Consideration of technique for prevention of phrenic nerve injury due to right pulmonary vein ablation of atrial fibrillation

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. Back ground: Right phrenic nerve injury has been known well as a rare complication associated with ablation of right pulmonary vein (RPV) in patients with atrial fibrillation (AF) and pace mapping of the sites where the nerve can be stimulated from the endocardium has been the most commonly accepted real-time technique. PURPOSE: To assess techniques of right phrenic nerve stimulation (PNS) and to consider effective ablation while avoiding phrenic nerve injury (PNI). METHODS: The consecutive 240 patients who underwent the initial radiofrequency catheter ablation (RFCA) of AF during May 2018 to July 2022 were studied retrospectively. All patients were performed point- by-point ablation and they had PNS from the ablation catheter for each point before ablation the anterior line of RPV. RFCA was performed with a 3.5 mm irrigated catheter using Carto3. RESULTS: Mean age 72.7-years, female 95 (39.6%), 123 patients (51.3%) with paroxysmal AF (PAF), mean body mass index (BMI) 23.4 kg/m2, mean left atrial diameter (LAD) 43.3mm. 5 patients (2.1%) confirmed capture on PNS given at 10v stimulation. Although the five patients had nothing in common in terms of age, gender, BMI, or LAD, the site of PNS capture was almost identical, from RPV carina to right superior pulmonary veins (RSPV) anterior area (Fig.1-5). The area captured by 10v stimulation is often large, diverting the ablation largely to the anterior wall to avoid PNI, which can contribute to recurrence if there is epicardial conduction from the right atrium. Therefore, in order to reduce the application area, pace map with 5v stimulation was performed and it detailed PN positioning. The yellow tags in Fig. 1-4 and light blue tags in Fig 5 showed pointes of PNS capture stimulated by 5v. There was no PNS capture exactly next to these tags and no PNI was occurred by RFCA there. RFCA including just next to the area of PNS capture was performed at the surgeon's discretion with an output of 30-45w, 10-25 seconds, and ablation index (AI) target of 400-450, and RPV isolation was achieved without PNI in all patients. Four months later, one patient showed in Fig.1 had recurrent AF, but no reconnection between 4PV and LA was recognized at the 2nd session. CONCLUSION: 2.1% of all patients showed PNS capture in this study. The area of PNS capture was almost same, and a pace map by 5v was effective for detailed identification of the area. Furthermore, PNI did not appear when the application was added just next to the area identified in 5v. [Figure: see text]