Heart Disease in Dogs


The canine heart is a hard-working organ and is divided anatomically into left and right sides; valves allow for blood flow through the heart. The left atrium, the right atrium, the left ventricle, and the right ventricle comprise the four heart chambers. The external heart "sac" is designated the pericardium, and the myocardium is the actual muscle of the heart. The endocardium is the inner layer of cells in the heart. Heart disease, or cardiac disease, can affect any of these components.

"Dirty" blood (carrying carbon dioxide from organs, tissues, and cells) enters the right atrium through large vena cavae veins and flows to the right ventricle via the tricuspid valve. It travels through the pulmonary artery (via the pulmonary valve) to the lungs to collect oxygen and eliminate carbon dioxide and re-enters the left atrium through the pulmonary vein. The mitral valve ferries the oxygen-rich blood to the left ventricle, and the aorta (entering through the aortic valve) carries "clean," oxygen-rich blood to the remainder of the body.

Heart disease, or cardiac disease, can be a devastating clinical condition in companion animals. Early recognition and treatment can facilitate appropriate clinical management and a long life.

Types of Heart Disease in Dogs

Cardiac disease is classified as either congenital or acquired.

What is a Heart Murmur?

A heart murmur is an extra sound in the heartbeat that is detected by the veterinarian during the physical examination; such murmurs usually develop secondary to turbulent blood flow. Heart murmurs are identified in patients with and without heart disease.

Many murmurs are innocent, or occur without any evidence of heart disease. These are especially common in young puppies. They are soft murmurs and usually disappear on their own. Other benign murmurs are seen secondary to anemia (decreased red blood cell count), pain, and intense excitement.

Pathologic murmurs (those that indicate the presence of heart disease) may have very characteristic sounds and locations and are associated with cardiac disease.

Clinical Signs and Complications of Heart Disease in Dogs

Clinical signs of heart disease in dogs include:

Breathing difficulties are an extremely common cardiac complication in dogs because of fluid retention inside or outside of the lungs.

Diagnosis of Heart Disease in Dogs

Diagnosis of canine heart disease is usually facilitated by a combination of cardiac ultrasonography (ultrasound), chest x-rays, blood pressure measurement, blood work/cardiac enzyme level measurement, urinalysis, and electrocardiogram analysis. Veterinary cardiologists may perform more advanced diagnostics in necessary cases.

Treatment of Heart Disease in Dogs

Treatment of heart disease in dogs is dependent on the cause; its goal is to slow the progression of heart failure (the inability of the heart to keep up with its necessary functions).

Treatment may include any of the following therapies and drugs:

Prognosis of Heart Disease in Dogs

Prognosis is completely dependent on the etiology, or cause, of the heart disease.

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