Hypertrophic cardiomyopathy (HCM) is the most commonly diagnosed cardiac disease in cats. Characterized by thickening of the walls of the left ventricle (the primary "pump" muscle of the heart), This thickening makes the heart muscle stiff and have difficulty filling appropriately. In some cases, the thickening of the heart muscle causes an obstruction to flow out of the heart resulting in a murmur. This particular form is known as hypertrophic obstructive cardiomyopathy (HOCM). In both cases, the stiffening of the heart muscle results in a buildup of pressure within the ventricle leading to enlargement of the left atrium and subsequent congestive heart failure or fluid formation in (pulmonary edema) and/or around the lungs (pleural effusion). Clinical signs of congestive heart failure include difficulty breathing, weakness, lethargy, inappetance, and collapse. Additionally, in some cases, the heart enlargement can lead to blood stasis and formation of clots within the heart secondary to this. These clots can be released into the body and most commonly can lodge in the vessel that feeds the hind legs leading to pain and sudden inability to use the hind legs or paralysis. This is a poor prognostic indicator especially with congestive heart failure, low body temperature, and multiple affected limbs. The prognosis for cats with HCM can be quite variable. Cats without clinical signs may survive for years, although the disease can often progress, and occasionally result in sudden death or congestive heart failure. Cats with congestive heart failure can live anywhere from 6 months 3 years in some cases with proper care and medical management.