120 males and 79 females, and the average age was (60.0±16.8) years. Thirty-one patients (15.6%) were treated with ECPR and IABP, and 168 patients (84.4%) only received ECPR. The total hospitalized mortality was 68.8% (137/199). The 1 : 1 nearest neighbor matching algorithm was performed with the 0.2 caliper value. The following variables were selected to generate propensity scores, including age, gender, race, marital status, insurance, admission type, service unit, heart rate, mean arterial pressure, respiratory rate, pulse oxygen saturation, white blood cell count. After the propensity score matching, 24 pairs of patients were successfully matched, with the average age of (63.0±12.8) years, including 31 males and 17 females. The in-hospital mortality was 72.6% (122/168) and 48.4% (15/31) in the ECPR group and the ECPR+IABP group [hazard ratio ( HR) = 0.48, 95% confidence interval (95% CI) was 0.28-0.82, P = 0.007]. Multiple regression model, adjusted propensity score, PSM and IPW model showed that the in-hospital mortality in the ECPR+IABP group was significantly lower compared with the ECPR group ( HR = 0.44, 0.50, 0.16 and 0.49, respectively, 95% CI were 0.24-0.79, 0.28-0.91, 0.06-0.39 and 0.31-0.77, all P < 0.05). The combined application of IABP could improve the ECMO withdrawal success rate [odds ratio ( OR) = 8.95, 95% CI was 2.72-29.38, P < 0.001] and neurological prognosis ( OR = 4.06, 95% CI was 1.33-12.40, P = 0.014) in adult cardiac arrest patients. Conclusion:In patients with cardiac arrest using ECPR, the combination of IABP was independently associated with lower in-hospital mortality, higher ECMO withdrawal success rate and better neurological prognosis.