acute coronary syndromes

Spectrum from unstable angina to STEMI, unified by acute plaque disruption. Classification drives reperfusion urgency: STEMI demands immediate reperfusion; NSTE-ACS is risk-stratified to determine timing of angiography. Initial management (the “ACS cocktail”) is shared across the spectrum.

classification

	NSTE-ACS (NSTEMI / UA)	STEMI
pathophysiology	subtotal occlusion, subendocardial ischaemia	total occlusion, transmural infarction
ECG	normal / ST depression / T-wave inversion	ST elevation / hyperacute T waves
biomarkers	troponin (+) NSTEMI, (−) UA	troponin (+), may be (−) early
reperfusion	risk-stratified invasive strategy	immediate (PCI or fibrinolysis)

initial assessment

ECG within 10 minutes of first medical contact
serial troponin (high-sensitivity — 0h and 3h, or 0/1h rapid rule-out if validated assay)
haemodynamic assessment — Killip class, signs of cardiogenic shock
risk stratification — GRACE score (NSTE-ACS), TIMI score

immediate medical management — the ACS cocktail

antiplatelet therapy

ASA 160–325 mg CHEWED (buccal absorption bypasses gastric delay)
P2Y12 inhibitor — choose one:

Agent	Loading dose	Key contraindication
ticagrelor	180 mg	prior intracranial haemorrhage
prasugrel	60 mg	ANY prior TIA/stroke; age >75 or <60 kg (relative)
clopidogrel	300–600 mg	use if thrombolysis planned (ticagrelor/prasugrel contraindicated with fibrinolysis)

fibrinolysis + P2Y12 selection

If thrombolysis is the reperfusion strategy → ASA + clopidogrel ONLY. Ticagrelor and prasugrel are not studied with fibrinolysis and increase bleeding risk.

anticoagulation

UFH or enoxaparin or fondaparinux
continue for 48h or until discharge/revascularisation
see Anticoagulants for dosing

adjunctive

beta-blocker within 24h if no contraindications (decompensated HF, heart block, bronchospasm)
nitrates PRN for ongoing ischaemic discomfort
oxygen only if SpO₂ <90% — routine supplemental O₂ may increase infarct size
opioids — use sparingly; delay P2Y12 absorption, may impair platelet inhibition

reperfusion strategy

STEMI → immediate reperfusion

See STEMI Management for full protocol including time targets, PCI vs fibrinolysis decision, and pharmacoinvasive strategy.

NSTE-ACS → risk-stratified invasive strategy

See NSTEMI Management for GRACE-based risk stratification and timing of angiography.

Risk category	Timing of angiography
very high (ongoing ischaemia, haemodynamic instability, arrhythmia)	immediate (<2h)
high (GRACE >140, dynamic ECG changes, rising troponin)	early (within 24h)
intermediate	routine invasive (<72h)
low	non-invasive testing or angiography if symptoms recur

DAPT duration — key summary

Scenario	Duration	Preferred regimen
post-ACS (STEMI/NSTEMI)	12 months standard	ASA + ticagrelor 90 mg BID (or prasugrel 10 mg OD)
post-ACS, high bleed risk	1–3 months then SAPT	SAPT with P2Y12i (favour ticagrelor)
post-ACS, low bleed risk at 12 months	extend up to 3 years	ASA + ticagrelor 60 mg BID (reduced dose)
elective PCI (DES)	3–6 months	ASA + clopidogrel
elective PCI (BMS)	1 month minimum	ASA + clopidogrel
ACS + AF (OAC indication)	triple therapy 1–30 days then dual pathway	clopidogrel + OAC (drop ASA)

See Antiplatelet Agents for drug-specific detail.

MINOCA

MI with non-obstructive coronary arteries — 6–15% of all MI; younger, more female; not benign.

diagnosis

Requires all of:

troponin meeting universal MI criteria
no coronary stenosis >50% on angiography
no overt alternative cause (e.g. myocarditis, takotsubo, PE)

mechanisms

plaque disruption (erosion/rupture with spontaneous lysis)
coronary vasospasm
microvascular dysfunction
thromboembolism
spontaneous coronary artery dissection (SCAD)

workup

careful angiogram review ± intracoronary imaging (OCT/IVUS)
echocardiography (wall motion pattern — takotsubo)
cardiac MRI (oedema/fibrosis pattern distinguishes ischaemic vs myocarditic)

treatment by mechanism

Mechanism	Approach
plaque disruption	DAPT + statin (standard ACS secondary prevention)
vasospasm	CCB ± long-acting nitrate; avoid beta-blockers
thromboembolism	anticoagulation; investigate source
SCAD	conservative management preferred; avoid PCI if possible

perioperative management — stents and DAPT

Stent type	Minimum delay for elective non-cardiac surgery
BMS	≥1 month
DES	≥3 months (1 month for semi-urgent)

hold clopidogrel/ticagrelor 5–7 days pre-op; prasugrel 7–10 days
continue ASA perioperatively whenever possible
restart DAPT post-op as soon as deemed safe