title: Novel Mechanistic Insights Into Atrial Functional Mitral Regurgitation　- 3-Dimensional Echocardiographic Study.
abstract: BACKGROUND
  Left atrial remodeling caused by persistent atrial fibrillation (AF) causes atrial functional mitral regurgitation (MR), even though left ventricular (LV) remodeling and organic changes of the mitral leaflets are lacking. The detailed mechanism of atrial functional MR has not been fully investigated.
  
  
  RESULTS
  Of 1,167 patients with AF who underwent 3D transesophageal echocardiography, 75 patients were retrospectively selected who developed no, mild, or moderate-to-severe atrial functional MR (n=25 in each group) despite an LV ejection fraction ≥50% and LV volumes within the normal range. Mitral valve morphology and dynamics were analyzed. Patients with moderate-to-severe MR had a larger mitral annulus (MA) area, smaller MA area fraction, and greater nonplanarity angle and tethering angle of the posterior mitral leaflet (PML) compared with other groups (all P<0.001). In the multiple regression analysis, the MA area, MA area fraction, nonplanarity angle, and PML angle were independent determinants of the effective regurgitant orifice area of MR after adjusting for LV parameters (adjusted R(2)=0.725, P<0.001). The PML angle and MA area had a higher standardized regression coefficient (β=0.403, P<0.001, β=0.404, P<0.001, respectively) than the other variables.
  
  
  CONCLUSIONS
  Functional atrial MR in persistent AF is caused by not only MA dilatation, but also by multiple factors including the MA contractile dysfunction, disruption of the annular saddle shape, and atriogenic PML tethering. (Circ J 2016; 80: 2240-2248).
authors.affiliation: Cardiovascular Division, Faculty of Medicine, University of Tsukuba.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Machino-Ohtsuka
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Seo
authors.forename: Tomoko
authors.initials: T
authors.lastname: Ishizu
authors.forename: Kimi
authors.initials: K
authors.lastname: Sato
authors.forename: Akinori
authors.initials: A
authors.lastname: Sugano
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Yoshie
authors.initials: Y
authors.lastname: Hamada-Harimura
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Aonuma
mesh_terms: D000368:Aged; D019560:Echocardiography, Three-Dimensional; D005260:Female; D006325:Heart Atria / Q000000981:diagnostic imaging / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D008944:Mitral Valve Insufficiency / Q000000981:diagnostic imaging / Q000503:physiopathology; D013318:Stroke Volume