Atrial tachycardias adjacent to the phrenic nerve: Recognition, potential problems, and solutions

Background: Ablation of atrial tachycardias (AT) arising from the crista terminalis region (CT) can be complicated by phrenic nerve (PN) injury. Objective: This study sought to describe epicardial protection techniques to prevent PN injury from endocardial ablation of AT. Methods: Ablation was attempted in 4 patients with focal AT arising from the CT in whom conventional endocardial ablation was limited by PN proximity identified by capture during pacing. Results: Four women ages 20, 28, 30, and 31 years with structurally normal hearts presented with symptomatic ATs failing medical therapy. In the first patient, endocardial cryoablation was performed during superior vena cava (SVC) PN pacing. After acute success, AT recurred. Open surgical ablation was then performed, but AT was noninducible under anesthesia, and an anatomic ablation was performed. AT was abolished, but sinus node dysfunction required pacemaker implantation. In the subsequent 3 patients with AT adjacent to the right PN, protection of the PN was attempted by inserting a peripheral angioplasty balloon (2 patients) or steerable ablation catheter and sheath into the epicardial space between the PN and atrium. Endocardial radiofrequency ablation was successful in all 3 patients without PN injury. Conclusion: Epicardial protection of the PN allowing for safe endocardial ablation of CT ATs is a feasible method of managing these challenging cases and seems to be preferable to surgery.