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:
- 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;
- 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.
- 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.
- 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.
- 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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Unfortunately, iv procainamide is not widely available.
Interesting, everywhere I’ve worked it has been available. You just have to dust of the bottle a bit 🙂
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Wasn’t much in the piece about how amio gained all the so-called market share. Can you expand more about how amio became the go to drug besides just saying it was from marketing? Thanks for your good work.
I posted this on twitter as well but thought I’d share here. In the AHA guidelines, procainamide is a IIa recommendation and amiodarone is a IIb recommendation. This is from 2010 and no update was made in 2015. From the AHA classification system: — Class II: Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment. Class IIa: Benefit >> Risk Weight of evidence/opinion is in favor of usefulness/efficacy. Class IIb: Benefit ? Risk Usefulness/efficacy is less well established by evidence/opinion. — I think this speaks to the effect of… Read more »
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It is not available in my whole system. Many years ago I used 60 minute infusions of procainamide to convert new onset atrial fibrillation. It worked reasonably well.
Interesting dosing here — 5mg/kg amiodarone in a typical 70kg patient is 350mg over 20 minutes which is a large dose over a relatively short period of time. Not terribly surprised the authors found higher rates of adverse events in the amiodarone group with this dosing strategy.
Great point! I completely agree. Michelle Hines addresses these very same concern in her recent clinical pearl at https://em.umaryland.edu/educational_pearls/3059/
And while you can certainly say that the aggressive dosing may have lead to the high rate of adverse reactions observed, you cannot equally account for the obvious inferiority in the drugs efficacy. Lower doses may reduce the harms associated with amiodarone, I can’t imagine they would improve its efficacy
Thanks for writing!!
Thanks for the reply! I agree that we cannot equally account for the obvious inferiority in efficacy. This being said, one could hypothesize that the 9 patients in the amiodarone group who required DCCV during infusion (6 for severe hypotension, 3 for peripheral hypoperfusion/dyspnea with hypotension) could have possibly responded giving the infusion over a longer period of time. These are stable VT patients with constant monitoring (hopefully with pads placed already) so there is no reason that we MUST give it over such a short period of time. Purely hypothetical of course but if that was the case then… Read more »
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