Abstract Body (Do not enter title and authors here): Background: Anticipating phrenic nerve (PN) location relative to right pulmonary vein (PV) anatomy based on pre procedure imaging may limit the risk of PN damage.
Aims: Analyze how the presence of a middle pulmonary vein (MPV) or its equivalent affects PN trajectory.
Methods: The study included consecutive patients undergoing AF ablation from 2018 to 2022. PN location was mapped by high-output pacing. 3 zones were defined based on the most distal PN capture spot: Zone 1–no PN capture or capture only within right superior PV (RSPV) ostium, Zone 2-capture along the septal antrum of RSPV until mid-carina and Zone 3-capture extending the antral region of right inferior PV (RIPV) (Figure 1). Right PV anatomy based on MRI/CT was classified into typical anatomy (no MPV) versus MPV present or large proximal septal branch of RSPV near ostium (MPV equivalent). The presence of a MPV or equivalent and its association with PN trajectory and the need for antral/septal ablation line adjustments to avoid PN injury was analyzed.
Results: Out of 103 patients included (median age 67y [IQR=12], 70% male; 73% paroxysmal AF). PN was mapped in zone 1 in 49% of patients, zone 2 in 21%, and zone 3 in 30%. PN capture in zone 3 was significantly higher in the presence of MPV (prevalence 59.1%, Prevalence ratio (PR)=16.6; CI95% 4-67.4) or MPV equivalent (64%, PR=17.9; CI95% 4.5-72.1) compared to no MPV group (3.6%). An ablation line modification more antral toward the septum was necessary in 28% of patients due to PN capture and was more common if MPV (50%, PR=7; CI95% 2.5-19.7) or MPV equivalent (56%, PR=7.8; CI95% 2.9-21.4) compared to no MPV (7%).
Conclusions: A distal PN location into the RIPV's antral region is significantly more likely with a MPV or MPV equivalent. Adjusting the PV isolation line more septal is crucial if MPV is present. This finding is essential for planning transeptal puncture sites and catheter placement for effective and safe PV isolation during radiofrequency ablation.