Two radiographic methods for assessing left atrial enlargement and cardiac remodeling in dogs with myxomatous mitral valve disease

Introduction: Two radiographic measures of the left atrial (LA) size, the vertebral left atrial size (VLAS) and the radiographic left atrial dimension (RLAD), have been described in dogs. The aim of this study was to determine their feasibility and diagnostic value in the prediction of LA enlargement and clinical stage in dogs with myxomatous mitral valve disease (MMVD). Animals: 111 client-owned dogs affected by MMVD. Methods: Retrospective study. In each dog, VLAS, RLAD, vertebral heart score (VHS), and left atrium-to-aorta-ratio (LA/Ao) were measured. The correlation between VLAS, RLAD, and LA/Ao was evaluated. The diagnostic accuracy of VLAS and RLAD was assessed for the detection of LA enlargement and clinical staging using the receiver operating characteristic curve analysis. Results: A positive correlation was observed between VLAS, RLAS, and LA/Ao (r = 0.816 and r = 0.855, respectively; p<0.0001). Both VLAS (area under the curve [AUC], 0.93; p<0.0001) and RLAD (AUC, 0.98; p<0.0001) showed high diagnostic accuracy in the detection of LA enlargement. In the stage B, the RLAD (AUC, 0.99; cutoff, ≥1.8; sensitivity, 100%; specificity 93%) performed better than VLAS (AUC, 0.90; cutoff, ≥2.4; sensitivity, 66%; specificity 100%) and VHS (AUC, 0.89; cutoff, ≥10.7; sensitivity, 88%; specificity 83%) in the detection of dogs fulfilling the echocardiographic criteria for stage B2. Conclusions: VLAS and RLAD represent useful radiological tools for the detection of LA enlargement in dogs with MMVD. In asymptomatic dogs, the RLAD performs better than VLAS and VHS in the prediction of those fulfilling the echocardiographic criteria for stage B2.