HEART MURMUR IN DOGS

A heart murmur in a dog is an unusual noise heard from the heart using a stethoscope. A heart murmur is an abnormal extra sound heard between the normal heart sounds. It is caused by turbulent blood flow within the heart or nearby blood vessels.

A murmur is a symptom of a potential problem and is not the actual problem. Murmurs can signal serious issues with the heart, but can also be simply benign variations. Innocent murmurs in puppies usually go away as their hearts develop; however, many other types of murmurs are indicative of heart conditions that will require both long term monitoring and treatment.

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Causes

There are several possible reasons why a dog develops a murmur and not all are due to serious heart problems.

The most common reason is degeneration of the heart valves. As time goes on, these valves become less efficient, allowing blood to back up into previous chambers of the heart. Degenerative valve disease occurs predominantly in older small breed dogs.

Congenital cardiac anomalies (present at birth), diseases affecting the muscular walls of the heart (cardiomyopathies), anemia, fever and parasites (heartworms) can all contribute to the development of a murmur.

Signs

• Mild tiredness after exercise
• Reduced stamina
• Occasional coughing
• Persistent coughing or breathing difficulty
• Fainting or collapse episodes
• Weakness or exercise intolerance
• Swollen abdomen due to fluid buildup
• Rapid or labored breathing at rest

Risks and Complications

The primary issue with a heart murmur is that it could be a symptom of an underlying cardiac problem. If the underlying heart disease progresses, it may eventually lead to congestive heart failure, as excess fluid accumulates in the lungs or abdominal cavity, making breathing very difficult.

Poor circulation resulting from inefficient heart performance can lead to renal and hepatic dysfunction. Advanced stages may have abnormal heart rhythms which can cause sudden collapse or potentially fatal consequences. While there are many harmless murmurs, ignoring a large one may delay diagnosing and treating serious disease.

Diagnosis

Typically, a heart murmur is first discovered during a standard physical examination by listening for sounds on the chest wall using a stethoscope. After discovering a murmur, additional testing will need to be done to establish the reason for the murmur and its extent.

Chest X-rays are used to show the size of the heart and provide details of the lungs’ health. Heart ultrasounds (echocardiograms) will provide information regarding the structure of the heart, including the flow of blood. An electrocardiogram (ECG) will be able to give you an assessment of your heart rhythm and blood tests will assist with evaluating other aspects of organ function.

In addition to these studies, veterinarians may choose to perform heartworm studies when a dog lives in, travels to or has traveled through heartworm-endemic regions. This testing can assist in determining if the murmur is associated with heart disease or not.

Grading of Heart Murmurs

Veterinarians classify heart murmurs on a scale of loudness from very soft to very loud and lower grades are usually less concerning than higher grades. However, the loudness alone does not determine how seriously sick your pet is. For that reason, diagnostic imaging is always required in order to evaluate the severity of the heart changes.

Treatment

Treatment for heart murmurs depends entirely upon what caused the heart murmur. If you own a puppy with an innocent heart murmur, no treatment is needed and it may resolve on its own with time. When there is evidence of heart disease, various medications can be used, such as diuretics which reduce fluid buildup, drugs that improve heart function and drugs that control blood pressure and heart rhythm. Supportive care is also important. This includes exercising controlled amounts, feeding a balanced low sodium diet and regular visits to your veterinary clinic to track progress.

Prevention and Monitoring

Regular checkups at your local veterinary clinic are essential for all dogs. Senior dogs and high risk breeds should see their veterinarian more frequently. Owners must watch for early signs of heart problems in their dog, including coughing, reduced stamina or breathing difficulty. Prevention of heartworm disease through the use of heartworm preventative medication is also critical.