Polymorphic Ventricular Tachycardia

Aka: Polymorphic Ventricular Tachycardia, Polymorphic VT, Torsades de Pointes, Torsades

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II. Pathophysiology

  1. Wide complex Ventricular Tachycardia
  2. Polymorphic VT Is higher risk than Monomorphic VT for degeneration into Ventricular Fibrillation
  3. Polymorphic Ventricular Tachycardia (VT) has a continuously changing QRS morphology
    1. Unstable ventricular activation from multiple shifting foci or reentrant rhythm
    2. Contrast with Monomorphic VT triggered from a single ventricular focus with uniform QRS
  4. Polymorphic VT is divided into 2 main types
    1. Polymorphic VT with Prolonged QTc (Torsades de Pointes)
    2. Polymorphic VT with Normal QTc (most commonly Myocardial Infarction)

III. Causes

  1. Polymorphic VT with Prolonged QTc (Torsades de Pointes)
    1. See QT Prolongation
  2. Polymorphic VT with Normal QTc
    1. Acute Myocardial Infarction (most common cause)
      1. Myocardial Ischemia alters myocardial ion gradients, Action Potential durations and refractory period
      2. Results in conduction velocity differences across different myocardial regions
      3. Triggers chaotic and irregular ventricular depolarization, and prevents regular reentry circuit of Monomorphic VT
    2. Concurrent factors contributing to Polymorphic VT risk
      1. Sympathetic activation
      2. Structural heart disease (e.g. Brugada Syndrome)

IV. Management

  1. See Ventricular Tachycardia Management in the Adult
  2. See Ventricular Tachycardia Management in the Child
  3. See Unstable Tachycardia
  4. INITIAL Steps
    1. ABC Management (and IV-O2-monitor)
    2. See Cardiac Arrest
    3. Differentiation based on QT Interval is directed at prevention of recurrent Arrhythmia
    4. Immediate Synchronized Cardioversion
      1. Immediate Defibrillation (non-Synchronized Cardioversion) if Defibrillator is unable to synchronize
  5. Prolonged QT interval (on baseline EKG): Torsades de Pointes
    1. Give Magnesium 2 grams IV
      1. May be repeated in 5-15 minutes
      2. May be continued as infusion Magnesium 3 to 20 mg/min IV for Prolonged QTc
    2. Correct other Electrolyte abnormalities (5H5T)
    3. Stop all medications that prolong QT Interval
      1. Do NOT give any AV Nodal blocking agents (e.g. Amiodarone, Beta Blockers, Calcium Channel Blockers)
      2. Do NOT give any agent that prolongs QTc (e.g. Procainamide)
    4. Reverse toxic ingestions and Poisonings
    5. Consider overdrive pacing to Heart Rate of 100 bpm
    6. Consider Isoproterenol in refractory cases with Bradycardia (used historically, controversial)
      1. Increases Heart Rate and shortens the QT Interval
  6. Normal QT Interval (on baseline EKG): Polymorphic Ventricular Tachycardia
    1. Exercise caution that QTc is normal (not Torsades de Pointes)
      1. All agents described below can be lethal in Torsades de Pointes
      2. If in doubt, treat as Torsades de Pointes (esp. Magnesium)
    2. Myocardial Ischemia (most common)
      1. Beta Blockers
      2. Emergent cardiac catheterization for revascularization
      3. Consider Amiodarone 150 mg IV (caution)
    3. Catecholaminergic Ventricular Tachycardia
      1. Consider Beta Blockers
    4. Brugada Syndrome
      1. Consider Isoproterenol
    5. Miscellaneous management of contributing factors
      1. Hypoxia management
      2. Electrolyte abnormality correction (e.g. Potassium, Magnesium)

V. References

  1. Vandersteenhoven and Brady (2026) Crit Dec Emerg Med 40(2): 13-4

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