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Heart disease in cats rarely looks like heart disease in dogs or people. There’s no equivalent of a dog’s telltale cough from congestive heart failure, and cats are experts at hiding weakness until a problem is advanced. The most common feline heart condition, hypertrophic cardiomyopathy, can quietly reshape a senior cat’s heart for years before any visible sign appears.
What Hypertrophic Cardiomyopathy Actually Is
Hypertrophic cardiomyopathy, usually shortened to HCM, causes the muscular walls of the heart to thicken. As the walls thicken, the heart’s chambers have less room to fill with blood between beats, so the heart has to work harder to pump the same amount of blood around the body. Over time that extra strain can lead to fluid backing up into the lungs or chest (congestive heart failure) or to the formation of blood clots, which is one of the more frightening complications of the disease.
Why Cats Hide It So Well
Many cats with HCM show no outward signs at all during the early and moderate stages, even though meaningful changes are already happening inside the heart. When signs do appear, they tend to be vague: lethargy, a reluctance to jump or play, breathing that looks slightly labored, or occasional fainting. Because cats already sleep most of the day, a slowing down can be easy to write off as normal aging rather than a heart problem.
A Home Warning Sign Worth Learning
One of the more useful things an owner can actually track at home is resting respiratory rate, meaning how many breaths a cat takes per minute while fully at rest or asleep, not panting or just back from activity. A healthy resting rate is generally under 30 to 35 breaths per minute. Counting it once a week or so, while a cat is sleeping, takes under a minute and can flag a developing problem well before more obvious symptoms show up.
Diagnosis
An echocardiogram, an ultrasound of the heart, is the gold standard for diagnosing HCM and for seeing exactly how thick the heart walls have become and how well the heart is functioning. Vets may also recommend a blood test called NT-proBNP, which measures a substance the heart releases under strain, as part of routine senior bloodwork for cats at higher risk. Because some cat breeds, including Maine Coons and Ragdolls, have a known genetic predisposition to HCM, vets may suggest earlier or more frequent screening for those breeds specifically.
Treatment
- No symptoms, low risk: many cats need no medication at all, just monitoring with vet checks roughly every six to twelve months.
- Symptomatic cats: diuretics such as furosemide help clear fluid buildup, while medications like pimobendan can help the heart pump more effectively.
- Clot prevention: cats at risk of thromboembolism, a dangerous blood clot complication, are often prescribed anti-clotting medication.
- Ongoing monitoring: even well-managed HCM is usually rechecked periodically by echocardiogram, since the disease can progress.
What Ties Back to Other Senior Cat Conditions
HCM doesn’t always show up on its own. Hyperthyroidism, a common condition in older cats, can cause a secondary form of heart thickening that looks similar to HCM on an ultrasound, which is part of why vets typically check thyroid levels alongside cardiac workups in senior cats. Chronic high blood pressure can do something similar. This is one of several reasons senior cat bloodwork tends to look at multiple organ systems together rather than one condition in isolation.
Living With an HCM Diagnosis
A diagnosis of HCM is not automatically a short-term prognosis. Cats with mild, asymptomatic HCM can live for years with nothing more than monitoring, while cats with more advanced disease benefit from a consistent medication routine and prompt attention if breathing changes or lethargy worsens. Stress reduction matters too: cats with HCM are sometimes more sensitive to the physiological stress of car rides, boarding, or major schedule changes, so vets may suggest planning ahead for anything that disrupts a cat’s routine.
The Bottom Line
Hypertrophic cardiomyopathy is common enough in cats, and quiet enough in its early stages, that it’s worth building basic awareness into ordinary senior cat care rather than waiting for obvious symptoms. Tracking resting respiratory rate occasionally, keeping up with senior wellness bloodwork, and mentioning any new lethargy or breathing changes to a vet promptly are the most practical tools an owner actually has.
Sources: VCA Animal Hospitals — Cardiomyopathy in Cats, PetMD — Feline Hypertrophic Cardiomyopathy (HCM) in Cats.
Photo: “Please pet me” by Simone Dalmeri, licensed under CC0 1.0.
