Hearing that your dog has a heart murmur can be unsettling, but it doesn’t always mean there’s immediate danger. A heart murmur is an abnormal sound caused by turbulent blood flow in the heart, often detected during a routine physical exam. While some murmurs are harmless and require only monitoring, others may be a sign of underlying heart disease.
Veterinarians use a grading system from 1 to 6 to assess the loudness and potential significance of a heart murmur. Understanding what each grade means can help you make informed decisions about your dog’s care and treatment plan.
In this article, we’ll break down each grade, explain what it might indicate about your dog’s heart health, and offer guidance on next steps including when to consider supportive options like supplemental oxygen therapy.
Table of Contents
What Is a Heart Murmur in Dogs?
A heart murmur is an unusual sound that your veterinarian hears when listening to your dog’s heartbeat with a stethoscope. Instead of the typical “lub-dub” rhythm, a murmur adds a whooshing or swishing noise which is caused by turbulent blood flow within the heart or nearby vessels.
Heart murmurs in dogs can occur for a variety of reasons. Some are innocent murmurs, especially in puppies, and may resolve on their own as the heart matures. Others are linked to underlying conditions such as:
- Congenital heart defects (present at birth)
- Degenerative valve disease, particularly common in older dogs
- Dilated cardiomyopathy, affecting the heart muscle
- Anemia or fever, which can alter blood flow temporarily
Murmurs are typically discovered during a routine wellness exam when your vet listens to your dog’s chest. To understand the severity and cause of the murmur, your vet may recommend additional diagnostics like chest X-rays, bloodwork, or most definitively, an echocardiogram (heart ultrasound). This allows for visualization of heart structure and function, helping to guide treatment decisions and monitor progression.
Understanding the Grading Scale: Grades 1 to 6
Heart murmurs in dogs are graded on a scale from 1 to 6 based on how loud they sound through a stethoscope and whether they can be felt as vibrations on the chest. This grading system helps veterinarians determine the potential severity of the murmur and whether further diagnostics or treatments are needed. Let’s break down what each grade means for your dog’s heart health.
Grade 1
- Very soft, barely audible.
- Usually an incidental finding with no clinical symptoms.
- Monitoring recommended.
Grade 2
- Soft but clearly heard with a stethoscope.
- May not indicate disease but should be monitored.
Grade 3
- Moderately loud.
- More likely to be associated with structural heart changes.
- May require diagnostic follow-up (X-rays, echocardiogram).
Grade 4
- Loud heart murmur, often palpable as a “thrill”. A thrill is a palpable, vibratory sensation felt on the skin, usually over the heart or blood vessels, caused by turbulent blood flow.
- Grade 4 heart murmurs are often linked to significant heart disease .
- Regular monitoring and treatment likely necessary.
Grade 5
- Very loud with a palpable thrill.
- Suggests severe underlying heart issue.
- Symptoms like coughing, fatigue, or exercise intolerance may appear.
Grade 6
- Loudest possible heart murmur; can be heard without a stethoscope.
- Typically indicates advanced cardiac disease with clinical symptoms.
- Aggressive management usually needed.
Heart Murmur Symptoms to Watch For
While some heart murmurs may be benign and cause no outward signs, others (especially those linked to underlying heart disease) can lead to noticeable symptoms. Being aware of these signs can help you catch complications early and seek timely veterinary care. Keep an eye out for the following:
- Coughing, particularly at night or after physical activity, as this may indicate fluid buildup in the lungs due to poor heart function.
- Lethargy or decreased activity can signal that your dog’s heart isn’t pumping efficiently, leading to fatigue.
- Labored or rapid breathing may occur as the body struggles to get enough oxygen, often due to fluid accumulation or reduced cardiac output.
- Fainting or collapse can result from inadequate blood flow to the brain, often triggered by excitement or exertion.
- Poor appetite or weight loss may develop as heart disease progresses and affects overall energy and well-being.
If your dog shows any of these signs, especially in combination, it’s important to consult your veterinarian promptly. Early intervention can significantly improve quality of life and long-term outcomes for your dog.
How Heart Murmurs Are Diagnosed
Diagnosing a heart murmur begins with a veterinary auscultation, where your vet listens to your dog’s heart using a stethoscope. If a murmur is detected, your veterinarian may recommend further testing to determine the cause and assess the severity of any underlying heart disease.
Key diagnostic tools include:
- Chest X-rays: These help evaluate the size and shape of the heart and check for fluid buildup in the lungs, a common sign of congestive heart failure.
- Echocardiogram: This is the most definitive tool for diagnosing heart conditions. It uses ultrasound imaging to visualize the heart's structure and function, allowing for a clear view of valve abnormalities, chamber size, and blood flow.
- Blood pressure measurement: High blood pressure can worsen heart disease and may be both a contributing factor and a result of heart dysfunction.
- Lab work: Blood tests can uncover conditions like anemia, infections, or thyroid imbalances that may contribute to or mimic heart-related symptoms.
These diagnostics help your veterinarian assign an accurate heart murmur grade, identify the root cause, and create a treatment plan tailored to your dog’s needs.
Are heart murmurs more common in certain breeds or species?
Yes, heart murmurs are more common in certain breeds and species due to genetic predispositions and specific anatomical traits. Some common dog breeds predisposed to heart murmurs are Cavalier King Charles Spaniels, Pomeranians, Chihuahuas, Boxers, Doberman Pinschers, German Shepherds, and Golden Retrievers.
Heart murmurs in cats are less breed-specific but can be linked to certain conditions like hypertrophic cardiomyopathy (HCM).
What do the grades of heart murmurs mean?
Heart murmurs are graded based on their loudness, which provides a general indication of their severity. The grading system ranges from Grade I to Grade VI , with higher grades indicating louder and potentially more concerning murmurs.
Can a heart murmur go away on its own, or is it permanent?
Whether a heart murmur goes away on its own or is permanent depends on the underlying cause. Innocent heart murmurs, like those seen in puppies and kittens due to turbulence in their blood flow, may resolve on their own. However, heart murmurs caused by congenital defects, acquired heart disease, and age-related changes to the heart are permanent.
Treatment Options Based on Heart Murmur Severity
Treatment for a heart murmur in dogs depends largely on its grade and the presence of underlying heart disease. Not all murmurs require immediate intervention, but higher-grade murmurs often signal more serious cardiac issues that need ongoing care.
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Grades 1–2:
These lower-grade murmurs are often considered mild and may not indicate structural heart disease. In many cases, your veterinarian will recommend regular monitoring through checkups and possibly echocardiograms. Lifestyle changes, such as maintaining a healthy weight and avoiding excessive exertion, may be advised. If any changes in symptoms occur, early intervention may be warranted.
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Grades 3–4:
These moderate murmurs are more likely to be associated with significant heart changes. Treatment often includes cardiac medications such as pimobendan to improve heart function or diuretics to reduce fluid buildup. Your vet may also suggest a heart-healthy diet with lower sodium content and specific nutrients like taurine and L-carnitine to support heart function.
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Grades 5–6:
These are the most serious murmurs, typically linked to advanced heart disease. Dogs with high-grade heart murmurs usually need comprehensive treatment, which may include a combination of medications, frequent monitoring, and supportive therapies such as oxygen therapy. Supplemental oxygen can be especially helpful during episodes of respiratory distress or as part of a long-term management plan for dogs with congestive heart failure or difficulty breathing.
No matter the grade, working closely with your veterinarian ensures your dog receives the best care tailored to their condition. Early detection and proactive treatment can significantly improve your pet’s quality of life.
How Supplemental Oxygen Can Help Dogs with Heart Murmurs
For dogs with higher-grade heart murmurs, especially those linked to congestive heart failure or advanced heart disease, supplemental oxygen therapy can be a valuable part of their care plan. Oxygen helps ease the burden on the heart by increasing the amount of oxygen available to the body, which can reduce symptoms like shortness of breath, fatigue, and cyanosis (a bluish tint to the gums or tongue).
When is Oxygen Therapy Useful?
Supplemental oxygen can be beneficial in a variety of situations:
During respiratory distress: Oxygen can help stabilize your dog and make breathing easier during acute episodes.
After fainting or collapse: Oxygen helps restore balance and improve circulation during recovery.
For chronic support: Dogs with Grade 5 or 6 murmurs may benefit from oxygen therapy as part of ongoing home care, especially if they experience frequent symptoms or reduced oxygen levels.
How Oxygen Therapy Works
There are several ways to administer oxygen to your dog at home:
- Oxygen concentrators paired with oxygen chambers or pet oxygen masks offer a consistent supply of therapeutic oxygen. These setups are ideal for daily support or prolonged use.
- Portable oxygen rescue kits provide immediate relief during emergencies or while traveling, offering a convenient and fast-acting solution.
Consult Your Veterinarian First
It’s essential to work closely with your veterinarian to determine if oxygen therapy is appropriate for your dog. They can help you choose the right equipment, set safe flow rates, and integrate oxygen into a comprehensive treatment plan tailored to your dog’s specific condition.
When to See a Veterinarian
If your dog has been diagnosed with a heart murmur, or you suspect something might be wrong, timing matters. Early evaluation can lead to better outcomes and more treatment options.
You should schedule a veterinary visit in the following situations:
- A murmur is suspected or newly detected: Even a soft murmur warrants further investigation to determine if it's harmless or linked to heart disease.
- Your dog’s symptoms are worsening: Signs like increased coughing, labored breathing, fainting, or reduced energy levels may indicate that the condition is progressing and needs medical attention.
- For diagnostic testing and follow-up care: Ongoing monitoring through echocardiograms, X-rays, and checkups is critical for managing heart disease and adjusting treatment as needed.
Don’t wait for severe symptoms to appear. Regular communication with your veterinarian can help you stay ahead of potential complications and ensure your dog continues to live a comfortable, happy life.
Key Questions to Ask Your Vet
When your dog is diagnosed with a heart murmur, asking the right questions can help you better understand their condition and make informed decisions about their care. Use the list below as a guide during your veterinary visit:
What grade is my dog’s murmur?
Understanding the grade gives insight into the potential severity of the murmur and whether treatment or monitoring is needed.
What is the likely cause?
Some murmurs are benign, while others may indicate underlying conditions such as mitral valve disease or congenital heart defects. Knowing the cause can guide long-term care.
What tests do you recommend?
Ask if diagnostic tools like chest X-rays, echocardiograms, or blood work are necessary to get a clearer picture of your dog’s heart health.
Should I begin treatment now?
Depending on the murmur grade and clinical signs, your vet may suggest starting medication or lifestyle adjustments right away.
Could my dog benefit from oxygen therapy?
If your dog has difficulty breathing, collapses, or shows signs of advanced heart disease, supplemental oxygen may help improve comfort and quality of life, especially for higher-grade heart murmurs.
Bringing these questions to your appointment shows you’re proactive about your dog’s health and helps ensure you’re aligned with your vet on the best path forward.
Keeping Your Dog’s Heart Healthy
Understanding your dog’s heart murmur grade is an important step in managing their heart health. The grading system, from 1 to 6, helps veterinarians determine how serious the murmur is and what kind of monitoring or treatment is needed.
Early detection, routine veterinary care, and a proactive approach can make a big difference in your dog’s long-term wellbeing. Whether your dog needs simple observation or a more comprehensive treatment plan, knowing the grade gives you the insight needed to take action.
If your dog is showing signs of heart-related symptoms or has been diagnosed with a higher-grade heart murmur, don’t hesitate to ask your veterinarian about all available options including the potential benefits of supplemental oxygen therapy. With the right care, many dogs with heart murmurs can continue to live full and happy lives.
