Reply

We thank Drs Masè and Ravelli for their insights and important work evaluating the concept of rapid, morphologically similar electrograms representing potential drivers of persistent atrial fibrillation (PeAF). Their work^1,2 and ours (Mitrani et al, unpublished data, January 2023)3, 4, 5 provide a strong body of observational and physiologic data that this mapping approach provides relevant information regarding PeAF. The need for a robust mapping approach has been underscored by the failure of adjunctive approaches such as linear ablation,⁶ targeting magnetic resonance imaging fibrosis⁷ and posterior wall isolation⁸ to improve outcomes compared with pulmonary vein isolation.

Arrhythmia mapping to identify ablation targets is the cornerstone for achieving high success rates for many supraventricular and ventricular arrhythmias. To date, an effective mapping approach for PeAF has not been identified, though several have been attempted, including mapping of complex fractionated atrial activity, dominant frequency, and rotors, among others. In the recent report of Zaatari et al,⁵ the electrogram morphology recurrence mapping was assessed in 32 patients undergoing initial ablation for PeAF and 10 patients undergoing repeat ablation due to recurrence of PeAF after prior ablation. Among the many findings, the recurrence cycle length, defined as the cycle length of only the most common electrogram morphology at each site mapped in the atrium, was shortest in the pulmonary veins in 59% of patients undergoing initial ablation for PeAF and in only 10% of those undergoing repeat ablation, providing an appropriate clinical context. While these initial studies (Mitrani et al, unpublished data, January 2023)1, 2, 3, 4, 5 are encouraging, we agree with Drs Masè and Ravelli that translating this into clinical practice still requires substantial research. Several important questions remain, some of which are:

• 1.As the technique is very sensitive to electrogram morphology, the optimal recording configurations need to be identified.
• 2.The optimal analysis or degree of electrogram similarity needs to be defined. Drs Masè and Ravelli have identified thresholds of 0.5¹ and 0.65² for similarity. In our approach, we focused only on the shortest recurrence cycle length site or those within 5 milliseconds. These parameters need validation.
• 3.Translation of the mapping findings into an ablation strategy may not be straightforward in some cases.

We agree with Drs. Masè and Ravelli that further careful evaluation and testing could lead to the translation of electrogram morphology recurrence “from a recurrent idea into clinical practice in AF mapping to improve therapeutic outcome and patient benefit.”