What therapy is contraindicated in patients with heart failure and reduced ejection fraction when treating paroxysmal atrial fibrillation?

Dronedarone is contraindicated in patients with heart failure and reduced ejection fraction when treating paroxysmal atrial fibrillation due to its potential to worsen heart failure. Dronedarone is considered a class III antiarrhythmic, designed to reduce the risk of cardiovascular hospitalization in patients with atrial fibrillation and to maintain sinus rhythm. However, clinical trials and safety warnings have indicated that dronedarone can have deleterious effects on patients with significant heart failure; its use in those with an ejection fraction below 35% can lead to increased mortality and worsening heart failure symptoms.

In contrast, the other options presented are considered more appropriate for patients with reduced ejection fraction. Amiodarone, for instance, is often used in patients with heart failure due to its favorable safety profile in this population, despite being a potent antiarrhythmic agent. Sotalol is also used to manage atrial fibrillation and has demonstrated efficacy in this context, although care must be taken due to its potential to cause QT prolongation. Flecainide is typically avoided in heart failure due to the risk of proarrhythmia, but it is still indicated in some stable patients.

Thus, the choice of