TIMI Score for STEMI Calculator
The TIMI Risk Score for STEMI estimates a patient's 30-day all-cause mortality after ST-elevation myocardial infarction. Answer nine yes/no questions based on information available at the bedside at presentation: age bracket, comorbidities, hemodynamic findings, ECG pattern, body weight and time to treatment. The calculator returns the score (0-14), the corresponding 30-day mortality rate from the original validation cohort, and a risk category to guide urgency of intervention.
What is the TIMI Risk Score for STEMI?
The TIMI (Thrombolysis in Myocardial Infarction) Risk Score for STEMI is a validated clinical scoring system that estimates 30-day all-cause mortality in patients presenting with ST-elevation myocardial infarction. Developed by Morrow et al. in 2000 and published in Circulation, the score was derived from the InTIME II trial involving over 14,000 STEMI patients treated with fibrinolytic therapy. The score uses nine easily obtainable clinical variables collected at the bedside at presentation, making it practical for rapid risk stratification in the emergency department or catheterization laboratory. A higher score indicates a greater risk of dying within 30 days, ranging from under 1% at a score of 0 to nearly 36% for scores of 9 or higher.
The nine scoring criteria explained
Each variable was selected because it independently predicted 30-day mortality in the derivation cohort. Age is weighted most heavily: patients aged 65 to 74 score 2 points and those 75 or older score 3 points, reflecting the substantially worse outcomes in elderly STEMI patients. A systolic blood pressure below 100 mmHg also carries 3 points, as this signals cardiogenic shock or severe pump failure. Heart rate above 100 bpm and Killip class II-IV each contribute 2 points; tachycardia and clinical heart failure signs (crackles, S3, jugular venous distension, or frank pulmonary edema) indicate compromised cardiac output. A history of diabetes, hypertension, or angina adds 1 point, as does anterior ST elevation or left bundle branch block (LBBB) on ECG, a body weight below 67 kg, and a time from symptom onset to reperfusion treatment exceeding 4 hours. The nine variables together account for 97% of the predictive capacity of the full multivariate model.
Clinical applications and limitations
The TIMI STEMI score is widely used in emergency medicine and cardiology to communicate mortality risk quickly and to inform decisions about escalation of care, including transfer to a tertiary center, consideration of mechanical circulatory support, or goals-of-care discussions. It was originally validated in the fibrinolytic era, and its performance in primary PCI populations is somewhat attenuated, though it remains predictive. For patients undergoing primary PCI, complementary tools such as the GRACE score or PAMI risk score may provide additional prognostic information. The score does not replace clinical judgment and is best interpreted alongside the full clinical picture, including ECG findings, echocardiographic data, and the patient's trajectory over the first hours of treatment.
How to use this calculator
Select the appropriate answer for each of the eight clinical questions. All inputs have a default of "No (0 points)" except the age field, which defaults to "Under 65 years." The score updates instantly as you change each answer. The 30-day mortality estimate is read directly from the published InTIME II mortality table: the table provides specific percentages for scores 0 through 8, and a combined figure of 35.9% for scores of 9 and above (since very few patients scored higher in the original trial). The result also shows a risk category (Low, Intermediate, High, or Very High) derived from commonly applied clinical groupings. The "Show your work" panel beneath the result breaks down each criterion's contribution to the final score.
TIMI STEMI Score - 30-Day Mortality Reference
| TIMI Score | 30-Day Mortality | Risk Category |
|---|---|---|
| 0 | 0.8% | Low |
| 1 | 1.6% | Low |
| 2 | 2.2% | Low |
| 3 | 4.4% | Intermediate |
| 4 | 7.3% | Intermediate |
| 5 | 12.4% | High |
| 6 | 16.1% | High |
| 7 | 23.4% | Very High |
| 8 | 26.8% | Very High |
| 9+ | 35.9% | Very High |
Estimated 30-day all-cause mortality rates from the InTIME II trial (n = 14,114 STEMI patients treated with fibrinolytic therapy). Risk categories are commonly applied clinical groupings.
Frequently asked questions
What is the maximum possible TIMI STEMI score?
The theoretical maximum is 14 points (age 75+ gives 3, systolic BP below 100 gives 3, heart rate above 100 gives 2, Killip class II-IV gives 2, plus 1 each for comorbidities, low weight, anterior ST elevation, and long time to treatment). In practice, very few patients score above 9, and the published mortality table groups scores of 9 and above together at 35.9%.
Is the TIMI STEMI score still valid in the primary PCI era?
The score was derived and validated in patients treated with fibrinolytic therapy in 2000. Primary percutaneous coronary intervention (PCI) has since become the preferred reperfusion strategy for STEMI, and mortality rates have fallen considerably. The score remains useful for identifying relative risk, but the absolute mortality percentages from the original table are higher than those seen with modern primary PCI. Use the score for risk stratification and trend direction, rather than treating the historical percentages as exact predictions for contemporary patients.
How is the TIMI STEMI score different from the TIMI score for NSTEMI/UA?
Despite sharing the TIMI name, the two scores are entirely separate tools for different patient populations. The TIMI score for STEMI (covered here) applies to ST-elevation MI and predicts 30-day all-cause mortality across 0-14 points. The TIMI risk score for unstable angina and NSTEMI is a 7-point score that predicts a 14-day composite of death, MI, or urgent revascularization. The inputs, point values, and clinical questions differ between the two; do not use this calculator for NSTEMI or UA patients.
What does Killip class mean, and how do I assess it?
The Killip classification grades the severity of acute heart failure in the setting of myocardial infarction. Class I: no signs of heart failure (clear lung fields, no S3). Class II: mild-to-moderate failure with pulmonary crackles in less than half of the lung fields, an S3 gallop, or elevated jugular venous pressure. Class III: severe failure with pulmonary crackles in more than half of both lung fields (acute pulmonary edema). Class IV: cardiogenic shock with systolic BP below 90 mmHg, cool extremities, and low urine output. For the TIMI STEMI calculator, any finding consistent with Killip II through IV scores 2 points.
Why does low body weight (below 67 kg) increase the TIMI STEMI score?
In the InTIME II derivation cohort, patients weighing less than 67 kg (approximately 147.7 lb) had higher 30-day mortality after STEMI. Low body weight is a proxy for frailty, older biological age, reduced physiologic reserve, and potentially underdosing of weight-based medications. The 67 kg cutoff was empirically determined from the original dataset and is specific to the TIMI STEMI score; it is not a marker of obesity or heart failure independently.
Can this score guide decisions about fibrinolytic therapy vs. PCI?
The TIMI STEMI score was not designed as a decision tool for choosing between fibrinolysis and primary PCI. Current guidelines favor primary PCI when available within guideline-recommended time windows, regardless of score. The TIMI score is primarily a prognostic tool for communicating mortality risk, identifying patients who need the most aggressive management, and informing risk-benefit discussions with patients and families.