Description
 Hypertrophic cardiomyopathy is one of several forms of heart muscle disease which commonly affects cats and is rarely diagnosed in dogs.

The disease is characterised by gross thickening of the muscle in the walls of the heart which makes the walls stiff and less compliant. This results in poor filling of the heart chambers with blood during the diastolic phase of contraction, and inadequate output of blood during systole. The clinical signs of this condition are those of heart failure.
 
 

                       Cause
The cause is unknown.
 
 

                       Breed Occurrence
The condition is rare in dogs but the German Shepherd Dog is cited as being the breed most likely to present with hypertrophic cardiomyopathy. In cats no particular breed or group are affected.
 
 

                       Age
Hypertrophic cardiomyopathy can occur at any age in cats (range 5 months-14 years)

                     Signs
Sudden death without prior warning can occur. Some cases present with "forward failure" of the heart and exhibit exercise intolerance. Cats are often off their food (called anorexia) and lethargic with increased respiratory rate (tachypnoea) difficulty breathing (dyspnoea) and in some cats feinting and lameness due to thromboembolism).
 
 

                       X-ray
 Chest X-rays may not show much heart enlargement, though left-sided enlargement is often seen. Evidence of fluid in the lung tissue (pulmonary oedema) tends to be diffuse in cats, and more localised in dogs. Sometimes free thoracic fluid (pleural effusion) masks the presence of oedema.
 
 

                       Ultrasound (Echocardiography)
Echocardiography clearly shows a small chamber to the left ventricle with thick muscular walls. Often can detect atrial enlargement and occasionally see thrombi when they are present. M-mode examination of the left ventricle also demonstrates the thickened free muscular wall and septum.
 
 

                       Treatment
The same as for the treatment of heart failure.
 
 

                       Prognosis
If the patient has mild to moderate severity of the disease a good response to treatment can be expected, but dysrhythmias and sudden death can still occur and in cats which develop thromboembolism the prognosis is much worse.