Natural history of atrial fibrillation-induced mitral valve remodelling in absence of significant mitral regurgitation: a three-dimensional echocardiographic study

Atrial fibrillation (AF) associates with mitral regurgitation (MR) due to progressive atrial dilatation and its deleterious effects on the mitral annulus (MA). Multiple studies have investigated the physiopathology of atrial functional MR, whereas the effects of AF on mitral valve (MV) remodelling before MR development are poorly characterized. This study aimed at characterizing MV remodelling in patients with AF without significant MR, according to AF progression. This retrospective study included patients undergoing transthoracic and transesophageal echocardiography (TEE) before AF ablation at a single center. The inclusion criterion was availability of a 3D-TEE MV dataset. The exclusion criteria included: ≥moderate MR assessed using a multiparametric approach; arrhythmias other than AF; inadequate image quality. A control group of subjects undergoing TEE before PFO closure, without AF history, was included. Standard echocardiographic measures were collected, and the 3D mitral datasets were processed with TomTec MV-4D. Fifty-six patients with AF were included (34 paroxysmal AF and 22 persistent AF), and 15 control subjects. Median age was 65 (55-70) years and 47 (84%) were male. Annular parameters exhibited significant evolutive variations across the three groups. MA anterior-posterior and commissural diameters, MA circumference as well as both 2D and 3D annular areas were larger in both AF groups as compared to controls, whereas 3D MA displacement and MA displacement velocity were smaller in both AF groups vs. controls. Leaflet parameters as well showed significant changes. Tenting volume, area and height were larger in both AF groups vs. controls. The anterior leaflet area was larger in both AF groups, whereas the posterior leaflet area was larger in persistent AF only. The anterior leaflet was longer in both AF groups vs. controls (Figure 1). The main findings are: i) annular remodelling starts early in the natural course of AF, before significant MR develops; ii) most annular parameters modify during the progression from sinus rhythm to paroxysmal and, finally, persistent AF; iii) initial annular enlargement is counterbalanced by augmented leaflet area to prevent regurgitation (Figure 2). AF promotes significant geometrical alterations of the MA, including increasing diameters, area and circumference, with most geometrical parameters exhibiting more pronounced changes in the persistent group. A certain degree of geometrical alterations of the MA is tolerated before MR develops and the increase in anterior (and posterior in persistent AF) leaflet area may serve as an adaptive mechanism. Limitations of the present study are its retrospective nature and limited sample size. In conclusion, MV remodelling and dysfunction are important in the pathophysiology of AF even before significant MR develops and are more pronounced in the persistent form.3D-TEE MV parameters of the three groups Stages of AF-induced MV remodelling