Heart Murmurs in Dogs and Cats: Should You Be Worried?
During a routine veterinary examination, your veterinarian may mention that they have detected a heart murmur in your dog or cat. For many pet owners, this can be concerning, particularly when their pet appears completely healthy.
Although a heart murmur can be associated with heart disease, it does not automatically mean that a pet has heart failure or requires medication.
At Lonsdale Place Veterinary Clinic, we want owners to understand what heart murmurs are, why they occur, and how veterinarians determine whether further investigation is needed.
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What Is a Heart Murmur?
A heart murmur is an additional sound heard when a veterinarian listens to the heart using a stethoscope.
Normally, the heart produces recognizable sounds as its valves close during each heartbeat.
A murmur occurs when blood flow creates vibrations that produce an unusual sound.
These sounds can vary in intensity, timing, and location.
Importantly, a heart murmur is a clinical finding rather than a specific diagnosis.
It tells the veterinarian that blood flow sounds unusual, but further assessment may be required to determine why.
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What Causes Heart Murmurs in Dogs?
One common cause of heart murmurs in older dogs is degenerative mitral valve disease.
The mitral valve separates the left atrium from the left ventricle. When this valve becomes thickened or fails to close properly, some blood can leak backward during contraction.
This abnormal blood flow creates a murmur.
Mitral valve disease is especially common in certain small dog breeds, although other breeds can also be affected.
Other potential causes include congenital heart defects, disease affecting the heart muscle, or conditions that alter blood flow.
Some puppies also have innocent murmurs that disappear as they mature.
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What Causes Heart Murmurs in Cats?
Heart murmurs in cats can have several causes.
One important possibility is hypertrophic cardiomyopathy, a condition in which the heart muscle becomes abnormally thickened.
However, not every cat with a murmur has heart disease, and some cats with significant heart disease have no audible murmur.
Stress, an elevated heart rate, anemia, and certain other conditions can also contribute to murmurs.
This is why the presence or absence of a murmur alone cannot reliably determine whether a cat has heart disease.
North Vancouver Vet
Does a Louder Murmur Mean More Serious Heart Disease?
Veterinarians commonly describe heart murmurs using a grading system from 1 to 6.
A grade 1 murmur is very quiet, while a grade 6 murmur is extremely loud and may be heard even when the stethoscope is slightly lifted from the chest.
Although murmur intensity can provide useful information, it does not always correspond directly to the severity of heart disease.
Some relatively loud murmurs are associated with manageable conditions, while serious heart disease may occasionally produce a quiet murmur or no murmur at all.
The significance depends on the underlying cause and the pet's overall health.
North Vancouver Vet
How Are Heart Murmurs Investigated?
The first step is a thorough physical examination.
Depending on the findings, the veterinarian may recommend additional testing.
Echocardiography: An ultrasound of the heart allows assessment of the heart chambers, valves, wall thickness, and blood flow. It is one of the most useful tests for diagnosing structural heart disease.
Chest radiographs: X-rays can help assess heart size and identify fluid accumulation within the lungs.
Blood pressure measurement: High blood pressure may contribute to cardiovascular changes and is particularly relevant in cats.
Bloodwork: Testing may help identify conditions such as anemia or hyperthyroidism that can influence heart function.
Not every pet requires every test. Recommendations depend on the murmur, the animal's age, symptoms, and other examination findings.
North Vancouver Vet
Does Every Heart Murmur Need Medication?
No.
Some pets with murmurs have no significant structural heart disease and require monitoring rather than treatment.
Others have diagnosed heart conditions that remain stable for years without medication.
However, certain dogs with enlarged hearts due to mitral valve disease can benefit from medication before the onset of congestive heart failure.
Treatment decisions should be based on an appropriate diagnosis and assessment of disease severity, rather than murmur intensity alone.
North Vancouver Vet
What Signs Should Owners Watch For?
Potential warning signs include:
Reduced exercise tolerance
Persistent coughing in some dogs
Increased breathing rate while resting or sleeping
Unusual fatigue
Fainting or collapse
Difficulty breathing
Breathing difficulty, open-mouth breathing in cats, or collapse requires immediate veterinary attention.
Owners of pets with diagnosed heart disease may be advised to monitor their pet's sleeping respiratory rate at home.
North Vancouver Vet
Final Thoughts
Hearing that your pet has a heart murmur can be unsettling, but a murmur is not automatically a diagnosis of heart failure.
Many pets with murmurs continue enjoying a good quality of life, particularly when underlying conditions are identified and monitored appropriately.
If your dog or cat has been diagnosed with a heart murmur, the team at Lonsdale Place Veterinary Clinic can help determine whether additional diagnostic testing, monitoring, or treatment is appropriate.
