HCM in cats

Feline hypertrophic cardiomyopathy (HCM) is the number one heart disease in felines. Though currently incurable, a combination of conventional and alternative therapies may help treat it.

Ranked as the number one heart disease in cats, HCM may go undetected for several years, causing irreparable damage and ultimately death. This stealthy condition with no known cause or cure most commonly strikes middle-aged male cats, but has been reported in cats ranging from kitten-hood to old age, regardless of sex or breed.

In HCM, the walls of the heart muscle grow abnormally and progressively thicker. It primarily affects the left ventricle, the chamber responsible for pumping blood through the aorta and to the body. Some breeds appear genetically predisposed to the disease, including the Maine coon, American shorthairs, Persians and ragdolls. “Ragdolls and Maine coons present with the most severe forms of HCM,” says veterinarian Dr. Cindy Kneebone.

Symptoms are variable

Symptoms vary from cat to cat depending on which stage of the disease they are in. In the early stages, some cats show no sign of illness while others may appear lethargic, lose their appetite or vomit. “If the disease has gone undetected for some time, affected cats may experience episodes of collapse or difficulty breathing,” says veterinarian Dr. Meghan Tibbs. “Sudden lameness in the rear limbs due to aortic thromboembolism (ATE) may occur.” ATE is caused when blood clots form in the heart, break apart and enter the circulatory system, clogging arteries and most commonly blocking the aorta, obstructing blood flow to the rear limbs. Sometimes sudden death is the only symptom.

As with Ricky, a heart murmur is often detected during a routine veterinary examination. “Murmurs are heard in about 50% of cats with HCM,” says Dr. Kneebone. “They could be in all cats with HCM, but may be beyond our range of hearing.”

Chest x-rays, an electrocardiogram (ECG or EKG) and echocardiogram (heart ultrasound) – considered the “gold standard” – may support the diagnosis and determine the severity of HCM in individual cats. “If you have a breed at risk, or a heart murmur is heard on physical examination, there is a blood test your veterinarian can use as a screening tool, a sort of early warning system,” says Dr. Kneebone. “This test measures a protein secreted by the heart muscle cells in response to stretching or injury. The test is used to identify subclinical disease or to differentiate the cause of breathing difficulties between the lungs or heart.”

Treatment is palliative

Since there is no cure for HCM, treatment is palliative and tailored to the individual cat. For asymptomatic cats, routine exams and tests like chest x-ray, heart ultrasound or electrocardiogram are recommended every six months to a year to check the progression of the disease. Treatment includes conventional Western medicine and alternative methods although none prevent, cure or reverse the disease. Recommended treatment depends on the symptoms and severity of the disease.

Dr. Kneebone says diuretics to remove excess fluid from the lungs are the primary therapy for acute and chronic cases of congestive heart failure.

Dr. Tibbs adds that she sees good results using Western therapies like beta-blockers or calcium channel blockers. A preventative daily aspirin regimen is used in cats prone to blood clots to prevent thromboembolism (stroke). “Herbs like hawthorn, glandular remedies and amino acids such as carnitine may be helpful,” says veterinarian Dr. Mark Newkirk.

“For stroke prevention, adding preformed Omega-3 fatty acids helps reduce infl ammation in the body, increasing the incorporation of fl exible fatty acids into the cell membranes of the body tissues,” says Dr. Kneebone. “Omega-3 fatty acids decrease platelet stickiness and can lower blood pressure. Although a dose hasn’t been given for cats, aim for more than 500 mg of a mix of eicosapentaenoic (EPA) and docosahexacroic acid (DHA) once a day.”

The prognosis for HCM varies and depends on which symptoms are present. “Average survival time for cats without congestive heart failure is about two years, while for cats that have experienced congestive heart failure it’s about three months,” says Dr. Tibbs. “The worst prognosis is in cats that have had a thromboembolic event; their average survival time is approximately two months.”

Thanks to Ricky and Steve, research is being done into finding a cure for HCM (see below). In the meantime, regular veterinary checkups help catch the disease in its early stages, while individualized treatment regimes can ease symptoms, improve quality of life and increase longevity.

The Ricky Fund

After his cat Ricky died of HCM, Steve collaborated with the Winn Feline Foundation, a non-profit organization devoted to funding research in cat health, to establish The Ricky Fund for HCM research. “We’ve raised over $100,000, which in feline health is significant,” says Steve. “As a result, a genetic test using a simple cheek swab can now be done for Maine coons and ragdolls to determine if the gene defect for HCM exists. Still, there is much to do to find a treatment for HCM. Cats are the most popular pet in America and too many are dying of heart disease.”


Ramona Marek is a writer who has been published in many national and international print and digital magazines. She is a former director of the Cat Writers’ Association and has been a professional member since 2007. She is also one of a handful of non-veterinarian members of the American Association of Human-Animal Bond Veterinarians, and a supporting member of the International Association of Animal Behavior Consultants (IAABC).