What medication should be started next in a patient with unstable Ventricular Tachycardia (VT) who has been reverted with Direct Current (DC) shock?

Post-Cardioversion Management of Unstable Ventricular Tachycardia

After successful DC cardioversion of unstable VT, start intravenous amiodarone immediately to prevent recurrence: 150 mg IV over 10 minutes, followed by 1.0 mg/min infusion for 6 hours, then 0.5 mg/min maintenance. 1, 2

Rationale for Amiodarone as First-Line

The primary goal after cardioversion is preventing recurrent episodes of VT, which can be life-threatening. Amiodarone is specifically indicated by the FDA for "prophylaxis of frequently recurring ventricular fibrillation and hemodynamically unstable ventricular tachycardia in patients refractory to other therapy." 2

Key supporting evidence:

• The European Society of Cardiology recommends intravenous amiodarone combined with beta-blockers for VT storm (recurrent unstable VT), emphasizing prevention of recurrence as the critical outcome. 1

• Multiple RCTs demonstrate that amiodarone reduces the number of life-threatening arrhythmias, required shocks, and episodes of symptomatic sustained VT in patients with recurrent refractory ventricular arrhythmias. 3

• Amiodarone has proven efficacy and safety for both termination and prevention of ventricular arrhythmia in different clinical settings. 4

Specific Dosing Protocol

Loading phase (first 24 hours):

• Initial bolus: 150 mg in 100 mL D5W infused over 10 minutes 2
• Rapid infusion: 1.0 mg/min for 6 hours (360 mg total) 2
• Maintenance infusion: 0.5 mg/min for remaining 18 hours (540 mg total) 2
• Total first 24 hours: Approximately 1000 mg 2

For breakthrough VT episodes:

• Administer supplemental 150 mg boluses in 100 mL D5W over 10 minutes as needed 2

Ongoing maintenance:

• Continue 0.5 mg/min infusion for 2-3 weeks if needed, then transition to oral amiodarone 2
• Most patients require IV therapy for 48-96 hours until arrhythmias are stabilized 2

Critical Administration Details

Delivery requirements:

• Use a volumetric infusion pump (never drop counters, which can underdose by 30%) 2
• Administer through a central venous catheter whenever possible 2
• Use an in-line filter during administration 2
• For concentrations >2 mg/mL, a central line is mandatory to prevent phlebitis 2
• Mix only in D5W using glass or polyolefin bottles (not PVC for >2 hours) 2

Monitoring requirements:

• Continuous cardiac monitoring for rhythm and rate 2
• Frequent blood pressure monitoring (hypotension is the most common adverse effect leading to discontinuation) 2
• Watch for bradycardia and AV block (may require slowing or stopping infusion) 2

Adjunctive Beta-Blocker Therapy

Consider adding IV beta-blockers concurrently with amiodarone, particularly if:

• The VT is polymorphic in nature 3
• Myocardial ischemia is suspected or cannot be excluded 3
• The patient is experiencing electrical storm (multiple recurrent episodes) 1

Beta-blockers represent the single most effective therapy for polymorphic VT storm and reduce recurrent refractory ventricular arrhythmias while improving survival. 3, 1

Alternative Agents (If Amiodarone Contraindicated or Unavailable)

Procainamide:

• Loading: 10 mg/kg at 50-100 mg/min IV (maximum 17 mg/kg) 3
• Maintenance: 1-4 mg/min infusion 1
• Contraindications: Severe heart failure, acute MI, renal dysfunction (requires dose reduction) 3, 1

Lidocaine (less effective but reasonable if ischemia-related):

• Loading: 1.0-1.5 mg/kg bolus, repeat 0.5-0.75 mg/kg every 5-10 minutes (max 3 mg/kg total) 1
• Maintenance: 2-4 mg/min infusion 1
• Reduce doses in elderly, heart failure, or hepatic dysfunction 1
• Note: Lidocaine is less effective than amiodarone, procainamide, and sotalol for VT termination and prevention 3

Common Pitfalls to Avoid

• Never use calcium channel blockers (verapamil, diltiazem) for wide-complex tachycardia of unknown origin, especially with history of myocardial dysfunction—this is a Class III contraindication. 3

• Do not exceed initial amiodarone infusion rate of 30 mg/min or daily doses above 2100 mg (increased hypotension risk). 2

• Avoid using drop counter infusion sets, which can result in 30% underdosing. 2

• Monitor for hepatocellular necrosis and acute renal failure with excessively high concentrations or rapid infusion rates. 2

Addressing Underlying Causes Simultaneously

While initiating antiarrhythmic therapy, aggressively treat:

• Electrolyte abnormalities: Correct hypokalemia and hypomagnesemia immediately 3
• Myocardial ischemia: Consider urgent angiography and revascularization if ischemia is evident 3, 1
• Heart failure: Optimize hemodynamics and volume status 1

These interventions are Class I recommendations and directly impact mortality and recurrence risk. 3, 1