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).