When the Heart Hurts

Hypertrophic Cardiomyopathy (HCM) is caused by the thickening of the muscle. The walls of the left ventricle become abnormally thickened. Both pedigree and non-pedigree breeds can get HCM. Among the pedigree cat breeds, the ones most susceptible to HCM are Bengals, Maine Coons, British Shorthairs, and Persians.

In most cases, the cause is unknown. However, age is considered an important factor for the development of HCM in cats. Comorbidity is also a risk factor for the development of HCM. In older cats, sometimes, hyperthyroidism and high blood pressure may lead to heart muscle thickening.

Stages of HCM

Stage A: Cats are at risk of developing cardiomyopathy

Stage B1: Subclinical cats with normal or mild left atrial enlargement (low risk)

Stage B2: Cats with moderate/severe left atrial enlargement (high risk)

Stage C: Cats with a current or prior history of congestive heart failure (CHF) or aortic thromboembolism (ATE), when either one or both hind legs become paralyzed due to a blood clot

Stage D: Cats no longer respond to medical treatment

Studies report that 15% of cats develop heart diseases 50% of these cases are HCM.

Signs Your Cat’s Heart May Be Asking for Help

Cats with HCM show different symptoms based on the severity of the disease as the heart disease progresses. In the early stages, cats may remain asymptomatic for months or even years if the disease progresses slowly. This stage is called asymptomatic HCM.

Over time, when the disease progresses to more advanced stages, cats may start showing symptoms like difficulty breathing due to the accumulation of fluid within or around the lungs. Cats may get paralyzed in their hind legs due to a blood clot or may even collapse due to abnormal heart rhythms. This stage is called symptomatic HCM.

If your cat has been diagnosed with HCM and has no symptoms as yet, it is important for you to know that symptoms can develop later, and hence it is critical to monitor your cat closely and get regular check-ups done by your vet.

The most common symptoms include –

• Lethargy or weakness
• Loss of appetite
• Difficulty breathing
• Rapid breathing during periods of rest
• Exercise intolerance
• Chronic coughing
• Fainting or collapse
• Sudden hind-leg paralysis

Do Cats with HCM Develop Blood Clots?

Some cats with HCM may develop blood clots in the heart, which may get pumped around the body. They may then block blood vessels and obstruct the flow of blood. An emergency may arise when the blood clots affect the hind legs, causing paralysis and pain in either one or both hind legs.

The Road to Diagnosis

Your vet may detect a heart murmur or an abnormal heart rhythm and may suspect HCM. Typically, your vet may recommend echocardiography or an ultrasound of the heart. This procedure is completely painless. Your cat will need to lie on its side and remain still. A mild sedation may be used to help the cat relax. Fur is removed on both sides of the cat’s chest, and a gel is applied. This will help in getting a clear ultrasound image.

The whole procedure takes up to 60 minutes, and your pet will be closely monitored throughout. Other tests that may be recommended are chest X-rays (to assess the presence of fluid in and around the lungs), blood tests, and blood pressure monitoring.

Love, Care, and Medications

Heart medications can neither treat nor prevent HCM. Meaning, once the heart muscles have thickened, there is no way you can treat or reverse them. However, they can help improve the quality of life of cats by controlling and reducing the risk of symptoms. Heart medications that your vet will recommend may help in delaying the rate of progression of the disease. Other medications provide nutritional support to your feline friend’s heart.

Your cat may also need a diuretic, a medication that is used to remove excess fluid from the body and help them breathe comfortably. Other medications that may be recommended include drugs to reduce blood pressure, drugs to reduce clot formation in the heart, and drugs for overactive thyroid gland, if these conditions are diagnosed.

(Dr. Ankur Narad -PhD, Principal Animal Husbandry Diploma College Bhopal, NDVSU, Jabalpur, Dr Giridhari Das- Director Diploma NDVSU Jabalpur, Dr Supriya Shukla-Professor & Head Dept. of Vet Pathology, COVS Mhow, NDVSU Jabalpur)