Polymorphic ventricular tachycardia

Background

• Form of ventricular tachycardia in which there are multiple ventricular foci, leading to QRS complexes with varying morphology
• Subtypes include Torsades de pointes, bidirectional polymorphic VTach (seen in digoxin toxicity

Etiologies

• Myocardial ischemia (most common)
• Acquired or congenital prolonged QT
  • TCAs, phenothiazines, Type I antiarrhythmics (quinidine, procainamide)
  • Hypokalemia
  • Hypomagnesemia
  • Elevated intracranial pressure
• Brugada syndrome, short QT syndrome, congenital catecholaminergic polymorphic ventricular tachycardia

Clinical Features

• Syncope
• Palpitations

Differential Diagnosis

Assume any wide-complex tachycardia is ventricular tachycardia until proven otherwise

• A-fib/flutter with variable AV conduction AND bundle branch block (fixed or rate-related)
• A-fib/flutter with variable AV conduction AND accessory pathway (e.g. WPW)
• A-fib + hyperkalemia

Evaluation

• Evaluate for underlying causes (e.g. electrolyte imbalances, ACS)

ECG Findings

• Wide QRS (>100ms or 3 small boxes)
• QRS complexes of varied amplitude, axis and duration
  • • Torsades: QRS complexes appear to twist around isoelectric line
• Rapid rhythm (usually 140-160 bpm, but can be up to 300 bpm)
• Irregular

Management

Pulseless

See Adult pulseless arrest and Pediatric pulseless arrest

Unstable

• Unsynchronized cardioversion (defibrillation) 200J (or 2J/kg for pediatrics)
• Correct any electrolyte abnormalities

Stable

• Correct any electrolyte abnormalities
• Torsades:
  • Magnesium sulfate (for Torsades):
    • 1-2gm IV, repeat in 5-15min; then 1-2gm/hr (3-10mg/min) drip
    • Peds: 25-50mg/kg (max 2g) IV
  • Sotalol (100mg IV over 5 minutes)
  • Isoproterenol, 2-8 mcg/min
  • Overdrive Pacing to goal HR 90-120
  • Avoid procainamide, amiodarone (may further prolong QT)
• Non-Torsades
  • Amiodarone, agent of choice in setting of AMI or LV dysfunction
    • 150 mg over 10min (15 mg/min), followed by 1 mg/min drip over 6hrs (360 mg total), then 0.5 mg/min drip over next 18 hrs (540 mg total)
    • Peds: 5mg/kg (max 300mg), may repeat twice
  • Procainamide
    • 100 mg q5min until termination of arrhythmia, then start 2-6 mg/min (or 1-2 mg/min for renal/cardiac failure)
    • Max dose 17mg/kg OR widening of QRS >50%
  • Lidocaine, 1-1.5mg/kg IV q5min, repeat prn up to 300mg/hr

Refractory

• ≥3 episodes within 24 hours considered electrical storm
• May require alternate treatment (i.e. beta blockers, sedation, ablation)

Disposition

• Admit, even if back in normal sinus rhythm

See Also

• Tachycardia (wide)
• Torsades de pointes
• ACLS (Main), PALS (Main)
• Adult Pulseless Arrest, Pediatric pulseless arrest
• Critical care quick reference
• Nonsustained ventricular tachycardia

References

Authors

Claire, Ross Donaldson, Neil Young