TIMI Risk Score For NSTEMI

The scoring system explained

Patients with acute coronary syndrome or who have suffered from a myocardial infarction (whether ST or non ST elevation), are at risk of further cardiac adverse outcome and at an increased mortality risk.

The TIMI tools, whether the original version or the score for ST elevation MI, along with this scoring method for non ST elevation, help clinicians stratify patients at risk based on cardiovascular factors.

The following table introduces the seven items in this cardiac risk score:

The TIMI scores are widely used in chest pain management in clinical stages. More recently, troponin testing models such as GRACE or HEART offer a more accurate risk stratification.

Result interpretation

Each of the seven cardiovascular risk factors is awarded 1 point if present. Therefore, the score ranges between 0 and 7. Scores of 0 and 1 carry a 5% mortality risk whilst scores of 6 and 7 carry a 41% mortality risk.

The table below present the association between scores and mortality risk:

About the study

The score was developed following a 2000 study by Antman et al. that involved three different trials of patients who were treated with unfractioned heparin or enoxaparin. The study was aimed at stratifying the risk for death and cardiac ischemic events. There were also three validation cohorts.

The seven risk factors introduced above were extracted and tested.

Event rates increased significantly as the TIMI risk score increased in the test cohort in TIMI 11B and this pattern of increase was confirmed in the validation cohorts.

It was concluded that in patients with UA/NSTEMI, the TIMI risk score can facilitate decision making and stratify mortality risk.

Non ST elevation MI

Non ST elevation MI or ST depression MI, is the less severe type of myocardial infarction and indicates that the coronary artery is only partially occluded.

In contrast to ST elevation MI, here only a part of the cardiovascular tissue (depth) is affected, thus the heart muscle is partially infracted.

There are some generic risk factors for this cardiac condition, such as:

■ Hypertension;

■ High cholesterol;

■ Family and personal history;

■ Diabetes mellitus;

■ Smoking.

The most common symptoms are chest pain (usually located in the middle of the chest and which may radiate towards the arm, shoulder, neck or jaw), difficulty breathing, palpitations (caused by nervous system activation) and even cardiogenic shock if the AMI is of increased severity.

Rapid diagnosis can be put after ECG, blood cardiac markers, full blood count with elevated WBC, chest X rays and/or echocardiography.

Common complications include heart arrhythmias and acute heart failure or cardiogenic shock. Because of the damage produced to the papillary muscle, mitral regurgitation can also occur.

Original source

Antman EM, Cohen M, Bernink PJ, McCabe CH, Horacek T, Papuchis G, Mautner B, Corbalan R, Radley D, Braunwald E. The TIMI risk score for unstable angina/non-ST elevation MI: A method for prognostication and therapeutic decision making. JAMA. 2000;284(7):835-42.

Validation

Pollack CV Jr, Sites FD, Shofer FS, Sease KL, Hollander JE. Application of the TIMI risk score for unstable angina and non-ST elevation acute coronary syndrome to an unselected emergency department chest pain population. Acad Emerg Med. 2006; 13(1):13-8.

Other references

1. Wiviott SD, Morrow DA, Frederick PD, Antman EM, Braunwald E; National Registry of Myocardial Infarction. Application of the Thrombolysis in Myocardial Infarction risk index in non-ST-segment elevation myocardial infarction: evaluation of patients in the National Registry of Myocardial Infarction. J Am Coll Cardiol. 2006; 47(8):1553-8.

2. Hess EP, Perry JJ, Calder LA, Thiruganasambandamoorthy V, Body R, Jaffe A, Wells GA, Stiell IG. Prospective validation of a modified thrombolysis in myocardial infarction risk score in emergency department patients with chest pain and possible acute coronary syndrome. Acad Emerg Med. 2010; 17(4):368-75.