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 LR s 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 .