HCM in Cats: Heart Screening, Echocardiography and Genetic Testing Before Breeding

A breeding cat can look healthy, eat normally, play, win at shows and still have an early heart condition that cannot be identified from appearance alone.

One of the most important cardiac diseases in feline medicine is hypertrophic cardiomyopathy, usually abbreviated as HCM.

For a responsible breeder, understanding HCM is important not because breeders should diagnose heart disease themselves, but because breeding decisions may influence several future generations.

Pedigree analysis, breed type and genetic tests are valuable tools, but they do not replace appropriate veterinary examination of the breeding animal.

What is HCM in cats?

HCM stands for hypertrophic cardiomyopathy.

In affected cats, the muscular walls of the heart — particularly the left ventricle — become abnormally thickened.

This can make the ventricle less able to relax and fill normally with blood.

As the disease progresses, changes may also affect:

• the size of the left atrium;
• blood flow through the heart;
• heart rhythm;
• the risk of congestive heart failure;
• the risk of blood-clot formation.

The severity and progression can vary greatly between individual cats.

Why is HCM important in breeding?

A breeding animal may produce many kittens during its lifetime.

One popular sire can contribute genetically to dozens or even hundreds of descendants over several generations.

If a family has an increased hereditary susceptibility to a disease, repeated use of affected or high-risk animals may spread that susceptibility widely through a breeding population.

For this reason, cardiac health should be considered together with:

• pedigree analysis;
• genetic diversity;
• breed-specific DNA testing;
• general veterinary health;
• temperament;
• reproductive history;
• breed type and conformation.

Can a cat with HCM look completely healthy?

Yes.

Some cats with HCM show no obvious clinical signs, particularly during early or subclinical stages.

A cat may continue to eat normally, play, mate and behave exactly as expected.

This is one reason that visual assessment alone is insufficient for evaluating the heart of a breeding animal.

Does a normal heartbeat at a routine examination rule out HCM?

No.

A veterinary examination with a stethoscope is valuable, and murmurs, abnormal rhythms or gallop sounds can provide important clues.

However, not every cat with HCM has an obvious murmur.

Likewise, hearing a murmur does not automatically mean that a cat has HCM.

Further examination may be required to determine the cause.

What is an echocardiogram?

An echocardiogram, often called cardiac ultrasound or heart ultrasound, uses sound waves to create moving images of the heart.

It allows a veterinary professional to evaluate structures such as:

• heart-wall thickness;
• heart chamber dimensions;
• movement of the heart muscle;
• valve function;
• blood flow;
• the size of the left atrium;
• other structural abnormalities.

Echocardiography is the principal imaging method used to diagnose feline HCM.

Who should perform breeding heart screening?

When cardiac screening is being used for an important breeding decision, examination by a veterinarian experienced in feline echocardiography or a veterinary cardiologist provides the most useful information.

The quality of echocardiography depends not only on the machine, but also on correct image acquisition, measurement and interpretation.

A breeder should therefore consider both the test and the professional performing it.

Is “heart ultrasound normal” a permanent result?

No.

An echocardiogram describes the heart at the time of examination.

A normal result means that diagnostic criteria for HCM were not identified at that particular examination.

It cannot guarantee that the cat will never develop HCM later.

This is especially important for breeding programmes because some cats may develop detectable changes only as they mature.

Why repeated screening may be useful

Responsible cardiac screening is better understood as a programme rather than a single lifetime event.

Depending on breed, family history, age and veterinary recommendation, a breeding animal may require repeat evaluation.

The appropriate schedule should be decided with a veterinary cardiology professional rather than by applying one universal interval to every breed and every cat.

What is a DNA test for HCM?

For some breeds, specific genetic variants associated with increased HCM risk have been identified.

DNA testing can determine whether a cat carries the particular variant included in that test.

This information can be extremely useful in a breeding programme because DNA does not change with age and the result can help breeders manage known inherited risk.

However, the meaning of the result must be understood correctly.

Does a negative HCM DNA test mean that the heart is healthy?

No.

This is one of the most important points for breeders.

A genetic test answers a specific genetic question:

Does this cat carry the variant or variants analysed by this particular test?

It does not answer:

Does this cat currently have no form of HCM and will it remain free from HCM for life?

A cat can test negative for a known breed-associated HCM variant and still develop HCM for another genetic or currently unidentified reason.

DNA testing and echocardiography are not competing tests

The two methods provide different information.

DNA testing:

• examines selected inherited variants;
• can identify carriers of a known risk-associated mutation;
• does not directly show the current structure of the heart.

Echocardiography:

• examines the heart phenotype;
• shows its current structure and function;
• can identify cardiac changes regardless of whether a known DNA variant is present.

In breeds for which a validated HCM-associated DNA test exists, the information can complement cardiac screening rather than replace it.

HCM testing in Maine Coons and Ragdolls

Specific variants in the MYBPC3 gene have been associated with HCM risk in Maine Coon and Ragdoll cats.

These discoveries made breed-specific genetic testing possible.

However, breeders must understand that these are particular identified variants, not a universal DNA test for every possible cause of feline HCM.

A Maine Coon or Ragdoll with a negative result for the tested variant should not automatically be considered permanently “HCM free” without considering cardiac phenotype and family history.

What about other breeds?

HCM is not restricted to Maine Coons and Ragdolls.

The disease can occur in cats of many breeds and in non-pedigree cats.

Therefore, a breeder should not assume that cardiac screening is irrelevant simply because no commercial breed-specific DNA test exists for the breed.

The absence of a DNA test is not the same as absence of cardiac disease.

Do all breeds need exactly the same screening programme?

No.

Breed populations differ in documented risks, available genetic information, family history and breeding structure.

A sensible programme considers:

• the breed;
• the age of the cat;
• the family history;
• results from parents and relatives;
• previous cardiac findings;
• available validated genetic tests;
• veterinary recommendations.

Family history matters

A single normal test result should not cause a breeder to ignore information from relatives.

Useful questions include:

• Have either parent or grandparents been diagnosed with HCM?
• Did related cats develop heart disease later in life?
• Have there been unexplained sudden deaths?
• Are several related cats affected?
• At what ages were relatives screened?
• Were the results based on echocardiography or only DNA testing?

This information should be stored alongside the pedigree.

Why the age of tested relatives matters

A family history stating that a parent was “HCM negative” is incomplete unless the breeder also knows:

• how the animal was tested;
• at what age;
• when the test was performed;
• whether further examinations were performed later.

A normal examination at a young age and a normal examination later in adulthood provide different amounts of information about the family history.

Keep the original cardiac report

Do not preserve only a message saying:

“The cardiologist said everything is fine.”

For a breeding animal, save the actual veterinary report whenever possible.

A useful record contains:

• the cat's full registered name;
• microchip or other identification when available;
• date of birth;
• date of examination;
• name of the clinic or specialist;
• echocardiographic findings;
• conclusion;
• recommendation for follow-up when provided.

Identification matters during health testing

The value of any breeding-health result increases when it is clearly connected with the animal that was actually examined.

Where possible, the veterinary record should identify the cat accurately through its registered name, date of birth, registration details and permanent identification such as a microchip.

This is especially useful in catteries with several visually similar related cats.

Heart screening belongs in the breeding record

A professional breeding file can combine:

• pedigree;
• COI and repeated-ancestor analysis;
• DNA-test results;
• cardiac screening;
• breed-specific veterinary examinations;
• blood type where relevant;
• reproductive history;
• information about previous offspring.

No single document tells the whole story.

What if HCM is diagnosed?

A diagnosis of HCM is a medical matter and should be managed by the cat's veterinarian or veterinary cardiologist.

For the breeder, it also becomes important pedigree information.

The breeder should preserve:

• the confirmed diagnosis;
• age at diagnosis;
• identity of the affected cat;
• parents and offspring;
• information about affected relatives where known.

This information can influence future mating decisions and help identify patterns within a family.

Do not hide important health information

Responsible breeding depends on accurate records.

Removing an affected animal from public discussion does not remove its genetics from descendants already born.

Health information should be handled professionally and factually rather than emotionally.

A diagnosis is not a reason to blame an individual breeder automatically. It is information that should be used to improve future decisions.

Do not diagnose HCM from a pedigree alone

A pedigree can reveal relationships and help identify families that deserve additional attention.

It cannot show the thickness of the living cat's heart walls.

Likewise, the absence of an affected cat in the visible generations does not guarantee that HCM cannot occur.

Pedigree analysis and veterinary screening serve different purposes and work best together.

Do not diagnose HCM from a photograph or video

HCM cannot be confirmed from a picture of a cat, from the shape of its body or from a video showing how actively it plays.

A highly active cat can still have subclinical cardiac disease.

Diagnosis requires veterinary assessment.

Possible warning signs

Many cats have no obvious early signs, but cardiac disease can eventually be associated with serious symptoms.

Urgent veterinary assessment is especially important if a cat develops:

• laboured breathing;
• open-mouth breathing;
• collapse;
• marked weakness;
• sudden severe distress;
• sudden painful weakness or paralysis of the hind limbs.

These signs can represent emergencies and should not be managed through online advice.

HCM and arterial thromboembolism

Some cats with significant cardiac disease can develop blood clots.

A clot may obstruct blood supply to the hind limbs, causing sudden severe pain, weakness or paralysis.

This is an emergency requiring immediate veterinary care.

HCM and pregnancy

Pregnancy, delivery and lactation place additional physiological demands on a female cat.

If a breeding queen has a known or suspected cardiac problem, reproductive decisions should be discussed with an appropriate veterinarian.

Breeding should never take priority over the health of the queen.

HCM and breeding males

Heart screening is not only a concern for females.

A popular breeding male may have an especially large genetic influence because he can sire far more litters than one queen can produce.

For this reason, preserving health results and family information for males is particularly valuable to long-term population management.

Should breeders remove every carrier immediately from breeding?

Genetic management decisions should not be reduced to a single universal rule.

In breeds with a known risk-associated variant, the frequency of that variant, the genetic diversity of the breed, the individual cat's genotype and phenotype, and the availability of suitable unrelated animals may all matter.

Removing a large proportion of a small population in one generation can itself reduce genetic diversity.

Breeding strategies should therefore be evidence-based, breed-specific and aimed at reducing disease risk without unnecessarily creating a new population problem.

What should a breeder ask before a mating?

Before planning a litter, consider:

1. Has each parent had an appropriate veterinary examination?
2. Is cardiac screening recommended for this breed or family?
3. When was the last echocardiogram performed?
4. At what age was it performed?
5. Are original reports available?
6. Are validated breed-specific genetic tests available?
7. What do the results actually mean?
8. Is there HCM or unexplained cardiac death among close relatives?
9. Have previous offspring developed heart disease?
10. Is follow-up screening planned?

Build a health history, not a collection of certificates

The goal of health screening is not to accumulate attractive laboratory documents.

The goal is to understand the animal and its family more accurately.

A useful breeding history follows cats over time and connects:

identity + pedigree + health results + relatives + offspring + age.

Useful WCA resources

• WCA Pedigree Verification
• Order a WCA Pedigree
• WCA Litter Registration
• WCA Recognized Breeds and Breed Standards
• WCA Online Services

Responsible breeding looks beyond appearance

A show result describes how a cat was evaluated against a breed standard on a particular day. A pedigree describes ancestry. A DNA test can identify selected genetic variants. An echocardiogram evaluates the heart as it exists at the time of examination.

None of these tools replaces all the others.

When breeders combine pedigree knowledge, veterinary screening, genetic information and long-term records of relatives and offspring, they are able to make better-informed decisions for future generations.

The purpose of screening is not to search for a “perfect” cat. It is to make breeding decisions with more knowledge and less guesswork.

This article is educational and does not replace veterinary examination, echocardiography, diagnosis or individual advice from a veterinary cardiology professional.