Heart Murmurs in Cats

by Dr Madi Hewitson MRCVS
sleeping cat

What is a heart murmur? 

A heart murmur is a sound that results from turbulent blood flow within or near the heart, in the same way that a stream of water ‘hisses’ when you obstruct the flow from the end of a hose with your finger. 

Murmurs are detected using a stethoscope but, in some animals, they may be heard intermittently. 

Cardiac ultrasound (echocardiography or echo) is used to determine the cause and seriousness of the murmur. In conjunction with chest x-rays and ECG, vets can make a full diagnosis and develop a treatment plan. 

What is involved in an echo examination? 

An echo is usually performed in conscious patients, sometimes with light sedation, with the patient gently restrained on its side. A small area of hair is usually clipped from both ‘armpit’ areas. A gel is applied to the skin and a plastic probe is held against the skin. A moving, 2-dimensional image of the heart appears on the screen that enables the vet to measure a variety of parameters such as chamber size and blood flow velocities but also to track blood flow through the heart in real time. Videos and still images are stored for evaluation. The procedure generally takes 30-40 minutes. 

How do we know if a murmur is significant? 

In a recent study, 40% of cats had heart murmurs although 70% of these were not associated with significant heart disease. It is important to note that a number of cats with significant heart disease have no murmur. Some of these cats may have other signs such as “gallop” sounds or rhythm abnormalities. 

Once a murmur has been detected it can be difficult to know if the murmur is associated with heart disease. Given that the murmur is likely to be detected at future vet visits, raising the same questions,

we would recommend further investigation in most cases. The most accurate test is a high-quality ultrasound examination (Echo) which is performed conscious or sometimes with light sedation. 

What causes a heart murmur? 

Hypertrophic cardiomyopathy (HCM) 

This is the commonest heart disease seen in cats. It causes thickening and stiffening of the muscle of the ventricles. This can lead to reduced effectiveness of the heart and ultimately to heart failure or even sudden death. 

Other cardiomyopathies. Other diseases of the heart muscle can also lead to murmurs. 

Congenital disease. These result from abnormal development (see dogs). 

Murmurs in Cats and Dogs Can Lead to Heart Failure 

Signs of heart failure include: 

• Increased breathing rate • Tiredness

• Difficulty exercising • Coughing

• Difficulty breathing • Fainting/collapse 

If you are concerned that your cat may be suffering from heart failure please seek immediate veterinary care. 

If your cat has been diagnosed with cardiac disease and you would like to know more or even have a little chat, our online team of trusted vets are available 24/7 to talk to, from the comfort of your own home.

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