A simple risk index for rapid initial triage of patients with ST-elevation myocardial infarction: an InTIME II substudy

BACKGROUND Rapid, effective triage is integral to emergency cardiac care of patients with ST-elevation myocardial infarction (STEMI). Available models for predicting mortality in STEMI include up to 45 variables, but have consistently shown advanced age, increased heart rate, and decreased blood pressure to be among the strongest predictors. METHODS On the basis of observed risk relations among 13,253 patients with STEMI from the InTIME II trial, we developed and assessed a simple risk index using age, heart rate, and systolic blood pressure (SBP) for predicting mortality over 30 days: (heart rate x [age/10](2))/SBP. FINDINGS The risk index was a strong (c statistic=0.78) and independent predictor of mortality risk (p<0.0001). When the risk index was categorised into quintiles for convenient clinical use, it revealed a more than 20-fold gradient of increasing mortality from 0.8 to 17.4%, p<0.0001. The risk index was also a robust predictor of very early events, including death by 24 h (c statistic=0.81). External validation in patients with STEMI from the TIMI 9 trials (n=3659) showed both a high discriminatory capacity (c statistic=0.79), and excellent concordance between the observed 30-day mortality in each of the five risk groups and the predictions based on InTIME II (goodness-of-fit, p=0.7). INTERPRETATION A simple risk index based on characteristics easily assessed by any paramedical or clinical personnel captures most of the information from more complex tools, and is likely to be useful in the rapid triage of patients with STEMI outside hospital or on first arrival in the hospital.