Radiographic Heart Size and Its Rate of Increase as Tests for Onset of Congestive Heart Failure in Cavalier King Charles Spaniels with Mitral Valve Regurgitation

BACKGROUND: In canine mitral regurgitation (MR) the rate of heart enlargement increases in the last year before congestive heart failure (CHF). Measurement of heart size and its rate of increase may be useful tests for CHF in MR. OBJECTIVES: To determine the value of vertebral heart scale (VHS) and its rate of increase (∆VHS units/month) for diagnosing the presence and predicting the onset of CHF. ANIMALS: Longitudinal study of 94 Cavalier King Charles Spaniels (CKCS). METHODS: VHS was measured at intervals before CHF. ∆VHS/month was calculated from sequential pairs of VHS measurements and the interval between them. Diagnostic accuracy and utility were determined by the areas under receiver operating characteristic plots (AUROC), and likelihood ratios (LR). RESULTS: AUROC for VHS at the onset of CHF was 0.93 (95% CI, 0.96-0.90), to predict CHF 1-12 months before CHF was 0.74 (95% CI, 0.81-0.66), and for ∆VHS/month at CHF was 0.98 (95% CI, 0.99-0.96). Interval LRs and their cutoff values for CHF were for VHS: 13 (95% CI, 20-7.3) at ≥12.7; 1.2 (95% CI, 2.0-0.68) between 12.7 and 12.0; 0.04 (95% CI, 0.18-0.01) at ≤12.0, and for ∆VHS/month: 15 (95% CI, 30-7.7) at ≥0.08; 0.72 (95% CI, 2.0-0.25) between 0.08 and 0.06; and 0.05 (95% CI, 0.13-0.02) at ≤0.06. CONCLUSIONS AND CLINICAL IMPORTANCE: Under the conditions of this study, VHS and particularly ∆VHS/month are useful measurements for detecting onset of CHF in CKCS with MR.