Summary

Acute coronary syndrome (ACS) encompasses a spectrum of conditions caused by acute myocardial ischaemia, most commonly due to atherosclerotic plaque rupture and coronary thrombus formation. The spectrum includes ST-elevation myocardial infarction (STEMI), non-ST-elevation myocardial infarction (NSTEMI), and unstable angina. STEMI represents complete coronary occlusion and requires emergent reperfusion therapy (primary PCI or fibrinolysis). NSTEMI/unstable angina are managed with antithrombotic therapy and a risk-stratified approach to invasive management. Early recognition, timely reperfusion, and optimal medical therapy significantly reduce mortality.

Key Facts

• Definition: Acute myocardial ischaemia due to coronary thrombus
• Spectrum: Unstable Angina → NSTEMI → STEMI
• STEMI: Complete occlusion, ST elevation, urgent reperfusion required
• NSTEMI: Partial occlusion, troponin positive, no persistent ST elevation
• Unstable Angina: Troponin negative, high-risk angina
• Door-to-Balloon Target: <90 minutes for primary PCI
• Door-to-Needle Target: <30 minutes for fibrinolysis if PCI not available

Clinical Pearls

"Time is Myocardium": Every minute of delay in STEMI increases mortality. Primary PCI within 90 minutes is the goal.

"STEMI Equivalents": New LBBB, posterior MI, de Winter T-waves, and hyperacute T-waves may represent acute occlusion despite no classic ST elevation — treat as STEMI.

"DAPT for All": Dual antiplatelet therapy (aspirin + P2Y12 inhibitor) is the cornerstone of management in all ACS patients.

Why This Matters Clinically

ACS is a leading cause of death worldwide. Rapid diagnosis and treatment save lives. Every minute counts in STEMI — delayed reperfusion leads to larger infarcts, heart failure, and higher mortality.

Physical Examination

General:

• Pallor, sweating, distress
• Cool peripheries

Cardiovascular:

• May be normal
• Tachycardia, hypotension (cardiogenic shock)
• S3 (LV dysfunction)
• Murmur (MR if papillary muscle dysfunction)
• Elevated JVP (RV infarct or failure)

Pulmonary:

• Crackles (pulmonary oedema)

Killip Classification (Acute MI)

Mortality

Prognostic Factors

• Age, Killip class, heart rate, BP
• Anterior MI worse than inferior
• Delayed reperfusion worsens outcome
• EF most important long-term predictor

Key Guidelines

1. ESC Guidelines for STEMI (2017) — Ibanez B, et al.

2. ESC Guidelines for NSTE-ACS (2020) — Collet JP, et al.

Landmark Trials

PLATO (2009) — Ticagrelor vs Clopidogrel

• Key finding: Ticagrelor reduced CV death, MI, stroke
• Clinical Impact: Ticagrelor preferred over clopidogrel in ACS

HORIZONS-AMI (2008) — Bivalirudin in STEMI

• Key finding: Bivalirudin reduced bleeding vs heparin+GPIIb/IIIa

Evidence Strength

What is ACS?

Acute coronary syndrome is a group of conditions caused by reduced blood flow to your heart. It includes heart attacks (STEMI and NSTEMI) and unstable angina.

What happens?

A fatty deposit (plaque) in your heart's arteries can rupture, forming a blood clot that blocks blood flow. This damages heart muscle.

What are the symptoms?

• Crushing chest pain lasting more than 15-20 minutes
• Pain spreading to your arm, jaw, or back
• Shortness of breath
• Sweating, nausea, feeling unwell

How is it treated?

1. Emergency treatment: Aspirin, blood thinners, and opening the blocked artery (angioplasty with stent or clot-busting drugs)
2. Long-term medicines: Blood thinners, cholesterol tablets, blood pressure tablets
3. Lifestyle changes: Stop smoking, healthy diet, exercise, cardiac rehabilitation

What to expect

• Most people recover well with prompt treatment
• You'll need medications for life to prevent future heart attacks
• Cardiac rehabilitation helps recovery

When to call 999

Call 999 immediately if:

• You have crushing chest pain lasting more than 15 minutes
• Pain spreads to your arm or jaw
• You feel short of breath, sweaty, or unwell