Heart Murmur in Dogs – Stages, Symptoms and Life Expectancy

Hearing that your dog has a heart murmur can be unsettling, but the term itself is not a diagnosis. A heart murmur is an abnormal sound heard between heartbeats—a whooshing or swishing that veterinarians detect with a stethoscope. It can be harmless or a sign of underlying heart disease. Understanding what a murmur means, how it is staged, and what to expect can help you make informed decisions about your dog’s care.

Many dogs live long, active lives with a murmur. Some murmurs disappear on their own. Others require lifelong management. The key is to determine the cause, grade the severity, and monitor your dog closely. This guide covers everything from symptoms and treatment to life expectancy, with a focus on the UK veterinary context.

What Is a Heart Murmur in Dogs and What Causes It?

• A heart murmur is a clinical finding, not a disease diagnosis.
• Up to 30% of dogs have a benign (innocent) murmur at some stage.
• Mitral Valve Disease (MVD) is the most common cause in older small breed dogs.
• Early detection and management significantly improve quality of life.
• No two murmurs are the same—treatment depends on the underlying cause.

What Are the Stages of a Heart Murmur in Dogs and When Should You Worry?

How Is a Heart Murmur Graded in Dogs?

Murmurs are graded on a 1 to 6 scale based on loudness. Grade 1 is so soft it is hard to hear; Grade 6 can be heard without a stethoscope touching the chest. Importantly, the grade does not always match the severity of the underlying disease. Some serious conditions produce only low‑grade murmurs, while a loud murmur may be well tolerated.

What Is the Difference Between a Benign and a Pathological Heart Murmur?

A benign (innocent) murmur has no underlying structural heart disease. It is common in puppies and often resolves by adulthood. A pathological murmur is caused by an abnormality such as valve disease, a congenital defect, or cardiomyopathy. The only way to tell them apart is through imaging. Cornell University’s Riney Canine Health Center notes that an echocardiogram is the gold standard for determining the cause of a murmur.

What Are the Symptoms of a Heart Murmur in Dogs?

What Are the First Signs of a Heart Problem in Dogs?

Many dogs with a murmur show no outward signs, especially early on. When symptoms do appear, they reflect the underlying heart disease rather than the murmur itself. Watch for coughing, labored or rapid breathing (especially at rest), reduced exercise tolerance, lethargy, fainting, pale or blue gums, poor appetite, weight loss, and abdominal swelling.

Can a Dog with a Heart Murmur Have No Symptoms?

Yes. Dogs with low‑grade murmurs or early‑stage heart disease often appear completely normal. This is why regular veterinary check‑ups are essential. A murmur found on routine physical exam may be the first—and sometimes only—sign of a developing problem.

What Treatment and Medication Options Are Available for Dogs With Heart Murmurs?

How Much Does Heart Murmur Medication for Dogs Cost in the UK?

Treatment depends entirely on the cause and stage. Benign murmurs require no medication, only monitoring. For structural heart disease, medications such as pimobendan (Vetmedin), diuretics (furosemide), ACE inhibitors (enalapril, benazepril), and spironolactone are commonly used. In the UK, monthly medication costs can range from £30 to £80 for basic prescriptions, plus the initial cardiologist consultation (£200–£500). Ongoing monitoring and repeat echocardiograms add to the long‑term expense.

Pimobendan is particularly important. PetMD notes that it can delay the onset of heart failure in dogs with myxomatous mitral valve disease when started at the right time.

Can a Heart Murmur in Dogs Be Cured?

A murmur itself is not a disease, so the question is whether the underlying cause can be cured. Innocent murmurs often resolve on their own. Some congenital defects, such as patent ductus arteriosus, can be corrected surgically. Most acquired valve disease cannot be reversed, but it can be successfully managed with medication and lifestyle adjustments for months to years.

Progression Timeline: From Murmur Detection to Heart Failure

What We Know vs. What Is Still Uncertain

Understanding Heart Murmurs in Dogs: Analysis and Owner Context

A heart murmur is a sign to investigate, not a terminal diagnosis. Many owners panic unnecessarily when they first hear the word “murmur.” Yet benign murmurs are extremely common, especially in puppies, and many adult dogs live full lives with a low‑grade murmur that never requires treatment. Breed predisposition plays a significant role—Cavalier King Charles Spaniels, for example, have a high incidence of mitral valve disease, while larger breeds may be more prone to dilated cardiomyopathy.

Age is another factor. Puppy murmurs often resolve by one year of age. In senior dogs, a murmur is more likely to reflect degenerative valve disease. The best step after detection is to schedule an echocardiogram with a veterinary cardiologist. This provides a clear picture of the heart’s structure and function, allowing your vet to stage the disease and recommend appropriate monitoring or treatment.

What Veterinary Experts Say About Heart Murmurs

“A heart murmur adds an extra sound to a heartbeat — introducing a whooshing noise that your veterinarian can hear when they listen to your dog’s heart.”

— Cornell Riney Canine Health Center

“A heart murmur is a clinical finding — not a disease diagnosis. Some heart murmurs are benign or harmless and may go away on their own.”

— Veterinary Specialists (myth‑busting article)

For further authoritative details, refer to the PDSA — Heart Murmurs in Dogs, VCA Hospitals — Heart Murmurs in Dogs, Cornell University College of Veterinary Medicine, British Veterinary Association (heart disease resources), and the AVMA — Canine Heart Disease Management.

Key Takeaways for Dog Owners

A heart murmur in your dog is a call for investigation, not panic. With proper diagnosis, many dogs enjoy a good quality of life for years. Monitor your dog’s resting respiratory rate—a rise above 30 breaths per minute may signal fluid buildup and should prompt a vet visit. Consider pet insurance that covers cardiology diagnostics. For a deeper look at advanced progression, read our detailed piece on Canine Congestive Heart Failure: A Complete Guide. And learn how to monitor your dog at home with How to Check Your Dog’s Resting Respiratory Rate.