Echocardiographic Assessment of Left Atrial Size and Function in Warmblood Horses: Reference Intervals, Allometric Scaling, and Agreement of Different Echocardiographic Variables

Abstract

BackgroundEchocardiographic assessment of left atrial (LA) size and function in horses is not standardized.ObjectivesThe 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.AnimalsThirty‐one healthy Warmblood horses and 91 Warmblood horses with a primary diagnosis of mitral regurgitation (MR) or aortic regurgitation (AR).MethodsRetrospective 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.ResultsAllometric 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 and Clinical ImportanceAllometric 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.

Diagnostic value of noninvasive pulse pressure measurements in Warmblood horses with aortic regurgitation

“…The following variables were measured or calculated for the AR and control group: pulmonary artery diameter at end diastole; aortic sinus diameter at end diastole; maximum left atrial (LA) area and maximum LA diameter (LAD max ) at end systole, before mitral valve opening; LV internal volume at end diastole (LVIV d ); LV ejection fraction (EF); LV stroke volume (SV); LV internal diameter at end diastole (LVID d ); LV fractional shortening (FS); LV relative wall thickness at end diastole (RWT d ); LV mean wall thickness at end diastole (MWT d ); and the ratio of maximum LA diameter to LV internal diameter at end diastole (LAD max /LVID d ). Where appropriate, allometric scaling was performed as previously described to correct for differences in body mass . Specifically, LA and LV dimensions were normalized to a body weight (BWT) of 500 kg using the following equations: diameter [500] = measured diameter/BWT 1/3 × 500 1/3 ; area (500) = measured area/BWT 2/3 × 500 2/3 , volume (500) = measured volume/BWT × 500.…”

“…Where appropriate, allometric scaling was performed as previously described to correct for differences in body mass. 27 Specifically, LA and LV dimensions were normalized to a body weight (BWT) of 500 kg using the following equations: diameter [500] = measured diameter/BWT 1/3 × 500 1/3 ; area (500) = measured area/BWT 2/3 × 500 2/3 , volume (500) = measured volume/BWT × 500. Abnormalities detected on the valve leaflets, extent of cardiac chamber enlargement, severity of the resultant volume overload, size of the regurgitant jet, and relative relationship of jet size to chamber size were judged by the operators.…”

Joint virtual issue on recent advances in veterinary cardiac imaging

“…Refinement of normal values in cats has been aided by a large‐scale study of nearly 20 000 animals, whereas the article by Visser et al provides narrow reference intervals from 122 dogs evaluated consistently and prospectively using current state‐of‐the‐art equipment by the same sonographer . Reference intervals are also critical for accurate assessment of the equine heart, which has been enhanced by work from the University of Zurich . Many articles focused on the most common heart disease of dogs—myxomatous mitral valve degeneration—highlighting the prognostic value of mitral regurgitation severity as well as improved methods to quantitate both the regurgitant orifice and degree of cardiac remodeling .…”

“…6 Reference intervals are also critical for accurate assessment of the equine heart, which has been enhanced by work from the University of Zurich. 7 Many articles focused on the most common heart disease of dogs-myxomatous mitral valve degeneration-highlighting the prognostic value of mitral regurgitation severity 8 as well as improved methods to quantitate both the regurgitant orifice 9,10 and degree of cardiac remodeling. 11 Advanced analysis of the geometry of the mitral valve by 3-dimensional (3D) echocardiography also expands our understanding of the disease phenotype.…”

Joint virtual issue on recent advances in veterinary cardiac imaging

“…Refinement of normal values in cats has been aided by a large‐scale study of nearly 20 000 animals, while the article by Visser et al provides narrow reference intervals from 122 dogs evaluated consistently and prospectively using current state‐of‐the‐art equipment by the same sonographer . Reference intervals are also critical for accurate assessment of the equine heart, which has been enhanced by work from the University of Zurich . Many articles focused on the most common heart disease of dogs – myxomatous mitral valve degeneration – highlighting the prognostic value of mitral regurgitation severity as well as improved methods to quantitate both the regurgitant orifice and degree of cardiac remodeling .…”