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Abstract Background Predicting progression of myxomatous mitral valve disease (MMVD) in dogs can be challenging. Hypothesis/Objectives The mitral regurgitation severity index (MRSI) will predict time to congestive heart failure (CHF) and all‐cause death in dogs with MMVD. Animals Eight hundred sixty‐nine client‐owned dogs. Methods Retrospective study pooling data from 4 previous samples including dogs with MMVD stage B2 or C. MRSI was calculated as: (heart rate [HR]/120) × left atrium‐to‐aorta ratio (LA:Ao) × (age in years/10) × 100. Alternative MRSI formulas substituting radiographic measures of left atrial size were also calculated. Cox proportional hazard modeling and time‐dependent receiver‐operator characteristic curves quantified prognostic performance. Results For Stage B2 pooled samples, MRSI > 156 was predictive of time to CHF (median 407 vs 1404 days; area under the curve [AUC] 0.68; hazard ratio 3.02 [95% CI 1.9‐4.9]; P 173 was predictive of all‐cause death (median survival 868 vs 1843 days; AUC 0.64; hazard ratio 4.26 [95% CI 2.4‐7.5]; P

Abstract Background In the absence of echocardiography, identification of cardiomegaly via thoracic radiography is a necessary criterion for classification of disease severity in dogs with myxomatous mitral valve disease (MMVD). Objective Modified‐vertebral left atrial size (M‐VLAS) facilitates objective radiographic assessment of the left atrium (LA) in 2 dimensions and identifies LA enlargement more accurately than existing methods. Animals Sixty‐four dogs with various stages of MMVD and 6 control healthy dogs. Methods Retrospective case–control study. Medical records were searched for dogs with varying severity of MMVD. Modified‐vertebral left atrial size, vertebral left atrial size (VLAS), vertebral heart size (VHS), and radiographic left atrial dimension (RLAD) were measured from thoracic radiographs and compared with echocardiographically derived measurements. Results Positive correlation to LA/Ao was identified for M‐VLAS (r = 0.77, P

Abstract Background Evaluation of left heart size helps determine disease severity in dogs with myxomatous mitral valve disease (MMVD). Hypothesis/Objectives Determine the ability of radiographic vertebral heart size (VHS) and vertebral left atrial size (VLAS) to predict LHEECHO in dogs with preclinical MMVD. Animals Seventy client‐owned dogs with MMVD and no historical or present clinical or radiographic evidence of congestive heart failure (CHF). Methods Retrospective cross‐sectional study of dogs with same‐day echocardiography and thoracic radiography. Receiver‐operating characteristic (ROC) curves were used to assess the ability of VHS, VLAS, and VHS + VLAS to discern dogs with and without LHEECHO, and clinically relevant cutpoints for these radiographic measurements were selected. Results The ability of VHS and VHS + VLAS to predict LHEECHO was moderate (area under the curve [AUC]VHS = 0.851; 95% CI, 0.762‐0.941; AUCVHS + VLAS = 0.865; 0.783‐0.947), and performance of VLAS and VHS + VLAS was not different from that of VHS alone. A VHS cutpoint of >10.8 had sensitivity = 91.1% (76.3%‐98.1%) and specificity = 69.4% (51.9%‐83.7%) for predicting LHEECHO. A cutpoint of >11.7 had sensitivity = 32.4% (17.4%‐50.5%) and specificity = 97.2% (85.5%‐99.9%) for predicting LHEECHO. Thirty (43%) of the 70 dogs had a VHS value of 10.9 to 11.7. Conclusions and Clinical Importance Vertebral heart size >11.7 identified dogs with LHEECHO and VHS ≤ 10.8 excluded dogs with LHEECHO. A large percentage of dogs had VHS values intermediate to these cutpoints.

Dogs suffering from Myxomatous Mitral Valve Disease (MMVD) show a potential heart enlargement, especially in the left atrium, detectable by radiography. Due to digital radiography, different radiographic measurements estimate cardiac size quite uncomplicatedly. The Vertebral Heart Size (VHS), Radiographic Left Atrial Dimension (RLAD), Left Atrial Width (LAWidth), and the Vertebral Left Atrial Size (VLAS) used anatomical landmarks for measuring cardiac size in relation to the vertebral column. This study aimed to compare VHS, RLAD, LAWidth, and VLAS measured in conventional and inverted radiographs by veterinarians with different levels of experience in healthy dogs and dogs with MMVD. The reliability and user-friendliness of these measurements were evaluated, and the staging was compared to the echocardiography staging. A total of 50 unaffected dogs and 150 dogs with MMVD in stages B1, B2, and C were assessed. Three veterinarians with different levels of experience examined 200 conventional radiographs and their corresponding inverted radiographs blinded to the echocardiographic and clinical examination results. Analyses were performed to compare the measurements’ grading and determine anatomical landmarks with measurement difficulties. Additionally, inter- and intraobserver agreement was assessed using intraclass correlation coefficient, and the agreement between radiographic and echocardiographic staging was compared using the kappa coefficient. The VHS, LAWidth, and VLAS were easier to define than the RLAD. The interobserver agreement was almost perfect for VHS (0.962) and good for the other radiographic measurements (RLAD: 0.778, LAWidth: 0.772, VLAS: 0.858). The VHS assigned the most dogs to the correct stage. However, VHS, RLAD, LAWidth, and VLAS presented an almost perfect intraobserver agreement. The dorsal left atrial margin of the RLAD was the most difficult measurement point to identify. The VHS is the most reproducible radiographic method for measuring the canine heart size and shows the highest agreement with echocardiography. An observer-related influence could be detected for RLAD, LAWidth, and VLAS.