LAA occluder device impeding pulsed field ablation of an anterior mitral line: a case report about the role of a dual energy source

Abstract

Background

Pulsed field ablation (PFA) and percutaneous closure of the left atrial appendage are increasingly used in patients with atrial fibrillation. An interaction between this form of energy and metallic structures in the heart is an emerging problem. We first report a left atrial appendage closure (LAAC)-limiting PFA using a novel dual energy ablation catheter, solved by switching to the classic radiofrequency ablation.

Case summary

An 85-year-old woman with heart failure with preserved ejection fraction and a history of persistent atrial fibrillation (status post pulmonary vein isolation in 2019, with a 25 mm Abbott Amulet LAAC implanted in 2023) presented with recurrent atrial tachycardia. During redo ablation, mapping revealed a macroreentrant circuit through an anterior left atrial low-voltage area. While extending a linear PFA lesion towards the LAAC, the generator repeatedly aborted applications due to invalid impedance values near the device—despite the device having been in place for 3 years. Switching to radiofrequency energy on the same catheter allowed the line to be completed successfully, achieving bidirectional block and tachycardia non-inducibility.

Discussion

The interaction between PFA and metallic cardiac devices may limit catheter ablation, a problem that can be solved by technologies that allow for the switch to radiofrequency sources. Dual energy technologies may be therefore preferred in patients with LAAC devices.

Learning points.

• Interaction between pulsed field ablation and left atrial appendage occluder devices may occur even after a long implant delay.

• These interactions may impede completion of the planned lesion set.

• Dual-energy platforms may allow switching to radiofrequency current to create lesions in proximity to intracardiac devices.

Introduction

Pulsed field ablation (PFA) and percutaneous left atrial appendage closure (LAAC) are increasingly used in patients with atrial fibrillation (AF), respectively, for symptom control and stroke prevention in those unsuitable for or unwilling to take oral anticoagulation. The interaction between pulsed field energy and metallic intracardiac structures is an emerging concern.¹ Recently, a novel dual-energy ablation catheter was developed: Building on the platform of a widely used contact-force-sensing catheter, a new generator now enables delivery of both radiofrequency current (producing thermal lesions) and pulsed field applications (offering greater cardioselectivity). Lesion quality is assessed in real time using a colour-coded index system incorporating contact force, catheter stability, and energy delivery parameters.

We report a case in which a previously implanted LAAC device impeded PFA delivery using this novel 3.5-mm catheter, which was resolved by switching to radiofrequency ablation.

Summary figure

Case description

An 85-year-old woman with hypertension, chronic kidney disease, and heart failure with preserved ejection fraction (HFpEF) was admitted with acute heart failure, presenting with dyspnoea on minimal exertion and peripheral oedema. A 12-lead ECG demonstrated atrial tachycardia. She had a history of persistent AF, first diagnosed in 2018, associated with mildly reduced ejection fraction during AF, requiring repeated cardioversions and intermittent treatment with amiodarone. In 2019, she underwent radiofrequency pulmonary vein isolation (PVI) with additional substrate modification, including an anterior line and posterior wall isolation (PWI); the procedure was complicated by a right groin pseudoaneurysm requiring surgical repair. During follow-up, she experienced recurrent atrial tachycardia despite amiodarone therapy. In 2023, following an episode of severe gastrointestinal bleeding requiring transfusion, a 25-mm Amulet device (Abbott Laboratories, St. Paul, MN) was implanted for LAAC, and her antithrombotic therapy was switched to aspirin monotherapy. After clinical stabilization with diuretics and resolution of orthopnoea, catheter ablation of the ongoing atrial tachycardia was planned.

On the day of the procedure, spontaneous cardioversion was recorded prior to the start. After ultrasound-guided access of the left femoral vein, a catheter was placed in the coronary sinus, and double transseptal access was achieved. A high-resolution bipolar 3D electroanatomical map of the left atrium (LA) during sinus rhythm (SR), obtained using a PentaRay catheter and the CARTO 3 system (Biosense Webster Inc., CA), confirmed durable PVI and demonstrated low-voltage areas (LVAs) at the anterior wall, roof, and posterior wall; no signals could be recorded from the LAA. The clinical tachycardia was then easily induced (cycle length 470 ms, with proximal-to-distal activation in the coronary sinus). High-resolution activation mapping identified a macroreentrant circuit involving the mitral annulus, a dense scar in the anterior wall, and the right-sided pulmonary veins, with a shared isthmus located between the anterior wall LVA and the right superior pulmonary vein. A dual-energy ablation catheter (Thermocool DE STSF, Biosense Webster, Inc., CA) was advanced to the suspected isthmus of slow conduction; entrainment was attempted but failed due to the absence of capture at lower outputs. Relying solely on the activation mapping results, a linear, point-by-point PFA lesion set connecting the LVA to the right superior pulmonary vein resulted in cycle length prolongation and subsequent termination of the tachycardia (see Supplementary material online, Video S1, Figure 1).

Figure 1.

Activation map of the atypical flutter revealing a macroreentry in the anterior wall. The purple dots represent focal pulsed field ablation applications, with the darker purple dots representing lesions that reached an index above the target of 550. In the lower panel, the recordings of the termination are reported.

During SR, residual conduction across the anterior line was identified, and further PFA applications targeting a PF index of 550 were delivered towards the anterior mitral annulus. However, despite the presence of recordable local signals, PF applications could not be successfully delivered in close proximity to the LAA occluder (Figure 2): the TruPulse generator repeatedly interrupted ablation sequences after 3 and 5 applications, due to detection of an invalid impedance value. The energy source was therefore switched to radiofrequency, and two additional applications were delivered at 35 W, targeting an RF ablation index above 500. Following completion of the line, the time to LAA basis activation increased from 150 to 199 ms. Bidirectional block across the line was confirmed by pacing from both sides, and the tachycardia was no longer inducible. In view of the posterior LVA, an additional roof line was created, and fragmented signals near the right pulmonary veins were targeted, achieving posterior wall isolation. The remainder of the procedure was uneventful. The patient was discharged the following day, and no arrhythmia recurrence was documented at 6-week follow-up.

Figure 2.

Fluoroscopic catheter position (ABL refers to the Thermocool STSF DE), 3D representation, and related electrograms of a pulsed field ablation application aborted due to proximity to the left atrial appendage closure device.

Discussion

We report a case of an implanted LAA occluder device interfering with PFA delivery during ablation using the newly available dual-energy Thermocool DE STSF catheter. PFA is becoming a leading modality for catheter ablation and PVI; however, its interaction with intracardiac metallic structures raises important questions that remain incompletely characterized. Prior reports have demonstrated interference between LAA closure devices and pentaspline ablation catheters,¹ in some cases impeding PVI and necessitating touch-up with radiofrequency ablation.²

Unlike radiofrequency energy, PFA relies on high-voltage electrical pulses that, due to their distinct biophysical properties, can interact with metallic intracardiac components in ways that may lead to thermal damage and arcing phenomena. Arcing—defined as a luminous electrical discharge bridging the PFA electrode and the LAAO device—was documented in an in vitro study³ testing three different PFA systems, predominantly but not exclusively in combination with lobe-disc occluder devices. Notably, when the Varipulse catheter (Biosense Webster Inc., CA) was tested in that study—a system sharing the same PF generator platform as the one used in our case—applications were more frequently aborted or interrupted by safety algorithm triggers. Whether the same mechanism was responsible for the generator interruptions observed in our case remains uncertain; accordingly, the occurrence of arcing in our patient remains speculative.

Importantly, the same in vitro study reported that no arcing occurred when the catheter was maintained more than 3 mm from the LAAC, raising the question of whether endothelialization of the device surface is sufficient to prevent PFA interference over time.

Following implantation, LAAC devices are expected to undergo progressive endothelialization. Although this process is generally assumed to be complete within approximately 6 months—forming the basis for standard post-procedural antithrombotic regimens—imaging studies have repeatedly demonstrated that endothelialization is frequently incomplete beyond this timeframe. An explant study found that the Amulet device may show endocardial coverage of only 60%–75% of the disc surface even 2 years after implantation.⁴

In the present case, PFA interference was observed despite the LAAC device having been implanted 3 years earlier, suggesting that endothelialization may have been incomplete or that the tissue layer was insufficiently thick to prevent electrical interaction. It is unknown whether this interaction led to true arcing; however, the early generator interruptions are consistent with safety check activations previously described with the same PF generator platform. Switching to radiofrequency energy allowed successful completion of the ablation line, underscoring the practical advantage of a dual-energy system in this setting. Notably, fluoroscopic imaging at the time of the interference (Figure 2) showed no direct contact between the catheter electrodes and the radiopaque disc of the LAAC. This observation suggests that initial PF applications could be delivered without triggering interruption, and that subsequent respiratory excursion, systo-diastolic, or PFA-induced muscular contraction movements may have caused catheter displacement into closer proximity to the device, thereby triggering the impedance-based safety interruptions.

Given the growing population of patients with implanted LAAC devices and the increasing interest in concomitant PVI and LAAC procedures,⁵ the potential interaction between PFA and intracardiac metallic devices warrants careful consideration. When a combined procedure is planned, PFA should be performed prior to LAAC implantation. In patients who already have a LAAC device in situ, a dual-energy ablation system—enabling seamless switching between PF and radiofrequency energy—may represent the more appropriate choice.

Lead author biography

He completed his medical studies at the University of Padua (Italy) and then specialized in cardiology at the Cardiology School in Padua. He then moved to Germany to undertake an EHRA training fellowship with a focus on catheter ablation. He was a consultant electrophysiologist at CCB in Frankfurt for 12 years and became Head of EP at Klinikum Frankfurt Höchst in 2025. He is a member of the EHRA Education Committee and an associate editor of the European Heart Journal Case Reports. He is the author and co-author of more than 120 publications in peer-reviewed journals.

Supplementary material

Supplementary material is available at European Heart Journal – Case Reports online.

Funding

None.

Data availability

The data will be shared on a reasonable request to the corresponding author.