Heart murmurs in cats

Published on: 14th November 2019

A heart murmur is an abnormal sound we hear using a stethoscope. Heart murmurs are common in cats with a recent study of 780 cats in a UK rehoming centre 40% of apparently healthy cats had an audible heart murmur.  The challenge is to establish which of these cats  have no underlying heart disease (and therefore an “innocent” murmur) and which cats have underlying disease such as hypertrophic cardiomyopathy.

The best test for this is echocardiography (ultrasound of the heart) performed by an experienced Specialist in Veterinary Cardiology.  A normal cat heart is about the size of a plum, often beating around 150-180 times per minute and the measurement tolerances are sometimes very small with fractions of a millimetre differentiating between normal and abnormal individuals so further training and experience increases the accuracy of diagnosis.  Experienced Specialists in Veterinary Cardiology will perform this examination on cats without any sedation or anaesthesia and, at our practice, you can stay with your cat to reassure them whilst the scan is performed.

About 15% of the cat population is affected by a heart disease called hypertrophic cardiomyopathy which is characterised by thickening of the heart muscle and also abnormal heart function.  This disease can be diagnosed using echocardiography and the outlook for these cats is very variable with some tolerating the disease for many years whereas other cats experience complications such as heart failure, blood clot formation or, sadly, succumb to sudden death.  As the progression of this disease is variable it is important to regularly monitor these cats to pre-empt problems whenever possible and this is often done by repeating echocardiography every 6 months.

However it is important to remember that some cats with significant heart disease do not have an audible heart murmur so if you have any concerns that your cat may be showing signs of heart disease such as a change in breathing rate or pattern, reduced level of activity, change in appetite, unexplained weight loss or signs of a blood clot (such as lameness or paralysis of a limb) then please contact your veterinary surgeon for advice.