Phrenic nerve injury after catheter ablation of atrial fibrillation

Abstract

Phrenic Nerve Injury (PNI) has been well studied by cardiac surgeons. More recently it has been recognized as a potential complication of catheter ablation with a prevalence of 0.11 to 0.48 % after atrial fibrillation (AF) ablation. This review will focus on PNI after AF ablation. Anatomical studies have shown a close relationship between the right phrenic nerve and it's proximity to the superior vena cava (SVC), and the antero-inferior part of the right superior pulmonary vein (RSPV). In addition, the proximity of the left phrenic nerve to the left atrial appendage has been well established. Independent of the type of ablation catheter (4 mm, 8 mm, irrigated tip, balloon) or energy source used (radiofrequency (RF), ultrasound, cryothermia, and laser); the risk of PNI exists during ablation at the critical areas listed above. Although up to thirty-one percent of patients with PNI after AF ablation remain asymptomatic, dyspnea remain the cardinal symptom and is present in all symptomatic patients. Despite the theoretical risk for significant adverse effect on functional status and quality of life, short-term outcomes from published studies appear favorable with 81% of patients with PNI having a complete recovery after 7 +/- 7 months.

Conclusion: Existing studies have described PNI as an uncommon but avoidable complication in patients undergoing pulmonary vein isolation for AF. Prior to ablation at the SVC, antero-inferior RSPV ostium or the left atrial appendage, pacing should be performed before energy delivery. If phrenic nerve capture is documented, energy delivery should be avoided at this site. Electrophysiologist's vigilance as well as pacing prior to ablation at high risk sites in close proximity to the phrenic nerve are the currently available tools to avoid the complication of PNI.

Figure 1

Endocardial site where phrenic nerve was captured in patients with phrenic nerve injury who had a redo procedure and completely recovered. (A) Endocardial right phrenic nerve course in the right atrium (RA) (posteroanterior view on anatomic Carto map). (B) Site where right and left phrenic nerve were captured in the left atrium (left anterior oblique [LAO] view on anatomic Carto map). RSPV: right superior pulmonary vein. Figure 3 from Journal of American College of Cardiology, V47 (12): 2502, Sacher F et al: "Phrenic nerve injury after AF ablation…" © 2006 The American College of Cardiology Foundation.