The role of shock index in acute coronary syndrome mortality prediction: a systematic review and meta-analysis

BACKGROUND: Shock index (SI) is a simple parameter in various diseases. Its performance in acute coronary syndrome (ACS) varies across studies. This systematic review evaluates SI's performance for ACS mortality prediction. METHOD: On 16 March 2025, we systematically searched six databases. This study included observational studies examining mortality outcomes in patients with ACS. Using random-effect models, we estimated the pooled odds ratio (OR), sensitivity, and specificity of SI in predicting ACS mortality. Additionally, we generated a summary receiver operating characteristics (sROC) curve and its area under the curve (AUC). RESULTS: This systematic review included 18 studies with 75,237 patients. High SI was significantly associated with all-time mortality (OR 4.82; OR 2.71 after publication bias adjustment). The association was stronger for in-hospital mortality (OR 6.46) but decreased for long-term mortality (OR 4.00). The SI cutoff values varied across studies, ranging from 0.5 to 1.6. The sensitivity and specificity of SI in predicting all-time mortality were 67.11% (95% CI: 61.48-72.74) and 73.21% (95% CI: 67.21-79.22), respectively, with an AUC of 0.69 (95% CI: 0.65-0.72). Its performance was higher for in-hospital mortality (sensitivity 64.22%, specificity 78.96%, AUC 0.71) and long-term mortality (sensitivity 61.23%, specificity 63.99%, AUC 0.70). CONCLUSION: High SI was associated with and has predictive value for short-term and long-term mortality prediction in ACS setting.