Introduction
- Implies that there is a dynamic coronary occlusion usually due to atherosclerotic plaque rupture and thrombus formation. It may or may not result in myocardial injury.
- Classically causes unprovoked chest pain occurring at rest or with minimal exertion. The pain may radiate to either arm, jaw or neck. There may be associated nausea. sweating and non-specific dyspnea.
- However, the range of symptoms can be varied and atypical including isolated symptoms
- Although risk factors are associated with coronary artery disease, even non-critical lesions in previously asymptomatic patient can spontaneously rupture resulting in an acute coronary syndromes. Chronic ischaemic heart disease increases the risk of an ACS but is not necessary for it
- Therefore, neither the absence of risk factors or typical symptoms can absolutely rule out the condition
- ECG ST/T wave changes are highly suggestive of ACS but a normal ECG does not rule out this possibility
- Serial ECGs or continuous ST segment monitoring is useful if there ongoing or unrelieved chest pain where there is reasonable clinical suspicion of an ACS
- The purpose of risk stratification is to identify patient most likely to be suffering the condition but more importantly, exhibit features that likely will lead to acute complications i.e. progression to myocardial infarction, arrhythmia, acute heart failure, cardiogenic shock or death. This determines need for admission, further investigation, continuous monitoring or anti-platelet/anti-thrombotic therapy.
Risk Stratification
| Clinical | ECG | Troponin 1 | Management | |
| Low Risk | Age < 65
Atypical history No risk factors |
Normal | Normal | Discharge
GP Review and manage secondary risk factors for vascular disease Return if further symptoms |
| Intermediate Risk | Multiple risk factors
Current aspirin use Pain relieved
|
Non-specific ST changes | Normal | Continous ECG monitoring not required
Provocation testing 2 |
| High Risk | Known ischaemic heart disease 3
Unrelieved pain Acute heart failure Episodes of Arrhythmias Hypotension Positive stress test High calcium score on Coronary CT |
ST depression / T wave inversion (persistent or transient) | Elevated | Continuous ECG monitoring
Dual anti-platelets and heparin Admit and determine if candidate for coronary angiography and revascularisation strategy
|
1 The timing and number of troponin evaluations is important. With high-sensivitity assays, an early rule out and discharge may be possible for ultra-low values. Consult your local health network guidelines.
2 Provocation testing can constitute either exercise or pharmacological testing using any of the following modalities: ECG, nuclear test, echocardiogram. They have similar accuracies but each has its own limitations depending on a number of factors. If a patient has had a recent test that was conclusively negative then repeating it is not necessary.
Provocation testing in low risk patients have poor yield and are more likely to give misleading false positive results that then may necessitate more invasive testing
Another valid alternative method to provocation testing is Coronary CT.
3 There is a subset of patients with known ischaemic heart disease who have had previous angiographic evidence of non-revascularisable lesions who do not warrant repeat angiography. If they suffer another ACS they only warrant brief admission until the acute episode resolves
Although a patient with stable coronary artery disease may previously been selected for medical management, an acute unprovoked episode consistent with an acute coronary syndrome still needs to be ruled out