Acute Coronary Syndrome
Rupture of an unstable atherosclerotic plaque triggers thrombus formation that partially or completely occludes a coronary artery, and the resulting ECG and troponin pattern (STEMI, NSTEMI, or unstable angina) dictates exactly how urgently the vessel must be reopened.
In a nutshell
Plaque rupture triggers thrombus formation over a spectrum of severity: non-occlusive ischaemia without necrosis (unstable angina), partial occlusion causing subendocardial necrosis (NSTEMI), or complete occlusion causing transmural necrosis (STEMI). The ECG and troponin together place a patient on that spectrum and dictate urgency.
Classic presentation
Sudden central crushing chest pain radiating to the left arm or jaw, with sweating and nausea, persisting beyond twenty minutes and not relieved by rest.
Key points
- ST elevation reflects transmural (full-thickness) ischaemia from complete occlusion; it needs immediate reperfusion, not risk stratification.
- Troponin, not the ECG, distinguishes NSTEMI from unstable angina, because it only rises once myocytes actually die.
- Radiation of pain to the arm and jaw reflects shared spinal segments (T1–T4) between cardiac sympathetic afferents and somatic dermatomes.
- Complications map onto the site and extent of damage: arrhythmia from electrically irritable tissue, cardiogenic shock from extensive loss of muscle, and mechanical complications from damage to specific structures.
- Presentation can be atypical or silent, particularly in diabetic, elderly or female patients, because autonomic neuropathy or atypical symptom processing blunts the classic pain pattern.
First-line investigation
12-lead ECG within 10 minutes: it identifies transmural ischaemia (STEMI) needing immediate reperfusion versus a picture needing troponin to interpret further.
First-line management
Aspirin, oxygen if hypoxic, nitrate and analgesia immediately, then emergency primary PCI for STEMI or risk-stratified antithrombotic therapy and angiography for NSTEMI.
Exam traps
- A normal ECG does not exclude ACS; unstable angina and early NSTEMI can have a normal or non-specific ECG; troponin and the clinical picture still matter.
- ST elevation means immediate reperfusion, not waiting for a troponin result; troponin is not needed to diagnose STEMI.
- Diabetic and elderly patients can present with silent or atypical ischaemia (breathlessness, confusion, epigastric pain) without classic chest pain.
- A single normal troponin taken too early after symptom onset does not exclude NSTEMI; serial troponin is required.
Educational content pending clinical review. Not medical advice.