II. Definitions

  1. QRS Interval
    1. Electrical signal on EKG representing depolarization of the ventricle (immediately preceding contraction)
    2. Interval from the start of the Q Wave to the end of the S Wave

III. Normal findings: Duration

  1. Limb leads (I, II, III): 0.05 to 0.10
  2. Precordial leads (V1 to V6): 0.06 to 0.12

IV. Causes: Wide QRS or Prolonged QRS Complex (over 0.12)

  1. Intraventricular Conduction Delay (IVCD)
    1. See Bundle Branch Block
    2. Hypothermia
    3. Hyperkalemia
    4. Wolff-Parkinson-White Syndrome (WPW)
    5. Ventrciular ectopy
    6. Ventricular Tachycardia
    7. Left Ventricular Hypertrophy
    8. Pacemaker with ventricular pacing
    9. Non-specific Intraventricular Conduction Delay (IVCD)
      1. IVCD does not meet criteria for other diagnoses
  2. Medications (e.g. Toxin Ingestion or Overdose)
    1. Results from Sodium channel blockade
    2. Emergency management
      1. See Toxin Ingestion
      2. See Tricyclic Overdose
      3. Sodium Bicarbonate 1-2 amps IV push with repeat bolus until QRS narrows (adults)
    3. Causes
      1. See Sodium Channel Blocker
      2. Tricyclic Antidepressants
        1. Dry and sedated
      3. Cocaine
        1. Diaphoretic and agitated
      4. Diphenhydramine (Benadryl)
      5. Local Anesthetics (esp. Bupivacaine)
      6. Antiarrhythmics (e.g. Quinidine, Flecainide)
      7. Propoxyphene (not available in U.S.)
      8. Digoxin Toxicity
        1. Associated with frequent PVCs and sagging ST depression

V. Causes: Low QRS amplitude (<5 mm in limb leads)

VI. Causes: High QRS amplitude

  1. Evaluate for Left Ventricular Hypertrophy (LVH)
    1. Avoid using QRS amplitude alone to diagnose LVH in age <40-45 years old
  2. High Left Ventricular Voltage (HLVV)
    1. Large amplitude QRS Complexes are a normal finding in young, healthy athletes (not LVH)

VII. References

  1. Mattu (2016) Crit Dec Emerg Med 30(8):16
  2. Mattu (2021) Crit Dec Emerg Med 35(5):16

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