TIMI Risk Score in Acute Coronary Syndromes
The TIMI risk score is a validated 7-point bedside tool that stratifies patients with unstable angina/NSTEMI into risk categories for death, myocardial infarction, or urgent revascularization within 14 days, with event rates ranging from 4.7% (score 0-1) to 40.9% (score 6-7), and should be calculated at presentation to guide intensity of therapy and timing of invasive strategy. 1
Components of the TIMI Risk Score
The score assigns 1 point for each of the following 7 variables present at admission: 1
- Age ≥65 years
- ≥3 risk factors for coronary artery disease (hypertension, diabetes, hyperlipidemia, family history, current smoking)
- Known coronary stenosis ≥50% (prior catheterization showing significant disease)
- ST-segment deviation ≥0.5 mm on presenting ECG
- ≥2 anginal events in the prior 24 hours
- Aspirin use in the prior 7 days
- Elevated cardiac biomarkers (troponin or CK-MB)
Risk Stratification and Event Rates
The composite endpoint risk (all-cause mortality, new/recurrent MI, or severe ischemia requiring urgent revascularization through 14 days) increases progressively: 1
- Score 0-1: 4.7% event rate (low risk)
- Score 2: 8.3%
- Score 3: 13.2% (intermediate risk)
- Score 4: 19.9%
- Score 5: 26.2% (high risk)
- Score 6-7: 40.9% (very high risk)
Clinical Application and Treatment Decisions
High TIMI risk scores (≥4) mandate early invasive strategy with coronary angiography and revascularization, intensive antiplatelet therapy with glycoprotein IIb/IIIa inhibitors, and low-molecular-weight heparin over unfractionated heparin. 1
Low TIMI risk scores (0-2) support conservative management with medical therapy and stress testing before discharge, though patient and physician preference should be considered in the absence of high-risk features. 1
The score demonstrates a significant treatment interaction, with enoxaparin showing greater benefit over unfractionated heparin as TIMI score increases (P=0.02 for interaction), and similar gradients exist for glycoprotein IIb/IIIa inhibitors and early invasive strategies. 2, 3
Pathobiologic Correlates
Higher TIMI scores correlate with more severe angiographic disease: patients with scores 5-7 have 81% prevalence of severe culprit stenosis versus 58% in those with scores 0-2 (P<0.001), and 80% versus 43% prevalence of multivessel disease (P<0.001). 4
Visible intracoronary thrombus, impaired epicardial flow, and left main disease all increase progressively with rising TIMI scores (P<0.001), explaining the particular benefit of potent antithrombotic agents in higher-risk patients. 4
Markers of endothelial damage (circulating endothelial cells, von Willebrand factor), inflammation (IL-6), and thrombogenicity (tissue factor) are significantly elevated in high versus low TIMI score patients (all P<0.05), with baseline endothelial cells and change in von Willebrand factor independently predicting 14-day and 30-day cardiac events (P≤0.01). 5
Validation and Performance
The TIMI risk score has been validated across multiple international trials including TIMI 11B, ESSENCE, and unselected emergency department populations with chest pain, maintaining consistent predictive ability across all cohorts (P<0.001 for trend in all validation groups). 1, 2
The score performs well in routine clinical practice, proving superior to ECG changes plus troponin alone for risk stratification in unselected patients with possible ACS (likelihood ratio difference 13.910, P=0.016). 6
The model is relatively insensitive to missing information, particularly regarding prior coronary stenosis, and maintains predictive ability with the 65-year age cutoff. 1
Practical Implementation
Calculate the TIMI risk score immediately at presentation using readily available clinical data without requiring computer assistance—the calculator is available at www.timi.org for verification. 1
For STEMI patients, a separate TIMI risk score exists using different variables (age, Killip class, systolic blood pressure, heart rate, anterior location/LBBB, diabetes/hypertension/angina, weight, time to treatment) to predict 30-day mortality. 1
Common Pitfalls
Do not use TIMI score as a diagnostic tool—it stratifies risk only in patients with suspected or confirmed ACS, not for diagnosing whether ACS is present. 1, 7
The score has only moderate predictive ability for nonfatal coronary events, and while it guides therapeutic decisions effectively, there is insufficient evidence that routine use translates into reduced cardiovascular events in all settings. 1, 7
GRACE risk score may provide superior discrimination (C-statistic 0.83) and has been found superior to subjective physician assessment for predicting death or MI, particularly for estimating longer-term outcomes (6-month, 1-year, 3-year mortality). 1, 7