Heart Disease in Cats

What Is Heart Disease in Cats?

Heart disease, also called cardiomyopathy, ultimately affects the ability of the heart to contract, the strength of those contractions, and the overall amount of blood distributed to the body. 

The feline heart is a muscle made up of four chambers—two atria and two ventricles. The atria serve as receptacles for blood entering the heart, from the lungs on the left side and the body on the right side. From there, blood is pumped into the ventricles and then either flows into the lungs from the right side to pick up oxygen or out from the left side into the aorta (the body’s largest artery) to deliver oxygenated blood to the body. 

Because the heart is a muscle, doing any work outside of its normal job causes it to thicken and become enlarged. As the muscle walls thicken, they become less elastic and less able to relax, preventing the ventricles from filling up with adequate blood.

As a result, the blood backs up into the lungs and heart failure develops. The thickening that occurs can also lead to arrhythmias (irregular heartbeats) as well as the development of clots.

Types of Heart Disease in Cats

Heart disease in cats can occur as the result of many different abnormal processes in the heart, such as abnormal rhythm, abnormal heart muscle, abnormal contraction, valve disease, or some combination of the above.

Heart muscle disease has traditionally been classified as either primary (congenital) or acquired.

Primary (congenital, meaning a birth defect)

•  Hypertrophic cardiomyopathy (HCM), either with or without systolic anterior motion of the mitral valve (SAM), is the most common form of heart disease in cats. In this disease, the left ventricular muscle walls become thickened.

  • HCM is a progressive disease and SAM occurs when the mitral valve gets “sucked” into the aorta during contraction, causing a temporary blockage, restricting blood flow, and increasing pressure.  

Acquired (developed as cat ages):

• Dilated cardiomyopathy (DCM) is often attributed to a nutritional deficiency in the amino acid taurine. DCM is a widening of all heart chambers, which leads to thinner walls and an increased workload of the heart, ultimately with loss of contraction strength and heart failure.

• Restrictive cardiomyopathy (RCM), where the muscle becomes tough and less flexible; usually the left ventricle is only mildly enlarged; however, the atria are enlarged and mitral valve insufficiency is usually present. 

• Arrhythmogenic right ventricular cardiomyopathy (ARVC), where the right ventricle becomes dilated with thinner walls. This cardiomyopathy often leads to right-sided heart failure.

• Unclassified cardiomyopathy (UCM) is used as a catch-all term for those diseases that do not fit into any specific category.

There are also other types of heart disease that can occur secondarily as a complication of another disease, such as cancer, hyperthyroidism, or hypertension (high blood pressure).

Symptoms of Heart Disease in Cats

Many cats with heart disease can be asymptomatic (show no visible signs), which makes diagnosing the condition challenging. Unfortunately, for some cats, the only symptom is sudden death. Other cats may experience the following:

• Abdominal distension

• Abnormal heart sounds such as murmur, arrhythmia, or gallop rhythm

• Collapse

• Cool extremities (cat is cold to the touch)

• Decreased appetite

• Heart failure

• Lethargy

• Pale or blue gums

• Respiratory changes such as increased respiratory rate, open mouth breathing, panting, labored breathing, and cough (rarely)

• “Stretching” postures

• Sudden hind limb paresis or paralysis, most often caused by a saddle thrombus (clot) and accompanied with pain and vocalization

• Vomiting

• Weak pulses, felt on the inside of the cat’s thighs

Causes of Heart Disease in Cats

HCM has been shown to be inherited, often by genetic mutation, in purebred cats such as Maine Coons and Ragdolls, and is more prevalent in male cats. Other predisposed breeds for HCM and heart disease include the Persian, Sphynx, American Shorthairs, and British Shorthairs. Testing for this condition is available through a DNA/genetics test.

How Veterinarians Diagnose Heart Disease in Cats

Cats with an underlying heart disease do not always have a heart murmur that can be detected in a routine exam. In fact, about one-third to one-half of cats diagnosed with HCM have no symptoms at the time of diagnosis, and many cats may sadly only experience sudden death. Therefore, when symptoms are present, it’s critical to have your cat examined by a veterinarian.

Several tests are often recommended to help determine the cause of your cat’s specific heart disease. An echocardiogram, or ultrasound of the heart, is considered the best diagnostic tool, as it can determine the ventricle wall thickness, pressures within the heart, valve conformation and ability, and presence of clots. It is the only method to differentiate the different types of heart disease.

Additional tests your vet may recommend for your cat include:

• Basic blood and urine laboratory testing: to understand your cat’s overall health and establish a baseline needed for future monitoring and response to treatment.
• Blood pressure and thyroid evaluation: to rule out secondary causes of heart murmur/disease.
• Chest X-rays: to look for heart enlargement and fluid in the lungs.
• Electrocardiogram: to determine the presence of arrhythmias and chamber enlargement.
• Nt-proBNP (proteins produced by the heart) testing: a screening tool to help determine if there is moderate to severe heart muscle disease present.
• Taurine level measurement in your cat’s blood and/or food: to determine if there is a deficiency of this amino acid—a major cause of DCM.

Treatment of Heart Disease in Cats

Treatment will depend on the type and degree of heart disease present, often influenced by the presence of heart failure, degree of thickening, strength of muscle contractions, and the ability of the valves to function.

Your cat will be assessed, a physical exam performed, and supportive care measures taken, which often will include oxygen therapy as well as mild sedation or anti-anxiety medication to minimize stress and slow your cat’s breathing. Thoracocentesis or abdominocentesis, a procedure where fluid is removed from the chest or abdomen, may be necessary to help your cat breathe. 

Medical management often includes some combination of the following:

• ACE inhibitors, such as enalapril: to help reduce blood pressure and the heart’s workload.

• Anticoagulants, such as heparin or warfarin: often utilized in the presence of known clots or to help break down clots.

• Antiplatelet therapy, such as aspirin or clopidogrel: to help prevent clot formation.

• Beta blockers, such as atenolol: an antiarrhythmic medication that also helps decrease the heart rate and helps regulate blood pressure.

• Calcium channel blockers, such as diltiazem: to relax the heart.

• Diuretics, such as furosemide: to draw the fluid off the lungs.

Dietary management with well-balanced, high-quality food that meets the requirements for taurine or taurine supplementation may be needed. In addition, diets low in sodium such as Royal Canin® Renal Support are typically recommended.

Cats that are diagnosed with hypertension (high blood pressure) or hyperthyroidism can often be regulated with medications. Hyperthyroidism can be treated with surgery, medication, diet, or radiation. 

Recovery and Management of Heart Disease in Cats

Unfortunately, resolution of an underlying heart disease is not possible in many cats, so it can only be managed as best as possible. Lifespan is variable, as some cats with heart disease can experience a normal life and then die from an unrelated condition. Other cats can die quite suddenly, even with the best of medical care. 

Providing a relatively stress-free lifestyle for your cat is important, as is monitoring for changes in her behavior, appetite, and breathing rate. There are certain phone apps you can use, such as Pet Breath Counter, to document your cat’s respiratory rate and show trends and values over time. (A respiratory rate of greater than 30 while at rest should prompt immediate veterinary attention!)

Medications are often the mainstay of acute and long-term therapy. It is important to never discontinue medication without consulting your veterinarian first.