Heart disease in dogs is very common. Approximately 3.2 million dogs in the United States live with some degree of heart disease. Heart disease in dogs includes infections of heartworms, arrhythmias, cardiomyopathy and congestive heart failure.

Causes of heart disease in dogs are similar to the causes of heart disease in humans. While congenital heart disease is mostly genetic, obesity, a lack of exercise, and poor diet account for a high percentage of acquired canine heart disease.

Contents at a Glance

Valve Disorders

Valve disorders are one of the most common types of heart disease in dogs. When one of the heart valves loses the ability to close properly, blood pools in the heart chambers or flows back into the heart.

Heart valve disorders range in severity: some only cause a slight heart murmur or unusual sound audible only with a stethoscope. More serious heart valve disorders reduce the flow of blood to the lungs or body, placing strain on the heart and sometimes contributing to congestive heart failure.


Cardiomyopathy is a disease of the heart muscle. Cardiomyopathy can cause thickened muscle walls, an enlarged heart and rigid, inflexible heart muscle.

Cardiomyopathy often occurs in response to other heart disease in dogs. A faulty heart valve, for instance, may force the heart muscles to work harder to deliver blood to the body or lungs. Over time, the chronic strain produces enlarged, thickened heart walls. Cardiomyopathy is often an indication of congestive heart failure. Large breeds of dog are more susceptible to cardiomyopathy than smaller breeds.


Heartworms are an invasive parasite spread from dog to dog by mosquitoes. Once heartworms infest a dog they migrate to the heart, where they may grow to fourteen inches. Heartworms are the most common heart disease in dogs.

Heartworms cause significant damage to a dog’s heart, and require prompt treatment to avoid heart failure and death.


Arrhythmias are irregular heart rhythms caused by disturbances in the heart’s electric impulses. Arrhythmias include irregular heart beats that pass without lasting harm. More serious arrhythmias can interfere with the heart’s ability to pump blood and can even result in sudden death.


Myocarditis is an inflammation of the heart muscle. Inflammation damages the heart wall, causing weakness and deterioration of the muscle. Oral bacterial infections, such as those associated with gum disease, can spread to the heart, causing myocarditis.

Some breeds of dog are more susceptible to myocarditis than others. Boxers, German Shorthair Pointers and Saint Bernards are all vulnerable to this type of heart disease.

Congestive Heart Failure

Many cases of heart disease in dogs are congestive heart failure. Congestive heart failure occurs when damage or disease prevents the heart from pumping sufficient blood to the body and lungs. Heartworms, cardiomyopathy, arrhythmias and myocarditis can all contribute to congestive heart failure.

Congestive heart failure is a progressive disease, and symptoms only develop after heart disease has already caused significant damage. Symptoms of congestive heart disease can include:

  • abdominal bloating
  • coughing/hacking
  • exercise intolerance
  • fatigue
  • loss of stamina
  • pale gums
  • salt retention
  • water retention
  • weakness.

Without treatment, congestive heart disease is fatal.

Congenital Heart Disease

Congenital heart disease is not as common in dogs as acquired heart disease. Of the types of heart disease present at birth, valve disorders, especially patent ductus arteriosis, or PDA, are common. PDA causes blood to flow back into the heart instead of out to the body.

Congenital heart disease is more common in some breeds than others. Breeds susceptible to congenital heart disease include:

Diagnosing Heart Disease in Dogs

In some cases, heart disease in dogs may be diagnosed by a physical exam. Electrocardiograms (EKG) can detect arrhythmias, cardiomyopathy and cardiac blocks. In addition to EKG, cardiac ultrasound and x-rays can be used to diagnose heart disease in dogs.

Treating Heart Disease in Dogs

Surgery can correct some forms of heart disease in dogs, including some valve disorders. Congenital heart disease is usually treated with medication. Diuretics prevent edema (“water retention”), while other medications improve heart muscle contractions and dilate blood vessels to improve circulation.

With the exception of congenital heart disease, most cases of heart disease in dogs are preventable. Overfeeding and poor diet contributes to heart disease in dogs, so discussing nutrition with your veterinarian is recommended. Giving your dog a preventive medication and controlling the mosquito population around your home can help prevent heartworm infection.

Regular exercise strengthens the heart and prevents obesity, a primary risk factor for heart disease in dogs and people. Exercising with your dog will be as good for your heart as for your dog’s and helps strengthen the dog-owner bond.