Comparison between real‐time 3‐dimensional and 2‐dimensional biplane echocardiographic assessment of left atrial volumes in dogs with myxomatous mitral valve disease

BACKGROUND: Assessment of left atrial (LA) size is important in medical decision making and prognostication in dogs with myxomatous mitral valve disease (MMVD). Real‐time 3‐dimensional (RT3DE) and 2‐dimensional echocardiographic (2DE) methods may be used to assess LA size. OBJECTIVES: To compare measured LA volumes obtained by RT3DE with those calculated by biplane Simpson's modified method of discs (SMOD) and the area‐length method (ALM) using the same RT3DE acquisition with the same timing. ANIMALS: One hundred twenty‐one privately owned dogs with naturally occurring MMVD. METHODS: Prospective observational study comparing LA volumes indexed to body weight using RT3DE and 2DE‐based biplane SMOD and ALM. Agreement between methods was evaluated using Bland‐Altman plots and linear regression analyses. RESULTS: Estimations of LA volume using SMOD or ALM did not show good agreement with RT3DE‐derived measurements. Absolute differences between methods increased with increasing LA volume, but SMOD underestimated whereas ALM overestimated calculated volumes compared to RT3DE‐derived measurements. The difference in LA volume between RT3DE and the biplane methods showed a systematic underestimation of 7% for SMOD and a systematic overestimation of 24% for ALM. Comparison of LA volumes obtained by SMOD and ALM did not show good agreement. The ALM yielded 30% larger LA volumes compared to SMOD. CONCLUSION AND CLINICAL IMPORTANCE: In comparison with RT3DE, SMOD systematically underestimated whereas ALM systematically overestimated LA volumes in dogs with MMVD. Because the systematic difference between RT3DE and SMOD was only 7%, SMOD might be considered the method of choice.