TIMI Risk Score for STEMI Calculator

About

The TIMI Risk Score for ST-elevation myocardial infarction was developed by Morrow et al. and published in Circulation in 2000 using data from the InTIME-II trial, which enrolled 14,114 patients with STEMI who were candidates for fibrinolytic therapy. The score identifies nine independent predictors of 30-day mortality, each assigned a weighted point value based on the strength of association with mortality: age ≥75 years (3 points), age 65-74 years (2 points), history of diabetes, hypertension, or angina (1 point), systolic blood pressure <100 mmHg on admission (3 points), heart rate >100 bpm on admission (2 points), Killip class II-IV on presentation (2 points), body weight <67 kg (1 point), anterior ST-elevation MI or new left bundle branch block (1 point), and time to treatment >4 hours from symptom onset (1 point). The total score ranges from 0 to 16, with higher scores indicating progressively higher 30-day mortality: scores of 0-4 correspond to mortality of 0.8-7%, scores of 5-8 correspond to 7-20%, and scores of 9-16 correspond to 20-36%. The score was externally validated in the TIMI 9, TIMI 10, and other trial populations, and subsequent studies have confirmed its prognostic value in primary PCI-treated patients as well. Its evidence level is Grade B, derived from large randomized trial databases with external validation in multiple cohorts. The TIMI STEMI score remains one of the most widely used risk stratification tools for STEMI patients and is referenced in international STEMI management guidelines.

Formula

Age ≥75 (3) + Age 65-74 (2) + DM/HTN/Angina (1) + SBP <100 (3) + HR >100 (2) + Killip II-IV (2) + Weight <67 kg (1) + Anterior MI/LBBB (1) + Time >4h (1)

The TIMI STEMI risk score assigns weighted points to nine clinical variables assessed at the time of presentation, reflecting their differential prognostic importance. Age is the most powerful predictor and is stratified into two categories: age ≥75 years contributes 3 points (the highest single weight), while age 65-74 years contributes 2 points. Patients under 65 contribute no points for age. A history of diabetes mellitus, hypertension, or angina prior to the index event contributes 1 point, recognizing the cumulative burden of these atherosclerotic risk factors. Hemodynamic instability carries substantial weight: systolic blood pressure <100 mmHg on admission contributes 3 points, reflecting the strong association between hypotension and mortality, while heart rate >100 bpm contributes 2 points, reflecting the prognostic significance of tachycardia-mediated increased myocardial oxygen demand. Killip class II-IV (any sign of heart failure on physical examination including rales, S3 gallop, pulmonary edema, or cardiogenic shock) contributes 2 points. Body weight <67 kg contributes 1 point, as lower body weight has been associated with higher bleeding risk with fibrinolytic therapy and independently predicts mortality. Anterior location of ST-elevation MI or new left bundle branch block contributes 1 point due to the larger territory of myocardium at risk. Time to treatment exceeding 4 hours from symptom onset contributes 1 point, reflecting the critical importance of early reperfusion. The maximum possible score is 16. The score stratifies patients into three risk tiers: low risk (0-4, 0.8-7% mortality), moderate risk (5-8, 7-20% mortality), and high risk (9-16, 20-36% mortality). Each tier guides intensity of monitoring, reperfusion strategy, and consideration of transfer to a tertiary center for primary PCI.

Score Interpretation

The TIMI Risk Score for STEMI is a cornerstone of early risk stratification in patients presenting with ST-elevation myocardial infarction, endorsed by the AHA/ACC STEMI management guidelines and the ESC guidelines for STEMI. Its clinical impact extends across several domains of acute MI care. First, it facilitates early identification of high-risk patients (score ≥9) who have a 30-day mortality rate exceeding 20% and may benefit from the most aggressive reperfusion strategies, including urgent transfer to a tertiary care center for primary PCI rather than on-site fibrinolysis when feasible. Second, it identifies low-risk patients (score 0-4) in whom a more conservative approach may be appropriate, with mortality rates below 7%. Third, the score aids in triage decisions regarding the level of care required — high-risk patients warrant intensive care unit admission with hemodynamic monitoring, while low-risk patients may be managed in a telemetry or step-down unit. Fourth, the score components (particularly Killip class, blood pressure, heart rate, and anterior location) guide the selection and aggressiveness of adjunctive pharmacotherapy, including the use of glycoprotein IIb/IIIa inhibitors, inotropic support, and mechanical circulatory support. The score has also been validated in patients undergoing primary PCI (not just fibrinolysis), extending its applicability in contemporary practice where primary PCI is the preferred reperfusion strategy. A systematic review and meta-analysis confirmed that the TIMI STEMI score maintains good discrimination (c-statistic 0.75-0.80) across diverse STEMI populations and treatment strategies. The score also stratifies risk of in-hospital complications including cardiogenic shock, heart failure, and major bleeding, providing comprehensive prognostic information beyond 30-day mortality alone.

Reference Ranges