Canine Heart Murmur Guide: Symptoms, Diagnosis, and Treatment
A comprehensive guide to canine heart murmur in dogs: causes, symptoms by severity, diagnostic tests, treatment options, costs, and life expectancy.
When your veterinarian listens to your dog's chest and mentions a canine heart murmur, it's natural to feel alarmed. But a murmur itself is not a disease — it's a sound. Specifically, it's the audible turbulence of blood flowing abnormally through the heart, detected via stethoscope during an exam. According to the Merck Veterinary Manual, heart murmurs occur when blood flow becomes disrupted by structural defects, valve dysfunction, or systemic conditions like anemia. Studies estimate that approximately 3.5% of dogs examined in general practice have an audible murmur, with prevalence climbing to over 25% in senior small-breed dogs.
Some murmurs are benign ("innocent" or "physiologic") and resolve on their own, particularly in puppies. Others signal underlying heart disease — from degenerative mitral valve disease (DMVD) to dilated cardiomyopathy (DCM) — that requires lifelong management. Understanding what a canine heart murmur means for your dog's health, what diagnostic steps to expect, and how treatment works is essential for making informed decisions about your dog's care.
What Is a Canine Heart Murmur?
A canine heart murmur is an abnormal sound produced by turbulent blood flow within the heart chambers or great vessels. A healthy heart produces two distinct sounds — "lub" and "dub" — corresponding to the closing of the atrioventricular valves (mitral and tricuspid) and the semilunar valves (aortic and pulmonic). When blood leaks backward through a valve that doesn't close fully, or when it's forced through a narrowed opening, the resulting turbulence creates the whooshing or swishing sound we call a murmur.
How Murmurs Are Graded
Veterinarians classify murmurs on a six-point intensity scale, which provides an initial — though imperfect — indicator of severity:
| Grade | Description | Clinical Significance |
|---|---|---|
| I/VI | Very soft; heard only in quiet environment with concentration | Often innocent; common in puppies |
| II/VI | Soft but readily audible | May be innocent or early disease |
| III/VI | Moderate intensity; heard on both sides of chest | Warrants investigation for underlying disease |
| IV/VI | Loud; no palpable thrill (chest vibration) | Likely pathological; imaging recommended |
| V/VI | Very loud; palpable thrill present | Serious structural disease likely |
| VI/VI | Extremely loud; audible with stethoscope partially off chest; thrill present | Advanced disease; urgent cardiology referral |
A critical point many owners miss: murmur grade does not always correlate with disease severity. A dog with early-stage heart failure can have a Grade V murmur, while a dog in congestive heart failure may present with only a Grade III. This is why echocardiography — not auscultation alone — is the gold standard for diagnosis.
Recognizing the Symptoms of a Heart Murmur in Dogs
A murmur itself produces no symptoms — it's a sound, not a condition. However, the underlying disease causing the murmur will eventually produce clinical signs as the heart's pumping efficiency declines. Symptoms progress along a continuum, and early detection significantly improves management outcomes.
Symptom Checklist by Severity
| Severity Level | Symptoms | What to Do |
|---|---|---|
| Early / Mild |
|
Schedule a routine vet appointment within 1-2 weeks |
| Moderate / Progressive |
|
See your vet within 48 hours; request cardiology referral |
| Advanced / Emergency |
|
Emergency vet visit immediately — this may indicate congestive heart failure |
Which Breeds Are Prone to Heart Murmurs?
While any dog can develop a heart murmur at any age, certain breeds carry significantly higher genetic risk for the conditions that cause them. Understanding breed predisposition helps you and your vet maintain appropriate screening schedules.
Risk Factors & Breed Predisposition
| Underlying Condition | Predisposed Breeds | Typical Age of Onset |
|---|---|---|
| Degenerative Mitral Valve Disease (DMVD) | Cavalier King Charles Spaniel, Dachshund, Miniature/Toy Poodle, Chihuahua, Pomeranian, Maltese, Cocker Spaniel | 5-8 years (earlier in Cavaliers) |
| Dilated Cardiomyopathy (DCM) | Doberman Pinscher, Great Dane, Irish Wolfhound, Boxer, Newfoundland, Cocker Spaniel | 4-8 years |
| Subaortic Stenosis (SAS) | Golden Retriever, Newfoundland, Rottweiler, Boxer, German Shepherd | Congenital; detected in puppyhood |
| Pulmonic Stenosis | Boxer, Bulldog, Beagle, Samoyed, English Springer Spaniel | Congenital; detected in puppyhood |
| Patent Ductus Arteriosus (PDA) | Pomeranian, Toy/Miniature Poodle, Collie, Shetland Sheepdog, German Shepherd | Congenital; detected by 6-12 weeks |
Additional risk factors include obesity (increases cardiac workload), chronic anemia (creates flow murmurs), hyperthyroidism (rare in dogs but possible), heartworm disease, and age (dogs over 7 years should have annual cardiac auscultation regardless of breed).
How Is a Canine Heart Murmur Diagnosed?
When your veterinarian detects a murmur, the diagnostic workup depends on the murmur grade, your dog's age, breed, and whether clinical signs are present. A Grade I-II murmur in an asymptomatic 10-week-old puppy may simply warrant monitoring, while a Grade IV murmur in a 7-year-old Cavalier King Charles Spaniel demands immediate imaging.
Diagnostic Process and Expected Costs
Step-by-Step Diagnostic Flowchart
- Physical Examination & Auscultation — Vet listens with a stethoscope, grades the murmur I-VI, notes timing (systolic vs. diastolic), and location on the chest. Cost: included in exam fee ($50-$90)
- Thoracic Radiographs (X-rays) — Two or three views of the chest to assess heart size (vertebral heart score), lung fields for fluid, and airway compression. Cost: $150-$350
- Echocardiogram (Cardiac Ultrasound) — The gold standard. A board-certified veterinary cardiologist measures chamber dimensions, valve function, blood flow velocities, and calculates fractional shortening (contractility). This determines the exact cause and stage of disease. Cost: $350-$650 (general practice) or $500-$900 (specialist)
- Electrocardiogram (ECG) — Records electrical activity to detect arrhythmias such as atrial fibrillation or ventricular premature complexes. Cost: $75-$200
- Blood Work & Biomarkers — Complete blood count (CBC) and chemistry panel to rule out anemia, kidney function, and electrolyte imbalances. Cardiac biomarker tests like NT-proBNP (cardiac stretch marker) and cTnI (cardiac damage marker) help stage disease. Cost: $120-$300 for full panel + biomarkers
- Blood Pressure Measurement — Systemic hypertension can worsen cardiac disease and must be evaluated. Cost: $40-$80
The total diagnostic workup for a canine heart murmur typically ranges from $400 to $1,500 depending on whether a specialist is involved and how many tests are needed. The echocardiogram is the single most important test — it's the only way to definitively determine what's causing the murmur and how advanced the disease is.
Treatment Options for Heart Murmurs in Dogs
A murmur itself doesn't require treatment — the underlying condition does. Treatment strategies depend entirely on the diagnosis and the stage of heart disease. The American Kennel Club emphasizes that treatment plans should be individualized based on echocardiographic findings.
Medical and Surgical Treatment Comparison
| Treatment Type | Specific Options | When Used | Monthly Cost | Success / Outcome |
|---|---|---|---|---|
| ACE Inhibitors | Enalapril (Enacard), Benazepril (Fortekor) | DMVD Stage B2 and above; reduces cardiac afterload | $15-$45/mo | Delays CHF onset; improves quality of life |
| Pimobendan | Vetmedin (pimobendan) | DMVD Stage B2+ and DCM; positive inotrope and vasodilator | $40-$120/mo | The EPIC study showed it extends pre-clinical period by ~15 months in DMVD |
| Diuretics | Furosemide (Salix), Spironolactone | CHF Stage C; removes excess fluid from lungs/abdomen | $10-$40/mo | Critical for managing pulmonary edema; lifelong use |
| Antiarrhythmics | Sotalol, Mexiletine, Diltiazem, Digoxin | Concurrent arrhythmias (atrial fibrillation, VPCs) | $25-$80/mo | Controls heart rate; reduces sudden death risk |
| Surgical Intervention | PDA occlusion (coil/ACDO device), balloon valvuloplasty for pulmonic stenosis | Specific congenital defects; performed by veterinary cardiologist | $3,000-$8,000 (one-time) | PDA closure has >95% success rate; potentially curative |
| Supportive / Lifestyle | Sodium-restricted diet, controlled exercise, weight management, omega-3 supplementation | All stages; adjunctive to medical therapy | $20-$60/mo (diet + supplements) | Reduces cardiac workload; improves overall outcomes |
Can a canine heart murmur be cured? In most cases involving acquired disease (DMVD, DCM), the answer is no — these are progressive conditions managed with lifelong medication. However, certain congenital defects like patent ductus arteriosus can be surgically corrected, effectively curing the murmur and preventing heart failure if caught early. Some "innocent" puppy murmurs resolve spontaneously by 6 months of age.
Prognosis and Life Expectancy by Stage
The prognosis for a dog with a heart murmur depends entirely on the underlying cause, the stage at diagnosis, and the response to treatment. The AVMA recommends regular monitoring to catch progression early.
ACVIM Heart Disease Staging and Prognosis
| Stage | Description | Typical Life Expectancy | Management Focus |
|---|---|---|---|
| A (At Risk) | No murmur, no disease; breed at high risk (e.g., Cavalier, Doberman) | Normal lifespan with screening | Annual auscultation; baseline echo at breed-recommended age |
| B1 (Asymptomatic, No Remodeling) | Murmur present; echo shows valve disease but normal heart size | 2-5+ years before progression; many live full lifespan | Monitor every 6-12 months; no medication typically needed |
| B2 (Asymptomatic, Heart Enlarged) | Murmur present; echo shows cardiac enlargement (LA/Ao ratio ≥1.6, LVIDdN ≥1.7) | 15-36 months median to CHF onset with pimobendan (EPIC study data) | Start pimobendan; consider ACE inhibitor; monitor every 3-6 months |
| C (Current or Past CHF) | Has experienced or is experiencing congestive heart failure symptoms | 6-18 months median survival with appropriate triple therapy | Furosemide + pimobendan + ACE inhibitor; home SRR monitoring; rechecks every 1-3 months |
| D (Refractory CHF) | Heart failure unresponsive to standard doses of medications | 3-6 months median; quality of life assessment critical | Escalated diuretic doses; add second diuretic; palliative focus; humane endpoints discussed |
It's important to emphasize that these are median survival times — many dogs live longer, especially with excellent home monitoring and timely medication adjustments. Some dogs in Stage C live 2-3 years with careful management. Individual prognosis should always be discussed with your veterinarian or veterinary cardiologist.
Home Care and Daily Management
Managing a canine heart murmur at home is about consistent observation, medication compliance, and lifestyle modification. Here's what daily life looks like for a dog with heart disease:
Daily Monitoring Protocol
- Sleeping Respiratory Rate (SRR): Count breaths while sleeping, 2-3 times per week minimum. Record in a log or app. Alert your vet if SRR consistently exceeds 30 breaths/min or increases by 25% from baseline.
- Medication Administration: Give all cardiac medications at the same times daily. Pimobendan must be given on an empty stomach (1 hour before or 2 hours after food) for proper absorption. Set phone alarms — missed doses can trigger decompensation.
- Weight Tracking: Weigh your dog weekly on the same scale. Sudden weight gain of 2-3% in 24-48 hours may indicate fluid retention and impending CHF exacerbation.
- Exercise Management: Replace long, intense walks with shorter, gentler outings. Avoid activities that cause heavy panting. Swimming and slow leash walks on flat terrain are ideal. Let your dog set the pace — if they stop or lag, head home.
- Dietary Adjustments: Transition to a moderate-sodium diet. Avoid high-sodium treats (jerky, deli meats, cheese). Veterinary cardiac diets like Hill's h/d, Royal Canin Cardiac, or Purina Pro Plan Veterinary Diets NF are formulated for cardiac patients. Discuss taurine and L-carnitine supplementation with your vet, especially for breeds prone to DCM.
Lifestyle Adjustments
- Avoid stress and extreme temperatures: Heat and cold increase cardiac workload. Walk during cooler hours in summer and bundle brachycephalic breeds in winter.
- Use a harness instead of a collar: Collars put pressure on the trachea and jugular veins, which can worsen coughing and impede venous return to the heart.
- Elevated sleeping position: Some dogs with pulmonary edema breathe easier with their front end slightly elevated. Orthopedic beds with bolstered heads can help.
- Dental care: Dental disease introduces bacteria into the bloodstream, which can colonize damaged heart valves (endocarditis). Maintain regular dental cleanings — your vet will assess whether your dog's cardiac status allows safe anesthesia.
- Resting respiratory rate suddenly exceeds 40 breaths/minute
- Blue, purple, or white (pale) gum color instead of healthy pink
- Coughing up pink, frothy fluid
- Repeated fainting or collapse episodes
- Sudden inability to use hind legs (possible aortic saddle thrombus — rare but emergent)
- Abdomen becomes visibly distended within 24-48 hours
- Dog refuses all food and water for more than 24 hours while on diuretics
If your dog shows any of these signs, contact your emergency veterinary clinic immediately. These may indicate acute congestive heart failure or other life-threatening cardiac events.
Cost of Treatment: What to Budget
Cardiac care is one of the more expensive chronic conditions to manage in dogs. Being realistic about costs helps you plan and avoid treatment gaps that could compromise your dog's health.
| Expense Category | Low Estimate | Average Estimate | High Estimate |
|---|---|---|---|
| Initial Diagnostic Workup | $400 | $800 | $1,500 |
| Specialist Echocardiogram | $500 | $700 | $900 |
| Monthly Medications (Stage B2) | $40 | $80 | $150 |
| Monthly Medications (Stage C/D) | $80 | $180 | $350 |
| Recheck Visits (per visit, 2-4x/year) | $100 | $200 | $450 |
| Emergency CHF Hospitalization | $1,500 | $3,000 | $6,000+ |
| First-Year Total (diagnosis + management) | $1,200 | $2,500 | $5,000+ |
| Annual Ongoing Cost (Stable Stage B2/C) | $800 | $1,800 | $3,500 |
Pet insurance can significantly offset these costs, but most policies will not cover pre-existing conditions. If your dog is young and healthy, enrolling in a comprehensive plan before a murmur is detected is the most financially strategic move. Companies like Trupanion, Healthy Paws, and Nationwide offer plans with chronic condition coverage — review exclusions carefully.
Prevention and Early Detection Strategies
While most causes of canine heart murmurs are genetic or age-related and cannot be entirely prevented, you can take meaningful steps to reduce risk and catch problems early:
- Annual veterinary exams with auscultation — The single most effective screening tool. Dogs over 7 years should be examined every 6 months.
- Breed-specific cardiac screening — If you own a predisposed breed (Cavalier King Charles Spaniel, Doberman Pinscher, Boxer), request a baseline echocardiogram by age 3-4 and repeat every 1-2 years. The Orthopedic Foundation for Animals (OFA) maintains a cardiac registry and screening protocols.
- Heartworm prevention year-round — Heartworm disease causes pulmonary hypertension and right-sided heart murmurs. Monthly preventives (Heartgard Plus, Interceptor Plus, Simparica Trio) cost $8-$25/month and are far cheaper than heartworm treatment ($1,000-$3,000+).
- Maintain ideal body condition — Obesity forces the heart to work harder. Keep your dog at a body condition score (BCS) of 4-5 on the 9-point scale.
- Avoid grain-free boutique diets for at-risk breeds — The FDA has investigated a potential link between grain-free, legume-rich diets and DCM in non-traditionally predisposed breeds. Until more is known, feed AAFCO-approved diets from established manufacturers (Purina, Hill's, Royal Canin, Iams) for breeds at risk of DCM.
- Responsible breeding practices — If you're acquiring a puppy from a predisposed breed, ask the breeder for OFA cardiac clearance certificates on both parents. Avoid breeders who cannot provide health testing documentation.
Frequently Asked Questions
Can a puppy outgrow a heart murmur?
Yes. Innocent (physiologic) murmurs are common in puppies, affecting up to 30% of young dogs. These are typically Grade I-II, systolic, and heard best at the left heart base. Most resolve spontaneously by 4-6 months of age. However, if a puppy's murmur is Grade III or louder, persists beyond 6 months, or is accompanied by poor growth, exercise intolerance, or a continuous "machinery" quality, congenital heart disease should be investigated with an echocardiogram.
Is a heart murmur the same as heart disease?
No. A heart murmur is a sound — a clinical sign, not a diagnosis. It indicates turbulent blood flow, which may or may not be caused by heart disease. Anemia, fever, pregnancy, and hyperthyroidism can all cause murmurs in dogs with structurally normal hearts. Conversely, some dogs with early heart disease have no audible murmur at all. The echocardiogram is the definitive test to distinguish innocent murmurs from pathological ones.
How much does an echocardiogram cost for a dog with a heart murmur?
A complete echocardiogram performed by a board-certified veterinary cardiologist typically costs $500-$900 in the United States as of 2026, with additional charges for the consultation fee ($150-$250). General practitioners who perform echocardiography may charge $350-$650. The investment is worthwhile because it provides the exact diagnosis, stage, and treatment plan — information that auscultation alone cannot provide.
Should I restrict my dog's exercise if they have a heart murmur?
It depends on the stage. Dogs in Stage B1 (murmur, normal heart size) can typically continue normal exercise. Once cardiac enlargement is present (Stage B2+) or heart failure has occurred (Stage C/D), exercise should be moderated — shorter, gentler walks with rest breaks. Avoid high-intensity activities like fetch marathons, agility, or off-leash running. Let your dog self-regulate; if they slow down or sit, respect that signal.
What is the life expectancy of a dog with a canine heart murmur?
This varies enormously based on the underlying cause and stage. A dog with an innocent murmur has a normal life expectancy. A dog diagnosed with DMVD at Stage B1 may live 4-8+ years before developing heart failure. A dog in Stage C heart failure on appropriate triple therapy (furosemide, pimobendan, ACE inhibitor) has a median survival of 6-18 months, with some living 2-3 years. Dogs with surgically correctable PDA often have a normal lifespan after successful intervention.
Can diet affect my dog's heart murmur?
Diet plays a supportive but important role. Sodium restriction becomes critical once heart failure develops, as excess sodium promotes fluid retention. Veterinary cardiac diets are formulated with controlled sodium, added taurine, L-carnitine, and omega-3 fatty acids. Additionally, the FDA's investigation into diet-associated DCM suggests that feeding grain-free, legume-heavy diets may increase cardiac risk in some breeds. Always discuss dietary choices with your veterinarian.
Marcus Aldridge
All our authors care for dogs every day — read more of their work on the authors page.
