Background

The current ACLS guidelines give both procainamide and amiodarone a class II recommendation as chemical therapy for the treatment of patients with stable ventricular tachycardia. Despite the fact that one drug does not appear to have an advantage over the other based on available literature, amiodarone appears to be agent preferred by intensivists, cardiologists and Emergency Physicians alike. Better evidence is needed to determine which drug is best for conversion as well as for safety.

Clinical Question

In patients with hemodynamically stable wide complex tachycardia, should we use IV procainamide or IV amiodarone as our go to medication?

Population

Patients > 18 years of age presenting with a regular, wide QRS complex (>/= 120 ms) tachycardia >/= 120 bpm and with good hemodynamic tolerance (SBP >/= 90 mm Hg, absence of dyspnea at rest, absence of peripheral hypoperfusion and no severe anginal symptoms)

Intervention

Procainamide 10 mg/kg over 20 minutes

Control

Amiodarone 5 mg/kg over 20 minutes

Outcomes

Primary: Major cardiac adverse events within 40 minutes after infusion initiation:
Clinical signs of peripheral hypoperfusion
Heart failure signs: dyspnea at rest and/or orthopnea associated with signs of pulmonary congestion
Severe hypotension: SBP ≤ 70mmHg if the pre-treatment SBP was ≤ 100mmHg or SBP ≤ 80mmHg if the pre-treatment SBP was >100mmHg
Tachycardia acceleration of >20 bpm of its mean value
Appearance of fast polymorphic VT
Secondary: Acute termination of tachycardia, Total adverse events during 24 hour observation period

Design

Multicenter, randomized, prospective, open-label study

Excluded

Poor hemodynamic tolerance requiring urgent termination
Presence of irregular tachycardia
Tachycardia that was thought to be supraventricular in origin
Contraindications to the study drugs

Primary Results

  • 74 patients recruited for the study. 12 excluded
  • 62 patients in analysis
    • Procainamide: n = 33
    • Amiodarone: n = 29

Critical Results

  • Primary Endpoint: Major Cardiac Adverse Events
    • Overall: 24% (15/62)
    • Procainamide = 9% vs. Amiodarone = 41%
    • Absolute difference = 32% NNH = 3
    • OR = 0.1 (95% CI 0.03 – 0.6)
  • Secondary Endpoints:
    • Tachycardia Termination within 40 min
      • Overall: 53% (33/62)
      • Procainamide = 67% vs. Amiodarone = 38%
      • Absolute difference 29% NNT = 3.3
      • OR = 3.3 (95% CI 1.2 – 9.3)
    • Adverse Events in Following 24 Hours
      • Procainamide = 18% vs. Amiodarone = 31%
      • Absolute difference = 13% NNH = 7.5
      • OR = 0.49 (95% CI 0.15 – 1.61)
  • Subgroup Analysis (Structural Heart Disease)
    • Major Cardiac Adverse Events
      • Procainamide = 11% vs. Amiodarone = 43%
      • OR = 0.17 (95% CI 0.04 – 0.73)
    • Ventricular Tachycardia Termination
      • Procainamide = 65% vs. Amiodarone = 39%
      • OR = 2.94 (95% CI 0.92 – 9.4)

Strengths

  • This is the first high-quality study investigating the chemical management of “stable” side-complex tachydysrhythmias
  • The study asks a clinically important question

Limitations

  • The providers were not blinded to which therapy the patient received. Although it is unclear what bias this introduces, it likely favors amiodarone as this is the preferred drug
  • Randomization was performed by having groups of 10 enclosed envelopes on location. Although in theory this would be successful in randomizing patients, it is possible to “game” this system (open + close envelopes, read through envelope when held up to the light)
  • Due to the limited amount of prior evidence addressing this issue, the authors had significant uncertainty in calculating an appropriate sample size
  • The investigators estimated they would need to collect > 300 patients to detect a 15% difference in major cardiac adverse events. Due to slow recruitment, the study was halted after just 62 patients were enrolled
  • Stopping the trial early may lead to an overestimation of the benefits of procainamide
  • Due to the size of the trial, the fragility index is low

Other Issues

  • The authors state this was an investigation of the treatment of monomorphic wide complex tachycardias that were presumably ventricular tachycardia because, as they note, distinguishing SVT with aberrancy from ventricular tachycardia can be difficult and it’s possible that some of the patients had a supraventricular rhythm.
  • All patients with “stable” wide-complex tachydysrhythmias should have paddles in place in anticipation of decompensation.

Author's Conclusions

“Procainamide therapy was associated with less major cardiac adverse events and a higher proportion of tachycardia termination within 40 min"

Our Conclusions

Although this is a small clinical study, it is by far the best available evidence on the topic. This prospective, randomized trial shows that procainamide is associated with less major cardiac adverse events and is more efficacious in terminating wide-complex tachydysrhythmias. Procainamide should be first line chemical therapy in patients with stable ventricular tachycardia.

Potential Impact To Current Practice

Amiodarone appears to be preferred to procainamide in most institutions where both are available based on no evidence of its superiority. This study should shift that practice to favoring of procainamide. It is also reasonable to skip all attempts at chemical cardioversion and immediately go to sedation and electrical cardioversion as the potential to decompensate for these patients is high.

Bottom Line

Procainamide should be the first line agent if chemical cardioversion is pursued in patients with stable, monomorphic, wide-complex tachydysrhythmias.

Read More

EM Nerd: The Case of the Dysrhythmic Heart

REBEL Cast: PROCAMIO Trial

The Bottom Line: PROCAMIO – Randomized Comparison of Intravenous Procainamide vs. Intravenous Amiodarone for the Acute Treatment of Tolerated Wide QRS Tachycardia