Dogs Heart Murmur: Understanding and Solutions

Hearing the words “your dog has a heart murmur” can feel scary, especially if your pup seems totally normal. Take a deep breath. A heart murmur is not a diagnosis by itself. It is a sound your veterinarian hears with a stethoscope that suggests blood flow is more turbulent than expected in or near the heart.

As a veterinary assistant, I have seen many dogs with murmurs live long, happy lives. The key is understanding what the murmur might mean, confirming the cause, and then building a plan you can actually follow at home.

Quick note: This article is educational and not medical advice for your specific dog. Your veterinarian or a veterinary cardiologist is the best source for diagnosis and treatment decisions.

What a heart murmur is

Normally, blood flow through the heart is quiet. A heart murmur is an extra “whooshing” sound caused by turbulent blood flow. That turbulence can happen for many reasons, including leaky valves, narrowed openings, holes between chambers, or changes outside the heart that affect circulation.

Murmur vs. heart disease vs. heart failure

• Murmur: A sound your vet hears.
• Heart disease: A structural or functional problem (like valve degeneration).
• Congestive heart failure (CHF): When the heart can no longer keep up and fluid builds up, commonly in the lungs.

Many dogs with murmurs have no heart failure at diagnosis. That is why the next step matters: identifying the cause and the risk level.

Step 1: Confirm grade and location

Veterinarians typically describe murmurs by:

• Grade (1 to 6): How loud it is. Grade 1 is very soft. Grade 6 is very loud and can sometimes be felt as a vibration on the chest.
• Where it is loudest: Left side, right side, or along the sternum. Location can hint at which valve or area is involved.
• Timing: Systolic (most common), diastolic, or continuous.

A higher grade murmur can be more concerning, but it is not a perfect predictor. Some serious issues can have softer murmurs, and some loud murmurs can be stable for a long time. That is why we pair the stethoscope findings with diagnostics.

When timing changes urgency

Continuous murmurs (heard throughout the heartbeat) can sometimes point to conditions like patent ductus arteriosus (PDA). PDA is often treatable, but it is also a reason to move diagnostics up the priority list, especially in younger dogs.

Step 2: Check for non-heart causes

Not every murmur means the heart is failing. Some murmurs are physiologic, meaning blood flow changes without structural heart disease.

Common non-heart causes your vet may check

• Anemia (low red blood cells)
• Fever, pain, or infection
• Excitement or stress at the vet (yes, it can make things louder)
• Very young puppies can have transient murmurs that disappear as they grow
• Pregnancy can cause higher-output circulation (uncommon in many pet populations, but possible)
• Thyroid disease: True hyperthyroidism is rare in dogs and is often linked to thyroid tumors, but your vet may still consider it based on the full picture

This is where basic lab work can be truly helpful. If the murmur is driven by something like anemia or a systemic illness, treating that root cause can reduce or resolve the murmur.

Once your vet has checked for these contributors, the next step is usually to look directly at the heart.

Step 3: Do the right tests

If your dog has a new murmur or a murmur that is getting louder, your veterinarian will usually recommend some combination of the tests below. These help separate “monitor only” situations from “start treatment now” situations.

Echocardiogram (cardiac ultrasound)

This is often the most informative test for a murmur. A cardiologist or trained veterinarian uses ultrasound to see valve motion, chamber sizes, and blood flow direction. It can confirm common conditions like myxomatous mitral valve disease (very common in small breeds) or dilated cardiomyopathy (seen more in some larger breeds).

Chest X-rays

X-rays help assess heart size and check for fluid in the lungs, which can signal congestive heart failure.

Electrocardiogram (ECG/EKG)

An ECG evaluates heart rhythm. Some dogs with murmurs also develop arrhythmias, and rhythm control can be a major part of treatment.

Blood pressure and lab work

High blood pressure can worsen heart workload. Lab work supports safe medication choices and can identify other contributors (kidney issues, anemia, infection).

Heartworm testing (in the right context)

Depending on where you live, your dog’s prevention history, and your vet’s exam findings, heartworm disease may also be part of the conversation. Heartworms can affect the heart and lungs and sometimes contribute to abnormal heart sounds.

What to expect at cardiology

If you are referred to a veterinary cardiologist, the visit is usually straightforward and very information-rich. Many appointments include:

• A detailed history and exam (including murmur grade and location)
• Echocardiogram
• Blood pressure
• ECG (or sometimes a longer rhythm monitor if needed)
• Sometimes chest X-rays if they are not already done or if breathing symptoms are present

Most dogs tolerate these tests well, and many do not need heavy sedation for an echo.

Step 4: Common causes

Mitral valve disease (MMVD)

This is one of the most common causes of a murmur in adult and senior small-breed dogs. The mitral valve becomes thickened and leaky over time, creating a systolic murmur on the left side. Many dogs do well for years with monitoring, then medications when heart enlargement or symptoms appear.

Breed pattern you may hear about: small and toy breeds are overrepresented (for example, Cavalier King Charles Spaniels, many little mixes).

Dilated cardiomyopathy (DCM)

With DCM, the heart muscle becomes weaker and chambers enlarge. A murmur may or may not be present. Some dogs show exercise intolerance, fainting, or rhythm changes. Diagnosis is typically via echocardiogram and ECG.

Breed pattern you may hear about: certain large breeds are at higher risk (for example, Doberman Pinschers and Boxers), though any dog can be affected.

Congenital (born-with) conditions

In puppies or young dogs, murmurs may be due to defects such as patent ductus arteriosus (PDA), pulmonic stenosis, or subaortic stenosis. These need early assessment because some can be corrected or significantly improved with timely care.

Step 5: Red-flag symptoms

If your dog has a murmur, call your vet promptly if you notice any of these changes. If breathing is labored or your dog collapses, treat it as an emergency.

• Coughing, especially at night or after rest
• Faster breathing or breathing effort at rest
• Exercise intolerance or tiring quickly on walks
• Fainting or sudden weakness episodes
• Distended belly (can suggest fluid buildup)
• Reduced appetite, weight loss, or restlessness

At-home breathing check

When your dog is asleep or very relaxed, count breaths for 30 seconds and multiply by 2.

• For many dogs, a sleeping resting respiratory rate is often under about 30 breaths per minute.
• A rate that is consistently above 30, or a clear upward trend for your dog over several days, is a good reason to call your vet, especially if your dog has known heart disease or any cough or breathing changes.

Solutions: What helps and when

“Solutions” for a murmur depend on the cause. Some dogs need monitoring only. Others benefit from medication, lifestyle adjustments, and regular rechecks. Your veterinarian will tailor this to your dog’s diagnosis and stage.

Monitoring and rechecks

• Mild murmur, no enlargement: Often recheck in 6 to 12 months, sooner if symptoms appear.
• Confirmed valve disease: Rechecks may be every 3 to 6 months depending on stage.
• On heart medications: Bloodwork and blood pressure checks are commonly used to keep dosing safe.

Medications commonly used

Your veterinarian may prescribe medications such as:

• Pimobendan: Commonly used for certain dogs with heart enlargement from MMVD (often referred to as preclinical Stage B2) and in many DCM cases, as directed by your vet or cardiologist. It is not automatically needed for every murmur or early valve disease without enlargement.
• Diuretics (like furosemide): If fluid builds up, especially in congestive heart failure.
• ACE inhibitors (like enalapril or benazepril): Used in certain cases to reduce workload on the heart.
• Anti-arrhythmics: If abnormal rhythms are present.

Important note: never start, stop, or change heart meds without guidance. Heart medications are powerful and very dose-dependent.

Nutrition and weight support

From an evidence-based standpoint, two of the biggest home wins are maintaining lean body condition and choosing a diet your veterinary team feels fits your dog’s stage.

• Keep your dog lean: Extra weight increases cardiac workload and can worsen breathing comfort.
• Sodium, stage matters: Evidence for strict sodium restriction in early, preclinical disease is mixed. A practical middle ground is to avoid very salty treats and table scraps, and follow your vet’s stage-specific guidance.
• Omega-3 fatty acids: Fish oil may support heart health in some dogs. Ask your vet for a dose based on your dog’s weight and condition.
• Homemade diets: These can be wonderful, but heart patients need balanced nutrients and minerals. Work with your veterinarian or a veterinary nutritionist so it is complete and appropriate for your dog’s stage.

Action plan for pet parents

1) Get the details in writing

Before you leave the appointment, ask: What grade is the murmur? Where is it loudest? Any symptoms today? What is our next recommended test and timeline?

2) Prioritize the next best test

If an echocardiogram is recommended, it is often the most direct way to understand what the murmur means. If finances are a concern, be honest. Many clinics can help prioritize which tests are most valuable first.

3) Start a simple home log

• Resting respiratory rate (a few times per week)
• Coughing episodes (yes or no, and when)
• Energy level on walks
• Appetite and weight

4) Keep movement gentle and consistent

Most stable heart patients do best with regular, moderate exercise, not bursts of intense activity. Your veterinarian can guide you based on diagnosis.

5) Recheck on schedule

Heart disease often changes slowly, and catching progression early can meaningfully improve comfort and quality of life.

Questions to ask your vet

• Is this murmur likely related to valve disease, a congenital issue, heartworm disease risk, or something outside the heart?
• Do you recommend an echocardiogram now or monitoring first?
• Should we do chest X-rays today?
• What symptoms should trigger an urgent visit?
• Is my dog at a stage where medication like pimobendan is beneficial?
• What diet changes, if any, do you recommend for our stage?

Hopeful perspective

A heart murmur is a clue, not a verdict. With the right diagnostics and a practical home routine, many dogs with murmurs stay playful, comfortable, and engaged for years.

Your best next step is simple: learn what is causing the murmur, track breathing at home, and partner closely with your veterinarian or a veterinary cardiologist.