What is the treatment for polymorphic ventricular tachycardia (VT)?

Treatment of Polymorphic Ventricular Tachycardia

Immediate defibrillation is the first-line treatment for polymorphic ventricular tachycardia (PVT), followed by targeted therapy based on the underlying cause, particularly whether QT prolongation is present. 1

Initial Management

1. Immediate Defibrillation

   • Unsynchronized defibrillation is recommended for all patients with sustained polymorphic VT with hemodynamic compromise (Class I, Level of Evidence B) 2
   • Defibrillation should be performed with appropriate sedation as necessary and can be used at any point in the treatment cascade 2

2. Identify Underlying Cause

   • Determine if QT interval is prolonged during sinus rhythm
   • Check for myocardial ischemia, electrolyte abnormalities, drug toxicity

Treatment Algorithm Based on QT Interval

For PVT with Long QT Interval (Torsades de Pointes)

1. First-line interventions (Class I) 2:

   • Withdraw any QT-prolonging medications (Level of Evidence A)
   • Correct electrolyte abnormalities, especially potassium and magnesium (Level of Evidence A)
   • Administer IV magnesium sulfate (2g) even if serum magnesium is normal (Class IIa, Level of Evidence B)

2. For bradycardia-dependent or pause-dependent Torsades:

   • Temporary cardiac pacing (Class IIa, Level of Evidence B) 2
   • OR isoproterenol infusion if no congenital LQTS (Class IIa, Level of Evidence B) 2
   • Beta blockade combined with pacing for sinus bradycardia (Class IIa, Level of Evidence C) 2

3. Additional measures:

   • Consider potassium repletion to 4.5-5 mmol/L (Class IIb, Level of Evidence B) 2
   • For LQT3: consider IV lidocaine or oral mexiletine (Class IIb) 2

For PVT without QT Prolongation

1. First-line pharmacological therapy:

   • IV beta-blockers, especially if ischemia is suspected (Class I, Level of Evidence B) 2, 1
   • IV amiodarone loading (150mg over 10 minutes, followed by infusion) for recurrent episodes (Class I, Level of Evidence C) 2, 1, 3

2. For PVT associated with acute myocardial ischemia:

   • IV lidocaine may be reasonable (Class IIb, Level of Evidence C) 2
   • Urgent coronary angiography with view to revascularization (Class I, Level of Evidence C) 2

3. For refractory cases:

   • Combination of IV amiodarone and beta-blockers 1
   • Consider overdrive pacing for recurrent episodes 1

Special Considerations

Catecholaminergic Polymorphic VT (CPVT)

• Beta-blockers are the cornerstone of therapy 4
• IV propranolol has been shown to be effective in emergency situations 4
• For refractory cases, cardiac transplantation may be considered in extreme cases 5

Contraindicated Medications

• Calcium channel blockers (verapamil, diltiazem) should NOT be used for wide-complex tachycardias of unknown origin (Class III, Level of Evidence C) 2
• Avoid adenosine in irregular or polymorphic wide-complex tachycardias 1

Post-Conversion Care

• Continuous cardiac monitoring is essential 1
• Urgent cardiological evaluation to determine etiology 1
• Transition to appropriate long-term therapy based on underlying cause

Pitfalls to Avoid

• Do not delay defibrillation for hemodynamically unstable patients
• Do not administer calcium channel blockers for wide-complex tachycardias of unknown origin
• Do not use isoproterenol in patients with congenital long QT syndrome
• Do not overlook potentially reversible causes (ischemia, electrolyte disturbances, drug toxicity)
• For amiodarone infusions, do not exceed 30 mg/min initial infusion rate to avoid hypotension 3
• For infusions longer than 1 hour, do not exceed amiodarone concentrations of 2 mg/mL unless using a central venous catheter 3

The management of polymorphic VT requires rapid assessment and treatment tailored to the underlying cause, with immediate defibrillation for unstable patients and targeted pharmacological therapy based on whether QT prolongation is present.