Which intervention is effective in both restoring and maintaining normal sinus rhythm?

Cardioversion is effective in both restoring and maintaining normal sinus rhythm. This intervention involves the delivery of a controlled electric shock to the heart, which can reset the heart's electrical cycle and convert atrial fibrillation back to normal sinus rhythm. It is particularly useful in cases of recent-onset atrial fibrillation and can be done either using synchronized direct current (DC) cardioversion or pharmacological agents.

In terms of maintaining normal sinus rhythm, once restored through cardioversion, the risk of the recurrence of atrial fibrillation can be reduced by using additional therapies, such as antiarrhythmic medications. However, the primary function of cardioversion is to restore rhythm, which is why it is the correct answer for both restoring and maintaining normal sinus rhythm.

Other interventions, such as AV node ablation, do not restore normal sinus rhythm but rather create a controlled rhythm often dependent on pacing; rate control medications, while helpful in managing the heart rate during atrial fibrillation, do not convert the rhythm back to normal; and antithrombotic therapy primarily focuses on reducing the potential for stroke rather than restoring normal sinus rhythm.