What are the components of the Thrombolysis In Myocardial Infarction (TIMI) score in patients with acute coronary syndromes?

TIMI Risk Score Components

The TIMI risk score for unstable angina/NSTEMI consists of 7 equally-weighted variables, each worth 1 point, assessed at initial presentation: age ≥65 years, ≥3 CAD risk factors, known coronary stenosis ≥50%, ST-segment deviation ≥0.5 mm on ECG, ≥2 anginal episodes in the prior 24 hours, aspirin use in the prior 7 days, and elevated cardiac biomarkers. 1, 2

The Seven Components

1. Age ≥65 Years

• One point is assigned for age 65 years or older at presentation 1, 2
• Age emerged as one of the strongest predictors of severe epicardial disease in validation studies 3

2. ≥3 Risk Factors for Coronary Artery Disease

• One point is given if the patient has three or more of the following: hypertension, diabetes mellitus, hyperlipidemia, family history of CAD, or current smoking 2
• This component captures the underlying atherosclerotic burden 1

3. Known Coronary Stenosis ≥50%

• One point is assigned for prior catheterization demonstrating coronary stenosis of 50% or greater 1, 2
• This variable remained a significant predictor even when data were missing, demonstrating robust predictive ability 1
• History of coronary disease showed the strongest association with severe epicardial disease on angiography 3

4. ST-Segment Deviation on Presenting ECG

• One point is given for ST-segment deviation ≥0.5 mm (0.05 mV) on the initial ECG 1, 2
• ST-segment changes strongly correlate with visible thrombus and impaired culprit artery flow 3
• Even minimal ST depression of 0.05 mV predicts adverse outcomes 1

5. ≥2 Anginal Events in Prior 24 Hours

• One point is assigned if the patient experienced two or more anginal episodes within 24 hours before presentation 1, 2
• This captures the accelerating pattern of ischemia characteristic of unstable angina 1

6. Aspirin Use in Prior 7 Days

• One point is given for aspirin use within the 7 days preceding presentation 1, 2
• Prior aspirin use emerged as a stronger correlate of visible thrombus and impaired flow, suggesting breakthrough thrombosis despite antiplatelet therapy 3

7. Elevated Cardiac Biomarkers

• One point is assigned for elevated troponin or CK-MB at presentation 1, 2
• Positive biomarkers of necrosis strongly correlate with intracoronary thrombus and impaired culprit artery flow 3

Risk Stratification by Total Score

The composite endpoint risk (all-cause mortality, new or recurrent MI, or urgent revascularization at 14 days) increases progressively with higher scores:

• TIMI 0-1: 4.7% event rate 1
• TIMI 2: 8.3% event rate 1, 2
• TIMI 3: 13.2% event rate 1, 2
• TIMI 4: 19.9% event rate 1, 2
• TIMI 5: 26.2% event rate 1, 2
• TIMI 6-7: 40.9% event rate 1, 2

Clinical Application

Calculate the TIMI score immediately at presentation using readily available clinical data without computer assistance, though verification is available at www.timi.org 2

High TIMI scores (≥4) mandate early invasive strategy with coronary angiography, intensive antiplatelet therapy including GP IIb/IIIa inhibitors, and low-molecular-weight heparin over unfractionated heparin 2

Low TIMI scores (0-2) support conservative management with medical therapy and stress testing before discharge, though patient and physician preference should be considered 2

Validation and Performance

The TIMI risk score has been validated across multiple international trials including TIMI 11B and ESSENCE, maintaining consistent predictive ability across all cohorts 1, 2

The score performs well in routine clinical practice and proves superior to ECG changes plus troponin alone for risk stratification in unselected ED patients with possible ACS 2, 4

Meta-analysis of 17,265 patients demonstrated that a TIMI score of zero has 97.2% sensitivity for 30-day cardiac events, with only 1.8% event rate 5

The score also predicts 1-year outcomes, with event rates ranging from 4% (TIMI 0) to 88% (TIMI 5-7) 6

Important Caveats

The TIMI risk score should not be used as the sole means of determining patient disposition, but rather integrated with clinical judgment, serial ECGs, and cardiac biomarkers 5

Patients with higher TIMI scores are more likely to have intracoronary thrombus, impaired flow, and increased burden of coronary atherosclerosis on angiography, explaining the particular benefit of potent antithrombotic therapy 3

A separate TIMI risk score exists for STEMI patients using different variables to predict 30-day mortality 2