Which statement about rhythm control in patients with structural heart disease is true?

• A. Class III antiarrhythmic agents are often preferred, especially amiodarone
• B. Class IA agents are preferred
• C. Class II agents are preferred
• D. Class IV agents are preferred

Answer: (A)

The main concept here is that in structural heart disease, the safety and effectiveness of antiarrhythmic drugs for rhythm control depend on how the drug interacts with damaged myocardium. Drugs that block sodium channels (Class I) tend to be proarrhythmic in scarred tissue and can worsen heart failure, so they are avoided for rhythm control in this setting. Class III agents, which prolong repolarization and increase the time the heart is in a refractoriness state, reduce reentry and ectopic activity without severely depressing contractility. Amiodarone stands out among these because it is effective against both atrial and ventricular arrhythmias and is usable even with reduced ejection fraction and structural heart disease, making it a preferred choice for rhythm control in such patients. While other classes are not ideal here—beta-blockers and non-dihydropyridine calcium channel blockers mainly help with rate control rather than maintaining sinus rhythm, and certain Class I agents carry higher proarrhythmic and hemodynamic risks—the emphasis is on choosing a Class III strategy, especially amiodarone, for rhythm control in the context of structural heart disease.