Heart Valve Disease in Dogs

Diseases of the heart valves are one of the most common types of heart disease in our companion animals. Although it is possible for many kinds of animals to suffer from this disease, the most commonly affected animals are small breed dogs. In many cases, the disease is discovered when a veterinarian hears an abnormal sound, or “heart murmur.”

What is a heart murmur in dogs?

A heart murmur is an abnormal sound that arises from turbulent blood flow in the heart. One of the more common causes is a valve that changes shape as the pet ages so that the valve no longer functions properly. When that happens, blood can flow backwards every time the heart beats, leading to the swishing sound of a heart murmur. Murmurs are graded on a six-point scale depending on how loud the sound is.

My veterinarian says my dog has a heart murmur. What does that mean?

Many dogs will have a heart murmur for years and never have any problems. A heart murmur by itself doesn’t cause any symptoms. If the leak in the heart valve continues to worsen over time, the dog’s heart will start to enlarge. For a period of time, the heart can compensate for a malfunctioning valve; however, some dogs’ hearts will become so affected by the disease that they will go into congestive heart failure.

What does congestive heart failure mean? Is my dog going to die?

Congestive heart failure occurs in dogs when the heart can no longer compensate for the presence of a faulty valve. When that occurs, fluid starts to build up in the lungs. At first, this may cause the pet to be less tolerant of exercise. As heart failure worsens, your dog may start to cough and then start having difficulty breathing. Dogs in congestive heart failure require treatment with medication. Once congestive heart failure occurs, your pet is likely to need daily medication for the rest of its life.

What kinds of tests are needed?

Diseases of the heart valves can often be diagnosed on a physical exam. The most commonly affected valve is the mitral valve that separates the upper chamber of the heart (atrium) from the lower chamber (ventricle) on the left side of the heart. In mitral valve disease, the murmur will be loudest on the left side of the chest. Chest x-rays are often used to see how large the heart is, how big the vessels leading to the lung are and whether there is fluid build-up in the lungs. On occasion, an electrocardiogram (EKG) will be needed if the rhythm is abnormal too. Sometimes an echocardiogram is also used to further define the extent and severity of the disease. Blood tests are usually not necessary to diagnose the disease but may be needed once medication is started.

What kinds of medications are used to treat my dog’s heart disease?

In most cases of heart failure in dogs due to valve leaks, one or more of the following is used:

• Ace-inhibitors: This class of drug includes enalapril and benazepril. These drugs help reduce blood pressure and alter the blood volume to improve the heart’s ability to deliver blood to the tissues. Because of how these medications work, monitoring your pet’s kidney function is necessary while on these medications.
• Diuretics: These medications work by drawing excess fluid out of the lungs and causing it to be eliminated in the urine. The most commonly used diuretic is furosemide (Lasix). Animals on diuretics require constant access to water, and increased urination is a common side effect. Your veterinarian may want to check your pet’s electrolytes, specifically potassium, when on a diuretic.
• Pimobendan: The only drug in this class commonly used in veterinary medicine is sold under the trade name Vetmedin. This drug helps improve the strength of the heart’s contraction and makes the blood vessels dilate, which improves the blood flow. It is also known to improve quality of life.

Congestive heart failure is very common in veterinary medicine. The presence of a murmur does not mean your dog will necessarily experience any signs of congestive heart failure. Even if your pet does go into heart failure, proper management with medication can allow it to live a long, quality life. Your veterinarian is likely to have managed many cases and will be a good source of information about how to best manage your pet’s disease.