EKG Changes in Syncope due to Arrhythmia

Aka: EKG Changes in Syncope due to Arrhythmia, Electrocardiogram in Syncope

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II. Precautions

  1. Intervals and duration (PR Interval, QRS Duration, QTc Interval) are critical to evaluate in Syncope

III. Interpretation: EKG changes suggestive of Syncope due to Arrhythmia

  1. Abnormal Heart Rate
    1. Sinus Bradycardia <50 bpm (consider Sick Sinus Syndrome)
  2. Prolonged PR Interval
    1. Second Degree Atrioventricular Block
    2. Third Degree Atrioventricular Block
  3. Short PR Interval
    1. Wolff-Parkinson-White Syndrome
  4. Abnormal QRS
    1. Left Bundle Branch Block, anterior or posterior hemiblock or Bifascicular Heart Block
      1. Associated with a 3 fold higher risk of serious cardiac cause
    2. QRS Duration > 120 ms
    3. Q Waves
  5. Prolonged QTc Interval
    1. See QT Prolongation
    2. See Prolonged QT Interval due to Medication
    3. Long QT Syndrome

IV. Interpretation: EKG changes related to specific syndromes

  1. EKG in Acute Coronary Syndrome
    1. ST Segment Elevation (or ST depression in coronary ischemia)
    2. Deep T Wave Inversion
  2. EKG in Tachy-Brady Syndrome (Sick Sinus Syndrome)
    1. Tachycardia or Bradycardia
    2. Atrioventricular Block (especially Mobitz II or third degree AV Block)
  3. EKG changes seen in Wolff-Parkinson-White Syndrome (WPW Syndrome)
    1. Short PR Interval (<120 ms)
    2. Delta Waves
  4. EKG changes seen in Brugada Syndrome
    1. Right Bundle Branch Block (RSR')
    2. ST Elevation in leads V1-V3
  5. EKG in Arrhythmogenic Right Ventricular Dysplasia (ARVD)
    1. T Wave Inversion in leads V1-V3
    2. QRS Complex duration > 110 ms in leads V1-V3
    3. Right Bundle Branch Block
    4. Terminal notch at end of QRS (Epsilon Wave)
    5. Septal T Wave Inversion (V1-3)
  6. EKG in Hypertrophic Cardiomyopathy
    1. High voltage
    2. Lateral (esp. I, aVL, V4-6) and inferior Q Waves (deep, dagger or needle-like, narrow)
    3. Septal, deep, symmetric T inversion (variable)
  7. Abnormal QT Interval
    1. Prolonged QT Segment >500 ms
    2. Short QT Segment <300 ms
      1. Autosomal Dominant condition associated with Sudden Cardiac Death
  8. EKG with right ventricular strain pattern (e.g. Pulmonary Embolism)
    1. See Right Ventricular Strain EKG Pattern
    2. Right Bundle Branch Block
    3. T Wave Inversion in anterior (V1-3) or inferior (II, III, avF) leads
    4. Prominent P Waves
    5. S1-Q3-T3 Pattern (S in I, Q in III, T inversion in III)
  9. EKG in Hyperkalemia
    1. Initial: Peaked T Waves in V2-3, II, III
    2. Next: ST depression, First degree AV Block, QT Interval shortening
    3. Next: QRS Widening with loss of P Waves
  10. EKG in Increased Intracranial Pressure
    1. Very large amplitude T Waves
    2. Prolonged QT
  11. EKG in Atrial Septal Defect (ASD, Ostium Secundum)
    1. Crochetage sign (correlates with severity of left to right shunt)
    2. Right Bundle Branch Block

V. Efficacy

  1. EKG is low yield in syncopal patients under age 40 years old (however most warrant EKG in ED evaluation)
    1. Sun (2008) Ann Emerg Med 51(3): 240-6 [PubMed]

VI. References

  1. Mattu in Herbert (2014) EM:Rap 14(7): 15-6
  2. Brignole (2001) Eur Heart J 22:1256-306 [PubMed]

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