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Objectives To determine the prevalence of mitral valve regurgitation (MR) in asymptomatic Swedish Norfolk terriers. Animals Seventy-nine privately owned Norfolk terriers. Materials and methods A prospective observational study was conducted where dogs were recruited via the Swedish Norfolk terrier club. All dogs were examined using the same protocol including physical examination and Doppler echocardiography. Results Fifteen dogs (19%) had a murmur at the time of the examination. A total of 35 dogs (44%) had MR, including 23 dogs (29%) with both MR and tricuspid valve regurgitation and 12 dogs (15%) with MR only, identified on Doppler echocardiography. In addition, 7 dogs (9%) had tricuspid valve regurgitation only. The prevalence of MR increased with increasing age (p Conclusions Mitral valve regurgitation is common in asymptomatic Norfolk terriers with and without murmurs and the prevalence increases with age. The impact of MR in this breed on survival remains to be elucidated by a longitudinal study.

Background Effective regurgitant orifice area (EROA), calculated from the vena contracta width (VCW) as the narrowest portion of the proximal regurgitant jet, might be used to estimate severity of mitral regurgitation. However, this simplified assumption only holds when the EROA is circular, which might not be true in dogs with myxomatous mitral valve disease (MMVD). Hypothesis Effective regurgitant orifice area in dogs with MMVD is noncircular, and using color Doppler real-time 3-dimensional (RT3D) echocardiography, measured EROA in the en face view will be significantly different from calculated EROA. Animals Hundred and fifty-eight privately owned dogs with naturally occurring MMVD. Materials and Methods Prospective observational study comparing en face view of EROA with calculated EROA using VCW in 4-chamber (4Ch) and 2-chamber (2Ch) view only or combined 4Ch and 2Ch views using RT3D echocardiography. Results The calculated EROA using the 2Ch view showed a systematic underestimation of 17% compared with the measured en face EROA corrected for body surface area. The calculated EROA using 4Ch and 4Ch + 2Ch views showed less agreement with the en face EROA, and the difference between methods increased with increasing EROA. The difference between calculated and measured EROA showed a systematic underestimation of the calculated EROA by 36% (4Ch) and 33% (4Ch + 2Ch), respectively, compared to measured en face EROA. Conclusion and Clinical Importance When replacing measured EROA with calculated EROA using VCW measurements, the 2Ch view is preferred in dogs with MMVD.

Background Two-dimensional (2D) and real-time three-dimensional (RT3D) echocardiography can be used to assess left atrial (LA) size, but their correlation in dogs remains unknown. Hypothesis Estimations of LA size differ depending on the echocardiographic technique. Animals Privately owned dogs; 70 with myxomatous mitral valve disease and 32 healthy control dogs. Methods Prospective observational study comparing RT3D volume at atrial end-diastole (RT3DLAd) with 4 different 2D methods of estimating LA size: LA diameter and area in short-axis (LAsax and LAarea) and LA diameter in long-axis (LAlax), both as indexed variables and as predictors of LA volume indexed to body weight (BW) using allometric scaling and geometric assumption of sphericity. Furthermore, agreement between indexed 2D based methods was studied using concordance correlation coefficient (ρc) and Bland–Altman plots. Results None of the indexed 2D methods of estimating LA size showed good correlation with BW-indexed RT3DLAd volumes. Estimates of LA volumes from 2D measurements using allometric scaling showed better correlation with RT3D volumes than corresponding calculated volume approximations. The best correlation was found between RT3DLAd and estimated LA volumes based on allometric scaling of LAlax (ρc = 0.89) followed by LAarea (ρc = 0.86) measurements. Comparing indexed 2D-based measurements of LA size, best agreement was found between LAsax to aortic diameter and LAsax to expected LA diameter, based on allometric scaling. Conclusions and Clinical Importance Allometric scaling of 2D-based measurements of LA showed good correlation with RT3DLAd, whereas corresponding indexed measurements or calculated volume approximations did not.

Background Real-time 3-dimensional (RT3D) echocardiography provides a novel technique for assessing left atrial ejection fraction (LAEF) in dogs. Hypothesis Left atrial ejection fraction is associated with severity of myxomatous mitral valve disease (MMVD). Animals Privately owned dogs; 101 with MMVD and 52 healthy control dogs. Methods Prospective observational study using RT3D echocardiographic estimations of LA volumes at atrial end-diastole and atrial end-systole to calculate LAEF in comparison with conventional 2-dimensional echocardiographic variables. Results Left atrial ejection fraction decreased with increasing LA to aortic ratio (LA/Ao), percentage increase in left ventricular (LV) internal dimension, corrected for body weight (BW), in diastole (LVIDd inc%) and systole (LVIDs inc%), and age for MMVD dogs, and with BW for control dogs. The final models in the multiple regression analyses included LVIDd inc% and age for MMVD dogs, and BW alone for control dogs. LAEF varied widely in both MMVD dogs and control dogs. Conclusion and clinical importance The wide variation of LAEF and the fact that LAEF does not appear to be an independent marker of disease severity suggest that the clinical importance of determining LAEF in dogs with MMVD might be limited.