Introduction, Hypothesis: Atrial mitral regurgitation (AMR) has been emerging pathophysiology relating to an increase in aged population with atrial fibrillation. The objective of this study was to analyze morphological changes of mitral annulus from saddle back to flat shape in a cardiac cycle in patients with AMR and compare it with different etiologies of mitral regurgitation (MR) and control subjects.
Methods: We analyzed 45 patients with moderate or more MR: AMR (N=15); tethered MR (TMR) (N=15); degenerative MR (DMR) (N=15) and compared to control subjects (N=15). The groups were defined as AMR: MR with preserved LVEF, dilated left atrium and no LV dilatation, TMR; MR with impaired LVEF and LV dilatation, DMR; MR with leaflet prolapse and preserved LVEF. The severity of MR was assessed by effective regurgitant orifice area (ERO) using the Proximal Isovelocity Surface Area method. The mitral annular height, angle and area from end diastole to end systole were measured using three-dimensional data sets acquired by transesophageal echocardiography (Fig.1) (Image arena MVA assessment).
Results: The annular area in end diastole was significantly larger in AMR (11.8±2.7cm2, P<0.0001), TMR (10.6±2.2cm2, P=0.0002) and DMR (9.9±2.6cm2, P=0.006) compared to the controls (7.6±1.5cm2). The dynamic changes of annular area was significantly smaller in AMR (3.9±2.3%, P=0.01) than the controls (7.1±3.8%), whereas TMR and DMR did not show significant differences (Fig.2). In AMR, annular height and annular angle in early systole correlated with ERO of MR (R2=0.49, 0.40 respectively, Fig.3).
Conclusions: The mitral annulus was flattened throughout the systolic phase and the dynamic changes were reduced in AMR, whereas the mitral annular area was dilated with preserved annular saddle back shape and dynamic changes in FMR and DMR. Suggesting that the mechanism of MR in AMR may depend on the aberrant shape and motions of the mitral annulus, which differ from TMR or DMR.