II. Definitions
- QRS Interval
- Electrical signal on EKG representing depolarization of the ventricle (immediately preceding contraction)
- Interval from the start of the Q Wave to the end of the S Wave
III. Normal findings: Duration
- Limb leads (I, II, III): 0.05 to 0.10
- Precordial leads (V1 to V6): 0.06 to 0.12
IV. Causes: Wide QRS or Prolonged QRS Complex (over 0.12)
- Intraventricular Conduction Delay (IVCD)
- See Bundle Branch Block
- Hypothermia
- Hyperkalemia
- Wolff-Parkinson-White Syndrome (WPW)
- Ventrciular ectopy
- Ventricular Tachycardia
- Left Ventricular Hypertrophy
- Pacemaker with ventricular pacing
- Non-specific Intraventricular Conduction Delay (IVCD)
- IVCD does not meet criteria for other diagnoses
- Medications (e.g. Toxin Ingestion or Overdose)
- Results from Sodium channel blockade
- Emergency management
- See Toxin Ingestion
- See Tricyclic Overdose
- Sodium Bicarbonate 1-2 amps IV push with repeat bolus until QRS narrows (adults)
- Causes
- See Sodium Channel Blocker
- Tricyclic Antidepressants
- Dry and sedated
- Cocaine
- Diaphoretic and agitated
- Diphenhydramine (Benadryl)
- Local Anesthetics (esp. Bupivacaine)
- Antiarrhythmics (e.g. Quinidine, Flecainide)
- Propoxyphene (not available in U.S.)
- Digoxin Toxicity
- Associated with frequent PVCs and sagging ST depression
V. Causes: Low QRS amplitude (<5 mm in limb leads)
VI. Causes: High QRS amplitude
- Evaluate for Left Ventricular Hypertrophy (LVH)
- Avoid using QRS amplitude alone to diagnose LVH in age <40-45 years old
- High Left Ventricular Voltage (HLVV)
- Large amplitude QRS Complexes are a normal finding in young, healthy athletes (not LVH)
VII. References
- Mattu (2016) Crit Dec Emerg Med 30(8):16
- Mattu (2021) Crit Dec Emerg Med 35(5):16