Hypertrophic (Obstructive) Cardiomyopathy

Spot is a 1.5 year old Sphynx. His astute veterinarian detected a heart murmur during a routine examination. He was seen at Apex and diagnosed with HOCM.

Hypertrophic cardiomyopathy (HCM) is a disease of the muscle in the pumping chambers of the heart (ventricles). It is an inherited disease, and certain breeds (such as Maine Coons, Ragdolls, and Sphynx) are at higher risk for passing on the genes that predispose to development of HCM. The muscle can develop scarring and thickening, and as a result, the ventricles become stiff and unable to fill properly and pump blood to the body and lungs. In the ‘obstructive’ form of disease (HOCM), the thickened muscle can pull the mitral valve into an abnormal orientation which increases the workload on the left ventricle even further.

In the early stages of heart disease, cats show no symptoms. Prognosis is variable in this stage, and many cats live years without significant progression of disease. Some cats will have a heart murmur, extra heart sound (gallop), or irregular heart rhythm detected when listening to their chests with a stethoscope, but other cats have no outward signs of heart disease unless it becomes severe. Diagnosis of feline cardiomyopathy requires an ultrasound (echocardiogram) by a cardiologist.

If the disease becomes severe, back up of blood can stretch out the upper filling chamber of the heart (left atrium). Cats with dilated left atria are at risk for forming blood clots, developing heart failure (fluid in the lungs) or experiencing arrhythmias.

Spot was started on a beta blocker called atenolol. This medication slows heart rate and reduces the workload on the left ventricle with aims to prevent further thickening of the muscle and reduce the risk for arrhythmia development.