Abstract 625: Distortion of Right Superior Pulmonar Vein Anatomy by Balloon Catheters as a Contributor to Phrenic Nerve Injury
Cryothermal, HIFU and laser catheter-based balloon technologies have been developed to simplify ablation for AF. Initial enthusiasm for their wide spread use has been dampened by phrenic nerve (PN) injury. The interaction between PN and pulmonary vein (PV) geometry contributing to PN injury is unclear. After right thoracotomy, the PN course along the epicardial right atrial surface was mapped directly in 10 dogs. The location of the PN and its relationship to the right superior (RS) PV, and potential RSPV surface distortions after 25/23 mm balloon inflation were established by electroanatomic mapping. In 5 dogs, the PN was captured within the RSPV, but could not be stimulated in the remaining 5 dogs. The distance between the RSPV and the PN was significantly shorter in observed diaphragm stimulated-cases than in the non-captured group (6.3±3.1 mm versus 10.2±3.2 mm, p<0.001). Importantly, 96% of the captured sites within the RSPV were observed at a distance >5 mm into the PV. The inflated balloon surface anteriorly extended 4.8±2.3 mm outside the PV diameter, with distortion of anatomy narrowing the distance of the balloon surface to the PN to 4.9±1.0 mm. (Distance of the original RSPV-to-PN: 9.4±2.7 mm, p<0.001). PN injury with balloon technologies may stem from anatomic distortion of the PV orifice/PN relationship, through increasing contact or shortening the relative distance between ablation site and PN, even without displacement of the balloon into the PV. These data are important in the refinement of these technologies to improve procedural safety.