What Does a Heart Murmur Really Mean for Your Dog's Health?
Grades, symptoms, treatment, and what to expect long-term.
Your vet just mentioned they heard a heart murmur during your dog’s checkup. Before your mind jumps to worst-case scenarios, take a breath. A heart murmur isn’t a diagnosis on its own. It’s a sound, specifically that whooshing noise that happens when blood doesn’t flow smoothly through the heart. What it means for your dog depends entirely on what’s causing it, and that’s what your vet is there to help figure out.
TL;DR
- A heart murmur is an abnormal whooshing sound caused by turbulent blood flow, not a disease itself.
- Murmurs are graded 1 to 6 based on loudness. Lower grades are often monitored; grades 4 and above warrant faster action.
- Common causes include mitral valve disease, congenital defects, dilated cardiomyopathy, and non-cardiac issues like anemia.
- Many dogs with murmurs live long, comfortable lives. Outcome depends on the underlying cause, grade, and how well it’s managed.
- Diagnostics and treatment can be costly, but Lemonade pet insurance may help cover eligible conditions that aren’t pre-existing.
What is a heart murmur in a dog, and what causes it?
A healthy heart pumps blood in a smooth, steady rhythm. When something disrupts that flow, it creates turbulence, and that turbulence produces a sound your vet can hear through a stethoscope. That sound is a heart murmur.
A murmur is a symptom, not a condition. Think of it like a warning light on your car’s dashboard: it tells your vet to look closer, but it doesn’t tell you what’s wrong until you dig deeper.
Here’s what’s typically behind them:
| Cause | What’s happening | Who’s most affected |
|---|---|---|
| Mitral valve disease | The heart’s mitral valve degenerates and stops closing tightly, letting blood leak backward | Adult and senior dogs; Cavalier King Charles Spaniels, Dachshunds, Chihuahuas |
| Congenital heart defects | A structural problem present from birth | Puppies and young dogs with a genetic predisposition |
| Dilated cardiomyopathy | The heart muscle weakens and enlarges, reducing its ability to pump effectively | Large and giant breeds: Doberman Pinschers, Great Danes, Boxers |
| Innocent/physiologic murmurs | Turbulent flow from rapid growth, excitement, or low red blood cell counts (anemia), not a structural heart problem | Puppies; often resolves on its own |
| Endocarditis | A bacterial infection inflames the heart’s inner lining and valves | Any dog; less common, usually accompanied by fever and lethargy |
Heart murmur grades, symptoms, and when to act
Vets grade murmurs on a scale of 1 to 6 based on loudness. It’s not a perfect measure of severity, but it helps track changes over time and guides next steps.
- Grade 1: Very faint. Often only detectable in a quiet room with careful listening.
- Grade 2: Soft but consistently heard.
- Grade 3: Moderate. Clearly audible but not overwhelming.
- Grade 4: Loud. Your vet can hear it on both sides of the chest.
- Grade 5: Very loud, with a vibration your vet can feel by placing a hand on the chest.
- Grade 6: Loudest. Audible even without pressing the stethoscope directly against the chest.
A murmur itself doesn’t cause symptoms. What causes symptoms is the underlying condition. If your dog’s heart is struggling to keep up, you may notice:
- A persistent cough, especially at night or after lying down
- Reduced energy or tiring quickly on walks
- Faster or labored breathing, even at rest
- A swollen belly
- Fainting or collapsing episodes
- Loss of appetite or weight loss
If your dog has a known murmur and you notice any of these, especially changes in breathing or a new cough, contact your vet promptly. These can be early signs of congestive heart failure, a condition where the heart can no longer keep up with the body’s demands and fluid starts to build up.
Diagnosis and treatment
Hearing a murmur is just step one. To understand what’s behind it, your vet will likely recommend:
- Echocardiogram (cardiac ultrasound): The gold standard. This lets your vet see the heart’s structure, measure its size, and watch the valves in real time. You may be referred to a veterinary cardiologist for this.
- Chest X-ray: Shows whether the heart is enlarged and whether fluid is present in or around the lungs.
- Electrocardiogram (ECG): Records the heart’s electrical activity to check for abnormal rhythms.
- Blood tests: Rule out underlying causes like anemia or infection, and assess organ health before starting medication.
Treatment is always aimed at the underlying cause, not the murmur itself. What that looks like in practice:
| Situation | Typical approach |
|---|---|
| Mild murmur, no symptoms | Watchful waiting with regular rechecks |
| Moderate murmur, early changes | Monitoring plus possible medication depending on findings |
| Advanced murmur or heart failure signs | Lifelong medication to reduce heart workload, remove excess fluid, and support the heart muscle |
| All stages | Possible dietary changes (lower sodium); avoiding intense exercise, extreme heat, and high-stress situations |
Your vet will tailor the plan to your dog’s grade, diagnosis, and overall health. Ask specifically about the right food and activity level for your dog’s situation.
Life expectancy: how long can a dog live with a heart murmur?
This is the question most owners want answered, and the honest answer is: it depends. Here’s a general picture:
- Grade 1–2 innocent murmur that resolves: Normal life expectancy, no impact.
- Grade 3 murmur, no symptoms (e.g., early mitral valve disease): Often stable for years with regular monitoring.
- Grade 4+ with symptoms: More variable. Dogs with early congestive heart failure can still live meaningful, comfortable lives, often one to three years after diagnosis, sometimes longer.
Early detection and consistent treatment genuinely make a difference. Stay consistent with vet visits, monitor your dog at home, and act quickly if anything changes.
Does pet insurance cover heart murmurs in dogs?
Managing a heart murmur adds up fast. An echocardiogram alone can run several hundred dollars, cardiology referrals add to that, and lifelong medication is an ongoing cost.
Lemonade pet insurance can help cover diagnostics and treatment for eligible conditions, as long as they aren’t pre-existing (meaning your dog showed no signs or symptoms until after your 14-day illness waiting period has passed). That’s why getting a quote while your dog is young and healthy matters: once a condition is diagnosed, it typically becomes pre-existing and won’t be eligible for coverage.
If your dog already has a known murmur, it’s still worth reviewing what may be covered. And for any dog without a current cardiac diagnosis, getting covered sooner rather than later is one of the most practical steps you can take.
Before we go
Finding out your dog has a heart murmur is unsettling, but it doesn’t have to be overwhelming. A murmur is information, and information is something you can work with. The next step is a conversation with your vet about whether further diagnostics make sense, what to watch for at home, and what a monitoring plan looks like for your dog specifically. You’re already asking the right questions, and that matters more than you might think.
Frequently Asked Questions
What is a heart murmur in a dog, exactly?
It’s an abnormal whooshing sound your vet hears through a stethoscope when blood flows unevenly through a heart valve. It’s a symptom, not a disease, and the cause needs to be identified to understand what it means for your dog.
Can a dog live a normal life with a heart murmur?
Many dogs do, especially those with low-grade or innocent murmurs. Dogs with more advanced murmurs caused by conditions like mitral valve disease can also live comfortable lives for years with proper monitoring and medication.
What does a Grade 4 heart murmur mean for my dog's life expectancy?
A Grade 4 murmur signals a more significant issue and often warrants faster action. With the right treatment, many dogs with Grade 4 murmurs and early heart failure still live for one to three years or more after diagnosis, though every case is different.
What should I avoid if my dog has a heart murmur?
Generally, intense exercise, extreme heat, and high-stress situations can put extra strain on a dog’s heart. Your vet will give you specific guidance based on your dog’s grade and underlying condition.
Is a dog heart murmur cough a serious sign?
A persistent cough in a dog with a known murmur, especially at night or when resting, can indicate fluid building up around the lungs, which is a sign of congestive heart failure. Contact your vet promptly if you notice this.
A few quick words, because we <3 our lawyers: This post is general in nature, and any statement in it doesn’t alter the terms, conditions, exclusions, or limitations of the policies issued, which differ according to your state of residence. You’re encouraged to discuss your specific circumstances with your own professional advisors. The purpose of this post is merely to provide you with info and insights you can use to make such discussions more productive! Naturally, all comments by, or references to, third parties represent their own views, and Lemonade assumes no responsibility for them. Coverage may not be available in all states. Please note that statements about coverages, policy management, claims processes, Giveback, and customer support apply to policies underwritten by Lemonade Insurance Company or Metromile Insurance Company, a Lemonade company, sold by Lemonade Insurance Agency, LLC. The statements do not apply to policies underwritten by other carriers.
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