Locating the right phrenic nerve by imaging the right pericardiophrenic artery with computerized tomographic angiography: Implications for balloon-based procedures

Background: Phrenic nerve (PN) injury, a known complication of radiofrequency (RF) catheter ablation of atrial fibrillation (AF), has been more commonly reported with balloon-based pulmonary vein isolation. Objective: We present a novel approach to locating the PN and predicting patients at higher risk of this complication. Methods: The study included 2 groups of patients. In the first group of 71 patients, computerized tomographic angiography (CTA) with 3-dimensional reconstruction of the left atrium (LA) was obtained prior to an RF ablation procedure. The location of the right pericardiophrenic artery (RPA) was identified on the axial CTA images, and the artery distance to the right superior pulmonary vein (RSPV) ostium was measured in the 3-dimensional image. During ablation, the location of the right PN was identified by pacing maneuvers. The distance to the ostium of the RSPV was measured by venography and compared with the CTA artery measurement. In the second group, CTA imaging from 37 subjects who were enrolled in 3 investigational balloon ablation trials were analyzed using the same PN location technique and compared against the clinical outcomes. In this analysis, the CTA segmentation and PN location was performed in a blinded fashion as to any clinical evidence of PN injury. Results: The mean measurement difference between PN capture and imaged RPA was 0.8 mm (P = .539). In all cases, the imaged RPA could reliably identify the approximate location of the right PN (R-square 0.984, P < .001). Moreover, this analysis suggests that a PN location within 10 mm of the RSPV poses a higher risk of PN injury using these balloon ablation devices. Conclusion: Imaging the right pericardiophrenic artery can reliably locate the right phrenic nerve. This technique might identify anatomy more vulnerable to phrenic nerve injury using balloon-based ablation systems.