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Cat cardiomyopathy: how to recognize and treat a cardiomyopathy?

Cat cardiomyopathy

Cat cardiomyopathy - which is what this enigmatic-sounding name means?

Nothing else but simply: "heart muscle disease ".

A disease that keeps cat breeders awake at night, especially the breed maine coon and ragdoll.

But does it only concern the cat aristocracy??

We learned from an article on heart failure in cats that myocardial disease can be broadly classified into primary and secondary cardiomyopathies.

Their further classification is based on anatomical and electrocardiographic changes and it is precisely depending on the type of predominant myocardial dysfunction that they are classified into one of several types.

I will describe briefly what some of the most common types of cardiomyopathy are characterized by, what symptoms accompany them and what the prognosis of a cat will be when it is diagnosed with the disease. I encourage you to read the entire article.

  • Primary cardiomyopathies
  • Hypertrophic cardiomyopathy in a cat
    • What happens to the heart in HCM?
    • What are the clinical consequences of cardiac hypertrophy?
    • When and how is the disease manifested?
    • Symptoms of hypertrophic cardiomyopathy in the cat
    • How to recognize a cat's hypertrophic cardiomyopathy?
    • Treatment of hypertrophic cardiomyopathy in cats
  • Dilated cardiomyopathy in a cat
    • Dilated cardiomyopathy symptoms
    • Dilated cardiomyopathy prognosis
  • Restrictive cardiomyopathy in a cat
  • Unclassified feline cardiomyopathies
  • Specific / secondary cardiomyopathies
  • Nutritional cardiomyopathy
    • Treatment of nutritional cardiomyopathy in cats
    • Prognosis of nutritional cardiomyopathy in cats
  • Metabolic cardiomyopathy in the cat
    • Symptoms of metabolic cardiomyopathy in cats
    • Treatment of metabolic cardiomyopathy in cats
    • Prognosis of metabolic cardiomyopathy in cats

Primary cardiomyopathies

This is a type of cardiomyopathy that cannot be explained by any tangible cause.

This means that heart disease appears first, and the symptoms manifested in its course are attributed exclusively to this disease entity.

It is not caused by disease of the valves, pericardium or coronary vessels, it is not caused by general or pulmonary hypertension, and there are no congenital heart defects or primary systemic diseases.

The fact is that most primary cardiomyopathies do not have an established etiology and are therefore called idiopathic.

As if they appeared "out of nowhere ".

Read on to learn which diseases belong to this group of heart diseases.

Hypertrophic cardiomyopathy in a cat

Hypertrophic cardiomyopathy in a cat

Hypertrophic cardiomyopathy (hypertrophic cardiomyopathy, hcm) is a disease of the heart muscle (especially of the left ventricle) in which there is a thickening of the ventricular wall and papillary muscles.

It is the most commonly diagnosed cat's cardiomyopathy, accounting for approx. 70% all heart diseases found in this species.

In most cases, the cause of its occurrence is unknown.

We only know that in some breeds of cats the disease is genetic. The fact of inheritance has been best studied in Maine Coons, where it is inherited as a dominant autosomal simple trait.

The same may be true for American shorthair cats. It is believed that in other breeds the disease may have a genetic background - they include:

  • Persian cats,
  • British shorthair,
  • Norwegian forest cats,
  • ragdoll,
  • Turkish van,
  • scottish fold fold cat.
Regardless of the fact that in purebred cats, cardiomyopathy is usually hereditary, but it is most common mixed breed domestic cats.

What happens to the heart in HCM?

In hypertrophic cardiomyopathy, there is a massive increase in the mass of the heart muscle (which may affect the whole heart or part of it) as a result of papillary muscle enlargement and left ventricular muscle thickening.

As a result, the lumen of the left ventricle may be reduced.

The walls of the heart become stiff, reducing their elasticity and contractility.

There are diastolic dysfunctions, and thus - the enlarged ventricle does not fill sufficiently during the heart's diastole.

The effect is catastrophic for both the heart and the organism as a whole:

  • less blood is pushed around the circumference with each contraction,
  • the blood flow through the coronary vessels deteriorates,
  • the heart becomes hypoxic.

All the changes bring about a picture of heart failure with a whole range of accompanying symptoms.

What are the clinical consequences of cardiac hypertrophy?

  1. Often in cats with HCM comes to appearance pleural fluid.
  2. Develops thromboembolism. Clots that break away from the left atrium flow with blood and become potential emboli. Usually, they stop at the end of the aorta, obstructing the circulation. As a result, blood flow to the pelvic limbs is blocked, which is associated with severe pain and the development of acute hind limb paresis or paralysis.
  3. Suddenly cardiac death - unfortunately, it can occur in every case and does not have to depend on the severity of the disease.

When and how is the disease manifested?

It all depends on whether cardiomyopathy is accompanied by heart failure.

HCM in cats can appear at any age, in both 6-month-old kittens and 16-year-olds.

Maine Coon cats typically develop severe HCM in males about 2 years old, while in females, the final maximum thickening of the heart walls usually occurs around the age of 3 years.

In hybrids, the average age of disease onset and the speed of progression of the changes vary.

However, it is significant that males get sick more often than females.

Symptoms of hypertrophic cardiomyopathy in the cat

Symptoms of hypertrophic cardiomyopathy in the cat

Cats with hypertrophic cardiomyopathy may be brought to the vet's office at very different stages of the disease.

  • Sometimes cats show no clinical symptoms at all and the disease is detected "by chance" during a routine clinical examination, e.g. before surgery. They may have mild to severe left ventricular hypertrophy (although with advanced hypertrophy, symptoms of heart failure are usually present). They are usually in good condition, young or middle-aged (peak incidence falls on 5 years old), mostly males.
  • In patients with severe HCM and moderate to severe heart failure, they come to the fore respiratory problemse (rapid breathing and / or shortness of breath). Usually they are caused by pulmonary edema or the presence of fluid in the pleural cavity (or both). Perceptive owners report that a few days before the appearance of clinical signs, their cat developed:
    • reluctance to eat,
    • he has become somewhat apathetic and too calm,
    • then there was difficulty in breathing, breathing became faster, and the kitten began to breathe through the open mouth (especially in times of stress or after exercise),
    • fainting can also happen,
    • coughing in cats is not a common symptom but can occur.
  • It also happens that the first motive for consultation in the office is paresis or pelvic limb paralysis. It is the result of the development of thromboembolism, and is characterized by an extremely painful paralytic condition the most common hind limbs. The sick animal pulls its hind legs behind it, cannot bend the ankles, and thus is unable to maintain the correct body position. The peripheral parts of the limbs are pale or blue, cold and very painful. The calf muscles often become hard, tense and painful. If the embolism has occurred in other blood vessels (mesenteric, kidney, cerebral vessels) - it causes severe pain and dysfunction of these organs. It is often accompanied by symptoms of congestive insufficiency:
    • dyspnoea,
    • loss of consciousness,
    • hypothermia.
Sudden cardiac death can occur in the course of cardiomyopathy, often without any prior clinical symptoms.

How to recognize a cat's hypertrophic cardiomyopathy?

How to recognize a cat's hypertrophic cardiomyopathy?

Before a diagnosis of hypertrophic cardiomyopathy is made, other conditions that may develop similar myocardial changes should be ruled out.

Diagnostics for cat cardiomyopathy include:

  • Full clinical trial. Myocardial disease may be indicated by:
    • the occurrence of heart murmurs,
    • gallop rhythm,
    • presence of suppressed or aggravated pulmonary murmurs,
    • hypothermia,
    • ripple or widening of the jugular veins.
  • Complete blood count, serum biochemical test, ionogram, determination of the level of thyroid hormones.
  • Radiological examination. The images of the chest in 2 projections show the enlargement of the silhouette of the heart.
  • Electrocardiographic examination - may indicate various types of arrhythmias.
  • Echocardiographic examination - decisive in the diagnosis of cardiomyopathy. It shows papillary muscle hypertrophy, various degrees of left ventricular wall thickening and (usually) left atrial enlargement.
  • Blood pressure measurement.
  • Genetic test. Studies on the inheritance of hypertrophic cardiomyopathy were carried out in two breeds of cats: maine coon and ragdoll. By performing a genetic test, the following results can be obtained:
    • Negative result N / N. This means that the cat is not a carrier of the mutation responsible for the development of HCM. However, since only two mutations have been tested and many more may contribute to the development of the disease (as in humans), a negative result does not mean that the cat will not develop cardiomyopathy.
    • Homozygous HCM / HCM. In this situation, the cat carries two copies of the mutant gene and is likely to develop the disease 18 times bigger than patient N / N.
    • Heterozgota N / HCM - the cat carries one copy of the mutated gene and the probability of developing the disease is 1.8 times bigger than the cat N / N.

Genetic testing is a good guideline for breeders, but is limited to two cat breeds only, and negative results do not rule out disease.

Treatment of hypertrophic cardiomyopathy in cats

Treatment of hypertrophic cardiomyopathy in cats

Hypertrophic cardiomyopathy is progressive disease.

This means that the changes in the remodeling of the heart will continue to worsen.

Unfortunately, there is no known treatment that can slow the progression of the disease.

Considering the cause of HCM in cats, treatment should in principle be either replacement of the damaged gene (by gene therapy), pharmacological correction of a protein defect caused by a mutation of that gene (substances that affect the receptors), or alteration of the internal environment of the heart muscle cells in some other way.

Unfortunately, the above methods are not yet available for HCM therapy.

Therefore, all therapeutic activities are aimed at alleviating clinical symptoms.

The decision to implement or modify the current treatment is not easy and depends on many factors, including.in.:

  • from the data obtained from the interview:
    • clinical symptoms,
    • cat activity,
    • family situation, etc.
  • on the speed of disease development, clinical complications, and response to current treatment,
  • on the time, financial (and other) possibilities of the owner,
  • from the patient's tolerance to taking medications.

Therefore, before starting treatment, the veterinarian must ask himself the following questions:

  • Is treatment necessary in the current situation?
  • Is the planned treatment safe?
  • Is the planned treatment effective??
  • Will the planned treatment be tolerated by the cat??
Treatment of asymptomatic patients causes the most clinical problems.

Treatment of the cat's hypertrophic cardiomyopathy should focus on the treatment of congestive heart failure and / or its complications.

These cats, with mild to severe HCM but no signs of heart failure, are often given medication, although there is really only a theoretical indication for pharmacological treatment.

Many veterinarians feel compelled to treat HCM even when the cat shows no clinical signs.

Is it justified? Unfortunately, there are no standardized studies that would outline detailed algorithms for the procedure.

Occasionally a cat has been diagnosed with a mild to moderate form of HCM that does not progress to severe.

In this case, it is questionable to administer the drugs once or twice a day for the rest of the cat's life, especially since there are no available data unambiguously confirming the legitimacy and effectiveness of such a procedure.

Therefore, all doubts are widely discussed with the owner, and depending on his expectations, life rhythm and possibilities, a decision is often made to implement the treatment.

The situation is completely different when the cat already presents symptoms of heart failure.

Then, the following groups of drugs are introduced into treatment (in monotherapy or combinations) with appropriate management:

  • Diuretics (furosemide).
  • Oxygen therapy.
  • Vasodilators (Nitroglycerin, angiotensin converting enzyme inhibitors).
  • Bronchodilators (aminophylline or theophylline).
  • Traffic restriction (cage).
  • Calcium channel blockers (Diltiazem, Cardizem, Dilacor XR, Cardizem CO).
  • Oral beta blockers (Atenolol).
  • Anticoagulants (aspirin, heparin).
  • Antiarrhythmic drugs (beta blockers or Diltiazem, lidocaine, procainamide).
  • Limit your sodium intake.
  • Other drugs (acepromazine, fluid therapy).

How the disease progresses and what symptoms to expect depends on several factors, including. in. from:

  • the current clinical picture and the stage of HCM,
  • the presence of signs of increased intracardiac pressure in echocardiography,
  • response to current treatment.

Generally speaking, it can be said that in cats with mild to moderate myocardial hypertrophy without left atrial enlargement and showing no clinical signs the long-term prognosis is good.

Usually such kittens survive on average 4-6 years.

If the left atrium is enlarged and the walls of the left ventricle are visibly thickened, the risk of developing heart failure is greater, and there is a high probability of developing heart failure thromboembolism.

It happens that cats with severe enlargement of the walls of the heart do not show clinical signs or signs of enlargement of the left atrium.

They also have a higher risk of developing the disease.

Perhaps the most important prognostic factor in cats is the presence or absence of heart failure.

With her presence, the prognosis worsens and the average survival time is approx. 3 months.

However, also here - in the event of a good response to treatment - patients may feel well for a longer period of time.

Prognosis in case of occurrence thromboembolism in the course of HCM is poor, and the average survival time is 2 months.

Cats who have had an episode of thrombosis may feel relatively well for a while, but the risk of relapse is high.

The symptom of HCM may be tragic sudden cardiac death.

Unfortunately, sudden death can occur in the course of cardiomyopathy, and sometimes it is the first and only symptom of the disease.

Dilated cardiomyopathy in a cat

Dilated cardiomyopathy in a cat

Until the late 1980s. last century dilated cardiomyopathy (dilated cardiomiopathy) was the most commonly diagnosed heart disease in cats.

Most of the cases were likely to be secondary deficiency cardiomyopathy taurine - an exogenous sulfuric amino acid that must be supplied to the animal with food.

Under natural conditions, taurine is present in high concentrations in rodent organisms.

Cats' predilection for hunting mice is therefore fully justified by the great wisdom of Mother Nature.

Unfortunately, the widespread introduction of commercial foods to cats initially did not take this into account and hence the frequent development of taurine deficiency cardiomyopathy.

Currently, manufacturers of commercial feed ensure the supply of this essential amino acid in their products, as a result of which the incidence of this disease has significantly decreased.

Currently dilated cardiomyopathy it is rare.

DCM is a disease of the heart muscle, especially of the left ventricle, characterized by primary heart failure.

However, before a cat is diagnosed with dilated cardiomyopathy, other causes of heart failure should be ruled out, including:

  • eating disorders,
  • metabolic causes,
  • toxic causes,
  • causes caused by volume overload or left ventricular ischemia.

The biggest problem in the course of this disease, manifested by a more or less severe clinical picture, is myocardial contractile failure.

As a result of this dysfunction, left ventricular dilatation, a decrease in stroke volume and cardiac output occurs.

As a consequence, symptoms of heart failure appear.

Dilated cardiomyopathy symptoms

The disease can appear at any age (from 5 months to 14 years), but is most often diagnosed in cats 7-8 years old.

Symptoms may be non-specific initially:

  • the cat becomes lethargic,
  • eats less,
  • avoids contact,
  • sleeps more.

The visible symptoms of heart failure are rapid breathing or dyspnoea resulting from pulmonary edema or the presence of fluid in the pleural cavity.

The development of general thromboembolism is also possible.

Dilated cardiomyopathy prognosis

If the diagnosis of dilated cardiomyopathy is made accidentally (during a routine examination) and the patient does not show clinical symptoms, he may survive several years, before full-blown congestive heart failure develops.

In symptomatic cats, the prognosis is very careful.

Such patients usually lose the fight against the disease shortly after diagnosis (on average 1-2 months).

As a rule, it develops with them cardiogenic shock, refractory to treatment congestive heart failure or thromboembolism.

Restrictive cardiomyopathy in a cat

In progress restrictive cardiomyopathy in the cat (restrictive cardiopyopathy, rcm) the filling of the heart is disturbed in diastole, while the systolic function of the left ventricle is preserved in most cases.

Its course most often involves endocardial, subendocardial or myocardial fibrosis, which results in the dysfunction of the diastolic function of the heart muscle.

This, in turn, can lead to development congestive heart failure.

The clinical symptoms are similar to those of other cardiomyopathies, but the prognosis is unfortunately it's bad and this even with a good initial response to treatment.

Cats usually survive from 4 to 6 monthsy.

Unclassified feline cardiomyopathies

Unclassified cardiomyopathies in cats (unclassified cardiomypoathies, ucm) are a wide variety of heart conditions in cats that do not qualify for HCM, DCM, or any other known heart condition.

They usually affect older cats, regardless of sex, race or age.

Clinical symptoms are similar to those seen in other heart conditions and prognosis is usually based on the patient's clinical status and response to treatment.

Specific / secondary cardiomyopathies

Secondary cardiomyopathies in cats

We are talking about them when the heart muscle disease and its dysfunction appear as a result of another cardiovascular or systemic disease.

In the diagnosis of heart disease in cats, it is very important to properly classify the underlying cardiac dysfunction.

This is mainly important because of the method of treatment.

For example - in cats with myocardial hypertrophy in the presence of hyperthyroidism, it is a mistake to diagnose hypertrophic cardiomyopathy even with the presence of typical changes.

Nutritional cardiomyopathy

Nutritional cardiomyopathy includes myocardial failure secondary to taurine deficiency.

As I mentioned earlier in the discussion of dilated cardiomyopathy, many of its cases were caused by the deficiency of this amino acid.

Today we know that DCM secondary to taurine deficiency is secondary cardiomyopathy, a supplementing this amino acid can reverse heart failure.

Little is known about the rare idiopathic DCM.

Currently, producers of commercial cat food supplement them with the addition of taurine, therefore the incidence of this disease has significantly decreased.

However, you should be careful in the selection of feeds - they may not contain enough of this amino acid (unless a study of a minimum duration of 6 months, which confirm that the product provides the appropriate concentration of taurine in the blood and tissues).

Taurine deficiency does not always lead to heart failure in cats.

However, when it does, the symptoms are very similar to those of other cardiomyopathies.

It can be very helpful in determining the cause of heart disease ophthalmological examination, in which it states central retinal degeneration (caused by taurine deficiency).

Generally speaking, it should be assessed in cats with diagnosed heart failure plasma taurine concentration.

There are cats fed a ready-made diet with the addition of taurine, which, however, does not cover the demand for this important ingredient.

Treatment of nutritional cardiomyopathy in cats

The treatment is twofold.

Initially, the patient is stabilized and treated symptomatically (if necessary, of course).

In parallel, cats with a known taurine deficiency are supplemented with this amino acid until the correct size of the left ventricle is found on echocardiography (usually within 4-6 months).

The patient usually feels much better after 2 weeks of supplementation.

Prognosis of nutritional cardiomyopathy in cats

The prognosis, as usual, depends on the stage of the disease.

In the case of full-blown heart failure, it is careful and largely depends on comorbid symptoms (hypothermia, thromboembolism).

In severe cases, the supply of taurine may unfortunately not be enough

If the patient survives about a week and responds to the treatment of the failure, the prognosis improves after 2 weeks to achieve the status of good.

In cats that respond well to taurine supplementation, clinical signs disappear.

Metabolic cardiomyopathy in the cat

Metabolic cardiomyopathy: which cats are at risk?

This group includes:.in. heart disease caused by the toxic effect of thyroid hormones.

Thyroid hormones in the course of hyperthyroidism affect the heart directly and indirectly, causing the following dysfunctions:

  • tachycardia - the heart breaks very quickly,
  • myocardial hypertrophy,
  • increased contractility of the heart muscle (it contracts faster and the strength of each contraction is greater),
  • Heart arythmia.

All these factors lead to a "strain" of the heart muscle and force it to work more.

Eventually, symptoms of congestive heart failure and high blood pressure may appear.

Metabolic cardiomyopathy in cats symptoms

The disease mainly affects older cats. This is due to the presence of hyperthyroidism, which usually occurs in elderly cats.

Race and gender do not contribute to the onset of the disease.

Usually, the patient is presented to the doctor for non-cardiac symptoms:

  • the cat drinks a lot,
  • he often urinates,
  • he eats a lot and loses weight.

Sometimes, however, the symptoms of heart failure come to the fore.

Treatment of metabolic cardiomyopathy in cats

Treatment is both causal (stabilization of hyperthyroidism) and symptomatic (treatment of DSN).

Prognosis of metabolic cardiomyopathy in cats

Patients who do not show cardiac symptoms do well after the initiation of thyroid treatment.

In those with heart failure, the prognosis depends on its stage.

Most cats respond well to treatment, but if the failure is severe the changes are irreversible and the prognosis is bad.


Myocardial diseases are now diagnosed much more often than they used to be.

Certainly, this is partly related to the dynamic development of diagnostics, but it is possible that there has been an actual increase in the number of heart diseases.

The increased awareness of cat owners, who subject their pets to routine clinical examinations much more often, also has a huge impact on recognition.

If you want to know more about cat cardiomyopathy, post a comment below the article. I will answer your questions as soon as possible.

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