Echocardiographic assessment:
Echocardiographic assessments were performed in line with the current recommendations and guidelines of the European Association of Echocardiography, including comprehensive echocardiography (12). The severity of MR was assessed by the semi-quantitative PISA-method, using the radius of proximal isovelocity surface area (PISA radius), the effective regurgitant orifice area (EROA), as well as the vena contracta width (VC) and the regurgitant volume (RegVol) (13). MG was estimated from the peak-systolic velocity from continuous-wave Doppler imaging of the MV. Right ventricular systolic pressure (RVSP) was estimated by the tricuspid systolic-peak velocity using the modified Bernoulli equation (instantaneous pressure gradient (ΔP) = 4 x velocity). The leaflet-to-annulus index (LAI) was calculated by a formula defined as the ratio between the summation of the lengths of the mitral valve leaflets (anterior mitral leaflet + posterior mitral leaflet) and the anteroposterior diameter (AP-diameter), as published previously (14). The leaflet lengths and AP-diameter were measured at 120-150° (three-chamber view) and SL-diameter at 0-20° (four-chamber view) in transesophageal echocardiography. The echocardiographic studies were performed with currently available ultrasound machines (iE33, Philips Medical Systems, Andover, Massachusetts; E9, GE Healthcare Vingmed Ultrasound, Horten, Norway).