Background: Following ablation of the cavotricuspid isthmus (CTI), many patients with atrial flutter (AFL) are diagnosed with atrial fibrillation (AF). Thus, prophylactic pulmonary vein isolation (PVI) has been proposed at time of CTI ablation.
Objective: To classify the incidence, duration, and burden of AF (using an implantable loop recorder [ILR]) observed following CTI ablation.
Methods: We enrolled consecutive patients with history of CTI dependent atrial flutter, no known history of AF, and CHA₂DS₂-VASc ≥ 2. An ILR (Medtronic [Minneapolis, MN] LINQ^TM) was implanted before, at the time of, or within 90 days of a CTI ablation; it wirelessly transmitted ECG data daily. The time to first occurrence of AF, duration of longest AF, and lifetime AF burden were determined.
Results: The cohort consisted of 40 patients (78% male; 74 ± 9 years; CHA₂DS₂-VASc 3.7 ± 1.2) who were followed for 755 ± 488 days. AF was observed in 37 (93%) patients at a median of 79 days (IQR 9, 298). Paroxysmal AF (longest episode 54 hours and 8 minutes) was observed in 27 (73%) patients, with all episodes being < 24 hours in 23 (85%) of these 27 patients. The median AF burden in PAF patients was only 0.1% (IQR, 0, 1.9). The remaining 10 (27%) patients developed persistent AF.
Conclusion: Following CTI ablation in patients with prior history of AFL only, AF occurs in virtually all patients, most commonly within the first 3 months. However, in ~3/4 of AFL patients, subsequent AF is paroxysmal with very low overall burden. Further studies are needed (1) to understand the need for anticoagulation in these patients with short duration, low burden AF; and (2) to determine which patients develop higher burden (e.g., persistent) AF and would derive greatest benefit with PVI at time of CTI ablation.