Heart Murmurs in Dogs: Grades, Causes & When to Worry

Quick Answer
  • A heart murmur is an abnormal whooshing sound from turbulent blood flow. It is a finding on exam, not a diagnosis by itself.
  • Dog heart murmurs are usually graded 1 through 6 by loudness. Grade helps describe what your vet hears, but it does not reliably predict how serious the underlying disease is.
  • Soft puppy murmurs can be innocent and may disappear by about 4 to 6 months of age, but any persistent murmur or louder murmur should be rechecked.
  • An echocardiogram is the best test to identify the cause of a murmur and decide whether monitoring, medication, or cardiology referral makes sense.
  • Typical US cost ranges in 2026 run from about $50 to $120 for a recheck exam, $180 to $350 for chest X-rays, and roughly $500 to $1,200 for an echocardiogram depending on region and whether a cardiologist is involved.
Estimated cost: $50–$2,000

What Is a Heart Murmur?

A heart murmur is an extra sound your vet hears with a stethoscope during the heartbeat. Instead of only the normal heart sounds, there is a swishing or whooshing noise caused by turbulent blood flow through the heart or nearby blood vessels.

A murmur is not a disease on its own. It is a clue. Some murmurs are harmless, especially in growing puppies or stressed dogs with fast heart rates. Others point to valve disease, congenital heart defects, heartworm disease, anemia, or other medical problems that need follow-up.

Heart murmurs are commonly graded from 1 to 6 based on loudness:

  • Grade 1: very soft and difficult to hear
  • Grade 2: soft but consistently heard
  • Grade 3: moderately loud
  • Grade 4: loud, usually without a chest-wall thrill
  • Grade 5: very loud with a palpable thrill
  • Grade 6: extremely loud and can be heard with the stethoscope slightly off the chest

The important part is this: loudness is only one piece of the picture. A softer murmur can still matter, and a louder murmur does not automatically mean a worse outcome. Your vet also considers your dog's age, breed, symptoms, murmur timing, and imaging results before deciding how concerned to be.

Signs That May Accompany a Heart Murmur

  • No symptoms at all, especially with incidental low-grade murmurs found during routine exams
  • Coughing, especially at night, after activity, or when lying down
  • Exercise intolerance, slowing down on walks, or tiring faster than usual
  • Resting breathing rate that is persistently elevated while asleep or relaxed
  • Rapid, labored, or open-mouth breathing
  • Fainting, collapse, or sudden weakness episodes
  • Pale or bluish gums
  • Distended abdomen from possible fluid buildup
  • Reduced appetite, weight loss, or decreased interest in normal activities

Many dogs with heart murmurs feel completely normal, especially early on. That is why murmurs are often first found during wellness visits. Still, symptoms matter more than murmur grade alone. See your vet promptly if your dog develops coughing, exercise intolerance, or a sleeping respiratory rate that trends upward. See your vet immediately for fainting, collapse, blue gums, or any breathing difficulty.

What Causes Heart Murmurs?

Some murmurs are innocent or physiologic, meaning the heart itself may be structurally normal. This is most common in puppies, where a soft murmur may be heard at 6 to 8 weeks and then disappear by about 4 to 6 months as the heart matures. Temporary flow murmurs can also happen with excitement, fever, pregnancy, or anemia.

Other murmurs are pathologic, meaning they are linked to heart disease. In adult dogs, the most common acquired cause is degenerative mitral valve disease, especially in older small-breed dogs. This condition causes the mitral valve to leak, creating turbulent backward flow. Large and giant breeds may be more prone to dilated cardiomyopathy, where the heart muscle weakens and the chambers enlarge.

Dogs can also be born with structural defects that create murmurs. Examples include subaortic stenosis, pulmonic stenosis, patent ductus arteriosus, and some septal defects. These congenital problems may be found in puppies or young adults, and some are more common in certain breeds.

Not every murmur starts in the heart. Severe anemia, heartworm disease, dehydration, and other systemic illnesses can change blood flow enough to create a murmur. That is why your vet may recommend bloodwork, heartworm testing, or imaging instead of assuming the murmur is from primary heart disease.

How Are Heart Murmurs Evaluated?

Your vet starts with the physical exam. They listen for the murmur's loudness, timing, and location, then combine that with your dog's age, breed, pulse quality, gum color, breathing pattern, and any symptoms at home. A soft systolic murmur in a bright puppy is approached differently than a new murmur in an older coughing dog.

The most useful next test is usually an echocardiogram, which is an ultrasound of the heart. It shows chamber size, valve motion, blood flow direction, and whether there is structural heart disease. This is the best way to tell whether a murmur is innocent, caused by valve leakage, linked to congenital disease, or associated with heart muscle changes.

Your vet may also recommend chest X-rays to look for heart enlargement or fluid in the lungs, ECG if an arrhythmia is suspected, blood pressure, bloodwork, and sometimes cardiac biomarkers such as NT-proBNP. A heartworm test is also important if prevention is not current or testing is overdue.

Not every dog needs every test on day one. Some low-grade, symptom-free murmurs can be monitored first. In contrast, any diastolic murmur, continuous murmur, persistent puppy murmur, symptomatic dog, or moderate-to-loud new murmur usually deserves a more complete workup and often a cardiology referral.

Treatment Options for Heart Murmurs

Spectrum of Care means you have options. Here are treatment tiers at different price points.

Monitoring & Reassessment

$50–$250
Best for: Soft grade 1 to 2 systolic murmurs in symptom-free dogs, likely innocent puppy murmurs, or dogs where a non-cardiac cause such as anemia is being investigated first
  • Physical exam and murmur grading
  • Review of symptoms, activity tolerance, and home breathing patterns
  • Resting or sleeping respiratory rate tracking at home
  • Heartworm test if due
  • Repeat exam in about 2 to 6 months depending on age and murmur characteristics
  • Basic bloodwork if anemia or systemic illness is suspected
Expected outcome: Often good when the murmur is innocent or tied to a reversible non-cardiac issue. Some dogs remain stable for long periods with monitoring alone.
Consider: Lower upfront cost, but it does not define the exact cause. A dog with early structural heart disease could still need imaging later.
Most Common

Diagnostic Workup With Targeted Treatment

$500–$1,200
Best for: Grade 3 or louder murmurs, new murmurs in adult dogs, persistent puppy murmurs, dogs with cough or exercise intolerance, and pet parents who want a clearer diagnosis and prognosis
  • Echocardiogram
  • Chest X-rays when cough, breathing changes, or heart enlargement are concerns
  • ECG if rhythm abnormalities are suspected
  • Blood pressure and bloodwork
  • Cardiac biomarker testing in selected cases
  • Treatment plan based on findings, which may include medications such as pimobendan, furosemide, spironolactone, or an ACE inhibitor if your vet feels they are appropriate
  • Home monitoring plan with follow-up schedule
Expected outcome: Variable and tied to the underlying disease. Early valve disease may be monitored for months to years before heart failure develops, while some congenital defects need earlier intervention.
Consider: Higher initial cost range, but it gives much better information for decision-making and can help avoid both under-treatment and over-treatment.

Veterinary Cardiologist Care & Interventional Options

$1,200–$5,000
Best for: Congenital defects, suspected severe valve disease, dogs with fainting or arrhythmias, dogs in congestive heart failure, or breeds needing specialized cardiac screening
  • Board-certified cardiologist consultation
  • Advanced Doppler echocardiography
  • Holter monitoring or extended rhythm monitoring when needed
  • Specialized medication planning and serial rechecks
  • Interventional procedures in selected cases, such as PDA occlusion or balloon valvuloplasty for pulmonic stenosis
  • Hospital-based management for congestive heart failure or complex arrhythmias
Expected outcome: Depends on diagnosis. Some congenital defects can improve dramatically with intervention, while chronic heart disease is usually managed rather than cured.
Consider: Most complete information and widest treatment options, but specialist access, repeat visits, anesthesia in some cases, and long-term medication costs can add up.

Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.

Questions to Ask Your Vet About Heart Murmurs

Bring these questions to your vet appointment to get the most out of your visit.

  1. What grade is the murmur, and is it systolic, diastolic, or continuous?
  2. Based on my dog's age and breed, what causes are highest on your list?
  3. Do you recommend an echocardiogram now, or is monitoring reasonable first?
  4. Should we take chest X-rays, run bloodwork, or test for heartworm disease?
  5. What resting or sleeping breathing rate should I track at home, and when should I call you?
  6. Are there exercise limits, diet changes, or weight goals that would help right now?
  7. At what point would medication be considered, and what benefits and side effects should I know about?
  8. Would a veterinary cardiologist referral change our options or timeline?

Can Heart Murmurs Be Prevented?

Many heart murmurs cannot be fully prevented because they come from age-related valve changes or congenital heart defects. Still, early detection matters. Routine exams are often how murmurs are first found, long before a dog looks sick.

Year-round heartworm prevention is one of the most practical ways to reduce one important cause of heart and lung disease. Keeping up with recommended testing also helps your vet catch problems before they become advanced.

If your dog is from a breed with known cardiac risk, talk with your vet about screening. Small breeds, especially Cavalier King Charles Spaniels, are commonly affected by degenerative mitral valve disease. Some larger breeds have higher risk for cardiomyopathy, and breeds such as Boxers, Newfoundlands, Golden Retrievers, and Rottweilers may be screened more closely for inherited heart conditions depending on family history and exam findings.

At home, one of the most useful habits is tracking your dog's sleeping respiratory rate if a murmur has already been diagnosed. A normal relaxed rate is often around 15 to 30 breaths per minute, and a persistent increase, especially above the mid-30s while asleep, is a reason to contact your vet promptly.

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