Asymptomatic heart valve dysfunction in healthy middle-aged companion dogs and its implications for cardiac aging.

Heart disease is the leading cause of death in the USA, accounting for about one in every four deaths. Age is the greatest risk factor for heart disease in both people and dogs; however, heart disease is generally not considered as a major cause of morbidity or mortality in dogs. As part of the preliminary selection process for a veterinary clinical trial, 40 companion dogs with no history of cardiac pathology that were at least 6 years old and weighed at least 18 kg underwent a cardiac screening using Doppler echocardiography. Eleven dogs from this cohort were diagnosed with valvular regurgitation by echocardiography, and seven of these cases were of sufficient severity to warrant exclusion from the clinical trial. In only one case was a heart murmur detected by auscultation. Serum alkaline phosphatase levels were significantly higher in the dogs with moderate to severe valvular regurgitation compared to the rest of the cohort. These observations suggest that asymptomatic degenerative valvular disease detectable by echocardiography, but not by a standard veterinary exam including auscultation, may be present in a significant fraction of middle-aged companion dogs, indicating a previously underappreciated similarity between human and canine aging. Further, these data suggest that companion dogs may be a particularly useful animal model for understanding mechanisms of age-related degenerative valve disease and for developing and testing interventions to ameliorate cardiac disease. Future studies should address whether dogs with asymptomatic valve disease are at higher risk for subsequent morbidity or early death.