When treating acute, wide-complex tachycardia deemed to be stable, monomorphic ventricular tachycardia, two agents remain prevalant among emergency medicine physicians: amiodarone and procainamide. This post examines some of the evidence behind these agents in achieving successful conversion of stable, monomoprhic VT.

Procainamide:
Loading Dose: IV 20-50 mg/minute or 100 mg every 5 minutes until arrythmia is controlled, hypotension occurs, QRS complex widens by 50% of original width, or max dose of 17 mg/kg is reached.
Maintenance Infusion: IV 1-4 mg/minute

Amiodarone:
Loading Dose: IV 150 mg over 10 minutes
Maintenance Infusion: IV 1 mg/minute for 6 hours followed by 0.5 mg/minute for following 18 hours.

deSouza, et al. "Antidysrhythmic Drug Therapy for the Termination of Stable, Monomorphic Ventricular Tachycardia: A Systematic Review." Emergency Medicine Journal. 2015:

• Systematic review of 3 prospective studies and 2 retrospective studies comparing the efficacy of different drug therapies for the termination of stable, monomorphic ventricular tachycardia.
• Efficacy of Procainamide: 57-80% termination rate
• Efficacy of Amiodarone: 24% termination rate
• Limitations: Prospective studies were limited by small sample sizes, suboptimal methodology, and significant bias. Retrospective studies were limited by selection bias, confounding. 

ACC/AHA/ESC 2006 Guidelines for Management of Patients with Ventricular Arrythmias and the Prevention of Sudden Cardiac Death-Executive Summary

Class I Recommendations:

• Wide-QRS tachycardia should be presumed to be VT if the diagnosis is unclear. (Level of Evidence: C)
• Direct-current cardioversion with appropriate sedation is recommended at any point in the treatment cascade in patients with suspected sustained monomorphic VT with hemodynamic compromise. (Level of Evidence: C)

Class IIa Recommendations:

• Intravenous procainamide is reasonable for initial treatment of patients with stable sustained monomorphic VT. (Level of Evidence: B)
• Intravenous amiodarone is reasonable for patients with sustained monomorphic VT that is hemodynamically unstable, refractory to conversion with countershock, or recurrent despite procainamide or other agents. (Level of Evidence: C)
• Transvenous catheter pace termination can be useful to treat patients with sustained monomorphic VT that is refractory to cardioversion or is frequently recurrent despite antiarrhythmic medication. (Level of Evidence: C)

Class IIb Recommendations:

• Intravenous lidocaine might be reasonable for initial treatment of patients with stable sustained monomorphic VT specifically associated with acute myocardial ischemia or infarction. (Level of Evidence: C)

Class III Recommendations:

• Calcium channel blockers such as verapamil and diltiazem should not be used in patients to terminate wide-QRS-complex tachycardia of unknown origin, especially in patients with a history of myocardial dysfunction. (Level of Evidence: C)

Check out Amal Mattu's Wide-Complex Tachycardias in the ED: Myths and Pitfalls for a deeper dive into this topic.

For resources to help you determine whether your patient with wide-complex tachycardia is in VT or SVT with aberrancy, check out:
ALiEM: Suprventricular Tachycardia (SVT) with Aberrancy Versus Ventricular Tachycardia (VT)
LITFL: VT versus SVT with Aberrancy