Differential Prognostic Impact of IABP-SHOCK II Scores According to Treatment Strategy in Cardiogenic Shock Complicating Acute Coronary Syndrome: From the RESCUE Registry

Background: Early risk stratification is necessary for optimal determination of the treatment strategy in cardiogenic shock (CS) complicating acute coronary syndrome (ACS). Therefore, we evaluated the prognostic impact of an intra-aortic balloon pump on the cardiogenic shock (IABP-SHOCK) II score according to the treatment strategies in ACS complicated by CS using the RESCUE (REtrospective and prospective observational Study to investigate Clinical oUtcomes and Efficacy of left ventricular assist device for Korean patients with cardiogenic shock) registry. Methods: The RESCUE registry contains multicenter observational retrospective and prospective cohorts that include 1247 patients with CS from 12 centers in Korea. A total of 865 patients with ACS complicated by CS were selected and stratified into low-, intermediate- and high-risk categories according to their IABP-SHOCK II scores and then according to treatment: non-mechanical support, IABP, and extracorporeal membrane oxygenators (ECMOs). The primary outcome was all-cause mortality during follow-up. Results: The observed mortality rates for the low-, intermediate-, and high-IABP-SHOCK II score risk categories were 28.8%, 52.4%, and 69.8%, respectively (p < 0.01). Patients in the non-mechanical support and IABP groups showed an increasingly elevated risk of all-cause mortality as their risk scores increased from low to high. In the ECMO group, the risk of all-cause mortality did not differ between the intermediate- and high-risk categories (HR = 1.21, 95% CI: 0.81-1.81, p = 0.33). The IABP-SHOCK II scores for the non-mechanical support and IABP groups showed a better predictive performance (area under curve [AUC] = 0.70, 95% CI: 0.65-0.76) for mortality compared with the EMCO group (AUC = 0.61, 95% CI 0.54-0.67; p-value for comparison = 0.02). Conclusions: Risk stratification using the IABP-SHOCK II score is useful for predicting mortality in ACS complicated by CS when patients are treated with non-mechanical support or IABP. However, its prognostic value may be unsatisfactory in severe cases where patients require ECMOs.