title: A comparison of the histopathologic pattern of the left atrium in canine dilated cardiomyopathy and chronic mitral valve disease.
abstract: BACKGROUND
  Dilated cardiomyopathy (DCM) and chronic mitral valve disease (CMVD) in dogs are associated with heart chamber enlargement, also of the left atrium. DCM is often accompanied by rhythm disturbances (mainly atrial fibrillation or ventricular arrhythmias). In CMVD, arrhythmias are observed less frequently. It is still unclear whether left atrial enlargement in these diseases results from volume overload or if it is also connected with other factors (e.g. rhythm disturbances). This study was conducted on the left atrial myocardial specimens from 31 dogs, including those from 16 dogs with clinically diagnosed DCM and 15 dogs with CMVD. After fixation and staining (using haematoxylin-eosin and Masson-Goldner trichrome stain), the specimens underwent evaluation. Parenchymal changes (fibrosis, fatty infiltration, and vessel narrowing), degenerative changes (loss of striation, changes in cardiomyocyte structure, and abnormal cell nuclei) and the presence of inflammatory infiltrates were assessed.
  
  
  RESULTS
  More interstitial fibrosis (median 4 vs. 2.5 grid fields; p < 0.05) and less perivascular fibrosis (median score 1 vs. 2; p < 0.05) was observed in the DCM group compared to the CMVD group. Moreover, less distinct vessel narrowing was observed in the DCM group than in the CMVD group (median lumen area ratio 0.3 vs. 0.26 respectively; p < 0.05). Dogs with DCM showed more strongly defined degenerative changes than the CMVD dogs (median nuclei enlargement score 3 vs. 1, median loss of striation score 3 vs. 2 and median structural alterations score 3 vs. 2, respectively; p < 0.05).
  
  
  CONCLUSIONS
  The obtained results indicate a different nature of changes occurring in the left atrial myocardium of dogs with DCM compared to dogs with mitral valve disease, including differences in vessel narrowing, cardiomyocyte degeneration and in the distribution of connective tissue.
authors.affiliation: Division of Pathomorphology and Veterinary Forensics, Department of Pathology, Wroclaw University of Environmental and Life Sciences, Wroclaw, 50375, Poland. izabela.janus87@gmail.com.
authors.forename: Izabela
authors.initials: I
authors.lastname: Janus
authors.affiliation: Department of Internal Medicine and Clinic of Diseases of Horses, Dogs and Cats Wroclaw University of Environmental and Life Sciences, Wroclaw, 50366, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Noszczyk-Nowak
authors.affiliation: Division of Pathomorphology and Veterinary Forensics, Department of Pathology, Wroclaw University of Environmental and Life Sciences, Wroclaw, 50375, Poland.
authors.forename: Marcin
authors.initials: M
authors.lastname: Nowak
authors.affiliation: Division of Pathomorphology and Veterinary Forensics, Department of Pathology, Wroclaw University of Environmental and Life Sciences, Wroclaw, 50375, Poland.
authors.forename: Rafał
authors.initials: R
authors.lastname: Ciaputa
authors.affiliation: Division of Pathomorphology and Veterinary Forensics, Department of Pathology, Wroclaw University of Environmental and Life Sciences, Wroclaw, 50375, Poland.
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Kandefer-Gola
authors.affiliation: Department of Internal Medicine and Clinic of Diseases of Horses, Dogs and Cats Wroclaw University of Environmental and Life Sciences, Wroclaw, 50366, Poland.
authors.forename: Urszula
authors.initials: U
authors.lastname: Pasławska
mesh_terms: D000818:Animals; D002311:Cardiomyopathy, Dilated / Q000473:pathology / Q000503:physiopathology / Q000662:veterinary*; D002908:Chronic Disease; D004283:Dog Diseases / Q000473:pathology*; D004285:Dogs; D005260:Female; D006325:Heart Atria / Q000473:pathology*; D008297:Male; D008944:Mitral Valve Insufficiency / Q000473:pathology / Q000662:veterinary*