Congestive Heart Failure in Cats

Written by Shula Berg BVSc CertAVP(GSAS) GPAdvCert(SASTS) MRCVS
Clinically reviewed by Elizabeth McLennan-Green BVM&S CertAVP(SAM) MRCVS

Table of Contents

- Overview
- Symptoms
- Diagnosis
- Treatment
- Outlook

What is Congestive Heart Failure?

The heart contains four chambers, which work to pump deoxygenated blood from the body towards the lungs, and oxygenated blood from the lungs back around the body. Heart disease reduces the heart’s ability to pump blood effectively, usually due to the chambers becoming enlarged and weaker. Sometimes the heart’s rhythm is also affected, known as an arrhythmia. Eventually, changes become severe enough that the cat enters congestive heart failure (CHF). 

When the heart is not pushing enough blood out around the body, the pressure within the heart increases. The causes congestion to develop in the blood vessels within the lungs, as they are unable to empty into the main vessel entering the heart. Fluid leaks from the blood vessels into the lung tissue, known as pulmonary oedema. Other blood vessels can also become congested, causing fluid to accumulate in the chest cavity around the lungs (known as pleural effusion) or in the sac surrounding the heart (known as pericardial effusion). 

What are the symptoms of Congestive Heart Failure? 

The most common symptoms of CHF are due to pulmonary oedema, which affects the breathing. Symptoms include fast or laboured breathing, known as dyspnoea, sometimes with panting or open mouth breathing. Pulmonary oedema reduces the amount of oxygen entering the bloodstream, so cats with CHF often spend more time resting or sleeping and are less active than usual. They may have a reduced appetite. Rarely, cats can collapse or faint. 

It is important to highlight that cats are extremely good at hiding signs of illness, and often enter congestive heart failure with no prior warning. Although heart disease will have been present for some time, it is very common for this to cause no symptoms, and neither you nor your vet would have been able to know there was a problem. 

Cats with heart disease, including CHF, are at increased risk of blood clot formation. This can lead to a condition known as thromboembolism, where a blood clot leaves the heart and blocks circulation to one or both back legs. Affected cats will suddenly lose use of their back legs. The feet may be cold to the touch, and cats are often distressed and very vocal due to discomfort. This requires urgent veterinary treatment. 

Which tests are used to diagnose Congestive Heart Failure?

A diagnosis of CHF is made when there is fluid in the lungs and/or chest cavity (pleural effusion) and heart disease occurring at the same time. Pleural effusion can be diagnosed using ultrasound or x-rays of the chest. There are several causes of pleural effusion, and more than one condition can be present at the same time. Blood tests are usually recommended to screen for other conditions, such as thyroid disease. A specialised ultrasound scan of the heart (known as echocardiography, or an “echo”) will be required to confirm the presence of heart disease. These are best performed by a vet who has had specific training, so may not be available immediately or may require referral. Blood pressure measurement is advised in all cats with heart disease, as abnormal blood pressure may require additional treatment. 

Cats that present with clinical signs of CHF have often been coping for some time at home before reaching a “tipping point” and becoming symptomatic. This means that they have very little reserve left, and can deteriorate rapidly with stress. It is essential to handle them very carefully, and this commonly limits the tests we are able to do. Often, giving emergency treatment to stabilise the cat takes priority over confirming a diagnosis. Additional tests may be performed hours or even days later, depending on how the cat responds to treatment. 

How is Congestive Heart Failure treated? 

Cats in congestive heart failure always require treatment, which is lifelong. The mainstay of treatment is diuretic therapy, which works to reduce fluid accumulation. This is most commonly a drug called Furosemide, which can be given by injection or as a tablet. Diuretic drugs often cause increased thirst and urination, especially in the early stages of treatment. They can also affect electrolytes, such as potassium, and kidney enzyme levels, so periodic blood tests are recommended. 

If a very large volume of fluid is present in the chest, diuretics alone may not be able to relieve it. Often, it is recommended to drain the fluid directly, known as thoracocentesis. This uses a small needle to remove fluid. It is usually performed under light sedation to ensure the cat stays still, however, it is not painful. Often, the cat’s breathing improves very rapidly after this procedure. 

Other medication may be prescribed, depending on the underlying heart disease present. This may include additional diuretic drugs, and a category of drugs called ACE-inhibitors, which help protect the rest of the body from the effects of heart failure (e.g. Benazepril). Occasionally, medication to improve heart function can be used (e.g. Pimobendan) though this is not appropriate for some cats, depending on the exact nature of their heart changes. Due to the increased risk of clot formation in cats with heart disease, they are commonly prescribed an anti-coagulant (e.g. Clopidogrel). 

Symptoms of CHF can develop rapidly, and may require immediate veterinary attention. Often, a short period of hospitalisation for intensive care is advisable, especially if thoracocentesis is required. Hospitalisation allows medication doses and intervals to be tailored to the individual cat’s response, and drugs can be given by injection. The majority of cases will respond to treatment, but will need to continue taking oral medication at home for the rest of their life. 

What is the outlook for cats with Congestive Heart Failure?

The prognosis for cats in congestive heart failure is fairly guarded, as the condition is progressive. Although some cats will remain stable on medication for the rest of their life, others may gradually stop responding to treatment. Most cats only survive for a few months after diagnosis. It is important that our pets maintain their quality of life, so if you feel like your cat is struggling, please speak to your vet. 

One of the best measurements of congestive heart failure is an increase in respiratory (breathing) rate. Counting the respiratory rate is an easy way to monitor your pet at home. When your cat is calm and relaxed, count how many breaths they take in 15 seconds (in and out is one breath). Multiply this by four to get a respiration rate per minute. Normal cats take less than 30 breaths per minute; if you repeatedly count over 40, or see a steady increase over several days, contact your vet. The smartphone app “Cardalis” can help with monitoring and recording respiratory rates. 


Please note that the content made available on this webpage is for general information purposes only. Whilst we try to ensure that at the time of writing all material is up to date and reflects industry standards, we make no representation, warranties or guarantees that the information made available is up to date, accurate or complete. Any reliance placed by yourselves is done so at your own risk.

Last review date: 13th February 2024

Next review date: 13th February 2026