Echocardiographic Evaluation of the Mitral Valve in Cavalier King Charles Spaniels

SIMPLE SUMMARY: The incidence of myxomatous mitral valve disease (MMVD) is particularly high in some breeds such as the Cavalier King Charles Spaniel (CKCS) with as many as 90% developing this pathology by the age of 10 years. Our study shows that the American College of Veterinary Internal Medicine (ACVIM) B1 class included extremely different animals. These subjects had significant variability in terms of age (from 6 months to over 11 years), presence and severity of regurgitation and prolapse of mitral valve, as well as presence and intensity of heart murmur. It would therefore seem that in this breed the pathology can essentially follow two different paths: some dogs remain in ACVIM class B1 for a long time (they have a slow progression and persist in class B1 until old age); in others the disease establishes early and progresses rapidly, until it yields symptoms of heart failure even before 8 years. It would therefore be useful to understand whether there are parameters that can early distinguish these two groups. ABSTRACT: This prospective cross-sectional study aimed to: (1) characterize echocardiographic features of mitral valve in MMVD affected Cavalier King Charles Spaniels (CKCS), focusing on dogs classified as American College of Veterinary Internal Medicine (ACVIM) class B1; (2) compare echocardiographic data in ACVIM B1 dogs divided on the basis of age at time of MMVD diagnosis, in order to understand if different aged subjects had different echocardiographic patterns. Length (AMVL), width (AMVW) and area (AMVA) of the anterior mitral valve leaflet, mitral valve prolapse, diameters of the mitral valve annulus in diastole (MVAd) and systole (MVAs) of 90 CKCS in different ACVIM classes, 64 of which in class B1, were measured. Valvular measurements were indexed to body weight using Wesselowski’s scaling exponents. The presence of heart murmur did not discriminate between A and B1 classes (p = 0.128). Heart enlargement was more frequent in males (r(2) = 0.07, p = 0.013). Within class B1, older subjects showed significantly higher values of AMVA, AMVW, MVAd, MVAs and lower sphericity index (SI). Since many CKCS with MMVD have no murmur and their mitral valve has peculiarities, a specifically designed echocardiographic screening should be realized. In addition, different aged B1 dogs have different echocardiographic patterns that may imply different genetic and prognostic profiles.