Acute Coronary Syndrome (ACS)

ACS includes STEMI, NSTEMI and unstable angina.

Take a good history. Not all chest pain is ACS, and not all ACS presents with chest pain.

Older patients, women and patients with diabetes may present with breathlessness, collapse, nausea, fatigue or other less typical symptoms.

A normal ECG or negative troponin does not exclude unstable angina.

1. Initial assessment – ECG first

12-lead ECG within 10 minutes of arrival when ACS is suspected.
Assess observations, haemodynamic stability and ongoing symptoms.
Repeat ECGs if pain persists, recurs or the initial ECG is equivocal.
Consider posterior leads (V7–V9) or right-sided leads when indicated.
Take bloods including high-sensitivity troponin, FBC, U&Es and renal function.
Consider alternative life-threatening diagnoses, particularly aortic dissection and pulmonary embolism.

STEMI or suspected acute coronary occlusion

Activate the PPCI pathway immediately. Do not wait for troponin.

Consider posterior MI, hyperacute T waves and other high-risk occlusion patterns even without conventional ST elevation.

EMbeds – Myocardial Infarction: PPCI/Thrombolysis

New ischaemic ECG changes or suspected unstable angina

New ST depression, dynamic T-wave changes, ongoing ischaemic pain or a convincing history of unstable angina require admission and monitoring.

Give appropriate ACS treatment.
Arrange telemetry.
Repeat ECG within 30 minutes if clinically indicated.
Discuss with Cardiology, particularly if ongoing symptoms or significant ECG changes.

2. Troponin pathway – CHFT 2025

For the intermediate pathway, the current CHFT algorithm specifies repeat troponin at 6 hours after the initial sample or 8 hours after symptom onset, whichever is sooner, alongside repeat ECG.

***A raised troponin does not automatically mean type 1 MI. Consider acute or chronic myocardial injury, including renal impairment, tachyarrhythmia, heart failure, sepsis and pulmonary embolism.***

Clinical assessment takes precedence over a reassuring troponin.

CHFT ED/AMU ACS Pathway – August 2025

3. ACS treatment – (not a STEMI proceeding directly to PPCI)

For established or strongly suspected NSTE-ACS, after considering bleeding risk, renal function, current anticoagulation and the planned invasive strategy:

Medication	Loading dose
Aspirin	300 mg orally, unless contraindicated
Ticagrelor	180 mg orally, when indicated under the agreed treatment strategy
Fondaparinux	2.5 mg subcutaneously, when appropriate

Important prescribing considerations

Do not routinely administer dual antiplatelet therapy to patients with undifferentiated chest pain before ACS is diagnosed.
If early coronary angiography (within 24 hours) is anticipated, routine P2Y12 pretreatment before coronary anatomy is known is not recommended by ESC guidance. Discuss with Cardiology.
Fondaparinux is generally preferred for NSTE-ACS not undergoing immediate angiography, provided renal function and bleeding risk permit.
Significant renal impairment may require an alternative anticoagulant strategy.
Check for active bleeding, previous intracranial haemorrhage and other relevant contraindications.

Already anticoagulated (DOAC or warfarin)

The existing CHFT regimen specifies:

Aspirin 300 mg.
Clopidogrel 300 mg.

Confirm the antithrombotic plan with Cardiology, considering the anticoagulant, last dose, INR where relevant, bleeding risk and likelihood of PCI.

Avoid automatically adding fondaparinux or creating prolonged triple antithrombotic therapy.

4. Aspirin allergy

Distinguish intolerance from true hypersensitivity.

Dyspepsia, nausea and gastrointestinal discomfort are not necessarily allergy. Aspirin may remain appropriate, with gastroprotection where indicated.
True hypersensitivity, including aspirin-induced bronchospasm, urticaria or anaphylaxis, requires avoidance and specialist advice.

For genuine aspirin allergy, discuss alternative antiplatelet treatment with Cardiology. The existing local pathway specifies ticagrelor with fondaparinux for selected NSTE-ACS patients, but treatment must be individualised.

5. Who needs CCU or urgent Cardiology discussion?

Consider direct CCU admission or urgent Cardiology review for:

STEMI not accepted for PPCI.
Ongoing or recurrent ischaemic chest pain despite treatment.
New or dynamic ST depression, particularly with ongoing pain.
Haemodynamic instability or cardiogenic shock.
Acute pulmonary oedema or heart failure associated with ACS.
Significant ventricular arrhythmia or other serious rhythm disturbance.
High-risk clinical history or concerning ECG changes.

Do not delay escalation while awaiting serial troponins in a patient with ongoing ischaemia or clinical instability.

Other patients with confirmed or strongly suspected ACS generally require admission to AMU or an appropriate monitored setting according to the CHFT pathway.

6. MI excluded – is discharge safe?

Ruling out MI does not rule out coronary disease, unstable angina or another serious diagnosis.

Before discharge, confirm:

The history is not suggestive of unstable angina.
There are no new or dynamic ischaemic ECG changes.
Troponin testing satisfies the local rule-out criteria.
Symptoms have resolved or have a satisfactory alternative explanation.
There are no other concerning clinical features requiring admission or investigation.

Suspected unstable angina

A convincing history of new, crescendo or rest angina can represent ACS despite negative troponins.
Admit for monitoring and inpatient Cardiology assessment.

Alternative life-threatening diagnoses

Not all chest pain is ACS. Consider other serious causes, particularly:

Aortic dissection – can mimic ACS, including STEMI, through coronary artery involvement. Consider particularly with abrupt severe chest or back pain, pulse/BP asymmetry, neurological symptoms or unexplained shock. Antiplatelet and anticoagulant treatment may cause catastrophic bleeding.
Pulmonary embolism – particularly with pleuritic pain, hypoxia, tachycardia or unexplained collapse.
Pericarditis/myopericarditis – consider with positional or pleuritic chest pain and characteristic ECG changes.
Pneumothorax – particularly with sudden pleuritic pain and breathlessness.

Important: Where aortic dissection is suspected, urgently assess and investigate before administering antithrombotic treatment. Do not delay emergency coronary reperfusion solely to exclude dissection in every patient with STEMI.

Key messages

1. ECG first. Troponin supports the diagnosis; it does not replace clinical judgement.
2. STEMI: activate PPCI without waiting for blood results.
3. NSTE-ACS: assess risk, initiate appropriate treatment and arrange the correct monitored destination.
4. Negative troponin ≠ no ACS. Always consider unstable angina.