title: Echocardiographic Assessment of Left Atrial Size and Function in Warmblood Horses: Reference Intervals, Allometric Scaling, and Agreement of Different Echocardiographic Variables.
abstract: BACKGROUND
  Echocardiographic assessment of left atrial (LA) size and function in horses is not standardized.
  
  
  OBJECTIVE
  The aim of this study was to establish reference intervals for echocardiographic indices of LA size and function in Warmblood horses and to provide proof of concept for allometric scaling of variables and for the clinical use of area-based indices.
  
  
  METHODS
  Thirty-one healthy Warmblood horses and 91 Warmblood horses with a primary diagnosis of mitral regurgitation (MR) or aortic regurgitation (AR).
  
  
  METHODS
  Retrospective study. Echocardiographic indices of LA size and function were measured and scaled to body weight (BWT). Reference intervals were calculated, the influence of BWT, age, and valvular regurgitation on LA size and function was investigated and agreement between different measurements of LA size was assessed.
  
  
  RESULTS
  Allometric scaling of variables of LA size allowed for correction of differences in BWT. Indices of LA size documented LA enlargement with moderate and severe MR and AR, whereas most indices of LA mechanical function were not significantly altered by valvular regurgitation. Different indices of LA size were in fair to good agreement but still lead to discordant conclusions with regard to assessment of LA enlargement in individual horses.
  
  
  CONCLUSIONS
  Allometric scaling of echocardiographic variables of LA size is advised to correct for differences in BWT among Warmblood horses. Assessment of LA dimensions should be based on an integrative approach combining subjective evaluation and assessment of multiple measurements, including area-based variables. The clinical relevance of indices of LA mechanical function remains unclear when used in horses with mitral or aortic regurgitation.
authors.affiliation: Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: I M
authors.initials: IM
authors.lastname: Huesler
authors.affiliation: Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: K J
authors.initials: KJ
authors.lastname: Mitchell
authors.affiliation: Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: C C
authors.initials: CC
authors.lastname: Schwarzwald
mesh_terms: D000818:Animals; D016279:Atrial Function, Left / Q000502:physiology*; D049628:Body Size; D004452:Echocardiography / Q000662:veterinary*; D005260:Female; D006325:Heart Atria / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D006736:Horses / Q000033:anatomy & histology*; D008297:Male; D012016:Reference Values; D012189:Retrospective Studies
keywords: Equine; Heart; Imaging; Valvular regurgitation