Impact of chronic mitral regurgitation on 3D atrial size and mechanics. Insights from the prospective 3D-PRIME study

Abstract

Abstract Background Chronic mitral regurgitation (MR) leads to progressive left atrial (LA) dilation. Its relative contribution to 3-dimensional (3D) LA structural and functional remodelling and the impact of concomitant clinical and hemodynamic factors, has been less explored. Aims To assess 3D LA size and mechanics, as well as mean LA pressure estimated from the pulmonary vein flow, in relation to chronic MR severity. Methods In the prospective 3D-PRIME (3D Echocardiography and Cardiovascular Prognosis in Mitral Regurgitation) study, 46 patients with chronic MR (69±13 years, body mass index (BMI) 26.2±4.3kg/m2, 50% women, 26% with atrial fibrillation, 30% with severe MR) recruited at one heart valve center were investigated with 2D and 3D transthoracic and transesophageal echocardiography. MR severity was quantified by the regurgitant volume (RV) and MR classified as organic, atrial functional or ventricular functional, as by current recommendations. LA size was measured by 3D maximum volume (LAV) indexed for body surface area (LAVI), LA mechanics by 3D peak relative increase in longitudinal volume in the reservoir phase (Sr), and mitral size by 3D annulus area and total leaflet area. Pulmonary vein Doppler flow profile was recorded in both right and left upper veins, and mean LA pressure was estimated from the average pulmonary vein systolic/diastolic velocity time integral ratio. Results Average mitral RV was 38±26ml, LAVI 53ml/m2, and Sr 17±11%. Increased mitral RV correlated with higher LAV and mean LA pressure (Figure 1), larger mitral annulus area (r=0.42) and total leaflet area (r=0.38) (all p<0.01), but not with Sr. In backward stepwise multivariate linear regression analyses, increased LAVI was independently predicted by larger mitral RV, higher age and atrial fibrillation (R2=0.62), higher mean LAP by larger mitral RV, body mass index and atrial fibrillation (R2=0.55), while lower Sr was associated with higher age and atrial fibrillation (R2=0.62) (all p<0.001). Patients with atrial functional MR (30% of the total group) had the largest LAVs and lowest Sr despite slightly lower mitral RV (Figure 2). Conclusion Chronic MR is associated with progressive increase in LA volume, mean LA pressure, and mitral annulus and total leaflet area. While MR is accompanied by low 3D LA longitudinal deformation, impaired LA mechanics is multifactorial and related closely to age and history of atrial arrythmias. Funding Acknowledgement Type of funding sources: Public hospital(s). Main funding source(s): Haukeland University Hospital Figure 1Figure 2