Feline Aortic Thromboembolism 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 Feline Aortic Thromboembolism?

Feline aortic thromboembolism (FATE) is a painful, life-threatening disorder seen in middle-aged and older cats. It almost always occurs due to underlying heart disease, though it is common that the heart caused no symptoms prior to the FATE occurring. Up to 20% of cats with heart disease will develop FATE due to a combination of factors including reduced blood flow, damage to the heart walls, and increased clotting ability. 

A thromboembolism occurs when a blood clot (thrombus) develops, and part or all of the clot travels elsewhere in the body via the bloodstream (an emboli). In cats, the blood clot commonly develops in the heart, most often in the left atrium. While clots are moving, they don’t cause a problem. However, if they travel into smaller vessels, they can cause an obstruction, cutting off blood supply to the surrounding tissues. In cats, the aorta divides into two blood vessels supplying the back legs, known as the iliac arteries. It is common for a blood clot to become lodged here, affecting blood supply to one or both of the hind-limbs. This is known as FATE, or a “saddle thrombus” if both limbs are affected. Rarely, a thromboembolism can affect a front leg, more often on the right-hand side. 

What are the symptoms of Feline Aortic Thromboembolism? 

The most common symptom of FATE is sudden onset weakness or paralysis of both back legs. The sudden loss of blood supply can be very painful, so affected cats are often vocal. It is common for owners to assume the cat has been hit by a car, but on examination, the feet are usually cold to the touch and there will be no external injuries. 

Since almost all cats with FATE have underlying heart disease, the stress of the embolism can cause them to enter congestive heart failure. This may cause increased breathing rates or laboured breathing in addition to the signs already mentioned. 

Which tests are used to diagnose Feline Aortic Thromboembolism? 

FATE is one of the few conditions that can be confidently diagnosed on examination alone. A blood pressure machine may be used to confirm a lack of blood flow to the feet. Sometimes the clot in the aorta can be visualised on ultrasound. However, this is often unnecessary, especially if the cat is in a lot of discomfort. 

Depending on the treatment option chosen, additional tests may include blood tests to assess organ function, blood pressure measurement, and an ultrasound scan of the heart (echocardiography). 

How is Feline Aortic Thromboembolism treated?

Treatment of FATE is imprecise with variable success rates. The most important treatment is very strong pain relief, usually an opioid given every few hours by injection. Cats can also be started on anti-coagulant medication, usually Clopidogrel, to try and prevent new clots forming. There is no specific treatment to break down the existing clot, so treatment is mostly focussed on pain relief and supportive care while the body addresses the blockage. This can take several days, and your cat will need to remain hospitalised throughout. For cats with advanced heart disease, this may require treatment as well. 

Unfortunately, many cats will not respond to treatment. Given the significant pain caused by FATE, and likelihood of underlying heart disease, many people feel that putting the cat to sleep (euthanasia) is preferable to attempting treatment. We can never be certain if an individual cat will or won’t recover, but will always support euthanasia as a compassionate option to prevent suffering. 

What is the outlook for cats with Feline Aortic Thromboembolism? 

The prognosis for all cats with FATE is guarded. Many cats won’t respond to treatment, and those that do can have a long road to recovery, with physiotherapy required to regain full hind-limb function. Uncommonly, reperfusion injury occurs when blood flow returns to the limbs, causing release of toxins and sudden death. 

It is important to note that all cats who have experienced FATE are at risk of future events, even with ongoing anti-coagulant treatment. It is also strongly advised to have a full cardiac work-up to ascertain the type and severity of heart disease present. This may require treatment in its own right, and regular follow-up appointments. 


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