title: Early left atrial tissue features in patients with chronic mitral regurgitation and sinus rhythm: Alterations of not remodeled left atria.
abstract: OBJECTIVE
  Left atrial (LA) enlargement, a compensatory mechanism in chronic mitral regurgitation (MR) increasing the risk of atrial fibrillation (AF) and predictive of cardiac events, involves structural alterations. We characterized LA features in patients in sinus rhythm with severe degree of MR, similar degrees of left ventricular remodeling but divergent LA size.
  
  
  METHODS
  Among a consecutive series of 163 patients in stable sinus rhythm undergoing isolated mitral valve surgery for severe non-rheumatic MR, two groups were arbitrarily selected according to their LA size (antero-posterior): NRLA group (non-remodeled LA) included 8 patients with LA≤40mm, RLA group (remodeled LA) included 8 patients with LA>55mm. LA biopsies were processed for paraffin inclusion and sectioning. Fibrosis, cardiomyocytes morphology, capillaries density, cytochrome c and F-actin expression were evaluated by microscopy.
  
  
  RESULTS
  Histology and immunohistochemistry demonstrated alteration of moderate entity: higher amounts of endomysial fibrosis (not of collagen type III) and of hypertrophic cardiomyocytes in RLA than in NRLA. Confocal microscopy displayed focally disorganized F-actin and no nuclear fragmentation in both groups, but more intra-cytoplasm cytochrome c in RLA vs. NRLA, possibly indicative of more successful escape to apoptosis by NRLA cardiomyocytes.
  
  
  CONCLUSIONS
  Our study shows the presence of early cellular and interstitial alterations in LA tissue in patients with chronic MR and sinus rhythm. These features were analogous to those of patients with AF, and suggest that macroscopic remodeling LA in the settings of MR is preceded by structural changes, paving the way to further investigation on the preventive role of early mitral valve repair.
authors.affiliation: Cardiovascular Research Area, IRCCS San Raffaele Scientific Institute, Milano, Italy. Electronic address: foglieni.chiara@hsr.it.
authors.forename: Chiara
authors.initials: C
authors.lastname: Foglieni
authors.affiliation: Cardiovascular Research Area, IRCCS San Raffaele Scientific Institute, Milano, Italy.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Rusconi
authors.affiliation: Cardiovascular Research Area, IRCCS San Raffaele Scientific Institute, Milano, Italy.
authors.forename: Maria Elena
authors.initials: ME
authors.lastname: Mantione
authors.affiliation: Clinical Cardiology, Heart Failure Unit, IRCCS San Raffaele Scientific Institute, Milano, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Fragasso
authors.affiliation: Department of Cardiac Surgery, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Ottavio
authors.initials: O
authors.lastname: Alfieri
authors.affiliation: Department of Cardiac Surgery, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Maisano
mesh_terms: D000368:Aged; D064752:Atrial Remodeling; D002908:Chronic Disease; D042241:Early Diagnosis; D004562:Electrocardiography / Q000379:methods; D005260:Female; D006325:Heart Atria / Q000473:pathology* / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008944:Mitral Valve Insufficiency / Q000175:diagnosis* / Q000503:physiopathology*
keywords: Atrial remodeling; Cardiomyocyte; Left atrium; Mitral regurgitation; Sinus rhythm