Remodeling Of Mitral Annulus And Left Atrium In Permanent Atrial Fibrillation: Relationship To Severity Of Mitral Regurgitation

Background: Left atrial (LA) size increases in atrial fibrillation (AF). How changes in mitral annulus and atrial volume over time relate to severity of mitral regurgitation (MR) is unknown. Methods: This cohort study included 160 patients with a history of permanent AF who had at least 2 transthoracic echocardiograms (TTE) performed between 2005 and 2010 at Vancouver General Hospital (British Columbia, Canada). Patients with structural mitral valve disease, congenital heart disease, more than mild-moderate mitral/tricuspid regurgitation on their first TTE were excluded from analyses. LA volume was determined using biplane area-length method, averaged over 3 cardiac cycles. The mitral annulus diameter (MAD), defined as the distance between the hinge points of the anterior and posterior mitral leaflets from the apical 4-chamber view, was measured during end-systole and end-diastole. Linear mixed effects modeling was used in analyzing the above measurements for change over time. Mitral regurgitation was classified into 3 grades (mild, moderate, or severe) using standard color Doppler and PISA easurements where available. Results: Of the 160 subjects included in this analysis, 100 were men (62.5%). The mean age at study entry was 74±10 years. The median number of TTE performed was 3 (range 2 - 6). All 160 patients showed a progressive increase in MAD over time. There was a significant increase in MAD at end-systole and end-diastole over a mean follow-up of 3.2 ± 2.8 years; the increases were 0.48 mm/year (95% CI 0.124 -0.75, P=0.0037) and 0.45 mm/year (95% CI 0.102-0.716, P=0.0029) respectively. LA volume increased from a mean of 43 mL/m2 to 75 mL/m2 for the cohort, or 10 mL/m2 per year. Adjusting for age, sex, and left ventricular ejection fraction, an increase in MR severity by at least 1 grade was strongly and independently associated with an increase in MAD. A 15% increment in MAD was associated with an increase in MR severity by 1 grade. Conclusion: Permanent AF was associated with significant increases in MAD and LA volume over time. Severity of MR also significantly increased over time, and was independently related to the change in MAD. Further investigations as to whether this represents a mechanism for left heart failure in patients with permanent AF are warranted.