Incidence and time course of atrial fibrillation following patent foramen ovale closure

Objectives: Determine the true incidence and time course of atrial fibrillation (AF) after patent foramen ovale closure (PFOc) using implantable loop recorders (ILR) placed during cryptogenic stroke evaluation. Background: Published trials report a 2%–6.6% incidence of postimplant atrial fibrillation (PIAF) after PFOc, which is probably a gross underestimation, as only patients presenting in AF were captured. Episodes of paroxysmal and silent AF would have been missed. Methods: Of 761 patients who underwent PFOc at a single center between January 2016 and December 2020, 35 patients had an ILR implanted before PFOc, without documentation of AF, and had ≥1 month of monitoring post-PFOc. The incidence, onset, and conclusion of AF episodes were determined from a review of patient records. Results: The mean duration of ILR monitoring was 54.6 ± 39.4 weeks after PFOc. AF occurred in 13/35 (37%) patients. PFOc patients who developed PIAF were older than those who did not (62 ± 11 vs. 52 ± 14 years, p = 0.03). In 12/13, the initial PIAF event occurred within 4 weeks of PFOc, with the greatest frequency around 2 weeks and conclusion by 12 weeks in all. No recurrent strokes occurred during ILR monitoring. Conclusion: The actual incidence of PIAF was far greater than previously reported and was significantly associated with older age at PFOc. The timing of PIAF onset and termination were consistent with a postimplant inflammatory mechanism. The higher actual PIAF incidence underscores its low stroke potential in this population. A larger prospective trial is required to validate these preliminary results.