Late occurrence of heart block after radiofrequency catheter ablation of the septal region: Clinical follow-up and outcome

Late Occurrence of Heart Block. Introduction: There are few data regarding the occurrence of delayed heart block at least 24 hours after radiofrequenc y catheter ablation (RFCA) of AV nodal reentry or posteroseptal accessory p athways (APs). We investigated the late occurrence of heart block in this p opulation, the clinical outcome, and whether findings at electrophysiologic study could have predicted its development. Methods and Results: Two of 418 patients with AV nodal reentry undergoing R FCA using a posterior approach and 1 of 54 patients with RFCA of a posteros eptal AP developed late heart block. Anterograde and retrograde AV nodal co nduction before and after RFCA were normal. Patients received 12, 15, and 3 2 RFCA lesions, respectively, using a mean maximum power of 44 W. The RFCA sites were the posterior septum for posteroseptal AP and the posterior and mid-septum for patients with AV nodal reentry, with no His electrogram ever recorded at the ablation site. During RFCA, junctional tachycardia occurre d with 1:1 VA conduction in the patient with a posteroseptal AP, but occasi onal intermittent single retrograde blocked complexes were present in both patients with AV nodal reentry. No rapid junctional tachycardia or >1 conse cutive retrograde blocked complex was ever observed during RFCA. Persistent high-degree AV block with junctional escape developed 2 days after RFCA in the posteroseptal AP patient. A permanent pacemaker was implanted, and nor mal conduction was noted 16 days after RFCA. Both patients with AV nodal re entry complained of fatigue, mainly on exertion, 3 to 3 days after RFCA, an d ECG-documented exercise-induced variable AV block was obtained. Because h eart block resolved in our initial patient, a prolonged monitoring period w as allowed. Symptoms disappeared at 13 and 8 days, and a follow-up treadmil l test showed normal PR interval and no heart block. No recurrence of heart block has been seen in any of these three patients. Conclusion: Late unexpected heart block after RFCA of AV nodal reentry and posteroseptal AP is rare, often resolves uneventfully in 1 to 2 weeks, and no specific electrophysiologic findings predicted its occurrence. Prolonged clinical observation is preferable to immediate pacemaker implantation in such patients.