Heart murmurs in dogs are more common than most pet owners realize. When a veterinarian tells you that your dog has a heart murmur, it can feel overwhelming—but understanding what it means and catching it early makes a world of difference. A heart murmur itself is not a diagnosis; it is a sign that blood is flowing through the heart abnormally. The sooner you understand the signals, the sooner you can get your dog the care they need.
Dogs of all ages can develop murmurs, from puppies born with congenital defects to senior dogs whose hearts have worn down over time. Some are harmless; others point to underlying cardiac disease. The key is knowing what to watch for and working with your veterinarian on an appropriate management plan.
What Is a Heart Murmur and Why Does It Matter
A heart murmur is an abnormal sound heard between the normal “lub-dub” of a dog’s heartbeat. It occurs when blood flow through the heart becomes turbulent, rather than smooth. This turbulence can happen for several reasons: a leaky heart valve, a narrowed passage, an increased blood flow rate, or structural abnormalities in the heart chambers themselves.
Veterinarians grade heart murmurs on a scale of 1 to 6 based on loudness and intensity. A Grade 1 is barely audible, while a Grade 6 is so loud it can be felt by placing a hand on the dog’s chest. Higher grades generally indicate more significant cardiac involvement, though grade alone does not determine severity of disease. The location of the murmur within the heart cycle—systolic (between heartbeats), diastolic (filling phase), or continuous—provides additional clues about what might be causing it.
Heart murmurs matter because they are often the first detectable sign of underlying heart disease or congenital defects. Left unmonitored and untreated, many cardiac conditions will progressively worsen, eventually leading to congestive heart failure. Early detection gives you the best possible window to slow disease progression and maintain your dog’s quality of life for as long as possible.
Early Warning Signs Every Owner Should Watch For
Many dogs with mild to moderate heart murmurs show no obvious signs for months or even years, which is why regular veterinary examinations are so important. However, when signs do appear, they often start subtly and can be mistaken for normal aging. Paying close attention to changes in your dog’s behavior and physical condition is essential.
Exercise intolerance is one of the earliest and most common signs. If your dog used to bounding after a ball but now lags behind on walks, or seems winded after minimal activity, that warrants investigation.
A persistent cough—especially one that seems worse at night or early morning—is another red flag. This type of cough often indicates fluid building up in or around the lungs due to poor cardiac function. While dogs can cough for many reasons, a cough that lingers for more than a few weeks or worsens over time should be evaluated.
Rapid or labored breathing during rest or sleep is concerning. A healthy dog at rest should breathe quietly and effortlessly. Watch for exaggerated chest movements, flared nostrils, or breathing rates that seem elevated even when your dog is relaxed. Some dogs also develop a bluish tint to their gums or tongue, which indicates poor oxygen circulation and requires immediate veterinary attention.
Unexplained weight loss or muscle wasting can accompany advanced heart disease, as the body redirects energy and nutrients away from non-essential tissues.
Breeds at Higher Risk for Heart Disease
Certain dog breeds are genetically predisposed to cardiac conditions that cause heart murmurs. Knowing your dog’s breed risk helps you stay vigilant and advocate for appropriate cardiac screening.
Cavalier King Charles Spaniels are among the most well-known predisposed breeds. Mitral valve disease is extremely common in this breed, often developing by middle age and progressing over time. Regular cardiac screening using echocardiography is strongly recommended for all Cavaliers, even if no murmur is detected during a routine exam.
Doberman Pinschers are prone to dilated cardiomyopathy, a condition where the heart muscle becomes enlarged and weakened. A heart murmur may develop as the disease progresses, and early detection through cardiac imaging is critical because sudden cardiac death is a risk in affected dogs.
American Bullies and other bully breed mixes have been increasingly recognized as having higher rates of certain congenital heart defects, sometimes detectable during early puppy wellness visits.
Dachshunds are predisposed to patent ductus arteriosus (PDA), a congenital defect where a blood vessel that should close after birth remains open. This creates a continuous heart murmur and typically requires surgical repair for the best outcome.
How Vets Diagnose and Stage Heart Murmurs
Diagnosis begins with auscultation—listening to your dog’s heart with a stethoscope. Your veterinarian will assess the murmur’s location, timing, loudness, and radiation to get initial clues about its origin. However, auscultation alone cannot determine the exact nature or severity of the underlying cardiac issue.
The gold standard for cardiac evaluation is an echocardiogram, or heart ultrasound. This non-invasive test allows the veterinarian to visualize the heart’s structure in real time, measure chamber sizes, evaluate valve function, and assess the strength of heart muscle contractions. Many general practice veterinarians refer patients to a veterinary cardiologist for this procedure.
Chest radiographs (X-rays) are used to evaluate heart size, identify fluid in the lungs, and assess the overall pulmonary condition. Radiographs are particularly helpful in staging heart disease and monitoring progression over time.
An electrocardiogram (ECG or EKG) records the electrical activity of the heart and is useful for detecting arrhythmias, which can accompany certain types of heart disease. This test is typically performed by a specialist or with equipment available in specialty practices.
Blood tests, including NT-proBNP, measure levels of a hormone released by stressed heart cells. Elevated levels can indicate the presence and severity of heart disease, providing useful baseline information and helping to monitor treatment effectiveness.
Managing a Dog With a Heart Murmur
Management depends entirely on the underlying cause and severity of the murmur. Not every heart murmur requires medication, but every murmur requires monitoring and lifestyle attention.
Dietary management plays a significant role, particularly reducing sodium intake to help minimize fluid retention and reduce strain on the heart. Therapeutic cardiac diets are available through veterinarians and are formulated to support heart function while maintaining optimal nutrition. Maintaining your dog at a healthy weight is equally important—excess body fat places additional demands on the heart and worsens breathing difficulties.
Exercise moderation is often necessary. While your dog still needs regular activity to maintain muscle tone and mental health, strenuous exercise that pushes them to exhaustion should be avoided. Short, regular walks on cool surfaces are generally better than long, intense sessions, especially in warm weather, since heat stress compounds cardiac strain.
Common medications include ACE inhibitors such as enalapril or benazepril to relax blood vessels and reduce the heart’s workload, diuretics like furosemide to remove excess lung fluid, and pimobendan (Vetmedin), a positive inotrope that helps the heart contract more effectively while dilating blood vessels. Regular recheck exams every three to six months allow your veterinarian to monitor progression and adjust treatment as needed.
Living well with a heart murmur is absolutely possible. Many dogs with properly managed cardiac disease enjoy years of good quality life when the condition is caught early and monitored consistently. Work closely with your veterinarian, stay vigilant for subtle changes in your dog’s energy and breathing, and remember that you are your dog’s best advocate. You see them every day, and subtle changes in energy, appetite, breathing, or behavior may be the earliest indicators that something is wrong. Trust your instincts—if something seems off, it is worth having it checked out. A heart murmur detected early and managed proactively gives your dog the best possible outlook.
