Overcoming Mirror Image Anatomy Using Pulse‐Field Energy and Three‐Dimensional Mapping System: Successful Zero‐Fluoroscopy Atrial Fibrillation Ablation Procedure for Situs Inversus

Combining pulse-field ablation with a 3D mapping system allowed a safe, zero-fluoroscopy atrial fibrillation ablation procedure in situs inversus, overcoming catheter loss of catheter orientation due to mirror-image anatomy. Atrial fibrillation (AF) is the most commonly detected arrhythmia in clinical practice, for which catheter ablation, especially pulmonary vein (PV) isolation, has become a first-line therapy, given its superior efficacy compared with medical therapy 1. However, PV isolation in AF patients with situs inversus remains challenging owing to its mirror-image anatomy, where conventional fluoroscopy-based procedure is particularly prone to loss of catheter orientation. To overcome this anatomical challenge, we present a case demonstrating successful PV isolation using pulse-field ablation (PFA) with a 3D mapping system under nonfluoroscopic guidance. A 66-year-old woman was referred to our hospital for palpitation. Surface 12-lead and Holter electrocardiograms revealed that the symptoms were caused by incessant short of AF (Figure 1A). Chest radiography demonstrated dextrocardia (Figure 1B). Given the insufficient efficacy of antiarrhythmic drugs, catheter ablation was selected for treatment. During the preprocedural evaluation, contrast-enhanced computed tomography (CT) confirmed the presence of situs inversus totalis (Figure 1B). After excluding left atrial appendage thrombosis and confirming the absence of venous anatomical anomalies such as an interrupted inferior vena cava, the patient was scheduled for admission to our hospital for catheter ablation for AF on a later date. Regarding PV isolation procedure for situs inversus patients with AF, if complications, such as PV stenosis and esophageal injury, were to occur, bailout strategies could be particularly challenging. Accordingly, PFA may be prioritized given its superior safety profile 1. And, to minimize the potential risk of loss of catheter orientation associated with fluoroscopy-dependent procedure, PFA was selected with a 3D mapping system (CARTO3 version 8; Biosense Webster Inc., Diamond Bar, CA, USA) under nonfluoroscopic guidance whenever possible (The procedure was carefully performed under continuous intracardiac echocardiography ICE; SOUNDSTAR; Biosense Webster Inc. and 3D mapping guidance to ensure maximal safety. Fluoroscopic equipment was fully prepared and immediately available in case any difficulties arose). Before describing the details of the procedure, the anatomical laterality of right and left atria and PVs was defined morphologically. The workflow of the procedure was as follows. Three guidewires were inserted via the left femoral vein and advanced to inferior vena cava, which were confirmed using surface cardiac echocardiography. After inserting two 8-Fr long sheaths, an ICE catheter was advanced through one sheath into the right atrium. Subsequently, an anatomical map of the coronary sinus (CS) was created using the CartoSound module of the 3D mapping system based on ICE images as previously described (Figure 2A) 2. Using this mapping image as a reference, a decapolar catheter (DECANAV; Biosense Webster Inc.) was placed in the CS via the second 8-Fr long sheath. After confirming with ICE image that the third guidewire had reached the superior vena cava, a steerable sheath (VIZIGO; Biosense Webster Inc.), which can be visualized on 3D mapping images, was inserted. The guidewire was exchanged for a transseptal needle (RF needle; Boston Scientific, Marlborough, MA, USA) introduced through the sheath. After adjusting the ICE to obtain a view of the atrial septum from the superior vena cava, the steerable sheath was gradually withdrawn while confirming contact with the atrial septum. The sheath tip was then carefully positioned to engage the inferoposterior area of the fossa ovalis under ICE guidance (Figure 2B), as recommended in a previous report 3. Finally, a PFA catheter (VARIPULSE; Biosense Webster Inc.) was advanced into the left atrium (LA) through a steerable sheath positioned in the LA. Before performing PV isolation, preacquired LA CT images were integrated into the 3D mapping system aligned with the four PV fast anatomical maps created using the PFA catheter (Figure 3A), because the artificial intelligence algorithm based on ICE images failed to reconstruct the LA anatomy. PFA was then delivered to each PV. The 3D mapping system facilitated precise identification of the sheath and PFA catheter positions in the LA, allowing smooth completion of morphological right PV isolation (Figure 3B). However, for morphological left PV isolation, it was essential to distinguish between the morphological left PV and the adjacent appendage. Therefore, PFA was performed after confirming that the PFA catheter was positioned in the morphological left PV based on ICE imaging. Having confirmed the absence of a voltage in each PV (Figure 3C), the procedure was completed successfully without using fluoroscopy. The total procedural time was 90 min, and the patient was discharged 2 days later without recurrence or complications. Situs inversus, occurs in approximately 1 in 10 000 individuals 4. Once AF develops in patients with situs inversus, PV isolation procedures are reported to be technically complex owing to its mirror-image anatomy even when using PFA catheter 5, which generally allows smoother procedural completion with conventional radiofrequency catheters 1. For this reason, we aimed to avoid fluoroscopy without compromising safety by employing a high-precision 3D mapping system to prevent fluoroscopy-dependent loss of catheter orientation. As a result, the procedure time was comparable to that in patients without situs inversus. While this outcome may have been case dependent, minimizing fluoroscopy eliminated the risk of loss of catheter orientation and facilitated relatively smooth procedural progress. Importantly, when performed by operators experienced with zero-fluoroscopy ablation procedure in conventional cases, this approach may be a viable option for situs inversus. Moreover, the successful application of this technique may broaden the utility of PFA under 3D mapping for other complex anatomical variations. Regarding the preoperative diagnostic imaging, the radiation dose associated with the contrast-enhanced CT examination performed in this case was a CTDIvol of 8.4 mGy and a DLP of 740 mGy·cm. These values were well below the diagnostic reference levels (DRLs) for single-phase chest-to-pelvis CT imaging specified in the Japan Diagnostic Reference Levels 2025 (CTDIvol, 13 mGy; DLP, 940 mGy·cm), indicating that radiation exposure was appropriately optimized. However, although optimization of radiation dose was achieved, justification of CT over magnetic resonance imaging (MRI) remains a separate consideration under As Low As Reasonably Achievable (ALARA) principle. And, selecting CT in this case reflected prevailing clinical practice rather than a strict adherence to the ALARA principle. Therefore, preferential use of MRI would have been more appropriate in accordance with the ALARA principle. In conclusion, although PV isolation in patients with situs inversus is technically challenging, the use of PFA combined with a 3D mapping system may simplify the procedure. Furthermore, a nonfluoroscopic approach can effectively eliminate catheter loss of catheter orientation associated with fluoroscopy in experienced hands. The authors thank Ms. Haruna Kiyomoto, Asahi Tominaga, Mr. Yushi Yamada, Yoshihisa Kiyota, and Yoshitaka Sakata for their technical support. This work was supported by Takeda Science Foundation. The authors have no conflicts of interest related to this report. The patient has provided consent for publication. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.