Now there’s a good question! Albeit, not one with an easy answer…
Firstly, we should remember that there is a difference between heart disease (a structural or functional change to the heart) and heart failure (a state where they show clear symptoms, arising from inadequate blood flow from or towards the heart).
Heart failure that arises secondary to an underlying heart disease will be overtly obvious as we will discuss below. However, prior to the state of heart failure – as experienced cat owners will know – this elusive species may typically “hide” their heart disease, as they do with many other medical illnesses. A cat with heart disease may therefore appear outwardly normal.
Why is this?
Cats can have asymptomatic heart disease
Which means that cats can suffer with moderate or severe heart disease yet show NO outward symptoms. Dependent on the nature of this disease, some cats remain symptom-free yet others may develop catastrophic heart-related events. Due to this asymptomatic state a cat with heart disease may behave and act normally at home with you their owner. Neither will they have any audible (auscultated) abnormal findings when the Vet checks their hearts at clinical examination.
Unfortunately, this makes life really difficult. In these cats, we have no reason to suspect their heart disease until the first signs of heart failure are present. These signs can be dramatic – as an episode of congestive heart failure (CHF), feline aortic thromboembolism (FATE – a clot forming an obstruction within the aorta) or even, sadly, sudden death in a young animal. Such signs may come out of the blue with no prior warning.
Some cats with heart disease do give us clues however. These clues are usually picked up on a routine check, such as at vaccination. Your vet may hear a fast or (less commonly) slow heart rate (tachycardia / bradycardia), an abnormal heart rhythm (arrhythmia – particularly a “gallop” rhythm) or abnormal heart sound (murmur). Such abnormalities, particularly if persistent, always warrant further investigation.
“But my cat has had a heart murmur for years”
Another complicating factor with cats is that some cats will have what we describe as an “innocent” heart murmur. This means they have a benign murmur. Whilst we hear abnormal sounds, this does not always relate to significant change within the heart. A diagnosis of an innocent heart murmur, however, can only be made following an ultrasound (echocardiogram) of the heart.
Furthermore, and again, making life more difficult for us (!) is the fact that cats may develop a heart murmur as a symptom of a separate disease within the body. Hyperthyroidism and hypertension (high blood pressure) are frequently seen examples. It may therefore be the case that a middle or older aged animal that develops a new heart murmur, warrants additional testing such as thyroid hormone and blood pressure measurements as part of their heart workup.
To try and summarise… Firstly, your cat can have heart disease and have no abnormal audible heart sounds / rhythms. Secondly, a heart murmur may reflect one of many things. Either an innocent murmur, significant structural or functional heart disease or another disease process altogether.
See why it’s difficult?!
Cats are NOT small dogs
As vets, we acknowledge indeed that “cats are not small dogs.” Nowhere is this clearer than with their symptoms of heart failure. Whilst dogs show exercise intolerance and possibly a cough as part of their symptoms, these are simply not seen with cats. Cats maintain more control over their lifestyle and regulate their own energy expenditure carefully. A cough in a cat more typically reflects airway or chest cavity disease.
Both species however, would have weakness and difficulty breathing in heart failure. Increased respiratory rate and respiratory effort are seen. Recognising such changes to breathing however, may be subtle signs and difficult to appreciate to the untrained eye.
So what are the particular symptoms of heart disease or failure in cats?
As mentioned above, cats with heart disease may often show no outward signs. Your vet will be the one who picks up abnormalities upon listening to the heart and may recommend further investigations.
Unfortunately for some, sudden death, feline aortic thromboembolism (FATE) and congestive heart failure (CHF) may be the first symptoms seen in cats with advanced heart failure.
FATE is a devastating consequence of heart disease and results from a clot having moved from where it formed within the heart, to the division at the end of the aorta (the major artery in the body). The “thrombo-embolus” (clot) typically lodges where the aorta splits, such that blood flow to the hindlimbs is compromised or altogether prevented. This causes a quick onset, severe level of pain in the hindlimbs. In addition, pale and cold feet, poor pulses and hindlimb paralysis are common. Owners may confuse symptoms with those of an injury such as a road traffic accident. Unfortunately, the prognosis for FATE cases is very poor, with minimal response to supportive therapy and / or, subsequent repeat embolic events.
Congestive heart failure (CHF) typically causes the cats distress and difficulty breathing. Cats may adopt changes in both posture or sleeping habits initially, to try to accommodate for this. Fluid may either accumulate diffusely within the lung tissues (as pulmonary oedema) or within the chest cavity itself (pleural effusion).
So what types of heart disease are there in cats?
By far and away the most common heart disease in cats is HCM – hypertrophic cardiomyopathy; literally translated this means thickening of the muscles of the heart. Along with this thickening of the ventricles (the strong pumping chambers of the heart), dilation of the atrial chambers (the collecting chambers) may also be seen.
The degree of this dilation of the left atrium (LA), along with velocity of blood flow in the chamber are the main factors which impact prognosis.
Rarer forms of heart disease include DCM (dilated cardiomyopathy), RCM (restrictive cardiomyopathy) and ARVC (arrhythmogenic right ventricular cardiomyopathy).
If HCM is found, what is the prognosis?
Essentially, the greater the degree of heart enlargement, the increased the risk for further problems. Based on the ultrasound findings, your vet may advise starting anti-clotting medication and diuretics for your cat. Further medications will vary on a case by case basis.
What should I do if my vet has detected a heart murmur in my cat?
As mentioned above, should your vet find any audible abnormalities on examination, a heart workup is advised. In the best-case scenario, your cat may be found to have an innocent murmur and your mind will be put at rest.
Heart disease such as HCM may be detected; that said, this has the potential to be a relatively benign diagnosis if no heart dilation is noted. Certainly, some cats with HCM may never develop clinical signs.
In the unfortunate event of more severe heart disease being discovered, your cat will usually have a better prognosis and outlook by starting treatment sooner.For further information, please take a look at International Cat Care’s pages on Cardiomyopathy.