Feline Aortic Thromboembolism (FATE)

Feline aortic thromboembolism (FATE) happens when a blood clot stops blood from reaching one or both back legs. This is very painful and can quickly cause life-threatening complications. FATE is unfortunately a common consequence of heart disease in cats. If your cat suddenly struggles to move their back legs, take them to a vet immediately.

FATE usually affects both back legs, but sometimes only one. In rare cases, a front leg can be affected instead. The legs become paralysed or very weak, and they feel cold to the touch. Cats are usually very distressed and in pain. This condition develops very suddenly. Often, it’s the first sign of heart disease, especially in cats that don’t get regular vet check-ups. It’s crucial to see a vet as soon as possible, so that pain can be relieved and medication can be administered to prevent further complications. Between 30-45% of cats survive an episode of FATE, with intensive care required for several days. 

What causes Feline Aortic Thromboembolism? 

In healthy cats, the blood clots really well, which is life-saving as it prevents excessive blood loss when they suffer cuts or other injuries. Unfortunately, sometimes blood clots form when they shouldn’t. 

In FATE, an underlying condition disrupts blood flow. In 90% of cases, it’s heart disease (usually hypertrophic cardiomyopathy). Other possible causes include hyperthyroidism, blood infections, and cancer (usually in the lungs). 

What happens during FATE?:

• A large blood clot forms inside the heart or a major blood vessel. A smaller piece of the clot breaks off and moves to the aorta.

• Eventually, the blood clot gets stuck in a narrow area, and blood can’t move past it to the body parts beyond. This usually happens in one of the blood vessels that goes to a leg, or in both legs at the same time.

• Lack of oxygen and fresh blood stops the legs from working properly. Some cells start to die, and toxins build up.

• In most cases, the blood starts flowing again after some time. Unfortunately, this may lead to the built-up toxins being distributed throughout the body. This, in turn, may cause severe secondary complications, such as heart arrhythmias and kidney failure. 

Symptoms of Feline Aortic Thromboembolism

In about 3 out of 4 cats with this condition, both back legs will be affected. In other cases, it will affect just one back leg, or rarely a front leg. 

Common symptoms include:

• Weakness or paralysis of affected leg(s)

• Sudden and severe pain in the affected leg(s)

• Cold and pale back paw(s)

• Fast or laboured breathing

• Distressed yowling (vocalisation)

• The affected leg may be stiff and tense

• Some cats vomit shortly before the other symptoms start

• Cats may become very lethargic as the condition worsens

Cats at higher risk of Feline Aortic Thromboembolism

• The greatest risk factor for FATE is heart disease, but currently, only about 1 in 5 cats have their heart disease diagnosed before they develop FATE 

• Male cats are more commonly affected by FATE, as they are also more commonly affected by heart disease

• Mixed breeds are commonly affected, but also the Abyssinian, Ragdoll, Birman, Maine Coon, Himalayan, Siamese and Persian

• This condition has been reported in adult cats of all ages, but is more common between 8 and 12 years of age

Diagnosis of Feline Aortic Thromboembolism

A vet can often diagnose FATE during a physical exam. This is based on the combination of symptoms known as the 5 P’s. This refers to Pain, Paralysis or weakness, weak or absent leg Pulse, Pale or purple toes, and Poikilothermy (cold legs). 

If the physical examination isn’t conclusive, the vet may recommend:

• Doppler ultrasound of the aorta and legs, to assess blood flow and try to find the clot

• Blood tests (blood sugar and lactate) comparing the affected leg(s) and a normal one

• Infrared thermography, a special test to assess temperature and blood flow differences in the legs

Additionally, heart disease and other complications are usually present. Assessing and managing these play an important role in choosing the right treatments and knowing what to expect. Tests for these purposes may include:

• Heart ultrasound scan, to check for heart disease and the presence of a blood clot within the heart.

• Chest x-rays, to check for signs of congestive heart failure and pulmonary oedema. These are common complications of heart disease and affect treatment decisions and prognosis. Chest x-rays also help rule out the presence of lung cancer, an uncommon cause of FATE.

• Electrocardiography (ECG), to check for heart arrhythmias, a potentially life-threatening complication. 

• Blood tests to check for signs of organ damage. Kidney parameters and electrolytes are especially important, and are usually monitored regularly while in intensive care, to look for signs of complications. 

Veterinary treatment of Feline Aortic Thromboembolism

FATE is an emergency, and your cat needs to see a vet as soon as possible. 

Initial treatment may include:

• Strong painkillers: This condition is very painful, and your cat is likely to be distressed. Fortunately, medication can help a lot.

• Anticoagulants: Prevent the clot from getting bigger and prevent other blood vessels from getting blocked.

• If the earliest symptoms started less than 6 hours ago, your vet may recommend medication to help break up the clot. The potential benefits and side effects of this treatment haven’t been fully clarified, so your vet will advise you about what to consider for your pet. 

Treating complications of FATE

An important step is to treat other complications that may be present. 

• Congestive Heart Failure is a consequence of heart disease in cats, and this is present in 50-70% of cats with FATE. Treatment for this may include:

  • Administering concentrated oxygen with a mask or oxygen cage

  • Diuretics to relieve congestion and fluid build-up, such as furosemide

  • Other medications to support heart function, such as Pimobendan

• Many cats with FATE quickly develop dehydration, and this must be corrected carefully to prevent kidney problems without worsening heart function.

• The combination of paralysis and poor blood supply can quickly lead to ulcers and wounds in the affected legs. Careful attention needs to be paid to hygiene, nursing care, and physical therapy to prevent this. 

Ongoing treatment

Once the cat is stable, other medications may be considered to improve the blood supply to the affected areas. This is an area currently under investigation, but medications currently being tested for this purpose include Pentoxyfiline, Cyproheptadine, Cilostazol and Flunarizine.

Cats usually require 2-5 days of intensive care to recover from an episode of FATE, and sadly, some don’t survive the first 12-48 hours. For those who improve enough to go home, the ability to walk may take several weeks to return. 

Some cats will develop secondary complications as blood flow returns to the legs, such as arrhythmias, kidney disease or severe skin and muscle damage:

• Arrhythmias are very dangerous, especially if the underlying cause of the FATE episode was heart disease. Managing this requires constant monitoring and intensive care with intravenous medications until the arrhythmias have resolved. 

• Kidney disease (Acute Kidney Injury) happens in about one in three cats. This makes treatment more difficult and often requires longer hospital stays. It may be fatal in some cases. Treatment mostly consists of managing the symptoms.

• In about 1 of 20 cats that survive the initial critical period, severe skin and muscle damage require partial limb amputation.

Home treatment of Feline Aortic Thromboembolism

• Many cats will still be weak in their affected legs when they go home. Gentle physiotherapy exercises will likely be required for several weeks. Additionally, extra care with hygiene (using low-edge litter trays, toileting assistance, and regular wiping) may be needed to prevent skin injuries and infections.

• Cats who have recovered will need lifelong medication to reduce the risk of more clots and to manage any underlying condition, such as heart disease.

Prevention of Feline Aortic Thromboembolism

• Maintaining a healthy diet, body condition (weight) and being active are always good strategies to improve health.

• Cats should have regular vet checks to detect signs of heart disease as early as possible. Starting anticoagulant medication before symptoms develop may reduce the risk of a FATE episode happening.

What to expect for my cat with Aortic Thromboembolism

• Aortic thromboembolism is a very serious condition. Sadly, less than half of cats suffering an episode survive, even with intensive care. 

• Intensive care is required for several days. In most cases, there is an extended period of recovery afterwards. This can be stressful and expensive.

• Cats that have only one leg affected have a significantly better chance of recovery. 

• Most cats that improve during the first 48 hours will do well. In some cases, serious complications develop 2-5 days after the start of the symptoms.

• Lifelong treatment will be required to prevent or delay further episodes, as well as manage any underlying disease.

• Unfortunately, many cats will have more episodes of FATE or other serious heart disease complications within months. Some cats will survive 1-2 years with ongoing care and medication.  

When to worry about Feline Aortic Thromboembolism

Seek help from a vet in practice immediately if:

• Your cat is struggling to breathe, is open-mouth breathing or gasping for air

• Has blue or grey gums

• Is very tired and you are struggling to wake them up

• Is meowing in pain

• Can’t move their back legs

Call a vet for advice as soon as possible if your cat:

• Has a resting respiratory rate consistently above 30 breaths per minute

• Is losing weight or has less appetite

• Is spending a lot of time sleeping

Joii can help if:

You need help looking after your cat with heart disease in a stress-free manner

• You need guidance on how to take your cat’s resting respiratory rate

• You need advice on feeding your cat with heart disease

• You need tips on how to give medication to your cat