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

Treatment of Unstable Ventricular Tachycardia

For unstable ventricular tachycardia, immediate synchronized electrical cardioversion is the first-line treatment, followed by antiarrhythmic medications such as amiodarone or lidocaine to prevent recurrence. 1

Initial Assessment and Management

Determining Stability

Unstable VT is characterized by:

• Systolic BP ≤ 90 mmHg
• Chest pain
• Heart failure
• Rate ≥ 150 beats/min
• Altered mental status
• Signs of poor perfusion

Immediate Management Algorithm

1. First Step: Synchronized Cardioversion

   • For hemodynamically compromising VT, urgent electrical conversion is indicated 1
   • Begin with 100 J synchronized shock
   • If unsuccessful, escalate to 200 J, then 360 J 1
   • Sedate patient prior to cardioversion if time permits and patient is conscious

2. Post-Cardioversion Pharmacological Management

   • Lidocaine (First-line): 1-1.5 mg/kg IV bolus (approximately 100 mg for average adult)

     • Additional boluses of 0.5-0.75 mg/kg every 5-10 minutes to maximum 3 mg/kg
     • Follow with infusion of 2-4 mg/min (30-50 μg/kg/min) 1
     • Reduce infusion rates in elderly, CHF, or hepatic dysfunction patients

   • Amiodarone (Alternative): 150 mg IV over 10 minutes

     • Follow with infusion of 1.0 mg/min for 6 hours
     • Then maintenance infusion at 0.5 mg/min 1, 2
     • FDA-approved for hemodynamically unstable VT refractory to other therapy 2

Special Considerations

Pulseless VT

• Treat as ventricular fibrillation
• Use unsynchronized shock (defibrillation) at 200 J 1
• Follow ACLS protocol for pulseless VT/VF

Refractory Cases

• Consider magnesium sulfate: 8 mmol bolus followed by 2.5 mmol/h infusion, particularly in cases associated with acute myocardial infarction 3
• For VT resistant to lidocaine and amiodarone, bretylium can be considered: 5 mg/kg IV, with possible increase to 10 mg/kg if unsuccessful 1
• Continue CPR for at least 20 minutes after bretylium administration due to delayed onset of action 1

Monitoring and Follow-up

• Continuous cardiac monitoring during and after treatment
• Monitor for drug toxicity:
  • Lidocaine: CNS effects (paresthesia, drowsiness, confusion, seizures)
  • Amiodarone: Hypotension, bradycardia, QT prolongation, hepatotoxicity
• Assess for underlying causes of VT (ischemia, electrolyte abnormalities, drug toxicity)

Important Caveats

• Amiodarone has a delayed onset of action (up to 30 minutes), making it less suitable as first-line therapy for acute unstable VT 1
• High-dose IV amiodarone can cause significant hemodynamic deterioration 4, 5
• Intravenous amiodarone concentrations >3 mg/mL in D5W have been associated with peripheral vein phlebitis; use concentrations ≤2 mg/mL for infusions longer than 1 hour 2
• Sustained VT occurring >48 hours after MI deserves careful evaluation, including consideration of electrophysiology studies 1
• Monomorphic VT at rates <170 bpm are unusual as post-MI arrhythmias and suggest a more chronic arrhythmic substrate 1