Chiara Foglieni1, Raffaella Rusconi2, Maria Elena Mantione2, Gabriele Fragasso3, Ottavio Alfieri4, Francesco Maisano4. 1. Cardiovascular Research Area, IRCCS San Raffaele Scientific Institute, Milano, Italy. Electronic address: foglieni.chiara@hsr.it. 2. Cardiovascular Research Area, IRCCS San Raffaele Scientific Institute, Milano, Italy. 3. Clinical Cardiology, Heart Failure Unit, IRCCS San Raffaele Scientific Institute, Milano, Italy. 4. Department of Cardiac Surgery, IRCCS San Raffaele Scientific Institute, Milan, Italy.
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.
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: Hou Bo; David Heinzmann; Christian Grasshoff; Peter Rosenberger; Christian Schlensak; Meinrad Gawaz; Jürgen Schreieck; Harald F Langer; Johannes Patzelt; Peter Seizer Journal: Clin Cardiol Date: 2019-09-09 Impact factor: 2.882
Authors: Ingrid van Hoek; Hannah Hodgkiss-Geere; Elizabeth F Bode; Julie Hamilton-Elliott; Paul Mõtsküla; Valentina Palermo; Yolanda Martinez Pereira; Geoff J Culshaw; Jeremy Laxalde; Joanna Dukes-McEwan Journal: J Vet Intern Med Date: 2020-10-29 Impact factor: 3.333