HCM in Cats: What a Murmur Misses, How Echo Screening Works, and What It Costs in India

Signs of Hypertrophic cardiomyopathy in cats

The 10 signs to watch for are listed below. Any one of them is a reason to consult your nearby vet; none of them is a diagnosis.

• No signs at all, which is how most affected cats are living right now
• Faster or harder breathing at rest, often the first change an owner sees
• Open-mouth breathing or panting, which is never normal in a resting cat
• A sleeping breathing rate that stays above 30 breaths a minute
• Sudden weakness or dragging of one or both back legs, with loud crying
• Cold back paws, with pale or blue nail beds and no femoral pulse
• Hiding, going off food, or a quiet drop in activity with no other cause
• Fainting or a brief collapse, then getting up again
• A murmur, a gallop sound or an irregular rhythm found at a routine check-up
• Muffled heart or lung sounds, from fluid around the lungs

Breeds on this site that document this condition

Each breed page below carries the figure for this condition with its denominator and its source. The 7 breeds listed are the ones on this site that document it, not a ranking of risk.

What HCM in cats is, and how many cats actually have it

Hypertrophic cardiomyopathy in cats is a thickening of the left ventricular muscle that stiffens the pump and, in a minority of cats, ends in heart failure, a blood clot or sudden death. In the largest screening study of apparently healthy cats, 14.7 percent of 780 cats had it, with a 95 percent confidence interval of 12.3 to 17.4 percent.

The disease is common and mostly silent. The ACVIM consensus panel puts the estimated prevalence at approximately 15 percent in the general cat population, and records that in older cats the prevalence is much higher, with up to 29 percent reported affected even when cats with hypertension and hyperthyroidism are excluded. Most affected cats have subclinical disease, and the same panel attaches a 5-year cumulative incidence of cardiac mortality of approximately 23 percent, independent of age at diagnosis.

The 2021 Journal of Feline Medicine and Surgery review reaches the same place from the clinic floor. It describes HCM as the most common form of feline cardiomyopathy observed clinically, affecting up to approximately 15 percent of the domestic cat population primarily as a subclinical disease, with severe disease leading to heart failure or arterial thromboembolism in only a small proportion of those cats. The Purina Institute states the same dominance as a share of the cardiomyopathies, saying HCM accounts for more than 50 percent of feline cardiomyopathies.

The figure most owners actually meet is the rounded one. The MSD Veterinary Manual says hypertrophic cardiomyopathy is the most common heart disease of cats, affecting as many as one in seven, with the vast majority of cases subclinical, and PetMD opens with the same framing, that as many as 1 in 7 cats will develop HCM at some point in their lives and most show no symptoms in the early stages. One in seven is 14.3 percent, which is the CatScan measurement rounded to a fraction, so the popular number does have a real study under it even on pages that never name one.

Where the CatScan denominator comes from

The CatScan study is why the 15 percent figure has a real denominator under it. Over 17 months, 1,007 apparently healthy cats aged six months or older and available for rehoming at two centres were weighed, body-condition scored, auscultated, blood-pressure tested and echocardiographed, with hypertensive and hyperthyroid cats excluded, and complete data were obtained in 780 of them. A left ventricular end-diastolic wall thickness of 6 mm or more on two-dimensional echocardiography was the threshold for calling a cat affected.

Everything else in that population was rare by comparison. Congenital disease came in at 0.5 percent, 95 percent confidence interval 0.1 to 1.3, and other cardiomyopathies at 0.1 percent, 95 percent confidence interval 0.0 to 0.7. HCM prevalence rose with age, and male sex, increasing age, increased body condition score and a heart murmur, particularly one graded III out of VI or louder, were the factors associated with a diagnosis in the binary logistic regression models.

Body condition is the only item on that list an owner controls. A Tehran referral study of 7,013 cats identified adult age with an odds ratio of 5.70 and high body condition score with an odds ratio of 4.05 as significant predictors of an HCM diagnosis. Being overweight does not cause a sarcomeric heart disease, and it sits on the risk list of two separate populations, which is reason enough to read obesity in dogs and cats alongside this page.

Fifteen percent and half a percent are both correct

The forty-fold spread in that table is a spread in populations, not in cats. The Indian figure is the clearest illustration. Of 2,872 cats presented to the Super-Speciality Veterinary Hospital at Sri Venkateswara Veterinary University in Visakhapatnam between April 2024 and March 2025, 164 with signs of cardiac disease were examined physically and by electrocardiography, echocardiography, pulsed-wave Doppler and haemato-biochemical analysis, and 10 were diagnosed with HCM and 6 with restrictive cardiomyopathy.

That produced an overall cardiac-disease prevalence of 0.56 percent across everything that walked through the door and 9.76 percent within the 164 cats actually screened. Neither figure contradicts the 14.7 percent from CatScan, because CatScan put a probe on every cat and the Indian hospital put a probe only on cats whose owners had already noticed something. The gap between those two numbers is the disease sitting undiagnosed in cats nobody has scanned.

Age changes the answer more than anything else on this page. One rehoming-centre population in the UK reported up to 29 percent of cats aged over 9 affected, which is the figure a 2025 case report cites when it opens on prevalence. In the Indian caseload, cardiomyopathy was most common in cats aged 5 to 10 years, 75 percent of the affected cats, with 68.7 percent male and 81.25 percent weighing 3 to 5 kg.

The murmur problem, and why a stethoscope is a weak test for HCM

A heart murmur predicts HCM correctly between 17.9 and 42.6 percent of the time, higher in old cats, so most cats with a murmur do not have the disease and no stethoscope can be the screening test. This is the single most useful thing on this page, and not one of the six ranking pages opened today prints it.

Murmurs are ordinary in healthy cats. In the CatScan population the prevalence of heart murmurs was 40.8 percent, with a 95 percent confidence interval of 37.3 to 44.3 percent, and 70.4 percent of those murmurs were considered functional. Two cats in five had a murmur and roughly one in seven had HCM, which is the whole arithmetic of why the finding is weak.

The test is better at ruling the disease out than at ruling it in, and even that is conditional. The negative predictive value of a murmur ran from 90.2 to 100 percent, higher in young cats. Read the bottom of that range against an old cat and roughly one quiet chest in ten still holds the disease.

The consensus statement describes the same weakness in clinical terms. A parasternal systolic heart murmur has been reported in up to 80 percent of cats with subclinical HCM, compared with 30 to 45 percent of healthy cats without it, and gallop sounds in 2.6 to 19 percent of cats with subclinical HCM, while many affected cats have no auscultatory abnormality at all. The panel's recommendation is therefore not to screen by listening. It is that further investigations are recommended if a heart murmur is detected in any cat.

A louder murmur is not a worse heart. A loud systolic murmur of grade 3 to 4 out of 6 is more common in cats with HCM than in normal cats, but an increase in heart murmur intensity over time does not necessarily indicate the presence or worsening of disease, and a palpable thrill of grade 5 to 6 out of 6 seldom means cardiomyopathy and is more likely to mean a congenital malformation.

A silent chest is the worse finding, not the better one

The absence of a murmur was a univariable predictor of an increased risk of cardiac death among 282 cats with HCM seen at the Royal Veterinary College between 2004 and 2009. The Purina Institute puts the finding in one line, that many cats with HCM have no heart murmur, gallop sound or arrhythmia, and that cats with HCM but no murmur have an increased risk of cardiac mortality. Cats with more advanced disease, and cats with restrictive or dilated phenotypes, may have no audible murmur at all.

One breed demonstrates it with a clean denominator. No murmur and no left ventricular outflow tract obstruction was found in any of 53 Norwegian Forest cats examined prospectively, and yet mild left ventricular hypertrophy was present in 13 of those 53 cats, 25 percent. A whole screened cohort of a predisposed breed was silent on auscultation and a quarter of it had thickened muscle.

The one breed where a murmur is worth acting on

The Royal Veterinary College's Birman study found heart murmurs more common in Birmans with cardiomyopathy than in healthy cats, and concluded that any Birman cat with a heart murmur should be investigated further for heart disease with echocardiography, while noting in the same paragraph that heart murmurs are not always a reliable indication of heart disease in other breeds. The value of the finding is breed-dependent, and the safe default for every other cat is that a stethoscope is a prompt, never an answer.

The practical instruction is short. Treat a murmur as a reason to book an echocardiogram, treat no murmur as no information, and do not let a clear auscultation at a vaccination visit stand in for a scan in a Maine Coon, a Ragdoll, a Sphynx or a Persian.

Sudden death, saddle thrombus, and the signs that mean go now

Take a cat to a veterinarian the same hour if it suddenly cannot use its back legs, cries out, has cold back paws with pale or blue nail beds, or is breathing fast or with its mouth open. Those are the presentations of arterial thromboembolism and congestive heart failure, the two complications that turn a silent disease into an emergency.

A clot forms in the enlarged left atrium, leaves the heart and lodges where the aorta divides, which is why the classic presentation is the back half of the cat. Cornell describes clots in cats with HCM most commonly blocking blood flow to the hind limbs, causing acute hind limb pain or, in extreme cases, hind limb paralysis. Among 127 cats reviewed with arterial thromboembolism at the University of Minnesota, tachypnoea was present in 91 percent, hypothermia in 66 percent and absent limb motor function in 66 percent.

The disease behind the clot is usually the heart. Of the 90 cats in that series with diagnostics performed, the underlying diseases were cardiomyopathy in 65, made up of 33 unclassified, 19 hypertrophic, 8 dilated and 5 hypertrophic obstructive, with hyperthyroidism in 12, neoplasia in 6, other conditions in 4 and none identified in 3. Left atrial enlargement was present in 93 percent, congestive heart failure in 44 percent and arrhythmias in 44 percent. Abyssinian, Birman, Ragdoll and male cats were overrepresented.

What actually happens to cats with a saddle thrombus

The general-practice numbers are bleak and they are worth knowing before the night happens. Over 98 months across three UK general practices, 250 cats were identified with arterial thromboembolism, a prevalence of approximately 0.3 percent, and 153 of them, 61.2 percent, were euthanised at presentation. Of the 97 that were not, 68, or 70.1 percent, survived more than 24 hours, and of those 68, 30, or 44.1 percent, survived at least 7 days.

Cats that get past the first week can do far better than the first night suggests. For cats that survived 7 days or more, median survival was 94 days with a 95 percent confidence interval of 42 to 164 days, and 6 of the 250 cats were alive a year after presentation. In the Minnesota series, 39 of 87 cats treated for acute limb thromboembolism, 45 percent, survived to be discharged, with a median survival of 117 days after discharge.

Body temperature is the closest thing the literature has to a dial. A logistic regression model based on rectal temperature predicted a 50 percent probability of survival at 37.2 degrees Celsius, and temperature separated survivors from non-survivors more strongly than any other variable tested. In the UK practice data, hypothermia carried a hazard ratio of 1.44 for euthanasia or death within 24 hours, and failure to receive an antiplatelet drug carried a hazard ratio of 8.26 for euthanasia or death within 7 days among cats that survived the first day.

How often cats actually die suddenly

Sudden death is the fear, and it is the rarest of the three cardiac deaths. Among 255 cats with HCM followed for two years at a veterinary teaching hospital, 44 of 255, 17.3 percent, died with congestive heart failure, 23 of 255, 9.0 percent, died with arterial thromboembolism, and 12 of 255, 4.7 percent, died suddenly, while 141 of 255, 55.3 percent, were still alive at the end of two years.

No multivariable model could be built for sudden death because the event rate was too low, but syncope at presentation and arrhythmias on auscultation were associated with it on univariable analysis. That is why a single fainting episode in a cat is worth an appointment rather than a wait-and-see. The consensus statement records the harder fact plainly, that in some cats with cardiomyopathy sudden death may occur with no premonitory signs.

Congestive heart failure announces itself through the lungs rather than through a cough. Cats presented to first-opinion practices for respiratory distress with respiratory rates above 80 breaths a minute, gallop sounds, rectal temperatures below 37.5 degrees Celsius or heart rates above 200 beats a minute were more likely to have congestive heart failure than another cause of dyspnoea. A cat breathing hard in a cool room is not hot, and a cat that pants is not a dog.

How HCM is diagnosed, and the two diseases that have to be ruled out first

To diagnose HCM in a cat, a veterinary cardiology specialist performs an echocardiogram, measures left ventricular wall thickness and left atrial size, and then excludes the two treatable conditions that thicken a ventricle for other reasons. Echocardiography performed by a veterinary cardiology specialist is the diagnostic test of choice for cardiomyopathies in cats.

The scan measures muscle, not symptoms. In both the CatScan study and the Indian caseload, a cat was called affected when the end-diastolic interventricular septum or left ventricular wall measured 6 mm or more, in one case on two-dimensional imaging and in the other on M-mode Vishnu Vardhan M, Basava Reddy K. Cornell notes that the images reveal the thickened walls and the constricted volume of the left ventricle, and warns in the same paragraph that similar heart thickening is caused by other conditions.

Those other conditions are the reason a thick ventricle is not automatically HCM. The ACVIM classification is deliberately built around this, so that a cat is first said to have a hypertrophic cardiomyopathy phenotype, and is only said to have hypertrophic cardiomyopathy once no underlying cause has been found. A cat with left ventricular hypertrophy and hyperthyroidism is described as having an HCM phenotype in conjunction with hyperthyroidism.

Hyperthyroidism, and how the two are told apart

Hyperthyroidism is the impostor that matters most in an older cat, and a blood test separates it from HCM. Hyperthyroidism is common in older cats and is associated with auscultatory abnormalities including murmurs, gallop sounds and arrhythmias, with cardiac remodelling such as left ventricular hypertrophy or increased chamber diameters, and in some cases with congestive heart failure or arterial thromboembolism. Everything in that list also describes HCM, which is exactly the problem.

The separation is made on serum thyroxine and on the severity of the thickening, not on the echocardiogram alone. The ACVIM panel recommends that serum thyroxine concentrations be measured in all cats aged 6 years or older with abnormal cardiac auscultation findings, with or without left ventricular hypertrophy on an echocardiogram. For most hyperthyroid cats the left ventricular hypertrophy is only mild to moderate, and where severe hypertrophy is seen in a hyperthyroid cat the panel's reading is that hyperthyroidism is suspected to be exacerbating pre-existing mild to moderate HCM rather than causing the thickening on its own.

That distinction changes what happens next, because one of the two diseases can be taken away. An overactive thyroid is treated, and the heart is then rescanned to see what is left. A sarcomeric cardiomyopathy is managed for life. The Indian caseload found 12 of the 90 fully worked-up cats in the Minnesota thromboembolism series had hyperthyroidism as the underlying disease behind the clot, so the thyroid is not a footnote on a cardiac page. Read hyperthyroidism in cats next if your cat is over six, losing weight and eating well, because that is the pattern that gets mistaken for a primary heart problem.

High blood pressure, the second impostor

Systemic hypertension thickens ventricles too, and it is commoner than owners expect. Diffuse or segmental left ventricular hypertrophy is common in cats with systemic hypertension and is observed in up to 85 percent of cases, although HCM and systemic hypertension may exist concurrently, and for many hypertensive cats the hypertrophy is only mild to moderate. Blood pressure determination should be considered for all cats with increased left ventricular wall thickness.

Hypertension in cats usually travels with kidney disease, which is why the two pages belong together. A senior cat being investigated for a thick heart should have its creatinine, its urine and its blood pressure measured in the same visit, and chronic kidney disease in cats sets out what those numbers mean.

Where a blood test fits, and where it does not

A point-of-care NT-proBNP test is the realistic second-best instrument when a cardiologist is a train journey away. In 146 asymptomatic client-owned cats with a murmur, gallop rhythm, arrhythmia or cardiomegaly, a point-of-care NT-proBNP ELISA separated moderate or severe occult heart disease with a sensitivity of 83.8 percent and a specificity of 82.6 percent, for an overall accuracy of 82.9 percent. Restricted to cardiomyopathic occult disease, sensitivity was 88.6 percent and specificity 81.3 percent.

A positive result increased the likelihood of moderate to severe occult heart disease by a factor of 4.8 against a negative one. That is a useful triage number and it is not a diagnosis. The Royal Veterinary College's Birman work found biomarkers helpful in that breed while stating that the overlap in biomarker levels between healthy and affected cats makes them not reliable enough to act as the sole test in screening breeding cats. Use the blood test to decide who gets scanned, never to decide who does not need scanning.

1. Ask for an echocardiogram by a veterinary cardiologist, because it is the diagnostic test of choice and the only test that finds the disease before signs appear.
2. Ask for a total thyroxine if the cat is six or older with any abnormal auscultation finding, because the consensus recommends it at that age with or without hypertrophy on the scan.
3. Ask for a systolic blood pressure, since left ventricular hypertrophy is observed in up to 85 percent of hypertensive cats and the reading changes the diagnosis.
4. Ask what the left atrial size was, not just whether the walls were thick, because atrial size is the marker that splits low risk from high risk.
5. Ask for an NT-proBNP test if no cardiologist is reachable, and treat a positive as a reason to travel rather than as a diagnosis.
6. Ask for the numbers in writing, so a second scan a year later can be compared against the first rather than against a memory.

The ACVIM 2020 stages, and what changes at each one

ACVIM stages a cat with cardiomyopathy from A to D on whether the disease is present, whether the cat has signs, and how enlarged the left atrium is, and the stage decides whether anything is treated at all. Ask your veterinarian which stage your cat is and write the left atrial measurement next to it.

The staging system is new enough that many pages still do not use it. The 2020 consensus statement introduced a staging system for cardiomyopathy that includes subdivision of cats with subclinical cardiomyopathy into those at low risk of life-threatening complications and those at higher risk, and it is built on cardiac structure and function rather than on a named disease. Atrial size is an important prognostic marker, and it is what subdivides cats with subclinical cardiomyopathy into low risk and higher risk.

The line between B1 and B2 is where an owner's money and worry should go. Cats with stage B1 cardiomyopathy are considered at low risk of congestive heart failure or arterial thromboembolism, and in general treatment is not recommended, although the majority will not develop clinical signs and annual monitoring for progression to moderate or severe left atrial enlargement is. Cats with stage B2 have an increased risk of developing congestive heart failure or arterial thromboembolism, and thromboprophylaxis is recommended when known risk factors for a clot are present.

Within stage B2 the consensus lists the additional risk factors explicitly, which is useful because a scan report may mention one without explaining it. A gallop sound, an arrhythmia, decreased left atrial function, extreme left ventricular hypertrophy, left ventricular systolic dysfunction, spontaneous echo-contrast or thrombus, and regional wall motion abnormalities each raise the risk inside that stage.

What the stages mean for how long a cat lives

The REVEAL study is the largest answer to that question and it followed cats from 21 countries. Among 1,730 client-owned cats, 430 with preclinical non-obstructive HCM, 578 with preclinical obstructive HCM and 722 apparently healthy, congestive heart failure or arterial thromboembolism or both occurred in 30.5 percent and cardiovascular death in 27.9 percent of the 1,008 cats with HCM.

Risk climbs with time rather than arriving at once. Measured at 1, 5 and 10 years after study entry, the risk of congestive heart failure and of arterial thromboembolism was 7.0 percent and 3.5 percent, then 19.9 percent and 9.7 percent, then 23.9 percent and 11.3 percent, while the risk of cardiovascular death was 6.7 percent, 22.8 percent and 28.3 percent. There were no statistically significant differences between obstructive and non-obstructive disease for cardiovascular morbidity or mortality.

The study also measured what happens after the disease turns. Cats that developed cardiovascular morbidity had short survival, a mean of 1.3 years with a standard deviation of 1.7 years, and prolonged longevity was recorded in a minority of preclinical cats, with 10 percent reaching 9 to 15 years. Both halves of that sentence are true at once, and an owner deserves both.

The two MYBPC3 DNA tests, what they cost, and what a clear result does not mean

Two breed-specific DNA tests exist for feline HCM, MYBPC3 A31P for the Maine Coon and MYBPC3 R820W for the Ragdoll, and neither one clears a cat of the disease. The ACVIM consensus recommends both in cats of those breeds intended for breeding at its highest level of evidence, and recommends regular echocardiographic screening even in Maine Coon and Ragdoll cats without these mutations.

Both variants are single base changes in the same gene, found a decade apart in two unrelated breeds. The Ragdoll variant is registered as OMIA:002951-9685, cardiomyopathy, hypertrophic, MYBPC3-related, autosomal dominant in Felis catus. UC Davis describes the R820W change as a single base pair change in MYBPC3 thought to alter the shape and function of a protein essential to normal heart muscle development, and notes that the same R820W mutation is associated with hypertrophic cardiomyopathy and left ventricular non-compaction in humans.

The tests are breed-specific in the strict sense, and the consensus is blunt about it. Genetic testing for the A31P and R820W MYBPC3 mutations in non-Maine Coon or non-Ragdoll cats is not recommended, because these 2 mutations are almost completely specific to Maine Coon and Ragdoll cats, at the panel's highest level of evidence. A European screen of 3,757 cats of many breeds found the A31P mutation only in Maine Coons, at a prevalence of 41.5 percent, except for a single British Longhair.

What the Maine Coon test actually predicts

The A31P mutation raises risk steeply in the homozygote and gently in the heterozygote. UC Davis summarises the published research as a relative risk for HCM of around 1.8 in cats carrying one copy and around 18 in cats carrying two copies, so a cat with two copies is 18 times more likely to develop HCM than a cat with normal alleles and 10 times more likely than a cat with one copy. About 63 percent of Maine Coon cats that were tested were free of the mutation.

The homozygotes are also rarer than inheritance predicts, which is itself a finding. The incidence of cats carrying two copies was 3 percent in non-phenotyped cats and 4 percent in phenotyped cats against an expectation of 7 to 16 percent, and UC Davis reads that deficit as considerable embryonic death. The British Isles survey saw the same signal from the other direction, finding the difference between expected and observed allele frequency significant in Maine Coons at P equal to 0.047 but not in Ragdolls at P equal to 0.092, and suggesting early death of homozygous Maine Coons as the explanation.

The French screening data put numbers on how loosely genotype tracks phenotype. In the 164 Maine Coons echocardiographed at a mean age of 2.6 years, 55 carried the mutation, 34 percent, while only 12 had HCM, 7 percent, made up of 5 of 48 heterozygotes, 5 of 7 homozygous mutated cats and 2 of 109 homozygous wild-type cats, with an overall relative risk of 9.91. Five of seven cats with two copies were affected and most cats with one copy were not.

What the Ragdoll test actually predicts

The Ragdoll pattern is sharper at the homozygous end. UC Davis states that cats heterozygous for the mutation are not likely to show signs of the disease and may live a normal lifespan, while homozygous cats are at high risk of developing severe HCM signs, usually between 1 and 2 years of age, with a greater likelihood of early cardiac death, and that infrequently a homozygous cat shows no clinical signs. Breedings between two heterozygous cats are expected to produce 25 percent high-risk kittens.

Mutation frequency in the breed is high enough that this is not a rare problem. The prevalence of R820W in 2,018 Ragdolls in the British Isles was 27 percent, 25.6 percent heterozygous and 1.4 percent homozygous, and the A31P prevalence in 742 Maine Coons in the same database was 39.4 percent. The median age of the cats tested was 6.4 months for Ragdolls and 5.9 months for Maine Coons, which is breeders testing kittens rather than owners testing adults.

Breeding advice follows from the genotype rather than from the scan. The consensus recommends that cats homozygous for either mutation not be used for breeding, and that heterozygous cats can be bred to genotype-negative cats if they have other outstanding characteristics. UC Davis says the same for the Ragdoll, that it is not recommended to use cats homozygous for the R820W mutation in a breeding program.

The breeds with no test at all

For every other breed there is no DNA test worth buying, and that includes breeds sold in India as heart-tested. Eight sarcomeric candidate genes associated with human familial HCM were sequenced in affected British Shorthair, Norwegian Forest, Siberian, Sphynx and Maine Coon cats without the known Maine Coon mutation, and no causative mutation was identified. Mutations within those cardiac genes do not appear to be the only cause of HCM in these breeds.

The Sphynx is the cautionary case, because a test exists and does not work. In 55 apparently healthy Sphynx cats in New Zealand the ALMS1 variant was present at a frequency of 70.9 percent, 11 homozygous and 28 heterozygous, and it was not associated with the HCM diagnosis in that population, even though 40 percent of the same cats had HCM. The review literature agrees that while a genetic cause of HCM has been identified in two breeds and is suspected in another, for most cats the cause is unknown.

The French screening data on the same breed put the phenotype ahead of the gene by more than a decade. Among 147 echocardiographic examinations on 114 Sphynx cats aged 2.62 years on average, 39 of 114 examinations were abnormal, 34.2 percent, with hypertrophic cardiomyopathy in 23 cats and congenital heart disease in 16, HCM prevalence rose significantly with age, and a pedigree analysis of one family of 81 cats suggested an autosomal dominant mode of inheritance with incomplete penetrance.

Treatment in general terms, and why a stage B1 cat is usually left alone

Treatment of HCM in cats is decided by stage rather than by diagnosis, and a cat with subclinical disease and a normal left atrium is generally given nothing but an annual scan. Nothing below is a prescription, this page prints no drug amounts, and your veterinarian chooses every drug and every dose for the cat in front of them.

Start from the honest frame. Cornell states that HCM has no known cure and that a specialised care plan can help manage the clinical signs of the condition. Every intervention below is aimed at delaying a complication or at managing one that has already happened, and a seller offering a supplement that reverses a thick heart is describing something no guideline contains.

Treatment of cats with subclinical cardiomyopathy is controversial because evidence is lacking, and the consensus says so in the first line of its own treatment section. Although the majority of cats with stage B1 cardiomyopathy will not develop clinical signs, it is recommended that stage B1 cats be monitored annually for development of moderate to severe left atrial enlargement, which is progression to stage B2.

Three drugs that owners often ask for have been tested in subclinical cats and have not delivered. Neither an angiotensin converting enzyme inhibitor nor spironolactone had any effect on left ventricular mass or diastolic function in cats with subclinical HCM in two randomised placebo-controlled studies, although the populations were small and limited to a single breed with heritable cardiomyopathy. A beta blocker has not been shown to have any effect on the 5-year survival rate in cats with subclinical HCM.

What changes when the left atrium enlarges

Stage B2 is where treatment begins, and the target is the clot rather than the muscle. Cats with stage B2 HCM have an increased risk of developing congestive heart failure or arterial thromboembolism, primary prevention of thromboembolism in subclinical cats has not been studied, and thromboprophylaxis is recommended when known risk factors for it are present. The general-practice data support treating rather than waiting, since failure to receive an antiplatelet drug carried a hazard ratio of 8.26 for euthanasia or death within 7 days among cats that survived the first day after a clot.

Once the left atrium is moderately to severely enlarged and antithrombotic treatment has started, the consensus records that management is unlikely to change until clinical signs develop, and that at a minimum owners should monitor the cat's resting or sleeping respiratory rate. That single instruction is the most useful thing an owner of a stage B2 cat can do, and it costs nothing.

Heart failure, and what treatment looks like then

Stage C is treated hard and reviewed often. A loop diuretic is the primary drug used for control of pulmonary oedema and effusions in cats with congestive heart failure, with intravenous administration preferred in cats with marked respiratory distress, and the maintenance amount is titrated to hold the resting or sleeping respiratory rate at home under 30 breaths a minute. Cats with stage C cardiomyopathy are re-examined at approximately 2 to 4 month intervals or as needed.

Stress is part of the treatment plan, which is unusual and worth knowing. The consensus recommends that cats in acute heart failure be discharged to the care of their owners as soon as possible, with re-evaluation 3 to 7 days after discharge to check that the failure has resolved and to measure kidney values and electrolytes. A cat kept in a cage longer than it needs to be is not being helped.

The one trial that moved the muscle

A single randomised trial has changed a measurement rather than an outcome so far. In the RAPACAT trial, 43 client-owned cats with subclinical non-obstructive HCM were allocated to low-dose or high-dose delayed-release rapamycin or to placebo in a double-blinded, multicentred, randomised, placebo-controlled design, and at day 180 the maximum left ventricular myocardial wall thickness at any location was significantly lower in the low-dose group than in placebo, at P equal to 0.01. The drug was well tolerated with no significant difference in adverse events between groups.

Cornell reports the same work with the caveat attached, that while no therapy has been definitively shown to cure HCM, a six-month clinical trial in a small number of cats showed that rapamycin forestalled the progression of heart muscle thickening, that enrolment is underway for a 12-month follow-up trial, and that it is premature to consider rapamycin a cure for HCM. Forty-three cats and one measurement at six months is a promising trial, not a treatment an Indian owner can ask for today.

What an echocardiogram costs in India, and where a cat can actually get one

An echocardiogram costs Rs 350 at ICAR-IVRI Izatnagar and Rs 300 at the Madras Veterinary College teaching hospital in Chennai, while the only published Indian private range, Rs 3,000 to Rs 8,000 at a specialist centre, is stated for dogs rather than cats Voice of Stray Dogs. Access, not price, is what stops Indian cats being screened.

Two government teaching hospitals publish their own rate cards and both price the scan in three figures. The ICAR-Indian Veterinary Research Institute at Izatnagar lists an echocardiogram, spelled Echocardiograohy on its own sheet, at Rs 350 in its Pets column, against Rs 100 for small animals and Rs 200 for large animals, with effect from July 2022 and plus tax as applicable. The same sheet prices abdominal ultrasonography at Rs 250 and plain radiography at Rs 150.

The Madras Veterinary College Teaching Hospital in Chennai, which belongs to the Tamil Nadu Veterinary and Animal Sciences University, publishes a single column headed COST IN RUPEES and prints ECHO at 300, ECG at 50, SCAN at 300, X RAY at 100 and a hormone assay at 400, against a small animal registration of Rs 100 valid for 7 days only. That hormone assay line matters on this page, because the thyroxine measurement the consensus wants in every cat over six with an abnormal auscultation is on the same rate card as the scan Tamil Nadu Veterinary and Animal Sciences….

Every rupee figure here was run through the exchange-rate test, and none of them is a converted dollar price in disguise. Rs 300 is about 3.6 US dollars at 84.38 to the dollar and about 4.1 at 74, Rs 350 is about 4.1 and 4.7, and the private range of Rs 3,000 to Rs 8,000 is about 36 to 95 dollars and 41 to 108 dollars. The government numbers are subsidised teaching-hospital rates and the private ones are market rates, and both are genuinely Indian.

The DNA tests are a dollar price, not an Indian one

Neither laboratory sells in rupees and this page does not pretend otherwise. UC Davis prices its Ragdoll HCM and Maine Coon HCM tests at 47 US dollars for one test per animal, with a turnaround of at least 15 business days, on cells brushed from the cat's cheeks and gums with household cotton swabs Veterinary Genetics Laboratory. NC State prices the same two tests at 35 US dollars per cat with a litter discount of 25 US dollars per kitten, accepting a cheek swab or whole blood in an EDTA tube.

Add international courier and the practical Indian cost of a DNA test is several times the cost of a government echocardiogram, for a result that applies to one of two breeds and does not clear the cat. For a pet Maine Coon or Ragdoll in India, the scan is the better purchase. For a breeder, the consensus wants both.

Where the machine and the person actually are

The constraint outside the metros is the cardiologist, not the rupee. The largest Indian small-animal chain lists its clinics in eleven cities, Gurgaon, Delhi, Noida, Ghaziabad, Faridabad, Hyderabad, Mumbai, Bengaluru, Pune, Kolkata and Chennai, which is the National Capital Region plus six metros, and the same site indexes its Bengaluru clinics under Bangalore as well. Government veterinary colleges extend that reach, and the two that publish echocardiogram rates sit in Chennai and in Izatnagar in Uttar Pradesh ICAR-Indian Veterinary Research Institute.

The published Indian cardiac series came out of a third kind of place, a Super-Speciality Veterinary Hospital run by a state veterinary university in Visakhapatnam, where cats were worked up with electrocardiography, echocardiography, pulsed-wave Doppler and haemato-biochemical analysis. A cat in a district town is realistically a journey away from any of these, which is what makes the NT-proBNP triage test and the sleeping breathing rate worth more in India than in London Luis Fuentes V, Abbott J, Chetboul V.

What is different in India, and the Indian data that does and does not exist

India has exactly one published feline cardiac denominator and this page prints it. Of 2,872 cats presented to the Super-Speciality Veterinary Hospital at Sri Venkateswara Veterinary University in Visakhapatnam between April 2024 and March 2025, 164 with signs of cardiac disease were screened and 16 had a cardiomyopathy, 10 with HCM and 6 with restrictive cardiomyopathy.

The arithmetic in that paper checks out and the shape of it is recognisable. Cardiomyopathy accounted for 9.76 percent of the 164 cats screened, HCM for 6.10 percent and restrictive cardiomyopathy for 3.66 percent, with an overall cardiac-disease prevalence of 0.56 percent across every cat presented in the year. HCM was diagnosed on an end-diastolic interventricular septum or left ventricular posterior wall thickness of 6 mm or more on M-mode, the same threshold the UK screening study used Payne JR, Brodbelt DC.

The breed split is the part an Indian reader should act on. HCM was more prevalent in Persian cats, 80 percent of the HCM cases, while restrictive cardiomyopathy was more common in non-descript cats, 66.6 percent. Cardiomyopathy was most commonly observed in cats aged 5 to 10 years, 75 percent, with a higher prevalence in males, 68.7 percent, and in cats weighing 3 to 5 kg, 81.25 percent, and the paper concludes that HCM is the most prevalent cardiomyopathy in Persian cats.

That matters because the Persian is the pedigree cat India actually keeps. An Indian veterinary chain's own article names Ragdoll, Persian, British Shorthair and Maine Coon as the breeds most commonly affected and tells the reader that if you have a Persian cat in India you need to put cardiac health check-ups on priority. The Tehran referral data put the Persian at the top of the within-breed table at 54.8 percent of 7,013 referred cats, ahead of the Sphynx at 46.9 percent and the British Shorthair at 45.0 percent.

A controlled absence: what both PubMed instruments actually return

Beyond that one Andhra Pradesh paper, there is no Indian feline cardiomyopathy literature, and this page publishes the search rather than the conclusion. Two NCBI E-utilities searches were run on 24 September 2026 across hypertrophic cardiomyopathy or cardiomyopathy, in cats or felines, with an Indian term. The title and abstract instrument returned 1 record and the author-affiliation instrument returned 15.

Every one of those 16 records is an artefact of an acronym, and opening them is the only way to know. The single title and abstract hit is a 2019 paper on curcumin-loaded mesoporous silica nanoparticles against doxorubicin-induced myocardial toxicity in rats, which matches because the abstract measures catalase and abbreviates it CAT. All 15 affiliation hits are rodent cardioprotection pharmacology from Indian institutions, on diabetic cardiomyopathy in mice, doxorubicin toxicity in albino rats and isoproterenol-induced cardiomyopathy, and they match the same way.

The instrument was working when it returned nothing, which is the part that makes an absence publishable. A positive control run in the same session, canine pyometra with an Indian author affiliation, returned 8 records, and a negative control with a nonsense affiliation term returned 0. So the correct statement is not that Indian cats do not get HCM. It is that no Indian prevalence study, screening cohort or survival series for feline HCM is indexed, and the one Indian caseload that exists is the Visakhapatnam short communication above.

This page also disagrees with its own roster row, which recorded the Indian PubMed count as 0 on a narrower term. Run today, the narrower shape of that search returns 1, and that 1 is the rat curcumin paper, so the roster's zero and today's one describe the same emptiness through different filters.

What changes for a cat kept in an Indian flat

Heat does not cause HCM and it does change what an owner sees. Open-mouth breathing in a cat is never normal and is never to be written off as the weather, because the two conditions that produce it are congestive heart failure and a genuine heat emergency, and both need a veterinarian the same hour. If the question in your head is whether the room is simply too hot, read heat safety for cats in India and then call a vet anyway.

The sleeping breathing rate is the tool that travels. A cat in Pune or Kolkata with a stage B2 scan and no cardiologist within reach still has a measurement its owner can take every week, and the consensus treats that owner-recorded rate as sufficient to adjust medication by telephone. That is a genuinely Indian answer to a genuinely Indian constraint, and it costs a phone timer.

Cost planning is the last Indian difference. A stage B2 or stage C cat needs re-examination at roughly 2 to 4 month intervals, on top of the scan itself, and Indian pet insurance is written around accident and illness cover that a cat diagnosed before the policy starts will usually fall outside, which is covered on pet insurance in India. Screening a Persian kitten before a problem exists is cheaper than managing a stage C cat, and on the Chennai rate card the screening scan is Rs 300.

Screening and prevention: what works, and what nothing prevents

Nothing prevents HCM in an individual cat, because for most cats the cause is unknown, so screening rather than prevention is the whole strategy. What breeding programmes can do is lower the frequency of two known mutations, and what owners can do is find the disease before it declares itself.

The honest starting point is that the cause is usually not identifiable. While a genetic cause of HCM has been identified in two breeds and is suspected in another, for most cats the cause is unknown. It is suspected that other cat breeds have a genetic cause of their HCM, but intensive efforts aimed at identifying such mutations have not been successful, and since mixed-breed cats with no family history most commonly develop HCM it is likely there is some other unknown cause.

Diagnosis is therefore an exclusion exercise rather than a confirmation. HCM in cats with mild to moderate left ventricular wall thickening is a diagnosis of exclusion, which means there is no definitive test for those cats and other disorders that can cause mild to moderate thickening, including hyperthyroidism, systemic hypertension, acromegaly and dehydration, need to be ruled out.

Who should be screened, and when

Breeding cats are the clearest case and the consensus is explicit about them. Genetic testing for A31P and R820W is recommended in Maine Coon and Ragdoll cats intended for breeding at the highest level of evidence, cats homozygous for either mutation should not be used for breeding, heterozygous cats can be bred to genotype-negative cats if they have other outstanding characteristics, and regular echocardiographic screening should be considered even in Maine Coons and Ragdolls without the mutations.

A single normal scan in a young cat is not a clearance for life, and the Birman data show why. HCM was most commonly diagnosed in adult Birmans at a median age of 8.4 years, which means cats may develop HCM later in life and a normal heart scan at a young age does not exclude the possibility of a cat developing it later, so serial heart scans and exclusion of HCM in previous generations are required to properly exclude the disease. The Danish British Shorthair cohort shows the opposite failure mode, with a median diagnosis age of just 2.7 years.

The CatScan II follow-up measured how often a normal cat turns. Among 107 cats adopted from rehoming centres and followed for a median of 5.6 years, 68 were normal at baseline, 18 equivocal and 21 already had HCM, and 19 cats developed HCM during the study period. Lower left atrial fractional shortening, higher left ventricular fractional shortening and higher body weight at baseline were the factors associated with an increased hazard of developing the disease.

1. Scan a breeding Maine Coon or Ragdoll and DNA test it too, because the consensus recommends the DNA test for breeding cats and echocardiographic screening even in cats that test clear.
2. Scan a breeding cat of any other predisposed breed annually, since no DNA test exists for the British Shorthair, Norwegian Forest, Siberian or Sphynx and sequencing eight candidate genes found no causative mutation.
3. Scan a British Shorthair early, because the median diagnosis age in a 329-cat Danish cohort was 2.7 years and 20.4 percent of males were affected.
4. Scan a Birman later as well as early, given a median HCM diagnosis age of 8.4 years in 162 screened cats.
5. Ask for a thyroxine and a blood pressure at the same visit for any cat aged six or over with an abnormal auscultation finding.
6. Repeat the scan yearly once a cat is stage B1, which is what the consensus asks for, rather than waiting for a symptom.

Buying a kitten is the one moment an Indian buyer has real leverage. Ask a Maine Coon or Ragdoll breeder for the parents' DNA results by the mutation name, A31P or R820W, and ask any other pedigree breeder for the date of the parents' last echocardiogram and the cardiologist's name. A breeder who has done neither is selling on colour, and dog breeder checks in India sets out how the same questions work in practice.

Body condition is the only modifiable factor with a measured association, and it is worth treating as real. Increased body condition score was one of the factors associated with an HCM diagnosis in the 780-cat screened population, and high body condition score carried an odds ratio of 4.05 in the 7,013-cat Tehran cohort Jalilian M, Pahlevaninezhad N, Yazdanjoo Z. Keeping a cat lean is not prevention, and it is the only lever on the list.

Living with it: how long cats actually live, and what to track at home

Many cats with HCM live for years and a minority die of it, and the split between those two groups is measurable. Of 255 cats with HCM followed for two years, 141, or 55.3 percent, were alive at the end of the two years, while 10 percent of preclinical cats in the international REVEAL cohort reached 9 to 15 years of age.

The risk is real and it is not immediate. Cardiovascular events were observed in 21 percent of the cats with HCM in the rehoming-centre cohort followed for a median of 5.6 years, a population deliberately chosen to avoid the bias of cats referred for suspected heart disease. The same study found that lower left atrial systolic function appears to precede overt HCM, which is why a cardiologist measures the atrium and not only the wall.

What the scan says predicts what happens next, better than how the cat looks. In 282 cats with HCM, left atrial dysfunction, low left ventricular systolic function and extreme left ventricular hypertrophy were the independent predictors of decreased cardiac survival time in a Cox proportional hazard analysis. Deaths occurred in 164 of those 282 cats, of which 107 were believed to be cardiac.

The univariable list from the same study is the one to read alongside your cat's report. Older age, absence of a murmur, a gallop sound or arrhythmia, presentation with congestive heart failure or thromboembolism, extreme hypertrophy of 9.0 mm or more, fractional shortening of 30 percent or less, regional wall hypokinesis, increased left atrial size, decreased left atrial function, spontaneous echo-contrast or thrombus, absence of outflow tract obstruction and a restrictive filling pattern each predicted increased risk of cardiac death.

What to actually do at home, every week

Three habits carry almost all the value and none of them costs anything. Count the sleeping breathing rate weekly against a target under 30 breaths a minute, weigh the cat on the same kitchen scale monthly and write the number down, and keep a note of any single fainting episode, because syncope at presentation was associated with sudden death in the 255-cat series.

• Count breaths while the cat sleeps, for 30 seconds doubled, once a week, with a target under 30 breaths a minute.
• Record any faint or collapse the same day, since syncope was associated with sudden death on univariable analysis.
• Check the back paws if a cat suddenly goes off its legs, because cold paws with absent motor function were present in 66 percent of cats presenting with a clot.
• Keep the cat lean, given that increased body condition score was associated with an HCM diagnosis in a screened population of 780 cats.
• Keep the last scan report, with the left atrial measurement on it, so the next scan is a comparison rather than a fresh start.
• Book the annual scan for a stage B1 cat, which is the consensus recommendation and the only way progression to stage B2 gets caught.

When the news is bad, how bad it usually is

Once a complication arrives, survival shortens sharply and owners deserve that number in advance. Cats in the REVEAL cohort that developed cardiovascular morbidity had short survival, a mean of 1.3 years with a standard deviation of 1.7 years. In general UK practice, 61.2 percent of 250 cats presenting with a clot were euthanised at presentation, and yet 6 of those 250 cats were alive a year later.

Prognosis is variable rather than uniform, and Cornell frames it the way a veterinarian will. Cats that do not display any clinical signs are often able to survive for years with only mildly compromised heart function, while congestive heart failure, thromboembolism and hypothermia are the findings that suggest a worse prognosis, and in many cases medical therapy can significantly improve a cat's quality of life.

A cat that is diagnosed at seven and dies at fourteen of something else has had HCM for half its life and never suffered from it. A cat that presents with a clot on a Tuesday may not see Wednesday. Both are this disease, the scan is what tells you which conversation you are having, and your own veterinarian is the person who should have it with you. Senior cat care in India sets out the rest of the annual check an older cat needs.