HCM in cats and pet insurance: the gene test, the murmur, and the record that decides the claim

A disease that is often silent, which is why the paperwork matters

Three facts from veterinary references shape every HCM claim. The first is that many affected cats look healthy. Cornell University's Feline Health Center (updated May 2025) says "Many cats with HCM do not appear to be ill", and the Merck manual, in its professional chapter by a University of California, Davis cardiologist (last updated September 2024), says many cats with mild to moderate disease have no clinical signs. The second is that the usual screening clue is unreliable in both directions. Merck: "A heart murmur is not present in at least one-third of cats with HCM." A cat can have the disease without a murmur, and a murmur on its own does not establish the disease. The third is that only one test settles it. Merck says "Echocardiography is required to make a definitive diagnosis of HCM", and Cornell calls echocardiography the gold standard.

Cornell adds a step that matters for the claim file: "similar heart thickening is also caused by other common conditions, including high blood pressure and hyperthyroidism", and those must be ruled out before HCM is diagnosed. An older cat with a thickened heart may be on the way to a thyroid diagnosis instead, which produces a very different claim; the hyperthyroid cat guide sets out how those four treatment routes are billed. Blood pressure checks, thyroid tests and the echo itself will all appear on the invoice and in the record, whichever diagnosis results.

Age gives little protection either. Merck says the disease occurs in cats from 6 months to 17 years old, with most cats middle-aged at presentation, and that male and female cats are equally predisposed although males tend to develop more severe disease at an earlier age. So a kitten enrolled at 10 weeks has usually cleared its waiting period long before the condition is likely to be found, while a cat enrolled at six has spent years in which a sign could have been recorded. Cornell describes the outlook as variable: cats without clinical signs may live for years, while congestive heart failure, thromboembolism and hypothermia point to a worse prognosis. Merck puts median survival for cats in heart failure at 3 months. That spread, from no bills for a decade to one emergency followed by a short and expensive course, is the range a policy has to be read against.

Breeds the veterinary references name

Breed is not a diagnosis, and HCM occurs in mixed-breed cats too. But insurers and owners both reason by breed, so it is worth seeing exactly what the two references say rather than relying on a listicle. Neither source ranks the breeds by risk, and the table does not either.

Cornell Feline Health Center, Hypertrophic Cardiomyopathy (updated May 2025); Merck Veterinary Manual, Hypertrophic Cardiomyopathy in Dogs and Cats (full review January 2023, updated September 2024). Merck also says penetrance "is often < 100%": not every cat that inherits a disease-associated variant develops the disease.

The genetic test exists only for specific mutations in specific breeds, which is why the rest of this guide spends so long on it. For a British Shorthair, a Sphynx or a mixed-breed cat there is no comparable DNA result to worry about; the record that matters is the exam and any imaging.

The words in the policy that a heart finding has to pass

Every policy decides an HCM claim with the same two questions. Is heart disease of this kind covered at all, or excluded as inherited? And did the condition exist, or show itself, before cover began? The documents read for this guide answer those questions in different words, and the words matter more than usual here, because a genetic result is not obviously a sign, a symptom, advice or treatment. The table sets them side by side.

Quoted from each document. Sample policies are single-state examples and your own declarations page and policy form govern. None of the seven documents mentions a feline HCM genetic test by name.

Read down the middle column and a pattern appears. Six of the seven tie pre-existing status to something observed: a sign, a symptom, an irregularity noticed, advice given or treatment received. One, the AKC sample, adds the word "existed", whether or not diagnosed. That single word is the widest net in the table, and it is the one a DNA result is most likely to be argued under. The broader mechanics of these definitions are compared in the pre-existing conditions guide, and the way inherited wording is drafted is in the hereditary and bilateral exclusions guide.

For a Maine Coon or Ragdoll, the inherited exclusion is the clause to settle first. A form that excludes inherited conditions, bought without the hereditary add-on, can leave HCM inside that exclusion, which an owner otherwise discovers at the first heart claim.

Six records a cat might carry into a policy, and how the wording reads them

This is the decision table owners of HCM-prone breeds usually cannot find. Each row is a record that exists before enrollment, and the reading applies the cited wording to it. It is not a prediction of how any insurer will rule, because none of the documents addresses these exact facts, and the Model Act (Section 5A) puts the burden of proving that a pre-existing exclusion applies on the insurer.

Two cautions apply to every row. First, records travel. Healthy Paws asks for the full medical history with the first claim, Fetch asks for the year before sign-up, and Embrace reviews 12 months, so a test result that sits in a clinic file will be read. Second, none of this is a reason to avoid examinations or tests. A record can exclude a condition, but it is also the only evidence that a heart was normal on a given date, and that evidence is what makes a later diagnosis payable.

Reading the gene test itself

The DNA test answers a narrower question than owners often think. It looks for one specific variant known in one breed. Merck describes the Maine Coon finding in terms of genotype: cats homozygous for A31P, carrying two copies, are primarily the ones that develop clinically important HCM, and it says penetrance in familial HCM is often below 100 percent. Cornell puts the practical consequence in one sentence: the results "should be interpreted carefully with the guidance of a veterinary professional, since not all cats that have these mutations will develop the condition."

From an insurer's side, that uncertainty is the point. A positive result says the cat's risk is raised; it does not say the heart is thickened. The Model Act's three triggers (advice, treatment, signs) are built around the condition as it shows itself, which is why the signs-based forms in the table above are hard to stretch to a genotype. The Spot sample's definition of "condition" does mention conditions that "may or may not show symptoms or have been diagnosed", but its pre-existing test still turns on when the condition first "occurs", and "occur" is defined by signs or symptoms. The AKC sample is the exception worth reading twice, both for "existed" and because its inherited exclusion takes HCM out of the base policy whatever the test says.

The test is also a bill the policy usually will not pay. Embrace lists "DNA testing or cloning" among its exclusions, and genetic screening of a healthy cat is preventive by nature, which the Spot sample excludes as preventive care without an occurrence unless an endorsement applies. If a breeder has already tested the parents or the kitten, that certificate costs you nothing more; if you are deciding whether to test, it is a cost you carry and a record you create, and both are worth knowing about before the policy starts. For dogs, the dog DNA test guide reads nine policy forms for what a genetic result and the cost of the test count as.

Two misreadings follow from that. A negative DNA result is not a clean heart: the test covers one variant, and Merck lists HCM as familial in breeds that have no test. And a breeder's "HCM negative" line is not an echo result. A genetic result and an imaging result answer different questions, and only the imaging report dates the heart as normal.

Murmurs, kitten exams and the "detectable" clause

Most HCM paperwork starts with a stethoscope. A murmur or a gallop heard at a vaccination visit is noted, and the next steps, a referral or an echo, follow in weeks or months. For insurance, the date of the note is what counts. The Spot sample goes further than most: a condition occurs when signs were observed by anyone, recorded, "or would have been detectable by a routine physical veterinary exam." In principle, a murmur first heard in month three of a policy could be argued back to before the start date if it would have been audible then. In practice, the insurer has to show it, and the Model Act puts that burden on the insurer. Dog owners meet the same clause with mitral valve disease, where a murmur can sit in the record for years before any treatment; the canine mitral valve guide follows those years from the first murmur to heart failure.

Some insurers make an early exam part of the bargain. Healthy Paws says that for pets 5 years old and under "an exam must have taken place within 12 months prior to enrollment", or within 15 days after the policy effective date. The Model Act requires an insurer that makes an exam a condition of coverage to disclose, before purchase, that "examination documentation may result in a preexisting condition exclusion" (Section 4F). That is a fair warning, not an argument for skipping the exam. A clean, dated exam is the baseline every later claim is tested against, and for a breed whose disease is often silent, it is one of the few documents that speaks for the cat.

If a murmur is heard during the waiting period, the timing is unlucky on any form: signs that first appear during a wait are pre-existing under the Model Act definition and every document in the table. Waiting periods for illness run from 5 days on the AKC sample to 14 on the Spot sample, and the waiting periods guide lays out more schedules on one scale. Many kittens are enrolled at the same visit that produces their first full exam, which means the first heart check can fall inside the wait. The remedy is on the enrollment side, not the exam side: buying the policy as early as possible, ideally when the kitten comes home or before, lets the wait run on its own while every exam stays on the schedule the veterinarian sets.

Chronic, one incident, and the clauses for a disease that does not end

HCM has no cure. Cornell says so plainly ("HCM has no known cure"), and describes treatment as a care plan to manage signs: controlling heart rate, relieving lung congestion and preventing clots. That puts it in the chronic category on every form that has one. The Model Act defines a chronic condition as one "that can be treated or managed, but not cured", the Spot sample uses the same words, and Healthy Paws lists heart disease among conditions needing ongoing medication that it does not consider cured. Three consequences follow.

• Renewal is the clause to secure. The Model Act says a condition covered on a policy "cannot be considered a preexisting condition on any renewal of the policy." The Spot sample warns that coverage and rates are subject to change at renewal. Ask how the policy treats a covered chronic condition at renewal and whether the insurer may decline to renew.
• Switching becomes costly. Once HCM is in the record, any new policy reads it as pre-existing, and none of the chronic definitions above lets it be cured back into eligibility. The switching guide works through what restarts.
• The diagnosis must be complete. The AKC sample says a claim "where a final diagnosis has not been made will be pended as ineligible" until the veterinarian sends a definitive diagnosis. Because Merck says echocardiography is required for a definitive HCM diagnosis, a heart workup that stops at a murmur and X-rays may sit unpaid until the echo is done.

Food and medication terms matter too. The Spot sample pays for prescription medications approved by the FDA and prescribed by a veterinarian, and for prescription food only for a covered condition. Not every daily drug comes from the clinic: a cat with asthma can be treated with a human inhaler filled at a pharmacy, and the cat asthma insurance guide tests that fill against five sample medication definitions. A cat with heart disease and a second chronic problem, kidney disease being common in older cats, will generate two streams of bills against one annual limit. The cat kidney disease guide shows how a multi-year kidney claim uses up a limit on its own.

Limits deserve the same scrutiny. For a lifelong disease, a per-incident or per-condition limit that does not reset can run out while the cat still needs treatment, and a policy allowed to lapse after a murmur is noted hands the next insurer a pre-existing note.

The emergency night: a clot or heart failure

For many owners the first sign of HCM is not a murmur but an emergency. Cornell describes the clot: a serious consequence of HCM is the formation of blood clots in the heart, which "most commonly result in blockage of blood flow to the hind limbs, causing acute hind limb pain or, in extreme cases, hind limb paralysis." Merck says cats with systemic thromboembolism most commonly show an acute onset of hind limb paresis or paralysis. Heart failure presents differently, with the labored, rapid or open-mouthed breathing Cornell describes. Both are illnesses, not accidents, so they are covered only after the illness waiting period and only if nothing related was on record before.

The bill from that night is built like other emergency invoices: an emergency exam, imaging, oxygen or medication to stabilize, hospital time, then the diagnostic echo once the cat can tolerate it. The emergency vet bill guide lists the lines and which of them a policy usually repays, including whether the emergency exam fee itself is covered. Two clauses are particular to this situation. Because outcomes after a clot or heart failure can be poor, families sometimes face an end-of-life decision within days. The Spot sample covers end-of-life expenses, defined as euthanasia, burial and cremation only, and the AKC sample covers euthanasia when advised by a veterinarian to alleviate suffering. And because the emergency often happens before any diagnosis, the date of that visit becomes the date of first sign for everything that follows.

Merck notes that clopidogrel is the only drug shown to decrease the incidence of systemic thromboembolism in cats. That is not advice for any cat. For insurance purposes it means a cat at risk may be prescribed a daily medication for years, which is exactly the chronic-medication pattern the clauses above are written for.

Before enrolling a Maine Coon, Ragdoll or another named breed

Gather the documents first, then ask the questions in writing. The answers are worth more than any premium difference between two quotes.

1. Collect every record: breeder health certificates, any DNA result for the parents or the kitten, every exam note, and any echo report. This is what the insurer will read with the first claim.
2. Check whether the form excludes congenital and inherited conditions, and if so what add-on restores them and what its own waiting period is.
3. Ask, in writing, whether a positive DNA result with a normal exam will be treated as a pre-existing condition, and whether a normal echo would change the answer.
4. Ask whether the policy has a per-incident, per-condition or lifetime limit, and whether any limit resets at renewal.
5. Note the end date of every waiting period on enrollment day. Enroll as early as you can so the wait runs out by itself, and keep every exam on your veterinarian's schedule.
6. Keep the declarations page, the written answers and the first clean exam record together, and read the indoor cat guide for the wider decision of whether a policy beats saving for this cat.
7. Get a live quote before deciding; this site publishes no cat premium figure to judge it against, so compare quotes on the clauses above.

With the records and written answers in hand, the claim payout simulator will run an echo and a year of heart medication through your own deductible and limit. The cat guides hub collects the other feline claim files, from teeth to thyroid.