About the TIMI Risk Score
The TIMI Risk Score is a validated, bedside risk-stratification tool for patients presenting with unstable angina (UA) and non-ST-elevation myocardial infarction (NSTEMI). Developed from the pooled TIMI 11B and ESSENCE trial databases (over 16,000 patients), it predicts the 14-day risk of all-cause mortality, new or recurrent MI, or severe ischemia requiring urgent revascularization. The score directly informs anticoagulation intensity, antiplatelet strategy, and the choice between early invasive (catheterization within 24–72 hours) vs. conservative management.
Each of the 7 risk factors is independently associated with increased 14-day event rates. The score was derived by Antman et al. and published in Circulation in 2000. It has since been incorporated into ACC/AHA guidelines and widely validated in contemporary ACS populations, including the CRUSADE registry and the TRITON-TIMI 38 pharmacodynamic studies.
How to Use the TIMI Risk Score
Apply the score at first physician contact for any patient presenting with symptoms suggestive of acute coronary syndrome. Gather the following information systematically:
- Age ≥65: Confirm patient age at time of presentation. Age is a strong independent predictor of 14-day mortality in UA/NSTEMI.
- ≥3 CAD Risk Factors: Count among: family history of premature CAD (first-degree male relative <55 or female <65), active hypertension, active hypercholesterolemia, diabetes mellitus, or current cigarette smoker. All 5 count if present.
- Known CAD (≥50% stenosis): Documented prior coronary angiography showing at least 50% stenosis in a major epicardial vessel, or any prior MI, PCI, or CABG.
- Aspirin within past 7 days: Any aspirin dose (including 81mg) taken within the past 7 days — indicating pre-existing antiplatelet therapy.
- ≥2 anginal episodes in past 24 hours: Assess frequency of chest pain episodes in the past 24 hours. Two or more distinct episodes within this window is a marker of unstable ischemia.
- ST-segment deviation: Review presenting 12-lead ECG for ST depression ≥0.5mm in contiguous leads or transient ST elevation <30 minutes. Exclude persistent ST elevation (which indicates STEMI).
- Elevated cardiac biomarkers: Use the first available troponin or CK-MB result. Score positive if either exceeds the institutional upper limit of normal.
- Sum the points (0–7) and interpret using the risk table below. Higher scores indicate greater benefit from early invasive strategy and more intensive anticoagulation.
Score Interpretation
| TIMI Score | Risk Category | 14-Day Composite | 14-Day Mortality | Recommendation |
|---|---|---|---|---|
| 0 – 1 | Low | ~4.7–7.3% | ~0.4–0.8% | Conservative approach acceptable; aspirin ± short-term anticoagulation |
| 2 – 3 | Intermediate | ~10.7–16.1% | ~1.4–1.8% | Consider early catheterization; DAPT + therapeutic anticoagulation |
| 4 – 5 | High | ~21.7–26.4% | ~2.8–3.5% | Early invasive strategy within 24h; aggressive DAPT + anticoagulation |
| 6 – 7 | Very High | ~34.4–39.9% | ~3.9–5.0% | Urgent angiography; maximum antithrombotic therapy; consider Gp IIb/IIIa |
Component Scoring Guide
| # | Factor | 0 Points (Absent) | 1 Point (Present) |
|---|---|---|---|
| 1 | Age ≥65 | Age <65 years | Age ≥65 years |
| 2 | ≥3 CAD Risk Factors | 0–2 risk factors | Family hx CAD, HTN, hypercholesterolemia, DM, or current smoker (≥3) |
| 3 | Known CAD (≥50% stenosis) | No known CAD | Prior MI, PCI, CABG, or angiographic stenosis ≥50% |
| 4 | Aspirin within past 7 days | No aspirin use in past 7 days | Aspirin taken within past 7 days |
| 5 | ≥2 anginal episodes in 24h | 0–1 anginal episodes | Two or more distinct episodes in past 24 hours |
| 6 | ST-segment deviation | Normal ECG, no ST changes | ST depression ≥0.5mm or transient ST elevation <30 min |
| 7 | Elevated cardiac markers | Troponin and CK-MB within normal limits | Troponin or CK-MB above institutional ULN |
Therapeutic Implications by Risk Tier
Each risk tier carries specific management implications derived from the TIMI 11B and ESSENCE trials and supported by current ACC/AHA NSTEMI guidelines:
Low Risk (0–1): Patients can often be managed conservatively with aspirin monotherapy or a short course of low-molecular-weight heparin (enoxaparin). Early stress testing prior to discharge is still recommended. Routine invasive angiography is not mandated but may be considered based on other clinical features.
Intermediate Risk (2–3): Dual antiplatelet therapy (aspirin + P2Y12 inhibitor such as clopidogrel, ticagrelor, or prasugrel) plus therapeutic anticoagulation (enoxaparin, fondaparinux, or heparin drip). Consider early catheterization within 24–72 hours. Fondaparinux is preferred per ESSENCE if bleeding risk is elevated.
High Risk (4–5): Early invasive strategy within 24 hours is indicated. Aggressive DAPT (ticagrelor or prasugrel preferred over clopidogrel per PLATO and TRITON-TIMI 38). Therapeutic anticoagulation with enoxaparin or bivalirudin. Glycoprotein IIb/IIIa inhibition (eptifibatide or abciximab) may be considered as a bridge to PCI. Cardiology consultation and cath lab activation.
Very High Risk (6–7): Urgent/emergent angiography with intent to revascularize. Maximum antithrombotic therapy. Gp IIb/IIIa inhibitor use in the cath lab is appropriate. ICU-level monitoring frequently required. These patients derive the greatest absolute mortality benefit from an early invasive strategy.
TIMI vs. GRACE Score
| Feature | TIMI Risk Score | GRACE Score |
|---|---|---|
| Components | 7 binary factors (0–7) | 8 continuous/binary factors (0–258) |
| Endpoint | 14-day death/MI/severe ischemia | In-hospital and 6-month death/MI |
| Ease of use | Simple bedside calculation | Requires calculator; more complex |
| Best for | UA/NSTEMI treatment planning | Overall long-term prognostic risk |
| Guideline integration | ACC/AHA 2020 NSTEMI guidelines | ACC/AHA and ESC guidelines |
| Mortality prediction | Moderate — simpler model | Higher discrimination for mortality |
Limitations & Considerations
- Not for STEMI: TIMI is not validated for ST-elevation MI, where immediate reperfusion (primary PCI or thrombolysis) is mandated regardless of score. TIMI ≥3 in NSTEMI should prompt early invasive strategy, but the score does not substitute for clinical judgment in any ACS subtype.
- Derived from pre-ticagrelor/prasugrel era: TIMI 11B and ESSENCE used LMWH and GP IIb/IIIa inhibitors as the backbone therapies. Contemporary practice favors ticagrelor or prasugrel over clopidogrel for high-risk ACS — the TIMI score thresholds for aggressive therapy remain valid, but the specific drug recommendations have evolved.
- Binary risk factor thresholds: Using ≥3 risk factors vs. ≥50% stenosis as binary cutoffs loses granularity. A patient with one severe risk factor (e.g., active smoking + uncontrolled DM + family history of MI at age 42) may be higher risk than a patient with exactly 3 mild factors.
- Bleeding risk not incorporated: The TIMI score optimizes for ischemic risk reduction. High scores often drive aggressive anticoagulation and DAPT, which increases bleeding risk — consider HAS-BLED or CRUSADE bleeding scores in parallel, especially in elderly patients or those on anticoagulants.
- Biomarker timing: The troponin component depends on the timing of biomarker measurement. A patient drawn at 2 hours vs. 6 hours post-symptom onset may have different biomarker results. Serial troponins (at 3 and 6 hours) are standard in current practice and may change the score over time.
- Cannot substitute for STEMI activation: Any patient with ST-elevation on ECG should have immediate cath lab activation — TIMI scoring is inappropriate and counterproductive in this setting.
References
Antman EM, Cohen M, Bernink PJ, et al. The TIMI risk score for unstable angina/non-ST elevation MI: A method for prognostication and therapeutic decision making. JAMA. 2000;284(7):835–842. doi:10.1001/jama.284.7.835
Cohen BM, Weber VJ, Reiss GA, et al. Comparative efficacy of dalteparin and enoxaparin in unstable angina and non-Q-wave infarction. J Am Coll Cardiol. 2000;35(5):1167–1174. doi:10.1016/S0735-1097(00)00558-7
Mahler SA, Riley RF, Hiestand BC, et al. The HEART Pathway Randomized Trial: identifying emergency department patients with acute chest pain for early discharge. Circ Cardiovasc Qual Outcomes. 2015;8(2):195–203. doi:10.1161/CIRCOUTCOMES.114.001384
Wiviott SD, Braunwald E, McCabe CH, et al. Prasugrel versus clopidogrel in patients with acute coronary syndromes. N Engl J Med. 2007;357(20):2001–2015. doi:10.1056/NEJMoa0706482
Wallentin L, Becker RC, Budaj A, et al. Ticagrelor versus clopidogrel in patients with acute coronary syndromes. N Engl J Med. 2009;361(11):1045–1057. doi:10.1056/NEJMoa0904327