Feline hypertrophic cardiomyopathy (HCM) is the most common type of heart disease and one of the most common causes of death in cats, but detecting it can be tricky because many cats who have HCM are asymptomatic.

HCM causes the muscular walls of a cat’s heart to thicken, decreasing the efficiency of the heart and sometimes causing clinical signs in other parts of the body. And although veterinarians have known about HCM for nearly 50 years, almost nothing was known about its epidemiology.

Until now.

The publication of a groundbreaking study has revealed new information on HCM and how it impacts the health of cats the world over.

The collaborative, 15-year investigation involving 50 veterinary hospitals in 21 countries was dubbed “The REVEAL Study.” The resulting article reports that HCM is a global feline health problem that might affect millions of pet cats.

1,730 cats were recruited for the study. Of these cats, 1,008 had HCM and 722 were considered healthy. Cats with HCM were generally older than healthy cats. And significantly, both intact and neutered male cats were much more common in the HCM group. That duplicates previous findings that suggest males are at higher risk of HCM. There was no difference in body weight between groups.

Lead author Philip Fox, DVM, MS, DACVIM/ECVIM (Cardiology), DACVECC, is head of cardiology at the Animal Medical Center in New York City and director of its Caspary Research Institute.

“The REVEAL Study documented that HCM puts cats at considerable risk to develop congestive heart failure, arterial blood clots, and cardiac death,” said Fox. “Heart failure or blood clots occur in nearly one-third of affected cats, and overall, one in every three or four affected cats experiences a cardiac-related death.”

Heart murmurs were heard in 82% of cats with HCM and in 46% of healthy cats. Cats with HCM were more likely to have loud murmurs, while healthy cats were more likely to have quiet murmurs. Arrhythmias were present in 12.7% of cats with HCM and in 4.2% of healthy cats. Systolic blood pressure did not differ between the two groups.

Cardiovascular drugs were prescribed in 52.3% of cats with HCM and none were prescribed for healthy cats. Drugs included beta blockers, ACE-inhibitors, diltiazem, clopidogrel, and aspirin.

The study also found that a large portion of cats who have cardiovascular events die within the first few months, but cats who survive a year are likely to have a more prolonged survival: The average survival time for cats who survived more than one year after a diagnosis of HCM was 1.3 years.

NEWStat asked Fox what impact his findings might have on the way veterinarians treat cats. “Because hypertrophic cardiomyopathy can have adverse health consequences, this might encourage veterinarians to consider screening cats using commercial biomarker tests such as the quantitative NT-proBNP test,” Fox said. “Also, when a heart murmur, gallop heart sound, or irregular heart rate [is detected], or heart enlargement [is] seen on chest radiographs, further evaluation via echocardiography should be considered.”

The study was funded by the Morris Animal Foundation and the Winn Feline Foundation. NEWStat reached out to Kelly Diehl, DVM, DACVIM (SAIM), senior scientific and communications advisor at the Morris Animal Foundation, to get her take on what the findings meant for veterinarians.

“The results of the REVEAL Study have huge implications for veterinarians in their daily practice,” Diehl said. “The study provides valuable prognostic information for veterinarians to share with their clients who have cats diagnosed with this condition.”

Diehl added, “The study also showed no difference in morbidity or mortality between the obstructive and nonobstructive forms of the disease in cats, dispelling the commonly held notion that cats with the obstructive form had a [less favorable] prognosis.”

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