This is the most common form of heart disease in dogs, affecting toy and small breed individuals in particular. (It is relatively uncommon in medium, large and giant breeds.) For unknown reasons the leaves of the valves become thickened and distended until the edges no longer meet when the valve shuts. This allows seepage back into the upper chambers (the atria) when the lower chambers (the ventricles) contract to expel blood out of the heart into the general circulation. This seepage, called "regurgitation", increases as the valve defect worsens. Sometimes, the muscular cords holding each leaf of the valve in place rupture. If this happens that part of the valve becomes flaccid; useless.
During the initial stages of valvular heart disease there are no clinical signs. The condition is usually discovered by one of us during a routine physical examination when we hear a heart murmur. The left valve, the mitral valve (shaped like a bishop's two-sided mitre), is almost always affected. The right valve, the three-sided tricuspid valve is affected in about one third of individuals with valvular heart disease. There is no evidence that treatment of valvular heart disease, before the earliest signs of heart failure, prolongs a cat or dog's life expectancy.
Dog Breeds With A High Incidence Of Valvular Heart Disease
- Cavalier King Charles Spaniel
- Lhasa Apso
- Miniature and Toy Poodles
- Miniature Schnauzer
- Yorkshire Terrier