Usefulness of the admission shock index for predicting short-term outcomes in patients with ST-segment elevation myocardial infarction.

Current risk scores of ST-segment elevation myocardial infarction (STEMI) need sophisticated algorithm and were limited for bedside use. Our study aimed to evaluate the usefulness of admission shock index (SI) for predicting the short-term outcomes in patients with STEMI. Included were 7,187 consecutive patients with STEMI. The admission SI was defined as the ratio of admission heart rate and systolic blood pressure. Patients were divided into 2 groups with SI <0.7 and ≥0.7, respectively, based on the receiver operating characteristic curve analysis. The major end points were 7- and 30-day all-cause mortality. Of 7,187 patients, 5,026 had admission SI <0.7 and 2,161 had admission SI ≥0.7. Those who presented with SI ≥0.7 had greater 7- and 30-day all-cause mortality and major adverse cardiovascular events than patients with SI <0.7. After multivariate adjustment, patients with SI ≥0.7 had a 2.2-fold increased risk of 7-day all-cause mortality (hazard ratio 2.21, 95% confidence interval [CI] 1.71 to 2.86) and 1.9-fold increased risk of 30-day all-cause mortality (hazard ratio 1.94, 95% CI 1.54 to 2.44). Moreover, admission SI ≥0.7 was also associated with 1.6- and 1.5-fold increased risk of 7- and 30-day major adverse cardiovascular events (hazard ratio 1.63, 95% CI 1.36 to 1.95 and hazard ratio 1.47, 95% CI 1.24 to 1.74, respectively). The C statistic of admission SI for predicting 7- and 30-day all-cause mortality was 0.701 and 0.686, respectively, compared with 0.744 and 0.738 from the Thrombolysis In Myocardial Infarction risk score. In conclusion, admission SI, an easily calculated index at first contact, may be a useful predictor for short-term outcomes especially for acute phase outcomes in patients with STEMI.