Dogs are susceptible to a variety of cardiovascular conditions with small dogs in particular being more likely to develop heart diseases, including heart murmurs. The condition may be congenital or acquired as a result of disease and ageing and can vary in seriousness from mild to severe, leading to congestive heart failure and death.

Heart murmurs occur when the heart function has deteriorated resulting in abnormal blood flow within the chambers. The heart is divided into four chambers: the left and right atria, and the left and right ventricles. The mitral valve, connected to the left atrium and left ventricle is key to regulating the blood flow through the heart. Age, disease and defects can cause this valve to wear out and allow blood to leak back into the ventricles. Known as mitral valve insufficiency, this condition produces a distinctive sound, or heart murmur.

Symptoms of heart problems in your dog may include a chronic cough, labored breathing, and inability to exercise. In serious cases, the dog may display a blue tint around the gums and tongue and may pass out. It is important to have the animal diagnosed and treated by a vet as early as possible as the presence of a murmur may rapidly lead to congestive heart failure. Diagnosis is done through the detection of abnormal heart rhythms, blood and urine tests, chest x-rays and an electrocardiogram to evaluate the heart's electrical activity, and an ultrasound (echocardiogram) to provide a view of the heart's chamber sizes and the thickness of the heart walls.

Treatment is usually begun with placing the dog on a low-sodium diet and using diuretic medications to eliminate retained salt and water. Following this other drugs are prescribed to dilate the arteries and veins, and make the heart beat slower and stronger.