A heart murmur is the most common finding that makes a Cavalier owner hear the word “cardiologist” for the first time. The word sounds alarming, but on its own it does not mean the dog is ill or that its life is in danger. A murmur is a sound, not a diagnosis.
This article explains what the vet actually hears, what grades 1 to 6 mean, when a murmur in a Cavalier does call for further investigation and when it does not.
What a heart murmur is
A healthy heart produces two clear sounds when listened to with a stethoscope. A murmur is an additional sound between them, arising when blood in the heart does not flow smoothly but turbulently.
Turbulence can have several causes. In Cavaliers by far the most common cause is mitral valve disease, in which the valve stops sealing so part of the blood flows backwards. But a murmur can also be caused by anaemia, fever, the dog being excited in the consulting room, and by congenital heart defects that are detected at an early age.
That is why the first finding of a murmur is never the end of the story, but its beginning.
Grading a murmur from 1 to 6
Vets use an internationally accepted six-grade scale that describes the loudness of the sound and nothing else:
- Grade 1: the quietest murmur that can be heard at all, and only in a completely silent room after prolonged listening.
- Grade 2: a quiet but easily audible murmur, confined to one small spot on the chest.
- Grade 3: a murmur heard immediately as soon as the stethoscope is placed in the right spot.
- Grade 4: a loud murmur heard immediately and over a wider area, but still not felt by hand.
- Grade 5: a very loud murmur with a vibration of the chest wall that can be felt with the palm.
- Grade 6: the loudest murmur, audible even when the stethoscope is lifted slightly off the chest.
In Cavaliers with mitral valve disease the murmur usually starts as grade 1 or 2 and grows louder over time. The speed of that progression differs from dog to dog and cannot be predicted from a single examination.
Why the grade is not the same as the severity of the disease
This is the part most often misunderstood. The grade measures how loud the sound is, not how damaged the heart is.
A dog with a grade 4 murmur may have a heart of normal size and no complaints at all, while a dog with a quieter murmur may have an enlarged heart. Grades 3 and 4 in particular correlate poorly with the actual state of the heart.
Only a cardiac ultrasound shows how enlarged the heart really is and how much blood flows backwards. That is why, after listening, a cardiologist almost always suggests an ultrasound, even when the murmur is quiet.
The innocent murmur in a puppy
In young dogs there is also what is called an innocent or physiological murmur. It arises because the heart is growing fast, it is not caused by disease and leaves no consequences.
An innocent murmur has recognisable features:
- it appears most often between the sixth and eighth week of life
- it is quiet, as a rule grade 1 or 2
- the puppy has no symptoms and grows normally
- it resolves on its own, usually by the fourth or fifth month
A murmur still audible after the sixth month is no longer considered innocent and calls for a cardiac ultrasound. The same applies to a murmur louder than grade 2, one that grows from check-up to check-up, or one heard best on the right side of the chest.
When a murmur in a Cavalier is a cause for concern
In this breed a murmur is viewed differently than in other dogs, simply because mitral valve disease is so common. A few circumstances call for closer attention:
- a murmur detected before the age of two, because that suggests an early onset of the disease
- a murmur that rises by two or more grades within a year
- a murmur accompanied by coughing, faster breathing at rest or tiring
- a murmur in a dog intended for breeding
On the other hand, a quiet murmur in a Cavalier over five years old, with no symptoms and with a finding that the heart is not enlarged, does not mean the dog needs medication. It means the dog needs a check-up once a year.
What follows a finding of “heart murmur”
If the vet hears a murmur, the usual sequence is as follows. First the grade and the spot where it is heard best are determined. The dog is then referred for a cardiac ultrasound with a specialist cardiologist, which measures the size of the heart and the amount of backflow. On the basis of those measurements the dog is placed in the appropriate stage of the disease, and only the stage determines whether medication is started and when the next check-up is due.
A chest X-ray is done when needed, most often when there is coughing or a suspicion of fluid in the lungs.
What a murmur means when buying a puppy
A responsible breeder does not mate a dog that has a heart murmur. Breeding dogs are examined by a cardiologist and must be free of murmur, and the report is issued on paper with the name and signature of the doctor.
If a breeder tells you the parents “have no murmur” but cannot show you a report, that claim carries no weight. A grade 1 murmur is not heard by every vet in a noisy consulting room, and that is precisely why the specialist examination exists.
In the puppy itself a quiet murmur at eight weeks of age is most often innocent, but it is sensible to have it checked again at around six months.
Conclusion
A heart murmur is a sign that calls for an explanation, not a verdict. In Cavaliers it should be taken seriously but without panic: the grade alone says nothing about how damaged the heart is, and an ultrasound settles that in a single visit. An annual check-up and choosing a puppy from a litter with examined parents remain the two things that change the outcome the most.
Note: this article is informational and does not replace examination and advice from a veterinarian. For diagnosis and treatment consult your vet, preferably a specialist in cardiology.
Related
- Mitral valve disease (MVD) in Cavaliers: stages, signs and treatment
- Syringomyelia and Chiari-like malformation in Cavaliers
- Why Cavaliers scratch their neck and shoulder — when it is a sign of illness
- Which health tests are required for the parents of a Cavalier litter
- The expected lifespan of the Cavalier and what affects it
- A schedule of veterinary check-ups by the age of a Cavalier
- Eye problems in Cavaliers: what occurs and how to recognise it
- Patellar luxation in Cavaliers: the slipping kneecap of small breeds
- Ear problems in Cavaliers — why drop ears need more care
- How to read a Cavalier cardiology report
- MRI screening for syringomyelia: when, how and what the report means
- Cavalier vaccination and deworming: schedule by age
- Living with a Cavalier diagnosed with MVD
- Health of the Cavalier King Charles Spaniel — an overview of all topics
- Puppies for sale from a kennel with health-tested parents
