Predictors of Late-Onset Atrial Fibrillation Following Isolated Mitral Valve Repairs in Patients With Preserved Ejection Fraction.

Background: We sought to determine the incidence of and risk factors for late-onset atrial fibrillation (LOAF) in patients with preserved ejection fractions undergoing mitral valve repair Methods: We included patients undergoing isolated mitral valve repair (MVR) for degenerative disease between 1997-2014 at our institution with EF >= 60%. Patients who had AF preoperatively were excluded from the final analysis. Our primary outcome, LOAF, was defined as AF occurring after discharge following MVR (>= 9 days). Results: 223 patients were included in the study with a mean follow-up of 4.8 +/- 4.6 years. A total of 25 patients developed LOAF, and freedom from LOAF was 93.9% at one year, and 87.3% at five years. Patients developing LOAF were of similar mean age (58 vs. 63 years in controls, p = 0.08) and had similar preoperative comorbidities, but did show a trend toward larger left atrial diameter (5.1 vs. 4.7 cm, p = 0.11). After risk adjustment with Cox regression analysis, only increasing left atrial size was associated with LOAF (HR 1.63, p = 0.04). On follow-up, 29 patients (10.8%) developed moderate or greater mitral regurgitation at a mean of 2.2 years. Using a mixed-effects model, we were unable to detect an association between recurrent mitral regurgitation following MVR and LOAF (OR 1.36, p = 0.42). Conclusions: LOAF occurs in about 13% of preserved ejection fraction patients undergoing MVR by five years. Increasing left atrial diameter is an independent predictor of LOAF. Concomitant anti-arrhythmic procedures may warrant further investigation in patients with preserved ejection fraction and enlarged left atria undergoing MVR.