Causes of Hypertrophic Cardiomyopathy
Most authorities believe that there is a hereditary component to hypertrophic cardiomyopathy (HCM), although the exact nature of the genetic abnormality is not known. Several different disease processes may together lead to HCM. Whatever the underlying cause, animals with hypertrophic cardiomyopathy have an inherent defect in certain heart muscle cells that are primarily located within the walls of the left ventricle. The walls of the ventricle thicken and become stiffer than normal. This allows blood to flow backwards into the left atrium and pulmonary vein rather than flowing forward into circulation. As a result, fluid builds up in and around the heart and lungs (pleural effusion and pulmonary edema). In severe cases, the blood becomes sluggish and can even become stagnant, increasing the risk of arterial thromboembolisms developing. In addition, the sluggish blood flow is unable to transport a sufficient amount of oxygen and other nutrients to bodily tissues.
Until the actual cause of hypertrophic cardiomyopathy is determined, there is no realistic way to prevent the disorder. In light of the suspected genetic component, dogs that have this condition probably should not be used for breeding, and their parents should be checked to determine whether they also have HCM.
Fortunately, hypertrophic cardiomyopathy is a fairly rare condition in domestic dogs. A different type of heart disease, known as dilated cardiomyopathy, is much more common in dogs.