BackgroundCavalier King Charles Spaniels (CKCS) are predisposed to myxomatous mitral valve disease (MMVD). Studies have indicated a strong genetic background.ObjectiveThe aim of this study was to evaluate the effect of a breeding scheme involving auscultation and echocardiography.AnimalsIn the Danish Kennel Club mandatory breeding scheme, 997 purebred CKCS were examined during the period 2002–2011. Each dog was evaluated 1–4 times with a total of 1,380 examinations.MethodsAuscultation and echocardiography were performed to evaluate mitral regurgitation murmur severity and degree of mitral valve prolapse (MVP). The odds of having mitral regurgitation murmur or MVP > grade 1 in 2010–2011 compared to 2002–2003 were estimated using logistic regression analysis including age and sex as covariates. Odds were estimated for dogs that were products of the breeding scheme (defined as dogs with both parents approved by the breeding scheme before breeding) and non‐products of the breeding scheme (defined as dogs with at least 1 parent with unknown cardiac status).ResultsIn 2010–2011, the odds of having mitral regurgitation murmur were 0.27 if dogs were a product of the breeding scheme compared with dogs in 2002–2003, reflecting a 73% decreased risk (P < .0001). If non‐products of the breeding scheme examined in 2010–2011 were compared with dogs in 2002–2003, no difference in odds was found (P = .49).Conclusion and Clinical ImportanceA mandatory breeding scheme based on auscultation and echocardiography findings significantly decreased the prevalence of MMVD over the 8‐ to 10‐year period. Such a breeding scheme therefore is recommended for CKCS.

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A substantive influence of circulating serotonin on MMVD stages prior to CHF development in Cavalier King Charles Spaniels was not supported by the study findings. An FSSP of highly activated platelets with pronounced serotonin binding was strongly associated with thrombocytopenia but not MMVD.

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Background: Cardiovascular disease has been associated with oxidative stress, which has been suggested to contribute to myocardial remodeling in human patients. Little is known about the relationship between myxomatous mitral valve disease (MMVD) and oxidative stress in dogs.Objective: To determine whether clinical stage of MMVD is associated with changes in the plasma concentrations of certain markers of oxidative stress in clinically healthy dogs and dogs with MMVD.Animals: Seventy five privately owned dogs: 59 cavalier King Charles Spaniels (CKCS) with different severities of MMVD and 16 dogs of different breeds with clinical signs of congestive heart failure (CHF) caused by MMVD.Methods: Markers of oxidative stress including malondialdehyde (MDA), oxidized low-density lipoprotein (oxLDL), and vitamin E (a-tocopherol and c-tocopherol) were measured in plasma and their association with clinical stage of MMVD was assessed by regression analyses.Results: Plasma oxLDL concentration was significantly lower in female dogs compared with males (P = .01). Significantly higher plasma c-tocopherol concentrations were found in neutered (P = .003) dogs. Vitamin E (a-tocopherol [P = .0004] and c-tocopherol [P = .003]) was associated with body condition score (BCS), but the association disappeared when cholesterol was included in the analyses. All markers of oxidative stress (MDA, oxLDL, and vitamin E) were positively associated with serum cholesterol concentration (P ≤ .04), but none were associated with clinical stage of MMVD.Conclusions: In conclusion, markers of oxidative stress are associated with sex, BCS, neuter status, and cholesterol. The results cannot confirm a relationship between oxidative stress and clinical stage of the disease in dogs with MMVD.