Cats with Heart Murmurs – Information for Prospective Adopters

This page is intended for people considering adopting a cat that has been diagnosed with a heart murmur. Prospective adopters will be advised if a heart murmur has been detected in a cat they are considering adopting from Animals In Distress (AID).

AID frequently faces the difficult decision of when to fund diagnostic testing for cats in our care when a heart murmur has been detected. Heart murmurs are common in cats, and the cost of screening can significantly increase the overall cost of rescue and care, creating a substantial financial burden for our non-profit organization. A full cardiology consultation, including an echocardiogram, costs approximately $1,200 and it can take months to get an appointment.

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Understanding heart murmurs

A heart murmur is an unusual sound produced by blood moving through the heart. It is typically described as a whooshing or swishing noise heard in addition to the normal sounds made by the heart as it beats.

Finding a heart murmur does not necessarily mean that a cat has heart disease. Heart murmurs are frequently detected in cats, and a recent study found that approximately 33% of cats have murmurs. Our cardiologist has informed us that in healthy cats where a murmur is detected, approximately 50% do not have an underlying heart problem. Even where heart disease is present, many affected cats can continue to have a normal quality of life and may never develop noticeable symptoms.

The opposite is also true: a cat can have significant heart disease without having a detectable murmur. Consequently, listening to a cat's heart cannot identify every case of heart disease.

Heart murmur grades

Veterinarians generally describe murmurs using a scale from 1 to 6. A grade 1/6 murmur is very quiet and a grade 6/6 is very loud.

The grade of a murmur can vary, sometimes even from one examination to another. Importantly, the loudness of a murmur does not necessarily tell us how serious any underlying heart condition may be. For example, a cat with a grade 4/6 murmur may have a completely normal heart, while a murmur in another cat could be associated with significant disease.

A murmur can also occur due to  an illness that does not originate in the heart. Hyperthyroidism, for example, can cause changes in circulation that result in a heart murmur.

Murmurs can change or disappear

A murmur is not necessarily present all the time. Some cats may have a murmur during one examination but not another.

Stress can also affect whether a murmur can be heard. A frightened or anxious cat may have an increased heart rate, making a murmur more noticeable. Once the cat relaxes and its heart rate decreases, the murmur may no longer be detectable.

For these reasons, the presence or intensity of a murmur alone cannot reliably tell us whether a cat has heart disease, how well its heart is functioning, or whether another illness is present. Many otherwise healthy cats have heart murmurs.

Kittens with Murmurs

Kittens commonly have heart murmurs that they grow out of by the time they reach adulthood. Congenital heart disease in kittens is uncommon, and accounts for less than 10% of feline cardiac disease cases. The most common congenital abnormality in kittens is ventricular septal defect (50%), other abnormalities include valve dysplasia, pulmonary or aortic stenosis, and atrial septal defect. 

When do we recommend further investigation?

AID takes both the financial and welfare implications of further investigation into account.

Cats entering rescue can already be under considerable stress, and additional veterinary examinations, travel, and diagnostic procedures can increase that stress. There can also be significant delays in obtaining appointments with a veterinary cardiologist, with some cats potentially waiting several months. This can extend the time they remain in rescue, rather than moving into a permanent home, and reduces the number of cats we are able to help overall.

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As a result, we have to balance the possible benefit of obtaining additional information against the financial cost and the potential impact on the cat's welfare.

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At present, AID pursues a cardiology work-up when a cat has clinical signs that may indicate heart disease, such as abnormal breathing or lethargy/weight loss that cannot be explained by other diagnostics.

Where financial resources permit, we may also investigate cats that have no obvious clinical signs but have one or more of the following:

• An arrhythmia, meaning an abnormal heart rhythm identified by the veterinarian;

• A gallop rhythm, which is a particular additional heart sound heard by the veterinarian; or

• A persistent grade 5/6 or 6/6 heart murmur.

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NT-proBNP testing

NT-proBNP blood testing is another option that has recently become available. This tests for cardiac “stress and stretching”, and helps identify cats in which an echocardiogram would be particularly appropriate. We perform this testing most commonly when a cat has a grade 4/6 to 6/6 murmur but is not showing clinical signs of heart disease. We currently perform this test for all senior cats before putting them under anesthesia for surgery, and for cats who have a grade 4/6 to 6/6 heart murmur before putting them under anesthesia for very short procedures such as spay/neuter. For more lengthy procedures, we may choose to have an echocardiogram performed [in some cases, depending on the veterinarian performing the surgery, they may be comfortable doing a chest x-ray instead of an echocardiogram]. 

If a NT-proBNP test comes back with an abnormal value, and financial resources permit, then AID will pursue a cardiology consult.

It should be noted that the NT-proBNP testing also carries an additional cost to the rescue, currently approximately $250 per test. 

When is a cardiology consult generally not pursued?

For cats that are otherwise well, we generally do not arrange a cardiology consultation or echocardiogram when the only finding is a grade 1/6 to 4/6 heart murmur and there is no arrhythmia or gallop rhythm.

As discussed above, when a cat with a heart murmur that we perform a NT-proBNP blood test on has a result that does not indicate stress or stretching, we will not pursue a cardiology consult.

Depending on the individual cat and the findings of the examining veterinarian, other investigations may still be recommended. These may be aimed at identifying conditions outside the heart that can produce a murmur, and could include checking blood pressure or testing for conditions such as hyperthyroidism or anaemia.

Will pet insurance cover a cat with a heart murmur?

Generally, a heart murmur that was present before an insurance policy was taken out will be considered a pre-existing condition. As a result, future veterinary treatment relating to the cat's heart may be excluded from coverage.

The precise exclusions applied to an individual policy can vary, so adopters should discuss this with their chosen insurance provider and establish exactly what will and will not be covered before purchasing a policy.

AID recommends pet insurance for all cats, even where particular conditions or aspects of their medical history are excluded from coverage.

If the cat has had an echocardiogram before adoption:

When a cat in our care has met our criteria for further cardiac investigation, we will arrange an echocardiogram as part of the cardiology assessment before the cat is adopted.

The results of the assessment will be documented by the veterinarian in a report and retained as part of the cat's medical records. This information will be provided to the adopter as part of the cat's medical history.

An echocardiogram provides information about the structure and function of the heart and can help establish whether an underlying cardiac condition is present.

If the heart murmur has not been investigated via echocardiogram:

Some cats with heart murmurs will be adopted without having undergone a cardiology consultation or echocardiogram.

In these circumstances, it is important that prospective adopters understand before making the decision to adopt that:

• A heart murmur has been detected;

• The reason for the murmur has not been established; and

• The future outlook (prognosis) for the cat cannot be determined based on the murmur alone.

The adopter can then discuss the situation with their own veterinarian and decide whether they wish to pursue additional investigations. Any further investigations arranged after adoption, including their associated costs, will be the responsibility of the adopter.