The correct answer is:

amiodarone

Educational Objective:

Discuss treatment for paroxysmal (intermittent) symptomatic atrial fibrillation in a patient with heart failure.

Key Point:

Paroxysmal, rapid atrial fibrillation can cause syncope due to lowered cardiac output. Patients with pre-existing low cardiac output (the above patient) are particularly sensitive to this effect.

The key point of this question is to know that most commonly used antiarrhythmic drugs for atrial fibrillation are contraindicated in patients with heart failure (the above patient).

Explanation:

This patient has heart failure and intermittent coarse atrial fibrillation (AF) with a rapid ventricular response of 145. In patients with heart failure (HF) and a low ejection fraction, most antiarrhythmics are detrimental because they act as negative inotropes, thus further exacerbating the preexisting HF, while also potentially have a proarrhythmic effect in the context of HF.

Different from the other commonly used drugs in this scenario (see algorithm), amiodarone has very little negative inotropic activity and a low rate of ventricular proarrhythmic effects, making it a common choice in patients with HF. Unfortunately, these advantages are paired with a relatively high incidence of adverse effects, making it a complicated drug to use safely.

Amiodarone has been found to have neutral effects on survival in patients with systolic HF but to improve quality of life, and thus can be considered when a drug is necessary to prevent (rather than convert) recurrent, intermittent AF with a rapid ventricular response in patients with significant congestive HF.

https://emedicine.medscape.com/article/151066-medication

In its 2020 advanced cardiac life support guidelines, the American Heart Association and others continued to recommend amiodarone (class IIa recommendation since 2011 guidelines) as a rate-controlling agent in patients whose condition is intolerant of or unresponsive to standard rate-controlling agents (eg, patients with congestive HF who are unable to tolerate metoprolol or diltiazem). 

If the patient is sufficiently stable, starting amiodarone should be preceded by a cardiac consult to make sure that the patient does not have a pre-excitation syndrome (e.g. Wolff-Parkinson-White), in which case amiodarone (as well as beta blockers and calcium channel-blockers) would be contraindicated because they can convert atrial fibrillation to ventricular fibrillation and death.

Coarse AF can be difficult to distinguish from atrial flutter. The "look-alike, sawtooth waves" in coarse AF are faster (400-600 beats/minute or > 1 wave/box; see Figures 2 and 3).

Figure 2.

Figure 3.

In cases of atrial flutter, the waves are more organized, taller, more uniform (lacking in Figure 1), and slightly slower (200-300 beats/minute or a < 1 wave/box; see Figure 4).

Figure 4.

References:

Panchal AR, Bartos JA, Cabañas JG, Donnino MW, Drennan IR, Hirsch KG, Kudenchuk PJ, Kurz MC, Lavonas EJ, Morley PT, O’Neil BJ, Peberdy MA, Rittenberger JC, Rodriguez AJ, Sawyer KN, Berg KM; on behalf of the Adult Basic and Advanced Life Support Writing Group. Part 3: adult basic and advanced life support: 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2020;142(suppl 2):S366–S468. doi: 10.1161/CIR.0000000000000916

Doyle JF, Ho KM. Benefits and risks of long-term amiodarone therapy for persistent atrial fibrillation: a meta-analysis. Mayo Clin Proc. 2009;84(3):234-242.

Goldschlager N, Epstein AE, Naccarelli GV, et al; Practice Guidelines Sub-committee, North American Society of Pacing and Electrophysiology (HRS). A practical guide for clinicians who treat patients with amiodarone: 2007. Heart Rhythm. 2007;4(9):1250-1259.

Rosenthal L. Atrial fibrillation. (Updated November 18, 2019). Accessed June 25, 2022.