Derivation and Validation of Shock Index as a parameter for Predicting Long-term Prognosis in Patients with Acute Coronary Syndrome

The objective of this study was to examine whether shock index (SI), defined by ratio of heart rate and systolic blood pressure, can predict long-term prognosis of acute coronary syndrome (ACS) in patients undergoing percutaneous coronary intervention (PCI) and to compare prognostic accuracy of SI with the Global Registry of Acute Coronary Events (GRACE) risk score. This study included individuals from 2 independent cohorts: derivation cohort (n = 2631) and validation cohort (n = 963). In the derivation cohort, we derived that higher admission SI was associated with a greater risk of long-term all-cause mortality [HR = 4.104, 95% CI 1.553 to 10.845, p = 0.004] after adjusting for covariates. We validated this finding in the validation cohort [HR = 10.091, 95% CI 2.205 to 46.187, p = 0.003]. Moreover, admission SI had similar performance to the GRACE score in determining all-cause mortality risk in both cohorts (derivation cohort, admission SI vs. GRACE, z = 1.919, p = 0.055; validation cohort, admission SI vs. GRACE, z = 1.039, p = 0.299). In conclusion, admission SI is an independent predictor of adverse outcome in ACS patients undergoing PCI, and can identify patients at high risk of death. SI and the GRACE score showed similar performance in predicting all-cause mortality, and SI is more readily obtained than the GRACE score.