Dog Heart Murmur: Signs, Causes, and Treatment Options

A heart murmur in dogs is an abnormal whooshing or swishing sound heard between normal heartbeats, caused by turbulent blood flow through the heart. Hearing that your dog has a heart murmur during a routine visit can be unsettling, but a dog heart murmur doesn’t automatically mean something is seriously wrong. At Plumtrees Animal Hospital in Danbury, CT, our veterinary team wants pet owners to fully understand what a heart murmur is, what might be causing it, and what treatment, if any, looks like.

What Is a Heart Murmur in Dogs?

A dog heart murmur is detected during a physical exam when a veterinarian listens to the heart with a stethoscope. Instead of the normal “lub-dub” sound of a healthy heartbeat, a murmur produces an additional sound caused by turbulent or irregular blood flow within the heart or major blood vessels.

Heart murmurs in dogs are graded on a scale from one to six based on how loud and easily detectable they are:

• Grades 1-2: Very soft murmurs, often only detectable by an experienced veterinarian in a quiet room
• Grades 3-4: Moderate murmurs, clearly audible and sometimes accompanied by a faint vibration felt through the chest wall
• Grades 5-6: Loud murmurs, easily heard and often felt even without a stethoscope

The grade of a heart murmur doesn’t always correlate directly with the severity of the underlying condition, which is why further diagnostics are often recommended.

Common Causes of a Dog Heart Murmur

There are several potential explanations behind a dog heart murmur, ranging from harmless to more serious.

• Innocent or physiologic murmurs are common in puppies and often resolve on their own as the puppy grows. These murmurs typically don’t indicate any structural heart problem.
• Valve disease, particularly degenerative mitral valve disease, is one of the most frequent causes of a heart murmur in adult and senior dogs, especially in smaller breeds. As heart valves weaken with age, blood can leak backward, creating the turbulent flow that produces a murmur.
• Congenital heart defects are structural abnormalities dogs are born with, and they’re sometimes first identified as a heart murmur during a puppy’s early wellness visits.
• Cardiomyopathy, a disease of the heart muscle itself, can also produce a murmur, particularly in certain larger breeds predisposed to this condition.
• Anemia or other systemic conditions can occasionally cause a murmur as well, since changes in blood consistency can alter how it flows through the heart.

Puppy Heart Murmurs vs. Adult-Onset Murmurs

One distinction our team at Plumtrees Animal Hospital often explains to pet owners is the difference between a heart murmur found in a young puppy versus one that develops later in life. Puppy murmurs are frequently innocent and tend to fade by the time a puppy reaches six months of age, though we continue to monitor them at each wellness visit to confirm they resolve as expected. A heart murmur that develops in an adult or senior dog, on the other hand, is more likely to be linked to valve disease or another structural change and typically warrants a more thorough workup.

Signs That May Accompany a Dog Heart Murmur

While many dogs with a heart murmur show no outward symptoms at all, especially with milder grades, others may display signs such as:

• Coughing, particularly at night or after exercise
• Reduced stamina or tiring more easily during walks
• Rapid or labored breathing
• Fainting or weakness, in more advanced cases

If your dog has a known heart murmur and begins showing any of these signs, it’s a good idea to schedule a follow-up exam with Plumtrees Animal Hospital to reassess the heart’s condition.

How Plumtrees Animal Hospital Evaluates a Heart Murmur

When our veterinary team detects a dog heart murmur during an exam, the next steps typically depend on the murmur’s grade, your dog’s age and breed, and whether any other symptoms are present. Diagnostic tools we may recommend include:

• Chest X-rays to assess heart size and shape
• An echocardiogram to visualize the heart’s chambers, valves, and blood flow in real time
• Blood pressure measurement and bloodwork to rule out other contributing factors

These tests help our veterinarians determine whether a heart murmur reflects a benign finding or an underlying condition that needs ongoing management.

Treatment Options for a Dog Heart Murmur

Treatment for a dog heart murmur depends entirely on its underlying cause. In cases where the murmur is innocent, particularly in puppies, no treatment is needed beyond periodic rechecks to confirm it resolves as expected.

When a murmur is linked to valve disease, cardiomyopathy, or another structural issue, treatment may include:

• Medications to support heart function and manage blood pressure
• Dietary changes tailored to heart health
• Regular monitoring through follow-up echocardiograms or physical exams to track any progression

Our team at Plumtrees Animal Hospital will walk you through exactly what your dog’s specific murmur means and build a monitoring or treatment plan suited to their individual needs.

Living With a Dog Heart Murmur

Many dogs with a heart murmur, particularly milder grades, go on to live full, active lives with little to no impact from the finding itself. The key is consistent monitoring, since a murmur’s grade or associated symptoms can change over time, and catching those changes early allows for timely adjustments to care. Keeping up with annual or biannual wellness exams gives our veterinarians a clear baseline to compare against at each visit.

Schedule a Heart Health Exam at Plumtrees Animal Hospital

If your dog has been diagnosed with a heart murmur, or if you’d like a thorough heart health evaluation as part of a wellness visit, call us at (203) 748-8878 to schedule an appointment with Plumtrees Animal Hospital in Danbury. Our veterinary team is here to answer your questions and help you understand exactly what your dog’s heart health looks like.