Which drug is listed as the first-line anti-arrhythmic for AFib in the absence of structural heart disease?

• A. Amiodarone
• B. Flecainide
• C. Propafenone
• D. Diltiazem

Answer: (B)

In atrial fibrillation where there is no structural heart disease, the goal is to restore and maintain normal rhythm using a drug that is effective for rhythm control without carrying undue risk. Class IC agents, such as flecainide, are favored for this scenario because they strongly suppress atrial excitability and have good efficacy in converting AF to sinus rhythm and keeping it there in patients with normal hearts. Flecainide is often listed as a first-line option for rhythm control in this population.

However, this approach hinges on the absence of structural heart disease. In people with prior myocardial infarction, left ventricular dysfunction, or other heart abnormalities, class IC drugs can provoke dangerous proarrhythmias, so they are avoided. That’s why flecainide isn’t suitable for everyone, but when the heart is structurally normal, it provides effective rhythm control with a favorable balance of benefits and risks.

Amiodarone, while highly effective for rhythm control, carries long-term toxicity risks (thyroid, liver, lungs, skin) and is usually reserved for patients with structural heart disease or when other first-line options fail. Diltiazem, a calcium channel blocker, primarily serves to control the heart rate during AF, not to maintain sinus rhythm, so it isn’t considered a first-line option for rhythm control in this context.