Which antiarrhythmic class is often preferred for rhythm control in patients with structural heart disease?

• A. Class III agents, especially amiodarone
• B. Class IA agents
• C. Class II agents
• D. Class IV agents

Answer: (A)

In patients with structural heart disease, you want an antiarrhythmic that can reliably maintain sinus rhythm without provoking dangerous new arrhythmias. Amiodarone, a Class III agent, fits this need especially well. It has broad antiarrhythmic effects across atrial and ventricular tissue and a lower risk of proarrhythmia in damaged hearts compared with other classes. This makes it a preferred choice for rhythm control in these patients, even though it can have long-term noncardiac side effects.

Other classes are generally less suitable for rhythm control in structural disease. Class IA drugs (like quinidine and procainamide) carry notable proarrhythmic risk and QT prolongation, which is problematic in diseased hearts. Class IC agents (such as flecainide and propafenone) are avoided in structural heart disease due to a high proarrhythmic risk. Class II agents (beta-blockers) and Class IV agents (calcium channel blockers) are effective mainly for rate control and are not ideal for maintaining sinus rhythm in this context.

So, amiodarone’s balance of effectiveness in sustaining rhythm and relative safety in structurally abnormal hearts makes it the best choice.