TIMI Risk Score For STEMI

The scoring method explained

This cardiovascular risk assesses risk of ischemic events and adverse outcome (exitus) in patients with presentation consistent with one of the following:

■ Acute coronary syndrome (ACS);

■ Angina;

■ ST elevation myocardial infarction.

TIMI is the acronym for Thrombolysis in Myocardial Infarction. The score helps clinicians stratify patients and initiate emergency procedures to reduce incidence of ischemic events in high risk cases. The 8 criteria used in the score are the following:

■ Age: <65 (0), 65 - 74 (2), ≥75 (3);

■ Systolic BP <100 mmHg (3);

■ Heart Rate >100 bpm (2);

■ DM or hypertension or angina (1);

■ Anterior ST elevation or LBBB (1);

■ Killip class II-IV (2);

■ Weight <147.7 lbs / 67 kg (1);

■ Time to Treatment >4 hours (1).

An increased heart rate may signal the existence of a heart condition. Anterior ST elevation or left bundle branch block (LBBB) are cardiac conduction abnormalities (indicative of myocardial infarction) observed on electrocardiogram.

The duration between the start of symptoms and access to treatment is considered independent risk factor of outcome.

Interpreting the result

The eight criteria are awarded a number of points that depends on their predictive value for adverse outcome. The final score is associated with a 30-day mortality risk in percentage:

The TIMI score facilitates medical decision in regard to the following steps, usually thrombolysis or percutaneous coronary intervention.

About the study

The 2000 study by Morrow et al. aimed to develop a simple and convenient bedside clinical risk score for predicting 30-day mortality at presentation of patients with STEMI.

Eight independent predictors of mortality are weighted according to the adjusted odds ratios from logistic regression analysis.

The Intravenous nPA for Treatment of Infarcting Myocardium Early II trial involved a cohort of 14,114 patients.

The prognostic discriminatory capacity of the TIMI score was comparable to that obtained in the full multivariable model (c statistic 0.779 versus 0.784).

This risk assessment model is recommended in the triage and management of patients with STEMI who are eligible for fibrinolytic treatment.

STEMI guidelines

ST elevation myocardial infarction is a type of MI that is characterized by abnormal cardiac conduction (ST elevation), as shown during ECG testing.

It is also known as transmural or Q wave myocardial infarction and occurs when a coronary artery is suddenly blocked, thus blood flow to the heart is diminished. The area of the heart supplied by the affected artery becomes infracted and soon ceases to function.

The ST elevation is a sign that a relatively large amount of heart muscle has been damaged because of the impaired blood flow.

The other type of MI, non-STEMI, is less severe because in that case, the coronary arteries are partially blocked, not almost completely. This type has different ECG characteristics as well.

Original source

Morrow DA, Antman EM, Charlesworth A, Cairns R, Murphy SA, de Lemos JA, Giugliano RP, McCabe CH, Braunwald E. TIMI risk score for ST-elevation myocardial infarction: A convenient, bedside, clinical score for risk assessment at presentation: An intravenous nPA for treatment of infarcting myocardium early II trial substudy. Circulation. 2000; 102(17):2031-7.

Validation

Morrow DA, Antman EM, Parsons L, de Lemos JA, Cannon CP, Giugliano RP, McCabe CH, Barron HV, Braunwald E. Application of the TIMI risk score for ST-elevation MI in the National Registry of Myocardial Infarction 3. JAMA. 2001; 286(11):1356-9.

Other references

1. Bradshaw PJ, Ko DT, Newman AM, Donovan LR, Tu JV. Validation of the Thrombolysis In Myocardial Infarction (TIMI) risk index for predicting early mortality in a population-based cohort of STEMI and non-STEMI patients. Can J Cardiol. 2007;23(1):51-6.

2. Bagur RH, Urinovsky FM, Contreras AE, Estrada CD. TIMI risk score validation for patients with acute coronary syndrome without ST elevation. Medicina (B Aires). 2009; 69(5):526-8.