Feline Aortic Thromboembolism (FATE): Causes, Symptoms, & Treatment

Prathankarnpap / Shutterstock.com

Other Names: Thrombus, Saddle Thrombus, Clot, Feline Arterial Thromboembolism

Common Symptoms: Sudden pain, paralysis of one or both back legs, cold and pale/blue foot pads, rapid breathing, vomiting, distress

Requires Ongoing Medication: Yes, preventative medication

Vaccine Available: No

Treatment Options: Pain relief, oxygen therapy, diuretics if needed, and anticoagulant therapy to prevent the clot from worsening.

Home Treatment: Requires 24/7 care in a specialized veterinary hospital.

Feline aortic thromboembolism (FATE) is a medical emergency that usually affects middle-aged cats, most commonly males. It usually occurs as a result of underlying heart disease, although this is often undiagnosed. Unfortunately, many cats with FATE are euthanized due to the distressing symptoms and poor prognosis. However, there have been recent advancements in treatment meaning treatment could be more successful.

The word thromboembolism is made up of thrombus and embolism. A thrombus is a blood clot, and embolism means it has travelled from one place in the body to another. In the case of FATE, this is through the aorta to another blood vessel.

When the clot lodges in a smaller vessel it blocks the flow of blood – and therefore oxygen – to that part of the body. This can cause sudden onset paralysis of one or both back legs, alongside cold, blue paws, and lack of pulses. It is often extremely painful and requires immediate veterinary care for any hope of survival.

FATE is a devastating condition that all cat owners should be aware of. Read on for everything you need to know, from how to recognize the symptoms, to the chances of recovery.

Causes of FATE in Cats

Underlying heart disease is the main cause of FATE in 90% of cases. Parfenish_579 / Shutterstock.com

A recent review of Feline Aortic Embolism: Recent advances and future prospects stated that 90% of cases of FATE are caused by underlying heart disease. Most commonly, a condition called hypertrophic cardiomyopathy (HCM). However, in most cases, this heart disease is undiagnosed, meaning the FATE will occur out of the blue – making it even more distressing.

In most cats, the thrombus – or clot – forms in the left atrium of their heart, due to their heart disease. This then travels out of the heart through the aorta, lodging in a smaller vessel towards the back of the body where it can get stuck. This blocks blood flow and triggers a cascade of effects in the body that cause circulation to shut down in an area of the body. This is usually one or both back legs. The resulting symptoms are due to a lack of blood flow to the affected area.

Causes that are not related to heart disease are rare but include cancer, hyperthyroidism, infection, inflammatory disease, and some drugs.

Symptoms of FATE in Cats

FATE is one of the most devastating conditions I see as a vet. It happens suddenly, in cats who seemed perfectly healthy just minutes before. The symptoms are often extreme and very distressing, for both cats and their owners:

• Sudden weakness or paralysis of one or both back legs
• Poor or no pulses
• Cold or bluish paw pads
• Rapid breathing
• Rapid, irregular heartbeat
• Howling, or other signs of pain and distress
• Vomiting

If you are worried your cat may be suffering from FATE, you should seek veterinary advice immediately.

Diagnosis of FATE in Cats

FATE can be diagnosed based on symptoms alone, but an ultrasound of the heart (echocardiogram) can help diagnose the underlying condition, such as hypertrophic cardiomyopathy. Sungthong / Shutterstock.com

Diagnosis of FATE is usually straightforward, as the symptoms are easily recognizable. However, your veterinarian may recommend some tests to help determine the next step.

This may include an x-ray or ultrasound of your cat’s heart (an echocardiogram) and chest, as over half of cats with FATE are also in congestive heart failure (CHF). This doesn’t worsen their prognosis, but it will need treatment. If your cat is stable enough, they may also recommend blood tests.

Recent research in the Journal of Feline Medicine and Surgery shows that some of these results are important ‘prognostic indicators’, meaning they can help your veterinarian understand your cat’s chance of survival. These include:

• One leg affected vs two legs: cats with only one leg affected have a higher chance of survival.
• Rectal temperature: Cats with low temperatures have a poorer prognosis. Two studies found that cats with rectal temperatures below 98.9°F and 96.2°F respectively, have a low chance of survival.
• Blood lactate levels in the affected limb: high levels of lactate in the blood from the affected limb indicate a poorer prognosis.
• Time since onset of clot and response to treatment: The quicker your cat is treated the better the chance of recovery. Showing a response to treatment within the first 24-48 hours is a positive sign.

Should Cats with FATE be Treated?

FATE is a serious and devastating disease. Although it is hard to consider, the first question in treating FATE is whether it should even be attempted.

Traditionally, FATE has carried a very poor prognosis. The symptoms are painful and distressing, and – even with the best medical care – many cats do not survive. Of those that do, recurrence of the clot is common, often within weeks or months. As a result, many owners choose euthanasia as the kindest option.

However, recent research has found more promising results, with approximately 25-45% of cats (depending on the study) surviving until discharge, with certain individual specialized clinics reporting success rates of up to 90%.

So, while previously, some veterinarians have recommended euthanasia for all cases of FATE, it seems this view should be challenged. However, it is vital to understand that treating FATE is difficult, and complications are common. Sadly, it is unusual for affected cats to survive more than 1-2 years.

Therefore, euthanasia should always be discussed with your veterinarian, especially if initial test results are poor.

Treatment of FATE

Cats being treated for FATE should be hospitalized in a 24/7 veterinary hospital. Lebedko Inna / Shutterstock.com

As FATE is so challenging to treat, cats should be hospitalized in a veterinary clinic with 24-hour care. Initial treatment will focus on pain relief, oxygen, diuretics (if needed), and medication to prevent the clot from worsening:

• • Pain relief: FATE is painful, so treatment with a strong pain relief such as the opioid methadone is recommended.
  • Oxygen: Oxygen can be given via a face mask, nasal prongs, or (preferably) an oxygen cage.

• Diuretics: More than half of cats with FATE also have congestive heart failure (CHF). This is where the heart is struggling to pump blood around the body, causing fluid to build up in the chest. This affects their breathing. A diuretic, such as furosemide, can help to relieve this fluid.
• Anticoagulants: Anticoagulant medications are recommended to help prevent the clot from worsening. Options include low-dose aspirin, clopidogrel, and low molecular weight heparin (LMWH) such as enoxaparin or dalteparin. The Consensus on the Rational Use of Antithrombotics in Veterinary Critical Care (CURATIVE) guidelines recommends a combination of clopidogrel and LMWH for initial treatment.

While your cat is being treated for FATE, they will need ongoing blood tests and imaging (such as repeat scans) to check how they are responding and to monitor for complications.

Nursing care is also vital for cats with FATE. Physiotherapy and warming of the affected legs are both helpful. But it can take several weeks to see an improvement.

Recent Advancements in Treating FATE

Recent studies at specialist veterinary hospitals have shown promising results using thrombolytics – drugs that may break down the clot. Options that have been used include alteplase and reteplase, the latter of which showed a nearly 90% survival rate in a small trial involving 12 cats. There is also interest in drugs that may improve collateral circulation, such as pentoxifylline and cyproheptadine.

Currently, these medications are only used in specialized hospitals and research studies. However, it is hoped that they may improve the prognosis for cats affected by FATE in the future.

Long-Term Management of Cats with FATE

Cats who survive FATE should be put on anti-coagulation medicine long-term to help prevent future clots. New Africa / Shutterstock.com

Cats who recover from an episode of FATE will need long-term treatment. This will include management of their underlying heart disease, as well as medication to prevent future episodes of FATE.

These medications are anti-platelet and anti-coagulant drugs, designed to reduce the risk of a clot developing. Many studies are looking at the best combination of drugs, but most include a combination of:

• Clopidogrel (an anti-platelet drug shown in the FATCAT study to be superior to aspirin), and an
• Anticoagulant, such as rivaroxaban or apixaban.

Complications

Unfortunately, cats treated for FATE commonly suffer from serious complications. These include kidney damage and reperfusion injuries. However, the Bilateral Lysis of Aortic Saffle Thrombus with Early Tissue Plasminogen Activator (BLASTT) study found that, with the right treatment, 40% of cats with complications will recover.

Caring for Cats with FATE

The ongoing care and monitoring of cats treated for FATE is complex. As a result, emergency and critical care specialist, Julien Guillaumin DVM recommends that “ongoing care for a cat following a FATE episode may be best suited to a 24/7 veterinary facility with solid expertise in nursing care and a multi-specialty medical team.”

How to Prevent FATE in Cats

There are two key steps you can take to prevent FATE in your cat:

1. Recognize and treat heart disease early
2. Give preventative medication

Recognize and Treat Heart Disease Early

Heart disease is the underlying cause of FATE in around 90% of cases. But in most of those, the heart disease had not been diagnosed.

Taking your cat for regular health checks will help your veterinarian spot early signs of heart disease (before any symptoms occur). They can start treatment, including medication to help prevent FATE, early, before an episode of FATE occurs.

Give Preventative Medication

Preventative medication should be considered for cats at risk of FATE, either because of heart disease or having already survived one episode. The current evidence for the prevention of future episodes of FATE recommends a combination of an anti-platelet drug (such as clopidogrel) and an anticoagulant (such as rivaroxaban).