Pulsed Field Ablation of Atypical Atrial Flutter in a Patient After Hybrid Ablation of Atrial Fibrillation

ABSTRACT

After hybrid surgical ablation of atrial fibrillation, a 73‐year‐old‐man underwent pulmonary vein isolation, roof, and anterior mitral line using Farapulse. He developed atypical atrial flutter from reconnection of the anterior mitral line; four “stamps” were applied along the line with immediate termination and no recurrence at 1 year.

Key Clinical Message

Pulsed field ablation (PFA) is a novel modality for the treatment of atypical atrial flutter but needs further research to ensure durable lesions.

1. Introduction

Catheter ablation of atypical atrial flutter is a reasonable first‐line treatment, although it requires extensive mapping and the reported success rates are lower than in typical atrial flutter [1, 2]. Pulsed field ablation (PFA) has emerged as an innovative treatment strategy for atrial fibrillation and is now being studied in both typical atrial flutter and atypical atrial flutter [3, 4, 5, 6, 7, 8]. We present a case of PFA for the treatment of atypical atrial flutter in a patient after hybrid ablation (combined surgical epicardial and catheter‐based endocardial ablation).

2. Case History

A 73‐year‐old man with a history of persistent atrial fibrillation underwent hybrid ablation. Stage 1 consisted of a subxiphoid endoscopic maze procedure with epicardial left atrial posterior wall ablation. In Stage 2, the Farapulse PFA system (Boston Scientific, Marlborough, Mass.) with pentaspline catheter was used to perform pulmonary vein (PV) isolation (PVI), create a roof line, and deliver an anterior mitral line extending to the right and left superior PVs, using the standard two PFA “stamp” applications per location (Figure 1A). After completion of the PFA lesion set, the patient converted to an atypical atrial flutter (Figure 2A). Using radiofrequency (RF) energy, an anterior mitral line to the left superior PV was created, resulting in flutter termination (Figure 2B).

FIGURE 1.

Voltage and activation maps from the first and second endocardial ablations. (A) This map of the left atrium from the first endocardial ablation shows the initial PFA anterior mitral line was delivered to the right and left superior PVs and the RF anterior mitral line ablation was delivered to the left superior PV. (B) The activation map from the second endocardial ablation shows recurrence of counterclockwise atypical atrial flutter encircling the initial PFA anterior mitral line to the right and left superior PVs. (C) The voltage map from the second endocardial ablation shows reconnection of the PFA anterior mitral line to the right and left superior PVs. (D) During the second endocardial ablation, repeat PFA anterior mitral lines were delivered using four PFA “stamp” applications. The first PFA application (white arrow) resulted in atypical flutter termination.

FIGURE 2.

Intracardiac electrograms during stage 2 of hybrid atrial fibrillation ablation. (A) Occurrence of atypical atrial flutter. (B) Termination of atypical atrial flutter upon RFA of the anterior mitral line to the left superior PV.

3. Investigations and Treatment

Two months after the endocardial ablation, the patient presented in atypical atrial flutter. Medical management was attempted, but symptoms persisted; therefore, 6 months after the first endocardial ablation, repeat ablation was pursued. Mapping revealed a counterclockwise anterior left atrial flutter encircling the prior PFA and RF anterior mitral lines, which had reconnected to both right and left PVs, and demonstrated a critical gap where the lesions had been administered from the anterior mitral annulus to the left PV (Figure 1B–D). Repeat anterior mitral lines to the right and left PVs were created using the Farapulse pentaspline PFA system (Figure 1D). The flutter terminated with the first PFA application (Figures 1D and 3). To help improve lesion durability, four PFA “stamp” applications were administered per location. Pacing from the high right atrium to the left atrial appendage was prolonged at 221 ms, supporting a complete line of block across the anterior left atrium. The patient was discharged home the next day without class I or III antiarrhythmic medications.

FIGURE 3.

Intracardiac electrogram of atypical atrial flutter termination with ablation. During the repeat endocardial ablation, the atypical flutter terminated upon the first PFA application along the anterior mitral line.

One year after the repeat atypical atrial flutter ablation, the patient remained in sinus rhythm without any atrial arrhythmia recurrence and reported resolution of his symptoms.

4. Discussion

Catheter ablation for the treatment of atypical atrial flutter has lower reported success rates than catheter ablation for typical atrial flutter [2, 9]. Often, atypical atrial flutters arise from atrial scarring due to cardiac surgery or atrial fibrillation ablation, resulting in complex circuits that require extensive mapping and ablation. Radiofrequency ablation (RFA), while approved as a first‐line treatment for atypical flutter, has demonstrated modest success. The rate of long‐term freedom from atypical atrial flutters after RFA has been reported at 88% after cardiac surgery or maze, 80% after repaired congenital heart disease, 75% after prior endocardial catheter ablation, and 57% among patients with idiopathic atrial scar tissue [2, 9]. Given the significant recurrence of atypical atrial flutter after RFA, newer ablation modalities are being studied.

PFA has emerged as an attractive strategy for the treatment of atrial fibrillation given its similar efficacy and superior safety profile compared to RFA [3]. PFA may achieve contiguous transmural lesions with high tissue specificity, which could improve outcomes over thermal modalities [10, 11, 12]. While PFA is primarily used for PVI, PFA for non‐PV targets is currently being investigated [4, 5, 6, 8, 12]. Initial studies of PFA for atrial fibrillation and atypical atrial flutter have reported procedural success rates ranging from 64% to 90%, likely owing to the advanced atrial substrate and a lack of defined procedural practice techniques [4, 5, 7]. In an effort to standardize and improve PFA outcomes, a recent expert practical guide recommended pairing/doubling PFA applications when performing mitral isthmus ablation to reinforce their effectiveness and durability [12]. Additionally, while the number of applications was left to the operator's discretion, it was suggested to limit the number of mitral isthmus applications (e.g., to 14) when performed in conjunction with PFA‐based PVI [12].

We hypothesize that the first PFA anterior mitral lines were not durable owing to insufficient lesion depth because the anterior left atrium is thicker than the PV antra for which the initial PFA applications were developed [13]. Therefore, an anterior mitral line likely requires more than the standard two PFA applications per location to form a durable line. Key factors to achieve deep lesions with PFA include sufficient contact force in synergy with the PFA dose, number of PFA pulses, PFA electric modality configuration, catheter ablation geometry, and catheter stability and orientation [14]. Catheter‐tissue contact guided by intracardiac echocardiography has been associated with better success rates and significantly lower reconnection rates than fluoroscopy‐guided ablation [15]. The use of intracardiac echocardiography to guide our case may have improved the anterior mitral line lesion durability. Differential pacing to define bidirectional block was not performed as we felt that the immediate termination of the atrial flutter with one PFA lesion, the high lesion quality with intracardiac echocardiographic guidance, and the prolonged conduction time after ablation from the high right atrium to the left atrial appendage was sufficient evidence for a complete line of block across the anterior left atrium. We acknowledge that clinical freedom at 1 year is a surrogate marker for lesion durability. Although unsuccessful in our case, Weyand et al. recently reported a promising approach that combined PFA and RFA on the same anterior mitral line to improve ablation outcomes with no atypical atrial flutter recurrence at 240 days in 14 patients [16]. Another encouraging approach for the treatment of atypical atrial flutter is the mitral isthmus line, which may have reduced atrial arrhythmia recurrence compared to the anterior mitral line [17]. Given the concern for coronary vasospasm of the left circumflex artery with PFA to the mitral isthmus line, we elected to perform the anterior mitral line. Randomized trials comparing different PFA techniques to combined PFA and RFA are needed to improve outcomes in atypical atrial flutter.

5. Conclusion

We describe a case of PFA for the treatment of atypical atrial flutter in a patient after hybrid ablation of atrial fibrillation. PFA is an innovative ablation strategy for the treatment of atypical atrial flutter but needs further research to ensure durable lesions and arrhythmia‐free survival.

Author Contributions

Daniel W. Nelson: visualization, writing – review and editing, writing – original draft. Jasbir Sra: conceptualization, writing – review and editing, supervision. Austin Deets: visualization, writing – review and editing, writing – original draft. Muhammad Zaman: visualization, writing – review and editing. Kathi Axtell: resources, writing – review and editing.

Funding

The authors have nothing to report.

Disclosure

Meeting: This case was presented at Heart Rhythm 2025, April 24–27, 2025, in San Diego, Calif. (Nelson D, Sra J. Pulsed field ablation of atypical atrial flutter in a patient after hybrid ablation of atrial fibrillation (PO‐01‐171). Heart Rhythm 2025;22(4):S203).

Ethics Statement

The authors have nothing to report.

Consent

The patient provided written consent for publication of this work.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

The authors have nothing to report.