British Shorthair and Longhair HCM Screening — A Complete Guide from Timing to Frequency

HeartBreed HealthMeongsiljang Veterinary Advisory Board

British Shorthair and Longhair cats are breeds for which regular screening for hypertrophic cardiomyopathy (HCM) is recommended. We’ve compiled essential information for pet owners, including when to screen, how it’s done, and how to interpret the results.

Why is Screening Important for British Shorthairs, Longhairs, and HCM?

A British Shorthair undergoing an echocardiogram (heart ultrasound)

If you’re raising a British Shorthair or British Longhair, it’s important to keep an eye on their heart health. Early detection is key. Hypertrophic cardiomyopathy (HCM) is the most common heart muscle disease in cats, but it often shows few or no symptoms in its early stages. Even if your cat seems perfectly healthy, it’s wise to have their heart checked with an ultrasound at least once and then follow up with regular screenings. While certain breeds are known to carry specific high-risk mutations, changes can still occur in the heart even when there are no outward signs. In fact, some cats are first diagnosed only after sudden emergency symptoms like severe breathing difficulties or sudden weakness in the hind legs appear. That’s why it’s so important to check their heart health proactively, even when they seem fine.

Why British Breeds Need to Be Cautious About HCM

Veterinary cardiology textbooks describe hypertrophic cardiomyopathy (HCM) as the most common myocardial disease in cats. HCM is a condition in which the ventricular walls thicken without any other hemodynamic or metabolic stimuli. Specific gene mutations (such as MYBPC3 A31P and R820W) have been identified in Maine Coons and Ragdolls, and textbooks note that HCM is primarily found in these two breeds. However, since many cases cannot be explained by these mutations, it is believed that other genetic and environmental factors are also involved. Although it is difficult to definitively classify British Shorthairs and British Longhairs as high-risk groups based on specific confirmed mutations, HCM is a disease that shows no symptoms in its early stages. Therefore, rather than assuming your cat is fine because they appear healthy, it is safer to have their heart examined with an echocardiogram at least once.

HCM Warning Signs to Watch for at Home

In the early stages of HCM, symptoms are often minimal, but as the disease progresses, several warning signs may appear. If you notice anything unusual, jot it down and share it with your vet during the next visit. - Changes in breathing: Breathing faster than usual even while resting, or panting with an open mouth (rapid breathing or difficulty breathing can indicate heart failure) - Lethargy and reluctance to exercise: A once-active pet suddenly becomes weak and avoids jumping or climbing stairs (weakness and exercise intolerance) - Decreased appetite: A noticeable drop in food intake over a few days - Hind limb paralysis: Sudden weakness or coldness in the hind legs (may be accompanied by arterial thromboembolism) - Changes in gum color: Gums appear pale or bluish instead of pink (cyanosis)

Observing the breathing of a resting British Longhair

Signs Requiring Immediate Emergency Care

Sudden hindlimb paralysis, open-mouth panting, and decreased consciousness may signal complications of hypertrophic cardiomyopathy (HCM), such as arterial thromboembolism (ATE) or pulmonary edema. Because the prognosis deteriorates rapidly over time, immediate transport to a 24-hour emergency animal hospital is essential.

How is HCM Screening Performed?

The standard screening test for HCM is an echocardiogram (cardiac ultrasound). Textbooks consider echocardiography the most sensitive non-invasive test and the gold standard for diagnosing HCM. It allows us to check for thickening of the left ventricular wall (hypertrophy) and simultaneously evaluate the size of the left atrium, as well as overall heart structure and function. However, because the pattern of hypertrophy varies significantly among cats and results can differ based on the operator’s expertise, experience is crucial. During the diagnostic process, we may also use chest X-rays, electrocardiograms (ECG), and blood tests to rule out other causes of myocardial hypertrophy, such as hypertension, hyperthyroidism, and aortic stenosis. Genetic testing is primarily focused on mutations in Maine Coons and Ragdolls, so its diagnostic value is limited for British Shorthairs.

Screening Timing and Frequency at a Glance

Item	Recommended test	Interval
6–12 months	Basic auscultation + consider first echocardiography	Once
1–7 years	Echocardiography + auscultation	Once a year
7+ years	Echocardiography + NT-proBNP + blood pressure	1–2 times a year
When a heart murmur is detected	Echocardiography + chest X-ray	Immediate detailed examination

It is most accurate to have it done at a hospital where a veterinary cardiology specialist is available

Screening Costs and What Owners Should Prepare

An echocardiogram is performed with your pet lying on their side, without anesthesia, and typically takes 10 to 20 minutes. If your pet is sensitive to their carrier or the clinic environment, it helps to gradually acclimate them to the carrier over several days prior to the appointment. Fasting is usually not required before the exam, but since sedation may occasionally be necessary, please follow your clinic’s specific instructions. Most importantly, ensure the procedure is performed and interpreted by a board-certified veterinary cardiologist or a clinician with extensive echocardiography experience, as diagnostic interpretation can vary significantly even when viewing the same images.

A British Shorthair heading to the vet in a carrier

If You Receive a "Borderline" Screening Result

If the heart wall thickness falls into a “borderline” range between normal and hypertrophic cardiomyopathy (HCM), veterinarians often opt to monitor the condition with a follow-up examination after a set period rather than starting medication immediately. During this time, regularly observing and recording whether your pet’s resting breathing rate increases can be very helpful in assessing any changes at the next visit. Please follow your veterinarian’s guidance regarding the specific follow-up schedule and monitoring criteria.

Daily Management Points After Diagnosis

HCM is not a curable disease but one that is managed by slowing its progression. Textbooks explain that it is managed by reducing the heart’s workload and aiding myocardial relaxation using medications such as beta-blockers (e.g., atenolol) or calcium channel blockers. Therefore, it is crucial never to discontinue prescribed medications without veterinary guidance, and you should follow your veterinarian’s instructions for diet and weight management. Most importantly, early detection of complications like arterial thromboembolism or pulmonary edema is key, so regularly monitoring your pet’s breathing at rest and contacting your clinic immediately if you notice faster or labored breathing compared to normal can be immensely helpful.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Can British Shorthairs, like Maine Coons, be tested for HCM through genetic testing?

Currently available genetic tests (MYBPC3 A31P, R820W) are designed for Maine Coons and Ragdolls, so their diagnostic value for British Shorthairs is limited. Veterinary textbooks also state that these tests are not useful for other breeds. Echocardiography is the most reliable screening method.

If my pet’s checkup results were normal when they were young, can I be reassured?

A single normal result only reflects your cat’s condition at that specific point in time. Even cats that test negative for genetic markers can develop HCM later in life, which is why veterinary textbooks recommend annual echocardiograms for at-risk cats. Therefore, regular follow-up examinations are essential.

Does the absence of a heart murmur rule out HCM?

Not necessarily. Echocardiography is a much more sensitive test than auscultation, so wall hypertrophy may be detected on ultrasound even when no distinct murmur is heard during auscultation. Therefore, it’s difficult to feel reassured based on auscultation alone.

I'm worried about the cost of the tests. Do I really need to have them done every year?

If your budget is tight, you can start with a stethoscope exam, chest X-rays, and blood tests, then proceed to an echocardiogram if any abnormalities are detected. However, if a heart murmur has ever been heard, do not delay the echocardiogram.

Can surgery or treatment cure it?

Currently, there is no cure for HCM. It is a condition managed by using medications to reduce the heart's workload and prevent complications such as blood clots and pulmonary edema. Therefore, early detection and consistent monitoring are the most important aspects of care.

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References

[1] Textbook of Cardiovascular Medicine in Dogs and Cats - Hypertrophic Cardiomyopathy chapter

[2] Small Animal Critical Care Medicine, 3rd Ed - Feline Cardiomyopathy Classification

[3] ACVIM Consensus Statement Guidelines for the Classification, Diagnosis, and Management of Cardiomyopathies in Cats (Luis Fuentes et al., 2020)