Dilated cardiomyopathy is characterized by enlargement of all four chambers of the heart with thinning of the heart walls. Secondary arrhythmias are not uncommon. This condition in cats has generally been associated with a dietary deficiency of the amino acid taurine. Commercial diets now have taurine added to combat the problem however some homemade diets may still be deficient. Low potassium may also play a role in dilated cardiomyopathy. The cause in dogs is unknown however viral infections may play a role in some cases.

Hypertrophic cardiomyopathy is enlargement of the heart due to thickening of the heart walls. This is a much more common condition in cats than in dogs. Arrythmias and heart valve failure are common secondary problems Various genetic causes have been proposed however no one factor has been identified.

Young (as early as 5 months) to middle aged cats are usually effected with clinical signs being lethargy, loss of appetite, and breathing difficulty with pulmonary edema (fluid in the lungs) and occasionally vomiting. Cardiomyopathy is also an important predisposing cause of thromboembolism (clots in blood vessels) which can block blood supply to limbs or organs.

Dilated cardiomyopathy in dogs is mainly seen in young, male, large breeds of dog. Signs tend to be more acute than in cats with coughing, breathing difficulty, syncope (fainting), weakness and swelling of the abdomen, however a milder form developing over 1-2 weeks can occur.

Radiographs (X-rays), ultrasound and electrocardiographs are used to diagnose both forms of cardiomyopathy.

Cardiomyopathy is treated with a combination of drugs including digoxin, ß-blockers, diuretics, hypotensive drugs such as diltiazem, ACE inhibitors and aspirin (to prevent clots). Other newer drugs such as amrilone may also prove effective in improving the cardiac function in the se animals Dilated cardiomyopathy secondary to taurine deficiency can usually be reversed by taurine supplementation however some supportive measures may be required to relieve the symptoms of heart failure in the short term.

The prognosis (outlook) depends on the severity of the changes in the heart and varies form fair to very poor.