What is Hypertrophic Cardiomyopathy in Cats?

Introduction

When Karen brought home her fluffy Maine Coon, Simba, she never imagined that a routine check-up at the vet would reveal a concerning diagnosis. After noticing Simba’s increased breathing rate and lethargy, she discovered that her beloved feline companion was suffering from hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy in cats, often called HCM, is characterized by an abnormal thickening of the heart’s walls, leading to insufficient blood supply throughout its chambers. It is caused by a genetic defect that causes the muscle of the ventricles, or lower chambers of the heart, to become enlarged and unable to contract normally. As this occurs, it results in an inability for proper circulation throughout the body. If not addressed properly and promptly, this can lead to difficulty breathing, fatigue, and other adverse medical consequences for your cat.

The most common form of cardiomyopathy in dogs is dilated cardiomyopathy (DCM). DCM causes enlargement of the left ventricle, which pumps oxygen-rich blood throughout the body. This condition usually occurs when a cat is between two and six years old.

Hypertrophic cardiomyopathy is another form. This is rare in cats, but some cases have been reported. HCM affects the thickening of the heart’s walls, causing them to enlarge. As a result, the heart becomes stiff and cannot pump efficiently. Cats with this condition often experience exercise intolerance, sudden death, congestive heart failure, and syncope (fainting).

Types of Hypertrophic Cardiomyopathy in Cats

Hypertrophic cardiomyopathy is a genetic condition that damages the heart muscle. HCM causes the thickening of the left ventricle’s walls (the heart’s main pumping chamber). In some cases, the right ventricle enlarges as well. As a result, the heart pumps less blood throughout the body. This thickening makes the heart pump inefficiently and may lead to congestive heart failure.

There are two types of HCM in cats: Hypertrophic obstructive cardiomyopathy (HOCM) and non-obstructive hypertrophic cardiomyopathic (NOHCM). Both affect older cats, especially males.

HCM is most common in Maine Coon cats, Persians, Siamese, Himalayans, and Abyssinians. NOHCM is rarer than HOCM and occurs mainly in domestic shorthairs.

Both forms of HCM may be inherited. Some cases occur spontaneously.

What Causes Feline Hypertrophic Cardiomyopathy?

There are a variety of factors that can contribute to the development of this infectious disease in cats. Some possible causes include genetics, infection (such as feline leukemia virus), dietary problems (e.g., feeding high-fat diets), and environmental toxins.

Genetics

Hypertrophic cardiomyopathy (HCM) is a genetic disease that causes the thickening of the heart muscle. HCM affects dogs and cats, although it is most common in large-breed dogs. The condition may be inherited or occur spontaneously.

Genetic testing is available for some breeds, including Doberman Pinschers, Golden Retrievers, Labrador Retrievers, Rottweilers, Boxers, German Shepherds, Great Danes, Saint Bernards, and Siberian Huskies. Unfortunately, genetic testing is not currently available for cats.

Infection

Feline leukemia virus (FeLV), a retrovirus that infects domestic cats, is known to cause HCM in cats. FeLV is spread through saliva and blood, and infected cats often develop enlarged lymph nodes, fever, and lethargy.

 Dietary Problems

Diet plays a huge role in managing heart disease. Therefore, a cat’s diet suffering from hypertrophic cardiomyopathies (HCM) should be carefully monitored.

Many cats with HCM often develop kidney problems due to dietary imbalances. They may also suffer from gastrointestinal issues because of poor digestion and absorption.

Environmental Toxins

Environmental toxins are chemicals in our air, water, soil, food, and household items that may cause health problems. They include lead, mercury, arsenic, pesticides, herbicides, PCBs (polychlorinated biphenyls), dioxins, and polybrominated diphenyl ethers (PBDEs).

How Do I Know if My Cat has Hypertrophic Cardiomyopathy?

HCM occurs most often in young adult cats, although it may occur at any age. The condition usually causes no symptoms until the cat reaches adulthood.

If your cat shows signs of weakness, lethargy, coughing, breathing difficulties, vomiting, diarrhea, or sudden weight loss, his veterinarian should immediately see him. Your vet will perform a physical exam and listen to your cat’s heartbeat through a stethoscope. Then, he may recommend additional tests, including echocardiography and cardiac ultrasound.

Diagnosis of HCM in Cats

To diagnose HCM, veterinarians perform a thorough physical examination, including checking the cat’s gait, pulse rate, temperature, and respiratory rate. 

Vets use echocardiography to detect HCM in cats. Echocardiography uses sound waves to create images of the cat’s heart. The vet looks at these images to determine whether there are any abnormalities. They may also use ultrasound imaging to determine whether there is an obstruction in the mitral valve.

An electrocardiogram (ECG) measures electrical activity in the heart. An ECG records nature muscle cells’ electrical signals during each heartbeat. The ECG traces show where the heartbeats occur and when they begin and end.

An ECG is used to diagnose problems with the heart rhythm, including arrhythmias (irregular heartbeat), conduction abnormalities (problems with the electrical pathways through which impulses travel within the heart), and structural defects (abnormalities in the structure of the heart).

Serum biomarkers are elevated in patients with HCM compared to healthy individuals. These biomarkers include brain natriuretic peptide (BNP), troponin I, and creatine kinase MB fraction (CKMB).

Blood samples are taken to test for abnormalities in electrolytes and hormones.

Treatment and Management

Your vet may suggest treatment options based on whether your cat has been diagnosed with obstructive or non-obstructive HCM. Treatment depends on the severity of the disease and its effects on your cat’s quality of life. Some cats live long lives with HCM; others die suddenly due to complications associated with the disease.

Although there is currently no cure for HCM, many treatments exist to help control the progression of the disease and improve your cat’s overall health. These include medications, dietary supplements, and surgery.

• Medications used to treat HCM include beta-blockers, calcium channel blockers, diuretics, nitrates, digoxin, and angiotensin receptor antagonists. Beta-blockers slow down the rate at which the heart beats, reducing the workload on the heart and improving exercise tolerance. Calcium channel blockers relax the heart muscles and reduce the force of contraction.

Diuretics remove fluid from the body and decrease the work required by the heart. Nitrates dilate the arteries and lower blood pressure. Digoxin slows the heart rate and reduces contractions. Angiotensin receptor antagonists block the action of the hormone angiotensin II, which constricts blood vessels and increases blood pressure.

• Dietary supplements used to treat HCM are available over the counter. They include omega-3 fatty acids, antioxidants, vitamins, minerals, and herbal extracts. Omega-3 fatty acids are essential nutrients found in fish oil.

Antioxidants protect cells against damage caused by free radicals. Vitamins and minerals support healthy cell function and growth. Herbal extracts contain compounds that may benefit the cardiovascular system.

• Surgery is sometimes recommended when medical management fails to control the disease. Surgical procedures to relieve obstruction in the left ventricular chamber include septal reduction, mitral valve repair, tricuspid annuloplasty, and mitral valve replacement.

In some cases, surgical intervention is not possible or advisable. Instead, medication may be prescribed to control the disease and improve your pet’s quality of life.

Frequently Asked Questions