What is the TIMI Score for STEMI?
The TIMI (Thrombolysis In Myocardial Infarction) risk score for STEMI is a validated bedside clinical tool developed from the InTIME II trial of 15,060 STEMI patients treated with thrombolytics. It estimates 30-day all-cause mortality in patients presenting with ST-elevation myocardial infarction.
The score uses readily available clinical variables assessed at presentation, making it practical for rapid risk stratification in emergency settings. Higher scores indicate greater mortality risk and may influence decisions regarding the aggressiveness of reperfusion therapy, transfer for primary PCI, and level of care.
Scoring Criteria
| Criterion | Points | Rationale |
|---|---|---|
| Age 65–74 years | 2 | Increased comorbidity and reduced physiologic reserve |
| Age ≥75 years | 3 | Highest age-related mortality risk |
| Diabetes / Hypertension / Angina | 1 | Underlying cardiovascular disease burden |
| Systolic BP < 100 mmHg | 3 | Cardiogenic shock or hemodynamic compromise |
| Heart rate > 100 bpm | 2 | Compensatory tachycardia indicating hemodynamic stress |
| Killip class II–IV | 2 | Heart failure / cardiogenic shock |
| Weight < 67 kg | 1 | Associated with higher drug levels and bleeding risk |
| Anterior ST elevation or LBBB | 1 | Larger territory at risk (LAD distribution) |
| Time to treatment > 4 hours | 1 | Delayed reperfusion = more myocardial damage |
Score Interpretation
| TIMI Score | 30-Day Mortality | Risk Level |
|---|---|---|
| 0 | 0.8% | Very low |
| 1 | 1.6% | Low |
| 2 | 2.2% | Low |
| 3 | 4.4% | Moderate |
| 4 | 7.3% | Moderate |
| 5 | 12.4% | High |
| 6 | 16.1% | High |
| 7 | 23.4% | Very high |
| 8 | 26.8% | Very high |
| >8 | 35.9% | Very high |
TIMI STEMI Risk Diagram
STEMI Overview
ST-Elevation Myocardial Infarction (STEMI) is the most severe form of acute coronary syndrome, caused by complete occlusion of a coronary artery. It is characterized by persistent ST-segment elevation on ECG and elevated cardiac biomarkers, indicating transmural myocardial ischemia and necrosis.
STEMI requires emergent reperfusion therapy, either primary percutaneous coronary intervention (PCI) or fibrinolytic therapy if PCI is not available within 120 minutes of first medical contact. The door-to-balloon time (for PCI) or door-to-needle time (for fibrinolytics) are critical quality metrics, as myocardial salvage is highly time-dependent.
Killip Classification
The Killip classification is a critical component of the TIMI STEMI score. It grades the severity of heart failure complicating acute MI:
| Class | Description | Approximate Mortality |
|---|---|---|
| I | No heart failure; no signs of decompensation | 6% |
| II | Heart failure; rales, S3 gallop, elevated JVP | 17% |
| III | Severe heart failure; frank pulmonary edema | 38% |
| IV | Cardiogenic shock; hypotension, oliguria, cyanosis | 81% |
Treatment Implications
- Low risk (0–2): Standard STEMI protocol. Primary PCI preferred. Consider early discharge pathways if uncomplicated post-PCI course.
- Moderate risk (3–4): Aggressive reperfusion strategy. Close hemodynamic monitoring. Consider transfer to high-volume PCI center.
- High risk (5–6): Intensive care admission. Consider mechanical circulatory support readiness. Multidisciplinary heart team evaluation.
- Very high risk (≥7): Anticipate complications. ICU level of care. Consider early mechanical circulatory support (IABP, Impella). Palliative care discussion if appropriate.
Validation and Evidence
The TIMI risk score for STEMI was derived from the InTIME II trial (n = 15,060) and validated in the TIMI 9 trial (n = 3,339). It has since been validated in multiple international cohorts and across different reperfusion strategies including primary PCI.
The c-statistic (area under the ROC curve) is approximately 0.78, indicating good discriminatory ability. The score demonstrates a clear gradient of increasing mortality across the point range, making it clinically useful for risk stratification.
Frequently Asked Questions
When should I use the TIMI STEMI score?
Use this score at initial presentation when a patient is diagnosed with STEMI. It helps triage patients and can guide the urgency and type of reperfusion strategy chosen. It should not delay definitive treatment.
Can TIMI STEMI score be used with primary PCI?
Yes. Although originally developed in a fibrinolytic-treated cohort, the TIMI STEMI score has been validated in primary PCI populations and maintains its predictive value for 30-day mortality across different reperfusion strategies.
How does TIMI STEMI compare to GRACE score?
The GRACE score is another widely used risk stratification tool for ACS. GRACE uses more variables (including creatinine and cardiac arrest) and is validated for both in-hospital and 6-month mortality. TIMI STEMI is simpler and can be calculated at the bedside without lab values, while GRACE may provide more refined prognostication.
Does the score account for troponin levels?
No. The TIMI STEMI score uses clinical and ECG variables available at presentation. It does not incorporate biomarker levels. For scores that include biomarkers, consider the TIMI score for UA/NSTEMI or the GRACE risk score.