Amiodarone has long held the position as the preferred antiarrhythmic medication in the patient presenting with hemodynamically stable wide-complex tachycardia. Its popularity so universal that other antiarrhythmic medications, like procainamide, have found themselves marginalized to a dusty corner in the medications we used last century closet. Despite its claims of superiority, which are often stated with a haughty certainty, the evidence supporting amiodarone is minimal. In fact, most of the data, all be it minimal, demonstrates that procainamide is the superior antiarrhythmic agent. But let us not mistake evidence for science, amiodarone’s rise to power was not based on its clinical superiority but rather the marketing aptitude of the pharmaceutical industry.

It was in this clinical climate that the authors of the recently published PROCAMIO trial chose to compare the efficacy of these two antiarrhythmic drugs in a randomized controlled fashion (1). Ortiz et al randomized 74 patients presenting to the Emergency Department with hemodynamically stable wide-complex tachycardia to either IV amiodarone (5mg/kg over 20 minutes) or IV procainamide (10 mg/kg  over 20 minutes). For those who believe in the mythical powers possessed by amiodarone, the results of this trial will come as somewhat of a shock.

The authors found procainamide to be far superior to amiodarone in both their primary and secondary endpoints. Patients randomized to receive procainamide experienced far fewer major cardiac events (MCE), defined as clinical signs of peripheral hypoperfusion, heart failure, severe hypotension, worsening of tachycardia, or the appearance of fast polymorphic VT, than patients who received amiodarone. Of the 33 patients randomized to receive procainamide, 3 (9%) experienced MCEs. In comparison, 12 (41%) of the patients who received amiodarone experienced MCEs. The majority of these MCEs were hypotensive episodes requiring DC cardioversion. Furthermore, procainamide appeared to be far more efficacious than amiodarone. 22 (67%) of the patients randomized to receive procainamide experienced termination of their wide-complex tachycardia within 20 minutes of the initiation of infusion, compared to only 11 (38%) patients who received amiodarone. The rates of conversion and MCEs were essentially identical when the subgroup of patients with a history of structural heart disease was examined separately.

Methodologically speaking there is not much to say. Patients randomized to the procainamide arm did significantly better in every variable measured. And while some of the endpoints failed to reach statistical significance this is likely due to the limited power generated by the small size enrolled in this cohort. This study is obviously severely underpowered to make any conclusive statements on the superiority of either medication. In fact, the authors originally intended on enrolling 302 patients, but after 6 years of enrollment at 29 medical centers, Ortiz et al were forced to stop the trial early due to slow recruitment. The previous literature examining the use of procainamide and amiodarone for the termination of wide-complex tachycardia has demonstrated similar results. Tomlinson et al reported in a cohort of 41 patients presenting to the Emergency Department with wide-complex tachycardia, amiodarone converted 15% within 20 minutes of presentation. 17% experienced hemodynamic compromise requiring DC cardioversion (2). Marill et al reported a success rate of 29% for IV amiodarone in patients presenting to the Emergency Department with wide-complex tachycardia (3). In comparison, Gorgels et al and Komura et al reported a termination rate of 80% and 75.7% respectively in patients presenting with wide-complex tachycardia treated with IV procainamide (4,5).

Some will cite the diminutive size of the PROCAMIO trial as reasons not to abandon amiodarone as the primary medication in patients presenting with hemodynamically stable wide-complex tachycardia, but it is important to remember that this standard was based not on evidentiary support but marketing prowess. And while the PROCAMIO trial possesses little statistical mass to shift practice and the prior evidence adds only minimal inertial support, certainly it is enough momentum to displace amiodarone from its tenuous position.

Sources Cited:

1. Ortiz M, Martín A, Arribas F, et al. Randomized comparison of intravenous procainamide vs. intravenous amiodarone for the acute treatment of tolerated wide QRS tachycardia: the PROCAMIO study. Eur Heart J. 2016;
2. Tomlinson DR, Cherian P, Betts TR, Bashir Y. Intravenous amiodarone for the pharmacological termination of haemodynamically-tolerated sustained ventricular tachycardia: is bolus dose amiodarone an appropriate first-line treatment? Emerg Med J. 2008;25:15–18.
3. Marill KA, deSouza IS, Nishijima DK, Stair TO, Setnik GS, Ruskin JN. Amiodarone is poorly effective for the acute termination of ventricular tachycardia. Ann Emerg Med. 2006;47:217–224.
4. Gorgels AP, van den Dool A, Hofs A, Mulleneers R, Smeets JL, Vos MA, Wellens HJ. Comparison of procainamide and lidocaine in terminating sustained monomorphic ventricular tachycardia. Am J Cardiol. 1996;78:43– 46.
5. Komura S, Chinushi M, Furushima H, Hosaka Y, Izumi D, Iijima K, Watanabe H, Yagihara N, Aizawa Y. Efficacy of procainamide and lidocaine in terminating sustained monomorphic ventricular tachycardia. Circ J 2010;74:864–869.

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Rory Spiegel

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University of Maryland
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