Utility of radiographic measurements to predict echocardiographic left heart enlargement in dogs with preclinical myxomatous mitral valve disease

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 LHE(ECHO) 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 LHE(ECHO), and clinically relevant cutpoints for these radiographic measurements were selected. RESULTS: The ability of VHS and VHS + VLAS to predict LHE(ECHO) was moderate (area under the curve [AUC](VHS) = 0.851; 95% CI, 0.762‐0.941; AUC(VHS + 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 LHE(ECHO). A cutpoint of >11.7 had sensitivity = 32.4% (17.4%‐50.5%) and specificity = 97.2% (85.5%‐99.9%) for predicting LHE(ECHO). 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 LHE(ECHO) and VHS ≤ 10.8 excluded dogs with LHE(ECHO). A large percentage of dogs had VHS values intermediate to these cutpoints.