ST-Elevation Myocardial Infarction (STEMI)

Cardiology

Acute coronary occlusion producing transmural ischaemia with ST elevation on ECG.

Causes

  • • Plaque rupture with occlusive thrombus
  • • Coronary spasm/embolism
  • • Spontaneous coronary artery dissection (SCAD)

Risk factors

  • • Age, male, smoking, HTN, DM, dyslipidaemia, family history, CKD, obesity

Clinical features

  • • Central crushing chest pain >20 min
  • • Diaphoresis, dyspnoea, nausea
  • • Radiation to arm/jaw

Examination

  • • Anxious, cool clammy
  • • Tachy/brady
  • • S4 gallop
  • • Signs of HF

Investigations

  • • 12-lead ECG within 10 min
  • • hs-troponin serial
  • • CBC, U&E, glucose, lipid, coag
  • • Portable CXR, echo

Diagnosis

  • • ECG ST↑ ≥1 mm in ≥2 contiguous limb leads OR ≥2 mm V2-V3 (M) / ≥1.5 mm V2-V3 (F)
  • • New LBBB with symptoms
  • • Posterior MI = ST↓ V1-V3 with dominant R

Differential diagnosis

  • • Aortic dissection
  • • PE
  • • Pericarditis/myocarditis
  • • Oesophageal spasm/rupture
  • • Pneumothorax

Management

  • • Aspirin 300 mg + P2Y12 (ticagrelor 180 mg / prasugrel 60 mg)
  • • Anticoag: heparin 60 U/kg or bivalirudin
  • • Primary PCI ≤120 min (door-to-balloon ≤90 min)
  • • Fibrinolysis if PCI unavailable ≤12 h (contraindication check)

Drug therapy

  • • High-intensity statin (atorvastatin 80 mg)
  • • β-blocker if no HF/shock
  • • ACEi/ARB within 24 h if EF<40 or DM
  • • MRA if EF≤40 + HF/DM
  • • Long-term DAPT 12 months

Complications

  • • Arrhythmia (VF/VT, AV block)
  • • HF, cardiogenic shock
  • • Papillary muscle/VSR rupture
  • • LV thrombus/embolism
  • • Dressler syndrome

Prevention

  • • Smoking cessation
  • • Mediterranean diet
  • • Exercise (cardiac rehab)
  • • Lipid + BP control

Follow-up

  • • Cardiac rehab at 4-6 weeks
  • • Echo at 6 weeks (LVEF)
  • • Lipid + HbA1c 3 months

Clinical pearls

  • • Time = muscle — activate cath lab bypass ED
  • • Right-sided leads in inferior MI (V4R)
  • • Sgarbossa criteria in LBBB

References

  • • ESC 2023 STEMI Guidelines
  • • AHA/ACC 2022 Chest Pain Guideline

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