ST segment elevation

Background

• Its presence must be explained (there is no "nonspecific ST elevation")
• Not specific only to STEMI

Clinical Features

• Depends on underlying etiology

Differential Diagnosis

ST Elevation

• Cardiac
  • ST-segment elevation myocardial infarction (STEMI)
  • Post-MI (ventricular aneurysm pattern)
  • Previous MI with recurrent ischemia in same area
  • Wellens' syndrome
  • Coronary artery vasospasm (eg, Prinzmetal's angina)
  • Coronary artery dissection
  • Pericarditis
  • Myocarditis
  • Aortic dissection in to coronary
  • Left ventricular aneurysm
  • Left ventricular pseudoaneurysm
  • Early repolarization
  • Left bundle branch block
  • Left ventricular hypertrophy (LVH)
  • Myocardial tumor
  • Myocardial trauma
  • RV pacing (appears as Left bundle branch block)
  • Brugada syndrome
  • Takotsubo cardiomyopathy
  • AVR ST elevation
• Other thoracic
  • Pneumomediastinum
  • Pneumothorax
  • Pulmonary embolism
• Metabolic
  • Drugs of abuse (eg, cocaine, crack, meth)
    • Cocaine chest pain
  • Hyperkalemia (only leads V1 and V2)
  • Hypothermia ("Osborn J waves")
• Medications
  • Tricyclic (TCA) toxicity
  • Digoxin

Evaluation

Measure ST elevation at the j-point

Early Repolarization versus STEMI

• Early Repolarization suggested by:
  • ST elevation <4mm
  • Notched J point
  • Concave or saddle-back ST morphology
  • No reciprocal changes
  • Consistent over short term
  • Young patient without risk factors

LVH versus STEMI

• Difficult to exclude MI in patient with LVH (patients with LVH are already at risk for MI)
• Best aid is prior ECG or serial ECGs

LBBB versus STEMI

See Sgarbossa's Criteria

STEMI

• ST elevation in those leads that reflect the distribution of a single coronary artery
  • RCA: II, III, aVF (inferior)
  • LAD: V1-V4 (antero-septal)
  • Circumflex: V5-V6, I, aVL (lateral)
  • Dominant left circulation: infero-lateral
• ST morphology
  • Concave up versus convex
    • Convex has Sp 97%, Sn 77%
• Look for reciprocal ST depression
  • 35% of anterior STEMI have ST depression in inferior leads
  • 80% of inferior STEMI have ST depression in anterior leads
    • However, may represent reciprocal changes OR posterior STEMI

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 with ST-segment elevation in II, III, aVF (inferior involvement)

STEMI Stages of Development

Stages of STEMI development

Stage	Duration	Timing	Finding	ECG
1		30min - hours	Hyperacute T waves >6mm limb leads >10mm precordial leads	Normalizes in days, weeks, or months
2		Minutes - hours	ST segment elevation 0.1mV in two or more contiguous leads	ST segment resolution occurs over 72hrs; completely resolves within 2-3wks
3		Within 1hr; completed within 8-12hr	Q waves	Persist indefinitely in 70% of cases

See Also

• ECG (Main)
• STEMI equivalents
• STEMI mimics