What Is A Heart Murmur?
A murmur develops when the normal flow of blood within the heart is disturbed, for example by a leaky or narrow valve. These abnormalities may be congenital- a defect that developed before birth or developmental - these occur as the animal becomes older. There are also ‘innocent’ murmurs in puppies and kittens which are usually quiet murmurs and disappear by the time the animal is a few months old.
Heart Murmurs In Dogs
In middle-aged small dogs, the most common heart condition is degenerative mitral valve disease.The valve between the left atrium (upper chamber) and ventricle (lower chamber), becomes thickened, irregular and leaks. The condition will usually progress over several years and in the vast majority of cases, the loudness of the murmur gives us a good indication how severe it is.
Bigger dogs are more prone to developing dilated cardiomyopathy (DCM). In this condition the left ventricle becomes weaker at pumping blood and then dilated (enlarged). There is no murmur early on, so the disease is more difficult to detect.
Heart Murmurs In Cats
The most common condition is hypertrophic cardiomyopathy (HCM), where the muscular ventricular wall becomes thickened. A murmur in cats doesn't tell us whether there is heart disease or how severe it is.
In cats and dogs, the left atrium may gradually enlarge and eventually can lead to congestive heart failure, in which fluid accumulates in or around the lungs and causes symptoms.
So How Do We Know Whether We Should Be Concerned About Our Pet's Heart Murmur Or Not?
Ask yourself the following questions:
- Can your pet play and exercise as normal?
- Are they panting or weaker than normal?
- What is your dog or cat’s resting respiratory (breathing) rate? One of the early signs of heart failure is an increase in the resting respiratory rate. Normal is less than 30/minute with no increased effort and you can measure this best at home.
- Is my pet coughing? Coughing is often a sign that people associate with heart failure. However, coughing is a usually a sign of airway disease. Coughing is rarely seen in cats with heart failure.
How Do You Measure Resting Respiratory Rate?
Watch your pet when they are calm, ideally asleep. Not just after exercise, excitement or when panting or purring. Count the number of breaths over 15 seconds and multiply by four to get the rate per minute. There is a helpful free app called Cardalis (download here for iOS or here for Android devices).
So to summarise, does your pet have a normal ability to exercise, normal respiratory rate, no cough or increased panting? Then he or she sounds stable and delaying a scan by a few months should not be a concern. Continue to monitor your pet for any significant change, and you can contact us by email for advice if you are unsure.