Heart Murmurs In Dogs: Causes, Diagnosis & Care Guide
Early detection and tailored treatments can keep your pet comfortable for years.
Heart Murmurs in Dogs: Causes, Diagnosis, and Management
Understanding Heart Murmurs in Dogs
A heart murmur in dogs is an abnormal soundâusually a whooshing or swishing noiseâdetected when listening to the heart with a stethoscope. While heart murmurs can be completely harmless (innocent), they sometimes signal serious underlying cardiac or systemic health issues. Early detection and proper diagnosis are vital to ensuring the best possible outcome for a dog’s heart health.
What Is a Heart Murmur?
A heart murmur is caused by turbulent or abnormal blood flow within the heart or neighboring blood vessels, resulting in sounds other than the normal âlub-dubâ heartbeat. These murmurs vary in intensity and timing during the cardiac cycle, and their significance ranges from benign to indicative of severe pathology. Heart murmurs themselves are not diseases, but rather signs that warrant further investigation.
Types of Heart Murmurs in Dogs
Murms are broadly classified based on their cause, timing, intensity, and location.
- Innocent (Physiologic) Murmurs: Common in puppies, especially large breeds, innocent murmurs usually have low intensity and disappear by 4â5 months of age. They are typically benign and not associated with any symptoms or structural heart disease.
- Pathologic Murmurs: These are associated with congenital or acquired heart diseases and may indicate structural issues or underlying systemic conditions.
- Functional Murmurs: Caused by conditions external to the heart, such as anemia or fever, rather than a structural cardiac abnormality.
Heart Murmur Grading Scale
Veterinarians grade heart murmurs on a scale of I to VI based on intensity:
| Grade | Description |
|---|---|
| I | Very quiet, often only detected by a trained veterinarian in a quiet environment |
| II | Soft but easily heard with a stethoscope |
| III | Moderately loud, heard immediately upon stethoscope placement |
| IV | Loud, radiating to other parts of the chest |
| V | Very loud with palpable vibration (thrill) on the chest wall |
| VI | Extremely loud, heard even when stethoscope is partially off the chest |
What Causes Heart Murmurs in Dogs?
The causes of heart murmurs in dogs are diverse and can be categorized by origin:
- Congenital Heart Defects:
- Structural abnormalities present at birth, such as patent ductus arteriosus, subaortic stenosis, pulmonary stenosis, and ventricular septal defect.
- Certain breedsâlike Bichon Frise, Poodles, Keeshonds, Maltese, Corgis, and Yorkshire Terriersâare more prone to congenital heart defects.
- Acquired Heart Disease:
- Degenerative valve disease (especially mitral valve disease) is most common in older, small-breed dogs. This causes blood to leak backward through the valve, producing a murmur and eventually leading to congestive heart failure.
- In large and giant breeds (like Doberman Pinschers, Great Danes, Boxers, and Irish Wolfhounds), dilated cardiomyopathy weakens the heart muscle and leads to valve leakage, murmurs, and heart failure.
- Endocarditis (infection of the heart valves) and myocarditis (heart muscle inflammation) can also cause murmurs.
- Extracardiac (Functional) Causes:
- Anemiaâcausing thinned blood and turbulence through the heart.
- Hypoproteinemia (low blood protein), fever, pregnancy, obesity, or severe emaciation.
- Young puppies may develop murmurs due to heavy parasitic infestations (intestinal worms, fleas, ticks).
Rarely, heart murmurs can be associated with hormonal conditions such as hyperthyroidism, which increases cardiac output and turbulence.
Symptoms of Heart Disease in Dogs
Many dogs with heart murmurs show no obvious clinical symptoms, especially in the early stages of disease. Most are detected by a veterinarian during routine examination. However, as heart disease progresses, symptoms may include:
- Coughing (especially at rest or during/after exercise)
- Difficulty breathing or faster than normal breathing
- Exercise intolerance (tires easily during walks or play)
- Weakness or collapse/fainting episodes
- Lethargy and reduced energy levels
- Weight loss
- Swelling of the abdomen or bloating (ascites)
- Pale or bluish gums (especially in advanced cases)
Puppies with severe congenital defects may show stunted growth or stunted development.
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Diagnosing a Heart Murmur in Your Dog
A thorough diagnosis of a heart murmur includes a physical exam and a series of advanced veterinary tests to determine the cause, severity, and impact on the heart and other organs.
Steps in Diagnosing Canine Heart Murmurs
- Auscultation: Listening with a stethoscope is the most common method to detect a murmur. The vet assesses the murmur’s timing, quality, and location.
- Pulse Examination: Palpating the femoral pulse for abnormalities, often in conjunction with auscultation.
- Chest X-Rays: Reveal heart size, shape, and any fluid buildup, providing clues about congestive heart failure or structural changes.
- Electrocardiogram (ECG): Measures the electrical activity of the heart, identifying arrhythmias or conduction abnormalities.
- Holter Monitor: A portable ECG that records the heart’s rhythm over 24 hours during normal activity.
- Echocardiography (Cardiac Ultrasound): The gold standard for evaluating heart murmurs. Visualizes the heart’s structure, pumping function, valve action, and estimates severity of regurgitation or stenosis.
- Blood and Urine Tests: Screen for heartworm disease, anemia, markers of organ function, and systemic diseases that may lead to murmurs.
- Blood Pressure Measurement: Though challenging in dogs, high or low blood pressure can influence heart disease and must be monitored, especially during therapy.
Treatment and Management of Heart Murmurs in Dogs
Treatment depends on the cause, severity, and presence of symptoms. Not all murmurs require immediate intervention. Management strategies include:
- Innocent Murmurs: Usually no treatment is needed. Regular monitoring is recommended to confirm resolution as the puppy matures.
- Treating Underlying Causes: If the murmur is due to anemia, infection, or other systemic disease, addressing the root problem often resolves the murmur.
- Medicating Acquired Heart Disease: Medication may be prescribed for heart failure or arrhythmias, often including:
- ACE inhibitors (to lower blood pressure and reduce heart work)
- Diuretics (to reduce fluid buildup, especially in lungs or abdomen)
- Positive inotropes (to strengthen heart contractions)
- Antiarrhythmics (when abnormal heart rhythms are present)
- Surgical or Interventional Procedures: Certain congenital defects can be corrected or improved by surgery or minimally invasive catheter-based interventions.
- Prescription Diets and Lifestyle Modifications: Reducing sodium intake, managing weight, and maintaining appropriate exercise and stress levels support cardiac health.
Some dogs with heart murmurs and mild symptoms can live comfortably for years with medical management. Regular check-ups and monitoring for new symptoms are crucial to adjust therapy as the disease progresses.
Prognosis for Dogs with Heart Murmurs
The outlook for a dog with a heart murmur depends on the underlying cause and the severity at diagnosis.
- Innocent murmurs in puppies commonly resolve and have an excellent prognosis.
- Mild acquired diseases detected early can often be managed for years with medications and check-ups.
- Severe congenital defects or advanced acquired heart disease may progress despite therapy, but supportive care still improves quality of life.
Some forms of heart disease can be progressive, eventually leading to congestive heart failure. Early detection and prompt intervention prolong comfort and life expectancy.
Frequently Asked Questions (FAQs)
What should I do if my dog is diagnosed with a heart murmur?
Follow your veterinarian’s recommendations regarding further testing and monitoring. Many murmurs are benign or manageable, but additional diagnostics may be needed to determine the cause and best treatment plan.
Can a young puppy outgrow a heart murmur?
Innocent or physiologic murmurs are common in puppies, especially large breeds, and frequently disappear by 4â5 months of age. Ongoing monitoring is important to confirm resolution.
Will my dog need medication forever if diagnosed with heart disease?
Many dogs with acquired heart disease will need lifelong medication and periodic adjustments. Regular veterinary check-ups are essential to monitor disease progression and treatment effectiveness.
Is a heart murmur always a sign of heart failure in dogs?
No. A murmur is only an abnormal sound; it may be harmless or a first sign of a progressing condition. Not all dogs with murmurs develop heart failure, and many live normal lives, especially with proper care and monitoring.
Which breeds are most at risk for heart murmurs and disease?
Small breeds like Cavalier King Charles Spaniels, Dachshunds, and Toy Poodles are prone to mitral valve disease, while large breeds like Doberman Pinschers, Boxers, and Great Danes are more at risk for dilated cardiomyopathy and secondary valve leakage.
Key Takeaways for Dog Owners
- Heart murmurs are common findings during veterinary exams and can be benign or a signal of underlying disease.
- Diagnosis often requires advanced imaging and laboratory tests to pinpoint cause and severity.
- Early intervention and ongoing management can help many dogs live longer, more comfortable lives.
- Always discuss findings and follow-up recommendations closely with your veterinarian or a veterinary cardiologist.
References & Resources
- American Kennel Club: Health Resources for Dogs
- Veterinary Cardiovascular Society
- VCA Animal Hospitals: Heart Health Guides
References
- https://www.akc.org/expert-advice/health/heart-murmurs-in-dogs/
- https://metro-vet.com/my-pet-was-diagnosed-with-a-heart-murmur-what-does-that-mean/
- https://vcahospitals.com/know-your-pet/heart-disease-in-dogs
- https://vcahospitals.com/know-your-pet/heart-murmurs-in-dogs
- https://www.akc.org/expert-advice/health/heart-disease-in-dogs/
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