HypertrophicCardiomyopathy is the most commonly seen cardiovascular disease in cats. Also the most devastating disease found in Maine Coons.

To understand the pathology of HCM, a brief lesson in heart anatomy is in order. The heart has four chambers that pump blood. The two chambers on the left side (the left atrium and left ventricle) are separated from the chambers on the right (the right atrium and right ventricle) by a dividing wall, called the septum. The atria are found near the top of the heart; the ventricles reside below the atria. The normal thickness of the walls of the feline heart have been measured and documented and are well-known to veterinary cardiologists. In cats suffering from HCM, the walls of the heart become progressively thicker and thicker. The thickening of the heart mainly affects the left ventricle, the chamber that pumps blood out through the aorta to the rest of the body. Very often, the lower part of the septum – the part that separates the left ventricle from the right ventricle – is also affected. When the left ventricle becomes thickened, the chamber becomes smaller and the muscle becomes very stiff, making it difficult to fill with blood. It also becomes difficult for the blood to be pumped out of the ventricle and through the aorta. Sometimes, a portion of the valve that separates the left atrium from the left ventricle gets sucked into the aorta’s outflow tract as the thickened ventricle tries to pump blood out of the aorta. This makes it even more difficult for blood to flow out of the aorta, and it also causes the valve to malfunction. As a result, the left atrium become stretched out and dilated. This can lead to increased pressure in the atrium. This increased pressure may be transmitted to the lungs, resulting in fluid retention in the lungs and eventual congestive heart failure. This phenomenon, in which one of the leaflets of the mitral valve is drawn into the aortic outflow tract, is called systolic anterior motion (SAM), and it occurs in about 2/3 of cats diagnosed with HCM.

Although there are specific conditions that can cause the heart muscle to become thicker (such as hyperthyroidism and high blood pressure), HCM is considered to be a primary disease because an identifiable disease process cannot be found. Excessive amounts of serum grown hormone and magnesium deficiency have been investigated as possible causes, but a cause-and-effect relationship could not be proven. For now, the cause remains unknown.

Katzen test for HCM by DNA swab, and yearly sonos done by a board-certified cardiologist. 

This information does not replace Veterinary advice nor care. If in question please see your Veterinarian.