title: Isolated annular dilation does not usually cause important functional mitral regurgitation: comparison between patients with lone atrial fibrillation and those with idiopathic or ischemic cardiomyopathy.
abstract: OBJECTIVE
  We sought to test whether isolated mitral annular (MA) dilation can cause important functional mitral regurgitation (MR).
  
  
  BACKGROUND
  Mitral annular dilation has been considered a primary cause of functional MR. Patients with functional MR, however, usually have both MA dilation and left ventricular (LV) dilation and dysfunction. Lone atrial fibrillation (AF) can potentially cause isolated MA dilation, offering a unique opportunity to relate MA dilation to leaflet function.
  
  
  METHODS
  Mid-systolic MA area, MR fraction, LV volumes and papillary muscle (PM) leaflet tethering length were compared by echocardiography among 18 control subjects, 25 patients with lone AF and 24 patients with idiopathic or ischemic cardiomyopathy (ICM).
  
  
  RESULTS
  Patients with lone AF had a normal LV size and function but MA dilation (isolated MA dialtion) significant and comparable to that of patients with ICM (MA AREA: 8.0 +/- 1.2 vs. 11.6 +/- 2.3 vs. 12.5 +/- 2.9 cm(2) [control vs. lone AF vs. ICM]; p < 0.001 for both lone AF and ICM). However, patients with lone AF had only modest MR, compared with that of patients with ICM (MR fraction: -3 +/- 8% vs. 3 +/- 9% vs. 36 +/- 25%; p < 0.001 for patients with ICM). Multivariate analysis identified PM tethering length, not MA dilation, as an independent primary contributor to MR.
  
  
  CONCLUSIONS
  Isolated annular dilation does not usually cause moderate or severe MR. Important functional MR also depends on LV dilation and dysfunction, leading to an altered force balance on the leaflets, which impairs coaptation.
authors.affiliation: First Department of Internal Medicine, Kagoshima University School of Medicine, Japan. yutaka@m.kufm.kagoshima-u.ac.jp
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Otsuji
authors.forename: Toshiro
authors.initials: T
authors.lastname: Kumanohoso
authors.forename: Shiro
authors.initials: S
authors.lastname: Yoshifuku
authors.forename: Keiko
authors.initials: K
authors.lastname: Matsukida
authors.forename: Chihaya
authors.initials: C
authors.lastname: Koriyama
authors.forename: Akira
authors.initials: A
authors.lastname: Kisanuki
authors.forename: Shinichi
authors.initials: S
authors.lastname: Minagoe
authors.forename: Robert A
authors.initials: RA
authors.lastname: Levine
authors.forename: Chuwa
authors.initials: C
authors.lastname: Tei
mesh_terms: D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology*; D003327:Coronary Disease / Q000503:physiopathology*; D004108:Dilatation, Pathologic / Q000503:physiopathology; D004452:Echocardiography; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000503:physiopathology; D008944:Mitral Valve Insufficiency / Q000503:physiopathology*; D010210:Papillary Muscles / Q000503:physiopathology; D012307:Risk Factors; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology