QRS Complex

Aka: QRS Complex, QRS Duration, Wide QRS, QRS Widening, Electrocardiogram QRS complex, EKG QRS Interval, High Left Ventricular Voltage, Low QRS Voltage, Low QRS Amplitude, QRS-T Complex

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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. QRS-T Complex (pseudo-Wide QRS)
    1. QRS-T Complex is a fusion of the QRS, ST, and T Wave (Shark Fin)
    2. Appears as a very Wide QRS in some leads with the appearance of a "shark fin"
    3. Some leads will demonstrate a discernable elevated J-Point between the QRS and the ST Segment
    4. Seen in massive acute Myocardial Infarction and are at high risk of Arrhythmia, decompensation and Cardiac Arrest
  3. 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 or Voltage (<5 mm in limb leads)

  1. Cardiac
    1. Diffuse Coronary Artery Disease or Myocardial Infarction
    2. Congestive Heart Failure or Pulmonary Edema
    3. Pericardial Effusion
    4. Constrictive Pericarditis
    5. Infiltrative Cardiomyopathy (e.g. Cardiac Amyloidosis)
    6. Myocarditis
  2. Respiratory
    1. Emphysema (COPD)
    2. Acute Respiratory Distress Syndrome
    3. Pleural Effusion
    4. Pneumonia
    5. Pneumothorax, Subcutaneous Emphysema or Pneumomediastinum
  3. Miscellaneous Extracardiac
    1. Normal variant
    2. Myxedema (severe Hypothyroidism)
    3. Obesity
    4. Anasarca

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. Berberian, Brady and Mattu (2024) Crit Dec Emerg Med 33(1): 14-5
  2. Berberian, Brady and Mattu (2024) Crit Dec Emerg Med 38(5): 12-3
  3. Mattu (2016) Crit Dec Emerg Med 30(8):16
  4. Mattu (2021) Crit Dec Emerg Med 35(5):16

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