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Acute coronary syndrome

Emergencies

ST elevation (or new LBBB with ongoing pain) is a STEMI until proven otherwise — call cardiology for primary PCI now.

A normal first ECG and troponin do not rule out ACS. Repeat both.

Act now

  1. 1

    Aspirin 300 mg loading dose now unless allergic.

  2. 2

    Oxygen only if SpO₂ is below 94% (88–92% if at risk of hypercapnia).

  3. 3

    GTN for pain if systolic BP is over 90 mmHg; IV opioid with an antiemetic if pain persists.

  4. 4

    Call cardiology: primary PCI if within 12 hours of onset and deliverable within 120 minutes of when fibrinolysis could have been given; otherwise fibrinolysis.

Assess

  • ABCDE. 12-lead ECG within 10 minutes of the bleep; repeat every 15–30 minutes while pain continues.
  • ST depression in V1–V3: add posterior leads (V7–V9). Inferior STEMI: add right-sided leads (V4R).
  • Think of the mimics before antithrombotics: aortic dissection (tearing pain to back, unequal arm BPs), PE, pericarditis.
  • Bleeding risk: recent surgery or bleeding, anticoagulants, previous stroke.

Investigations

  • Serial ECGs, high-sensitivity troponin, FBC, U&E, glucose, lipids, HbA1c, clotting; CXR (widened mediastinum, oedema).

Manage

  • Second antiplatelet loading as directed by the cath lab — prasugrel for most having PCI, unless on an oral anticoagulant (then clopidogrel).
  • Fibrinolysis: give an antithrombin with it; repeat ECG at 60–90 minutes and transfer for PCI if reperfusion has failed.
  • Secondary prevention once stable: beta-blocker, high-intensity statin, ACE inhibitor.

Escalate when

  • Every STEMI: cardiology now. Cardiogenic shock, arrhythmia or pain despite treatment: senior and critical care too.

Doses and prescribing

Aspirin

300 mg oral (chewed or dispersed) once, then 75 mg daily.

Glyceryl trinitrate

400 micrograms sublingual spray, 1–2 sprays, repeat after 5 minutes if needed. Avoid with PDE-5 inhibitors and in right ventricular infarction.

Morphine

2.5–5 mg IV titrated slowly, with metoclopramide 10 mg IV.

Prasugrel

60 mg oral loading (5 mg maintenance if 75 or over or under 60 kg) — cardiology decision.

Check the BNF and your local formulary before prescribing.

Written to current guidance (NICE NG185, CG95, DG40) · sources checked 14 Nov 2026. We watch NICE for updates weekly.

Sources (5)

Reviewed by Aboodee Alhasso, MPharm MRCPharm IP on 14 Nov 2026

Calculators for this

For healthcare professionals, as an aid to clinical judgement — not a substitute for it. Follow your local policy and ask a senior when in doubt.