What is the next step in managing monomorphic ventricular tachycardia (VT) that persists after a 360 joules direct current (DC) shock?

Management of Monomorphic VT Persisting After 360J DC Shock

For monomorphic ventricular tachycardia (VT) that persists after a 360 joules direct current (DC) shock, administer intravenous amiodarone 150 mg infused over 10 minutes followed by a constant infusion of 1.0 mg/min for 6 hours and then a maintenance infusion of 0.5 mg/min. 1

Pharmacological Management Algorithm

First-Line Treatment

• Administer amiodarone 150 mg IV over 10 minutes, followed by 1.0 mg/min infusion for 6 hours, then 0.5 mg/min maintenance 1, 2
• For breakthrough episodes of VF or hemodynamically unstable VT, repeat the initial 150 mg loading dose 2

Alternative Medications if Amiodarone is Unavailable or Ineffective

• Procainamide: 20-30 mg/min loading infusion up to 12-17 mg/kg, followed by infusion of 1-4 mg/min 1
• Lidocaine: bolus 1.0-1.5 mg/kg with supplemental boluses of 0.5-0.75 mg/kg every 5-10 minutes to maximum 3 mg/kg total loading dose, followed by infusion of 2-4 mg/min 1

Additional Interventions

Correct Contributing Factors

• Assess and correct electrolyte abnormalities, particularly potassium and magnesium 1, 3
• Correct acid-base disturbances that may be contributing to arrhythmia refractoriness 1
• Consider underlying myocardial ischemia and implement appropriate interventions 1

For Drug-Refractory VT

• Consider aggressive attempts to reduce myocardial ischemia, including:
  • Beta-adrenoceptor blockade (if not already administered) 1
  • Intra-aortic balloon pumping for hemodynamic support 1
  • Emergency revascularization (PTCA/CABG) if ischemia is suspected 1
• Consider transvenous catheter pace termination for VT refractory to cardioversion or frequently recurrent despite antiarrhythmic medication 1
• In extreme cases of drug-refractory VT, low doses of IV epinephrine (0.5-1 mg administered over 30-60 seconds) may be considered, though this approach requires further study 4

Important Considerations

Monitoring

• Continuous ECG monitoring is essential during treatment 1
• Monitor blood pressure closely, especially during amiodarone administration 2
• For amiodarone infusions exceeding 2 hours, use glass or polyolefin bottles containing D5W 2
• For concentrations greater than 2 mg/mL, use a central venous catheter to minimize phlebitis 2

Cautions and Pitfalls

• Amiodarone alone has relatively low efficacy (29%) for acute termination of sustained monomorphic VT 5, 6
• Intravenous amiodarone loading at higher concentrations or faster rates than recommended can result in hepatocellular necrosis and acute renal failure 2
• Avoid calcium channel blockers such as verapamil and diltiazem for wide-QRS-complex tachycardia of unknown origin 1
• Be prepared for possible hemodynamic deterioration during antiarrhythmic administration, which may necessitate emergency cardioversion 6

Long-term Management

• After successful termination, infusions of antiarrhythmic drugs should be continued for 6-24 hours, then reassess the need for further arrhythmia management 1
• Consider catheter ablation for patients with recurrent episodes, particularly those with electrical storm (≥3 episodes in 24 hours) 7