Skip to main content

Health condition · Clinically reviewed

Acute coronary syndrome, from the 999 call to the cath lab and cardiac rehab.

Unstable angina, NSTEMI and STEMI sit on one spectrum. This guide sets out how the UK pathway actually works, why time matters, and what long-term protection looks like.

Jump to treatment
A radiographer guides a patient onto the bed of an advanced 3 Tesla MRI scanner in a London imaging suite

Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against NICE, ESC and Resuscitation Council UK guidance you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK practice including primary PCI networks, GRACE-based stratification and 12-month DAPT.

Key facts

ACS at a glance.

The essentials, in plain English: the spectrum, the first hour, the two pathways and what happens next.

  • What it is

    A medical emergency covering unstable angina, NSTEMI and STEMI, driven by atherosclerotic plaque rupture, platelet activation and coronary thrombus.

  • Spectrum

    Unstable angina (troponin negative), NSTEMI (troponin positive, no ST elevation) and STEMI (ST elevation or new LBBB) sit on one continuum.

  • First action

    Call 999. A 12-lead ECG within 10 minutes of first medical contact decides the pathway.

  • STEMI pathway

    Primary PCI within 120 minutes of diagnosis, or fibrinolysis where PCI is not available inside that window.

  • NSTEMI pathway

    Risk-stratified with the GRACE score; early invasive angiography within 24 to 72 hours for intermediate and high risk.

  • Secondary prevention

    DAPT for 12 months, high-intensity statin, ACE inhibitor, beta blocker, cardiac rehab and lifelong risk-factor control.

Why this guide matters

Time is muscle, and the plan is stepped.

ACS is common, treatable and, with the right pathway, survivable. Three ideas shape everything else on this page.

  • One diagnosis, three faces

    Unstable angina, NSTEMI and STEMI share a mechanism (plaque rupture and thrombus) but need different urgency and different reperfusion strategies.

  • The first hour decides a lot

    A 12-lead ECG within 10 minutes, aspirin plus a P2Y12 inhibitor, and a defined door-to-balloon target save heart muscle and lives.

  • Secondary prevention is lifelong

    DAPT, a high-intensity statin, an ACE inhibitor, a beta blocker and cardiac rehab together halve the risk of a second event.

How the diagnosis is made

From 999 call to a clear pathway.

The steps a UK ambulance crew, emergency department and cardiology team follow in order, so you know what to expect and why.

  1. 01

    Immediate

    999 and pre-hospital ECG

    Chest pain suggestive of ACS is a 999 call. Ambulance crews transmit a 12-lead ECG so the receiving centre can activate the cath lab early.

  2. 02

    Immediate

    Door-to-ECG under 10 minutes

    A 12-lead ECG within 10 minutes of arrival triages STEMI (ST elevation or new LBBB) from non-ST elevation ACS.

  3. 03

    Immediate

    MONA and dual antiplatelet load

    Morphine if pain is severe, oxygen only if hypoxic, nitrates for ongoing ischaemia, aspirin 300 mg chewed plus a P2Y12 inhibitor (ticagrelor, prasugrel or clopidogrel).

  4. 04

    Stratifying

    High-sensitivity troponin, repeat 3h

    A baseline hs-troponin with a repeat at 1 to 3 hours separates unstable angina (negative) from NSTEMI (rising or elevated).

  5. 05

    Stratifying

    GRACE risk stratification

    For non-ST elevation ACS the GRACE 2.0 score guides timing of angiography: very high risk within 2 hours, high within 24, intermediate within 72.

  6. 06

    Treating

    Coronary angiography and PCI

    STEMI goes straight to primary PCI. NSTEMI proceeds to invasive angiography with PCI or CABG based on coronary anatomy and comorbidities.

  7. 07

    Treating

    Echocardiogram and rehab referral

    An inpatient echo assesses left-ventricular function and complications; every patient is referred to a cardiac rehabilitation programme before discharge.

Typical timeline: first medical contact to reperfusion in minutes for STEMI, hours for NSTEMI.

Symptoms

What ACS actually feels like.

Classic central chest pain remains the dominant presentation, but atypical patterns are common in women, older adults and people with diabetes.

  • Central chest pain

    Heavy, crushing or tight pain, often radiating to the jaw, neck or left arm and lasting more than 15 to 20 minutes.

  • Breathlessness

    New or worsening breathlessness at rest can be the dominant symptom, especially in older adults.

  • Sweating and nausea

    Cold sweat, clammy skin, nausea or vomiting alongside chest discomfort are classic autonomic features.

  • Radiation to arm or jaw

    Pain travelling to one or both arms, the neck, jaw or upper back raises concern for a cardiac cause.

  • Atypical presentation

    Women, people with diabetes and older adults may present with fatigue, epigastric pain or breathlessness rather than classical chest pain.

  • Palpitations and syncope

    Arrhythmia can accompany ACS and sometimes causes collapse, especially with inferior infarcts.

  • Ongoing angina at rest

    Angina that occurs at rest, wakes you from sleep or is not settled by GTN is unstable angina until proven otherwise.

  • Red flag - haemodynamic collapse

    Cardiogenic shock, pulmonary oedema, cardiac arrest or new mechanical complication needs immediate resuscitation and revascularisation.

Treatment

How ACS is treated in the UK.

Primary PCI for STEMI, GRACE-guided invasive angiography for NSTEMI, dual antiplatelet loading for all, and lifelong secondary prevention.

  • Primary PCI (STEMI)

    The first choice for STEMI. Target is diagnosis-to-balloon within 120 minutes; radial access is standard in UK cath labs.

  • Fibrinolysis

    Where primary PCI cannot be delivered within 120 minutes, a fibrinolytic is given, followed by transfer for rescue or routine PCI.

  • Early invasive angiography (NSTEMI)

    Timing is set by GRACE: within 2 hours for very high risk, within 24 hours for high risk and within 72 hours for intermediate risk.

  • PCI with stent

    A drug-eluting stent is placed across the culprit lesion; complete revascularisation of significant non-culprit disease is often planned in the same admission.

  • Coronary artery bypass (CABG)

    Preferred for left main disease, complex three-vessel disease or where PCI is not feasible, particularly in diabetes with multivessel disease.

  • Dual antiplatelet therapy (DAPT)

    Aspirin plus a P2Y12 inhibitor (ticagrelor, prasugrel or clopidogrel) for 12 months as standard, then aspirin monotherapy.

  • Secondary prevention drugs

    High-intensity statin (atorvastatin 80 mg), ACE inhibitor, beta blocker and, where left-ventricular function is impaired, a mineralocorticoid receptor antagonist such as spironolactone or eplerenone.

  • Cardiac rehabilitation

    A structured programme of supervised exercise, education and psychological support, offered to every patient after ACS.

What this guide is based on

The sources behind every claim on this page.

UK national guidance, European society standards and Resuscitation Council UK, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

If you or someone with you has sudden chest pain, breathlessness or collapse, call 999 immediately. Do not drive to hospital.

  • NICE NG185. Acute coronary syndromes.

  • ESC 2023 Guidelines for the management of acute coronary syndromes.

  • Resuscitation Council UK. Advanced Life Support guidelines.

  • British Cardiovascular Society standards for primary PCI networks.

Red flags

When ACS needs immediate escalation.

Every suspected ACS is time-critical. These features raise urgency further and change what happens in the first minutes.

  • Cardiac arrest

    Sudden collapse with no pulse. Start CPR, call 999 and use a defibrillator if available. Every minute of delay reduces survival.

  • Cardiogenic shock

    Cold, clammy, hypotensive and confused after chest pain. Needs immediate transfer to a PCI centre with mechanical support available.

  • Acute pulmonary oedema

    Sudden severe breathlessness with pink frothy sputum after chest pain suggests a large infarct with pump failure. Blue-light transfer.

  • Mechanical complication

    New murmur, hypotension or worsening breathlessness days after MI can signal papillary muscle rupture, VSD or free-wall rupture. Emergency echo and surgery.

  • Ongoing ischaemic pain despite therapy

    Pain that does not settle with GTN, aspirin and analgesia is a signal to escalate to urgent angiography, not to wait.

  • New LBBB with chest pain

    Treated as STEMI-equivalent when the clinical picture fits. Do not wait for troponin, activate the primary PCI pathway.

  • Bleeding on DAPT

    Melaena, haematemesis, uncontrolled epistaxis or unexplained bruising while on dual antiplatelets needs urgent review, not self-discontinuation.

  • Post-MI arrhythmia

    Palpitations, syncope or sudden breathlessness in the weeks after ACS may be VT or new AF and needs urgent cardiology review.

  • Recurrent chest pain after discharge

    Chest pain returning after PCI can mean stent thrombosis. Call 999, chew 300 mg aspirin and get to a PCI centre.

Living with it

Life after ACS, a plan that keeps you well.

The first year after ACS is the highest-risk window. Four habits, kept steadily, cut the odds of a second event far more than any single intervention.

A quiet reminder

The tablets and the treadmill both matter.

Medicines protect the plumbing; cardiac rehab retrains the confidence and fitness that were lost in the event.

  1. 01 Medicines

    Take DAPT for the full 12 months

    Stopping a P2Y12 inhibitor early is a leading cause of stent thrombosis. Any planned break needs a cardiologist conversation.

  2. 02 Rehab

    Start cardiac rehab within weeks

    Supervised exercise, education and psychological support after ACS reduces future events and improves confidence. Every patient is eligible.

  3. 03 Risk

    Own the risk factors for life

    Blood pressure, LDL cholesterol, HbA1c, weight and smoking are the levers that keep the next event away. Aim for tight, sustained control.

  4. 04 Return

    Know when to seek help again

    Recurrent chest pain, new breathlessness, palpitations or bleeding on antiplatelets are not to be watched at home. Call 999 or your cardiology team.

Frequently asked

Everything we get asked about ACS.

Quick answers on the pathway, DAPT duration, rehab and what to do if symptoms return.

  • What is acute coronary syndrome?

    ACS is an umbrella term for unstable angina, NSTEMI and STEMI. All three are caused by acute reduction in blood flow through a coronary artery, usually because an atherosclerotic plaque has ruptured and formed a clot. They differ in whether the ECG shows ST elevation and whether troponin rises.

  • How is STEMI treated differently from NSTEMI?

    STEMI needs immediate reperfusion, ideally primary PCI within 120 minutes of diagnosis. NSTEMI is stabilised medically and taken for early invasive angiography within 24 to 72 hours, guided by the GRACE risk score.

  • What is MONA?

    A memory aid for the initial pharmacological package in suspected ACS: Morphine for severe pain, Oxygen only if oxygen saturation is low, Nitrates for ongoing ischaemic pain and Aspirin 300 mg chewed. Modern practice adds a P2Y12 inhibitor (ticagrelor, prasugrel or clopidogrel) as part of dual antiplatelet loading.

  • Why do I need two blood thinners after a heart attack?

    Dual antiplatelet therapy, aspirin plus a P2Y12 inhibitor, reduces the risk of stent thrombosis and recurrent ischaemic events during the first 12 months. After that, most patients continue on aspirin alone unless a specialist advises otherwise.

  • What is cardiac rehabilitation?

    A structured NHS or private programme of supervised exercise, education about medicines and risk factors, and psychological support. It typically runs for 6 to 12 weeks after ACS and is one of the most effective interventions for reducing future cardiac events.

  • How can I reduce my risk of another event?

    Take secondary prevention medicines exactly as prescribed, complete cardiac rehab, stop smoking, keep blood pressure below 130/80 where tolerated, drive LDL cholesterol below 1.4 mmol/L on a high-intensity statin, control diabetes and stay physically active. These lifestyle and drug measures together halve the risk of recurrence.

Related content

Keep reading.

Pulse Healthcare concierge

Send us your enquiry

A concierge service for UK private healthcare. We match you with the best vetted clinics and consultants in our network - they then contact you directly.

So we can match you to the right clinician close to you.

We reply to every enquiry within 24 hours (Mon–Fri). Confidential - your details are never shared outside our vetted consultant network.