Auscultatory, echocardiographic, biochemical, nutritional, and environmental characteristics of mitral valve disease in Norfolk terriers

In order to more fully understand degenerative mitral valve disease (DMVD) in the Norfolk terrier, we sought to characterize findings from the physical and echocardiographic examination; biochemical, biomarker, and nutritional profiles; and select environmental variables from a cohort of apparently healthy Norfolk terriers. Overtly healthy Norfolk terriers ≥6 yrs old were recruited by 3 different veterinary hospitals and underwent historical, physical, electrocardiographic (ECG), and 2D/color-flow Doppler echocardiographic examinations. Anterior mitral valve leaflet length, maximal thickness, area, and degree of prolapse were measured or calculated from two-dimensional images. Blood samples were obtained for serum biochemistry, serum serotonin, plasma NT-proBNP, amino acid profile, C-reactive protein, and cardiac troponin I. Of the 48 dogs entered into the study, 23 (48%) had murmurs, 2 (4%) had mid-systolic clicks, 11 (23%) had ECG P pulmonale, and 41 (85%) were deemed to have echocardiographic evidence of DMVD, including 18 Norfolk terriers without a murmur. Seven (15%), 28 (58%), and 13 (27%) dogs were classified as normal (stage 0), International Small Animal Cardiac Health Council (ISACHC) stage 1a, and 1b, respectively. Mean indexed echocardiographic mitral leaflet thickness (P = 0.017), area (P = 0.0002), prolapse (P = 0.0004), and left atrial to aortic diameter (P = 0.01) were significantly different between ISACHC 0, 1a, and 1b. DMVD is relatively common in Norfolk terriers and echocardiographic changes consistent with mild DMVD can be seen in dogs without a heart murmur.