ACS - ECG

ST Segment Elevation

• Stage 1
  • Timing: 30min - hours
  • Finding: hyperacute T waves
    • >6mm limb leads
    • >10mm precordial leads
  • Duration: normalizes in days, weeks, or months
• Stage 2
  • Timing: minutes - hours
  • Finding: ST segment elevation
    • ≥0.1mV in two or more contiguous leads
  • Duration: ST segment resolution occurs over 72hrs; completely resolves w/in 2-3wks
• Stage 3
  • Timing: within 1hr; completed within 8-12hr
  • Finding: Q waves
  • Duration: persist indefinitely in 70% of cases

• a: 30min after chest pain onset
• b: 45min after chest pain onset (hyperacute T waves)
• c: 70min after chest pain onset (ST elevation)
• d: 3hr after PCI (ST segment has decreased, TWI incdicates reperfusion)
• e: 5 days after PCI (ST segment back to baseline, TWI is near baseline)

Reciprocal Changes

1. Anterior STEMI
   • Reciprocal ST-segment depression in at least one of leads II, III, aVF
   • Occurs in 40-70% of cases
2. Inferior STEMI
   • Reciprocal ST-segment depression usually present in I, aVL; often in V1-V3
   • Occurs in 56% of cases
3. Posterior STEMI
   • Reciprocal ST-segment depression in V1-V4
     • Differentiate from inf STEMI reciprocal depression based on upright T waves, posterior leads showing STEMI
   • Often associated w/ ST-segment elevation in II, III, aVF (inferior involvement)

See Also

• ACS - Anatomical Correlation
• ACS - Risk Stratification
• ECG (Main)

Source

• Electrocardiography in Emergency Medicine. ACEP Textbook.