Heart Disease in Cats

Heart disease in cats is a broad term that includes problems affecting the heart muscle, valves, rhythm, or the way blood moves through the heart. In adult cats, the most common form is cardiomyopathy, especially hypertrophic cardiomyopathy, or HCM. In HCM, the heart muscle becomes abnormally thick, which can make it harder for the heart to fill and pump effectively. Over time, this can lead to fluid buildup in or around the lungs, abnormal heart rhythms, or blood clot formation.

One challenge for pet parents is that cats often hide illness very well. Many cats with heart disease have no obvious signs early on, and some are first identified after your vet hears a murmur, gallop rhythm, or arrhythmia during a routine exam. Others do not show clear symptoms until they develop congestive heart failure or an arterial blood clot. Because of that, subtle changes like sleeping more, hiding, eating less, or breathing faster at rest matter.

Heart disease may be primary, meaning it starts in the heart itself, or secondary to another condition such as hyperthyroidism or high blood pressure. Some breeds, including Maine Coons and Ragdolls, have known inherited risk for certain forms of cardiomyopathy. Still, any cat can be affected, including mixed-breed cats.

The good news is that many cats can do well for months to years with appropriate monitoring and a care plan tailored to their stage of disease. The right approach depends on whether your cat has mild disease with no symptoms, active congestive heart failure, a clotting risk, or another underlying illness that also needs treatment.

Diagnosis starts with a careful history and physical exam. Your vet may hear a heart murmur, gallop rhythm, or irregular heartbeat, but some cats with significant heart disease have a normal-sounding chest. Because signs can overlap with asthma, pleural effusion, anemia, hyperthyroidism, and other conditions, testing is important to sort out what is happening.

Common first-line tests include chest X-rays, bloodwork, urinalysis, blood pressure measurement, and an ECG to assess rhythm. A cardiac biomarker test such as NT-proBNP may also help your vet decide whether breathing signs are more likely related to heart disease. If fluid is present around the lungs, your vet may recommend removing some of it both to help your cat breathe and to guide diagnosis.

Echocardiography, or heart ultrasound, is the key test for defining the type of heart disease. It shows heart wall thickness, chamber size, pumping function, blood flow patterns, and whether the left atrium is enlarged. This matters because enlarged atria can increase the risk of clot formation. In many cases, your vet may recommend referral to a veterinary cardiologist for the ultrasound and treatment plan.

Your vet may also look for diseases that can cause or worsen heart changes, especially hyperthyroidism and systemic hypertension in older cats. Identifying those conditions can change the treatment plan and sometimes improve the heart problem if the underlying issue is controlled.

The most common cause of heart disease in adult cats is cardiomyopathy, a disease of the heart muscle. Hypertrophic cardiomyopathy is the form diagnosed most often. Other forms include restrictive cardiomyopathy, dilated cardiomyopathy, and less commonly unclassified cardiomyopathy. Cats can also have congenital heart disease, meaning they were born with a structural defect, though this is less common than adult-onset cardiomyopathy.

Some heart disease is inherited. Maine Coons and Ragdolls are well-known examples of breeds with genetic risk for HCM, and other breeds may also be predisposed. Male cats appear to be affected more often in some HCM populations. Still, breed and sex are only part of the picture, and many affected cats are domestic shorthairs with no known family history.

Secondary heart disease can develop when another illness changes the heart over time. Hyperthyroidism and high blood pressure are especially important in older cats. Historically, taurine deficiency caused some cases of dilated cardiomyopathy, but this is now much less common in cats eating complete commercial diets. Inflammatory disease, infiltrative disease, and rhythm disorders can also affect heart function.

Risk does not always equal symptoms. A cat may have a murmur without severe disease, or significant disease without a murmur. That is why screening and follow-up matter, especially in cats with breed risk, older cats with thyroid or blood pressure disease, or cats with unexplained breathing changes.

Not all feline heart disease can be prevented, especially inherited cardiomyopathies. Still, there are practical ways to reduce risk and catch problems earlier. Routine wellness exams matter because your vet may detect a murmur, gallop rhythm, arrhythmia, weight change, thyroid issue, or high blood pressure before your cat looks sick at home.

Feeding a complete and balanced commercial cat diet is also important. Taurine deficiency used to be a major cause of dilated cardiomyopathy in cats, but it is now uncommon in cats eating properly formulated diets. If you feed a home-prepared diet, ask your vet or a board-certified veterinary nutritionist to review it.

For breeds with known inherited risk, screening can help. Breeders may use genetic testing in some lines, but a normal genetic test does not rule out all heart disease. Echocardiographic screening may still be recommended for breeding cats or cats with family history. For older cats, managing hyperthyroidism and high blood pressure promptly may reduce secondary strain on the heart.

At home, one of the most useful habits is learning your cat’s normal resting breathing rate and behavior. A gradual increase in breathing rate, new hiding, reduced appetite, or lower activity can be an early warning sign. Prevention is not always about stopping disease from starting. Often, it is about finding it sooner and avoiding a crisis.

Prognosis varies widely. Some cats with mild cardiomyopathy and no symptoms live comfortably for years with monitoring alone or limited medication. Others progress more quickly, especially if they develop congestive heart failure, significant left atrial enlargement, difficult arrhythmias, or arterial thromboembolism. The exact type of heart disease and whether there is an underlying condition like hyperthyroidism also affect outlook.

Cats in heart failure can sometimes improve noticeably within hours to days once oxygen support, diuretics, and fluid drainage are provided. Recovery from the immediate crisis does not mean the heart disease is gone, though. Most cats need ongoing follow-up, medication adjustments, and home monitoring after discharge. Your vet may recommend tracking resting breathing rate, appetite, energy, and comfort.

Blood clot complications can be especially serious and painful. Some cats recover partial or even good limb function with treatment and nursing care, while others have recurrent clots or poor circulation that worsens prognosis. Cats with repeated episodes or severe heart enlargement usually need a very careful quality-of-life discussion.

The most helpful approach is to ask your vet what stage of disease your cat has now, what changes would count as an emergency, and what realistic goals fit your cat and household. Heart disease is often managed rather than cured, but many cats still enjoy meaningful time at home with a plan that matches their needs.