Dog Heart Murmur: Your Questions Answered

A dog heart murmur is an unusual whooshing or swishing sound your veterinarian hears between normal heartbeats, caused by turbulent blood flow inside or near the heart. Hearing the words “dog heart murmur” during a routine exam can be unsettling, but a murmur itself is not a diagnosis. It is a clinical sign that prompts further investigation into what is happening inside your dog’s heart. At Veterinary Healthcare Associates in Winter Haven, FL, our team evaluates every dog heart murmur individually, because the cause, severity, and outlook can vary enormously from one dog to the next. Some murmurs are harmless quirks of a young, growing heart, while others signal early valve disease that benefits from monitoring and treatment. 

What Does a Heart Murmur Mean in a Dog?

A dog heart murmur happens when blood flow through the heart becomes turbulent instead of smooth, creating an audible vibration your veterinarian can pick up with a stethoscope. Veterinarians grade a dog heart murmur on a scale from one to six, with one being extremely faint and six being loud enough to feel through the chest wall. The grade alone does not tell the whole story. A soft dog heart murmur in an older dog might indicate significant valve wear, while a moderate murmur in a puppy sometimes resolves entirely as the dog matures.

Murmur Location and Timing

Location matters too. Veterinarians note whether the murmur is loudest over the mitral valve, the aortic valve, or elsewhere, since that location often points toward the underlying cause. Timing also plays a role in the evaluation. A murmur heard during the contraction phase of the heartbeat is described as systolic, while one heard during the relaxation phase is called diastolic, and each pattern narrows down the list of likely explanations.

Age as a Factor

Puppies sometimes develop what veterinarians call an innocent or physiologic murmur, a soft sound tied to rapid growth that typically fades on its own by six to twelve months of age. Older dogs, on the other hand, are more likely to develop a murmur tied to a structural change in the heart itself, which is why age is one of the first factors a veterinarian considers when interpreting the finding.

What Is Mitral Valve Disease in Dogs?

Mitral valve disease is the most common cause of a dog heart murmur, particularly in small and toy breeds such as Cavalier King Charles Spaniels, Chihuahuas, and Dachshunds. The mitral valve sits between the left atrium and left ventricle, and over time its edges can thicken and lose their ability to close tightly. When the valve does not seal properly, blood leaks backward with each heartbeat, producing the turbulent flow that creates a dog heart murmur.

This condition, sometimes called myxomatous mitral valve disease, tends to progress slowly over months or years. Many dogs live full, active lives for a long time after diagnosis, especially when the condition is caught early through routine wellness exams. Congenital heart defects, heartworm disease, and infections can also produce a dog heart murmur, which is why a thorough workup matters before assuming mitral valve disease is the cause.

What Are the Symptoms of a Heart Murmur in Dogs?

Many dogs with a mild dog heart murmur show no outward symptoms at all, which is exactly why the finding often comes as a surprise during a routine physical exam. As a murmur progresses or the underlying heart disease advances, though, physical signs tend to appear.

• Coughing, particularly at night or after lying down, which can signal fluid buildup around the lungs
• Reduced stamina during walks or play, where a dog that once ran eagerly now tires quickly
• Labored or rapid breathing, even at rest, which warrants prompt veterinary attention
• Pale or bluish gums, fainting spells, or a swollen abdomen, all signs of more advanced disease

What to Avoid if Your Dog Has a Heart Murmur

Once your dog has been diagnosed with a heart murmur, a few precautions help protect their heart health while you work with your veterinary team on a long-term plan.

• Avoid strenuous, unsupervised exercise until your veterinarian has assessed the severity of the dog heart murmur
• Skip high-sodium treats and table scraps, since excess sodium can strain a compromised heart
• Do not stop or adjust any prescribed heart medication without veterinary guidance, even if symptoms seem to improve
• Avoid delaying follow-up appointments, since a dog heart murmur can change grade or significance over time

Dog Heart Murmur Treatment

Treatment for a dog heart murmur depends entirely on its underlying cause and severity, which is why diagnostic imaging plays such an important role. Your veterinarian may recommend chest X-rays, an echocardiogram, or bloodwork to pinpoint exactly what is driving the murmur and how much the heart has been affected. A young, healthy dog with an innocent murmur often needs nothing more than periodic rechecks to confirm the sound resolves on its own.

Managing Diagnosed Heart Conditions

For dogs whose dog heart murmur stems from mitral valve disease or another structural issue, treatment frequently centers on medications that support heart function, manage blood pressure, and reduce fluid buildup in the lungs. Dietary adjustments, weight management, and controlled activity levels often round out a treatment plan. Regular monitoring through follow-up exams allows our veterinary team to adjust medications as the condition changes, giving your dog the best possible quality of life at every stage.

When Specialist Care Comes In

In some cases, especially when a congenital defect is involved, your veterinarian may discuss referral to a veterinary cardiologist for advanced procedures. Most dogs, however, are managed successfully right in a general practice setting with a combination of medication, nutrition, and consistent follow-up care. Bloodwork and repeat imaging every six to twelve months typically become part of the routine, giving the veterinary team a clear picture of how the heart is responding over time.

How Long Can a Dog Live With a Heart Murmur?

The prognosis for a dog heart murmur varies widely, and many dogs live for years, sometimes their entire natural lifespan, without significant complications. A young dog with an innocent murmur typically has an excellent long-term outlook, with the murmur often fading away completely within the first year of life. Dogs diagnosed with mitral valve disease tend to progress slowly, and with appropriate monitoring and medication, many maintain a good quality of life for several years after diagnosis.

Factors That Influence Outlook

Breed, age at diagnosis, murmur grade, and how quickly the underlying condition advances all influence the outlook for an individual dog heart murmur. Regular checkups allow your veterinarian to track any changes early, adjusting the treatment plan before symptoms become severe.

Supporting Your Dog’s Heart Health Long-Term

Body condition also plays a meaningful role in prognosis, since dogs at a healthy weight place less strain on an already compromised heart. Working closely with your veterinary team on nutrition, gentle exercise appropriate to your dog’s condition, and consistent medication schedules gives affected dogs the best chance at a long, comfortable life despite the diagnosis.

Partnering With Veterinary Healthcare Associates for Your Dog’s Heart Health

A dog heart murmur diagnosis can feel overwhelming, but you do not have to navigate it alone. Our team at Veterinary Healthcare Associates combines thorough diagnostics with a personalized approach, so you understand exactly what your dog’s murmur means and what comes next. Whether your dog needs a simple recheck in six months or ongoing management for a diagnosed heart condition, our veterinarians will walk you through every option and answer your questions along the way. Scheduling regular wellness visits gives us the best chance to catch changes in a dog heart murmur early, when treatment tends to be most effective. Call us at (863) 324-3340 today to schedule an exam and give your dog’s heart the attention it deserves.