Sandra Tou

Mitral valve degeneration is the most common cause of heart disease in the dog. It is particularly common in small breed dogs including Cavalier King Charles Spaniels, Yorkshire Terriers, Miniature Poodles, Dachshunds and small mixed breed dogs. Although some dogs live comfortably with the disease, many affected dogs die of congestive heart failure and sometimes sudden death due to left atrial rupture. Mitral valve degeneration is known to be an inherited disease, at least in some breeds, although the causative mutation(s) have not been identified. Failure to understand the underlying cause of mitral valve degeneration has slowed the development of effective treatment and prevention plans. Here, we propose to identify genetic variants that lead to the development of mitral valve degeneration and to use this information to begin to develop treatment and prevention plans for dogs with high-risk DNA variants.

Congestive Heart Failure (CHF) is a common problem in cats, resulting from disease processes such as cardiomyopathy, hyperthyroid heart disease and hypertensive heart disease. Pimobendan is a drug that increases myocardial contractility and promotes vasodilation to improve “forward flow” and cardiac output. FDA-approved in 2007 for use in dogs, pimobendan is now a mainstay of canine CHF therapy. Dogs receiving pimobendan show both prolonged survival and improved quality of life. With similar perceived effects in cats, pimobendan is now widely used in the treatment of feline CHF. A dose similar to that recommended for dogs has been shown to be safe and well-tolerated in cats with congestive heart failure, with pharmacokinetic data confirming rapid oral absorption and high plasma concentrations in healthy cats. Currently, pimobendan is commercially available only as chewable tablet. Cat owners commonly struggle with the large tablet size, potentially resulting in frequently missed doses, suboptimal control of clinical signs, disruption of the human animal bond, and premature death or euthanasia of the pet. Pimobendan transdermal gels are currently offered by various veterinary compounding pharmacies, but no studies exist to support transdermal absorption in dogs or cats. Effective delivery of pimobendan in a transdermal form could greatly enhance owner compliance and optimize the management of cats with congestive heart failure.

Currently there is no cardiac drug licensed for the treatment of preclinical myxomatous mitral valve disease. Pimobendan has been proven to be safe and to reduce mortality as well as morbidity associated with congestive heart failure (CHF) due to myxomatous mitral valve disease. The combination of preload and afterload reduction in combination with inotropic support may result in a reduction in cardiac size and filling pressures in dogs with significant remodelling secondary to myxomatous mitral valve disease. These effects are considered to be cardioprotective and therefore, in dogs with preclinical myxomatous mitral valve disease, would be anticipated to delay the onset of pulmonary oedema and clinical signs. The objective of the study is, to determine whether chronic oral administration of pimobendan (Vetmedin® chewable tablets) in dogs with evidence of increased heart size secondary to preclinical myxomatous mitral valve disease, can delay the onset of signs of congestive heart failure.

Clinical Trial