The two most common types of heart disease in the adult dog are:

Valvular heart disease

Valvular heart disease is particularly common in Cavalier King Charles Spaniels (CKCS) but can occur in almost any breed. As a dog ages its heart valves may become worn and degenerate and therefore get more and more leaky. Instead of closing properly each time the heart pumps, the valves flop open allowing blood to move backwards as well as forwards through the heart chambers. This results in a reduced blood supply to the body.

Dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a form of heart disease most commonly seen in large and giant breeds, particularly Dobermann pinschers, Great Danes and Irish Wolfhounds. Some spaniels are also affected and it could rarely affect dogs of any breed. The disease causes a stretching of the heart muscle walls so that the heart swells (like a balloon filled with water). The contractions of the heart muscle become very weak so blood is not pumped around the body effectively.

For more information on these forms of heart disease read the specific factsheet on each. In humans, heart disease is the result of damage to the heart muscle caused by blood clots (myocardial infarction) - this causes the signs of a heart attack. However, dogs do not get this kind of heart disease.