🫀 Vet 2025 Guide: Hypertrophic Cardiomyopathy in Cats – Causes, Symptoms & Management 🐱❤️

Hypertrophic Cardiomyopathy (HCM) is the most common heart disease in cats and a condition that every cat owner should understand. In this Vet 2025 guide, Dr Duncan Houston explores what HCM is, what causes it, how it affects your cat, and what treatments and monitoring can help manage the condition. 🩺

💡 What is Hypertrophic Cardiomyopathy (HCM)?

HCM is a disease of the heart muscle where the walls of the left ventricle thicken abnormally. This is not a response to exercise or strain (as in athletic humans), but a disorder of the muscle tissue itself. In cats, this thickening makes it harder for the heart to relax and fill with blood between beats, ultimately affecting circulation and oxygen delivery. 🧬

🧬 What Causes HCM in Cats?

HCM in cats is thought to be genetic in origin, especially in breeds like the Maine Coon and Ragdoll. These breeds have documented mutations in the Myosin-binding protein C gene. However, domestic shorthairs—our everyday beloved house cats—are also frequently affected, suggesting that many cases may be hereditary but not yet linked to a specific gene. 🧬🐾

• 🔍 No viral or nutritional causes have been confirmed
• 🧬 Affected cats may not always have a known family history

💥 What Happens to the Heart?

Thickened walls in the left ventricle lead to:

• ⛔ Reduced heart relaxation
• 💧 Blood backing up into the lungs (pulmonary edema)
• 🌊 Fluid in the chest (pleural effusion)
• ❤️ Congestive heart failure (CHF)

Occasionally, the condition may cause:

• 💔 Arrhythmias
• 🩸 Sudden death (<5% of cases)
• ⚠️ Feline Aortic Thromboembolism (FATE) – a clot that blocks blood to the rear legs

🕵️ How Do Cats Present with HCM?

Many cats with mild or early-stage HCM show no obvious signs. They may appear perfectly healthy until the disease progresses. Common symptoms include:

• 😿 Rapid or labored breathing
• 📉 Decreased appetite
• 🐾 Sudden hind limb paralysis (if clot forms)
• 😴 Lethargy or subtle changes in behavior

Oftentimes, a vet discovers HCM during a routine check-up after hearing a murmur, gallop rhythm, or arrhythmia. 🩺

🔬 How is HCM Diagnosed?

• 🖥️ Echocardiogram (ultrasound): Gold standard for diagnosis—non-invasive and accurate
• 📊 NT-proBNP blood test: May show elevated heart stress but not definitive
• 🧪 Additional tests to rule out causes like hyperthyroidism and high blood pressure

Referral to a veterinary cardiologist is highly recommended for an accurate diagnosis and treatment plan. 🏥

🧬 Genetic Testing

Breeds like Maine Coon and Ragdoll cats can be tested for a known HCM gene mutation. Genetic testing is offered through veterinary institutions and helps breeders make informed decisions. 🧬

💊 How is HCM Treated?

There is no cure for HCM. The goal is to manage symptoms, prevent complications, and improve quality of life.

💓 Common treatments include:

• 🧘 Beta blockers or calcium channel blockers – to slow heart rate and improve filling time
• 💦 Diuretics – to reduce fluid buildup during CHF
• 🩺 ACE inhibitors – may support heart function
• 🩸 Clopidogrel or other anti-clotting agents – to reduce the risk of thromboembolic events

It's important to note: treatment is usually not started until signs of heart failure or clot risk appear. Preventative medication in mild or asymptomatic cases remains controversial. 😬

🩺 Monitoring at Home

If your cat has been diagnosed with HCM, you can help by:

• 📈 Monitoring their resting respiratory rate weekly
• 📞 Calling your vet if breathing rate rises above 30 breaths per minute at rest
• 🍽️ Watching for appetite or behavior changes

🧠 Prognosis

The outlook for cats with HCM varies depending on severity and response to treatment:

• 🐾 Mild cases: May live normal lifespans with minimal care
• ❤️ Moderate to severe cases: Risk of CHF, sudden death, or clots
• 💊 With CHF: Median survival is 12–18 months
• 🩸 With thromboembolism: 40–50% recover, but recurrence is common

Close vet supervision and early detection are key to a better outcome. 🐱

🐾 Should You Breed Cats with HCM?

If your cat has tested positive for an HCM mutation:

• 🧬 Breeding is not recommended for cats with two copies of the mutation
• 🧪 Cats with one copy may be bred to a negative partner under close monitoring
• 🧑‍⚕️ Seek advice from a veterinary geneticist or cardiologist

⚠️ Inbreeding is a concern in purebred populations, so breed management must balance health and diversity. Speak with a vet familiar with feline genetics. 🧬

📱 Need Support with HCM?

HCM can be overwhelming, but you don't have to face it alone. For guidance on diagnosis, care plans, and monitoring tips, visit AskAVet.com or download the Ask A Vet app for expert support from trusted professionals like Dr Duncan Houston. 🐾❤️

With knowledge, compassion, and the right veterinary care, your cat can enjoy a good quality of life—even with heart disease. 🩺