Heart Murmur Causes, Treatment, and Prevention in Dogs

Any dog can develop a heart murmur, regardless of age, sex, size or breed. While heart murmurs are not always a problem, they can be a sign of other serious problems in the body and may indicate the presence of heart disease. Heart murmurs are detected by veterinarians as abnormal sounds during an exam. There are several reasons why your veterinarian may notice this sound while listening to your dog's heart through a stethoscope. Structural abnormalities and extracardiac disease are common causes, and often a "harmless" heart murmur occurs that does not require treatment and resolves on its own. Puppies of large breed breeds are more likely to develop harmless heart murmurs, while smaller breeds are at higher risk for acquired heart murmurs.

If left untreated, heart disease can lead to serious health problems, so a heart murmur requires your veterinarian's attention to determine if another medical condition is present. Even if there are no symptoms, your veterinarian may discover that your dog has a heart murmur during a routine wellness exam. Since heart murmurs may go undetected without regular visits to the veterinarian, it is important for dog owners to schedule check-ups for their dogs at least once a year.

What is a heart murmur?

A heart murmur is an abnormal heart sound that occurs when blood flow in the heart is turbulent, similar to a hissing sound when listening with a stethoscope. 1While a heart murmur is not a disease in itself, it may indicate heart disease or other problems with the body.

Any disturbance in the heart's natural blood flow can cause turbulence that is heard with a stethoscope. The heart has four chambers: right atrium, right ventricle, left atrium, and left ventricle. In a normally functioning heart, oxygen-poor blood from the veins enters the right atrium and is pumped into the right ventricle. Blood flows through the pulmonary arteries, becomes saturated with oxygen, and then enters the left ventricle. This oxygenated blood is pumped into the left atrium and then through the arteries to the body. Valves between each chamber and blood vessels keep blood flowing in the correct direction.

Heart murmurs are typically graded from 1 to 6 in intensity (I-VI). Grade I heart murmurs are the mildest and difficult to detect. These murmurs are quiet and may occur intermittently. Grade VI murmurs are the most severe. The sound is very loud when listening with a stethoscope and can usually be felt by placing your hand on the dog's chest. The higher the level of the heart murmur, the greater the turbulence of blood flow in the heart.

Symptoms of heart murmur in dogs

Dogs with heart murmurs may or may not show any clinical signs of the disease. Because a heart murmur is a sign of a possible heart problem but not an actual disease, the presence of other symptoms depends on the extent of the underlying disease, if any. If your dog has a history of heart murmur, be on the lookout for signs of a serious problem, such as heart failure, or moderate symptoms that indicate other conditions that require further investigation. Dogs with heart disease often exhibit the following symptoms, which can be indicated by a heart murmur:

symptom

cough

Drowsiness, exercise intolerance, or weakness

Wheezing or abnormal breathing

Pale gums

Abdominal distension (the appearance of a swollen abdomen)

crash plot

cough

A swollen heart can put pressure on the lungs, causing dogs with heart disease to cough. Coughing is a sign of many different types of heart disease, as various cardiovascular diseases can cause a dog's heart to enlarge. 3

Drowsiness, exercise intolerance, or weakness

Exercise intolerance is another common symptom of cardiovascular disease in dogs. 3. Dogs may tire quickly after activity, appear weak, or appear lethargic at home due to insufficient heart function.

Panting or breathing abnormally

Your dog may continue to pant or breathe abnormally. Breathing problems may affect dogs more severely at night when they sleep or when they stand up from lying down. 1

Pale gums

Pale gums are associated with more severe stages of heart disease in dogs. While this is also a sign of dental disease, if you notice your dog's gums are any color other than pink, make an appointment with your veterinarian to determine the cause.

abdominal swelling

Dogs with heart disease may develop abdominal swelling. This is caused by a buildup of fluid in the abdomen, also called ascites. 3

crash plot

When your dog collapses, be sure to get your veterinarian's attention. In dogs with heart disease, these symptoms occur when the disease causes a lack of blood flow to the brain (and ultimately renders the dog unconscious). 3

Causes of heart murmur

Heart murmurs can have a variety of causes and are not always a sign of other conditions. Further diagnosis is often required to find the actual cause, especially for high-grade murmurs.

Structural abnormalities of the heart

Structural problems such as leaky valves or holes in the ventricles may cause abnormal blood flow. This creates turbulence and a heart murmur can be heard. Some structural abnormalities are present at birth, while others may appear later in life. Common structural heart abnormalities include:

Mitral valve disease (also called mitral regurgitation, more common in small dogs)

tricuspid valve disease

Subaortic or pulmonary stenosis (narrowing of the valve)

Patent ductus arteriosus (extra blood vessel present at birth)

Endocarditis (inflammation of the heart; sometimes caused by infection)

extracardiac disease

Even if the heart itself is functioning normally, certain problems in the body can affect the flow of blood to the heart.

anemia

heartworm disease

Hyperthyroidism

hypoalbuminemia

Infect

innocent heart murmur

"Harmless" or physiological heart murmurs are benign, meaning they are not caused by a disease process. These murmurs are usually mild to moderate (Grade I-II). Puppies can have innocent heart murmurs that disappear as they grow.

If your veterinarian detects a mild to moderate heart murmur in the absence of other signs, your veterinarian may simply want to re-examine your dog periodically to monitor for the murmur rather than immediately recommend further diagnosis.

Diagnosing a heart murmur in dogs

A heart murmur is detected when a veterinarian hears an abnormal hissing sound while listening to a dog's heart through a stethoscope. Mild or moderate murmurs are usually discovered at routine veterinary appointments if there are no other symptoms, but severe murmurs are often accompanied by signs of more serious disease. Dogs with murmurs related to extracardiac disease or structural heart problems will often exhibit other symptoms that can help your veterinarian diagnose the cause.

After getting a detailed medical history from you about your dog, your veterinarian will perform a thorough physical examination. If a heart murmur is heard, it is given an intensity rating (from I to VI).

Your veterinarian will then determine if another disease is present. Several diagnostic tests are needed to evaluate heart function and overall physical health. Blood chemistry, complete blood count, and urinalysis will be performed to assess organ health and cell counts. A chest radiograph (X-ray) is needed to see the size of the heart and details of the heart and lungs.

Specialized heart testing may be needed next to take a closer look at the heart. Your primary veterinarian may refer you to a veterinary cardiologist for this test. An electrocardiogram (ECG or EKG) measures the heart's electrical activity by displaying a waveform and analyzing the waveform to look for abnormalities. An echocardiogram is an ultrasound test of the heart that shows the beating of the heart and the blood flow through it. Sonographers can measure the heart's chambers and valves and look for abnormal blood flow patterns. 2

Treatment and Prevention

Because a heart murmur is not a disease in itself but a sign of an underlying condition, treatment will depend on the underlying cause of the heart murmur, if any. Asymptomatic dogs with mild heart murmurs may not require any treatment. However, moderate to severe murmurs require further action, especially if clinical symptoms are noted.

Once a diagnosis is made, treatment recommendations can be discussed. Some heart abnormalities require surgery to repair. In addition to supportive care from the owner, other conditions can be treated with specialized diet or medication. 1 Dogs with heart disease require routine follow-up with their primary veterinarian and/or cardiologist to monitor response to treatment and assess disease progression.

Prognosis for dogs with heart murmur

Some heart murmurs disappear over time. Many innocent murmurs in puppies will go away on their own as the dog grows, but some serious conditions, such as dilated cardiomyopathy, can be serious or even fatal. Congenital heart disease can have significantly different prognosis—some can be corrected with surgery, but others may require long-term treatment or be more severe. 1 Your dog's specific prognosis will depend on the cause of his heart murmur, which your veterinarian can diagnose to determine the correct treatment plan.

How to Prevent Heart Murmur

Not all heart murmurs are preventable, but early detection allows your veterinarian to treat underlying conditions before they become serious. Be sure to follow your veterinarian's recommendations for treatment and follow-up. If you are unable to follow the recommendations, consult your veterinarian, as consistency of treatment is critical to your dog's survival. While harmless murmurs and murmurs caused by structural problems may not be preventable, the following methods can prevent some heart murmurs caused by extracardiac conditions:

Teeth cleaning regularly

Keeping your dog's teeth healthy is an important way to prevent heart disease like endocarditis. 1. Continuous dental cleaning at the vet's office and regular brushing of your dog's teeth are important home care items. Dental chews may also be beneficial, but treatment should be monitored to help your dog maintain a healthy weight.

Diet and Nutrition

Gaining too much weight puts your dog at a higher risk of heart disease and other serious health problems. Since this is the most common preventable canine disease, this is one way owners can help prevent heart problems in dogs. 5 Feed your dog a high-quality dog food and consult your veterinarian to determine the appropriate portion size based on your dog's specific needs.

exercise

Regular exercise with your dog throughout his or her life is an effective way to support heart health. Dogs with underlying medical conditions should receive daily exercise under the supervision of a veterinarian to ensure their heart and lungs can support their activity levels.

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