Three-dimensional reconstruction of the anatomic course of the right phrenic nerve in humans by pace mapping

BACKGROUND Endocardial catheter ablation at the right atrial to superior vena cava junction or right pulmonary vein isolation, especially in balloon-guided procedures, is associated with risk for phrenic nerve palsy. OBJECTIVE The purpose of this study was to obtain a three-dimensional reconstruction of the individual phrenic nerve course. METHODS Electroanatomic reconstruction (CART0, Biosense Webster) of the superior vena cava, right atrium, left atrium, and right superior and inferior PVs was performed. The phrenic nerve pace map was obtained using maximal stimulation output (10 V, 2.9 ms) and annotated on the three-dimensional map. RESULTS Eighteen patients with paroxysmal atria[ fibrillation (12 men and 6 women, mean age 61 10 years) were included in the study. The phrenic nerve course was reconstructed over a mean craniocaudal length of 40 17 mm (mediolateral 11 +/- 4 mm). Median phrenic nerve distance to the right superior PV ostium was 12 mm (range 2-39 mm). The phrenic nerve could be captured in 16 of 18 patients but only in 7 of 18 patients from the right superior PV. The complete electroanatomic map was performed in 48 +/- 23 minutes, including the phrenic nerve pace map (14 +/- 6 min). CONCLUSION Pace mapping of the phrenic nerve using etectroanatomic mapping can be performed within a reasonable time frame and provides important information on the true anatomic course of the phrenic nerve. The three-dimensional display of its position in relation to potential ablation targets may be of value in preventing phrenic nerve palsy, particularly when innovative ablation energies are used. However, phrenic nerve pacing exclusively from the right superior PV appears insufficient to exclude a close anatomic relationship.