Coronary Artery Disease (CAD) Probability Assessment

As previously mentioned, the presence of an appropriately timed negative troponin in a patient with a normal or non-diagnostic ECG and low risk chest pain, risk stratifies the patient to a very low 30 day risk of an adverse cardiac event and allows safe discharge from the ED; it does not exclude coronary artery disease (CAD) as a cause of their presenting complaint.

For this, further risk stratification is required and, in appropriate patients, further investigation. Until recently, there has been no evidence-based guidance on exactly which patients require further investigation and which investigation is most appropriate. The National Institute for Health and Clinical Excellence (NICE) has recently (2010) produced Guidance on this [1]: it advises the use of pre-test CAD probability assessment for patients who have presented with cardiac-sounding chest pain and who have had an acute coronary syndrome or AMI clinically and biochemically excluded. The pre-test probability of CAD will determine the need for further investigation. Clearly this only applies to patients who are not previously known to have CAD.
CAD probability assessment can be done by the emergency physician using a combination of factors as shown in Table 1.

Table 1

The typicality of chest pain, the patient’s age and gender, and the presence of risk factors are combined to determine the probability of CAD.
For the purposes of stratification in the Table, the typicality of a chest pain is defined as follows:

Anginal pain is:

• Constricting discomfort in the front of the chest, or in the neck, shoulders, jaw or arms
• Precipitated by physical exertion
• Relieved by rest or GTN within about 5 minutes

The presence of all three features defines “Typical angina”; the presence of two of these features defines “Atypical angina”; the presence of one or none of these features defines “Non-anginal pain”.
The patient is ascribed a value for the probability of CAD based on the combination of factors as shown in Table 1.