Zoya's Cats

FATE (Feline Aortic Thromboembolism, or Saddle Thrombus)

 

One tends to feel apprehensive about a condition with the acronym of FATE. Rightly so.

FATE (feline aortic thromboembolism) is a serious and painful condition with serious

implications. It comes on suddenly and appears to paralyze the cat, causing one or both

rear legs to become useless and even noticeably cold. The cat will hyperventilate and

cry out with extreme pain. Despite the extreme presentation, the cat may be able to

recover from the episode but it is important to understand how it came to be in order to

make decisions.

 

A thrombus is a large blood clot. An embolism is a small blood clot lodged somewhere

inappropriate.

 

What is a Saddle Thrombus?

The aorta is the largest artery in the body. It stems from the heart itself, where it arches

back and runs down the length of the back, ultimately splitting into the arteries supplying the back legs. The split where the aorta becomes the left and right iliac arteries is called the saddle.

 

A saddle thrombus is a blood clot that breaks off from a larger blood clot in the heart, travels down the aorta and lodges at the saddle. Not only is the blood supply to one or both rear legs cut off but a metabolic cascade results leading to the release of assorted inflammatory mediators, especially serotonin. The muscles of the rear legs become hard, and the foot pads become bluish in color; the condition is extremely painful. The inflammatory mediators readily lead to circulatory shock.

 

72% of cats with a saddle thrombus have both rear legs affected.

 

Where the Saddle Thrombus Came From

The saddle thrombus comes from a larger clot in the left atrium of the heart. This obviously begs the question as to why there would be a large blood clot in a cat’s heart. In fact, 89% of cats with a saddle thrombus have heart disease. Heart disease leads to turbulent blood flow which encourages the formation of clots.

 

Not every cat with heart disease will form an abnormal clot. In fact, most will not, but there is presently no clear why to predict which cats will form these clots and which ones will not. In cats with hypertrophic cardiomyopathy, the most common form of feline heart disease, the size of the left atrium is one factor that is considered. The presence of “smoke” in the atrium during echocardiography is another factor. (Smoke is the wispy material seen in the circulating blood.) Both these factors are considered controversial.

See a video of an echocardiographic imaging of a person who presented with recurrent postural syncope, looking much like it would in a cat, click here. The clot in her left atrium looks like a round ball moving around.

 

In 76% of cats with saddle thrombus, the FATE episode was the first sign of heart disease.

 

Will the Cat Regain Normal Use of his Legs?

The cat with a saddle thrombus is likely in shock. There is a question of survival from the shock as well as a question of whether or not there is heart failure. Obviously, heart failure is potentially as life threatening as is circulatory shock. Assuming everything goes well, and the heart failure and/or shock are either not present or are readily controlled, you still end up with a cat with heart disease and a big blood clot that could spit off another embolism at any time. Because of the potential for repeat episodes and need for long-term treatment of heart disease, not to mention the seriousness of the cat’s predicament, 25% of pet owners elect euthanasia without attempting treatment.

 

Of the remaining cats who get treatment, the following statistics have been published:

• 50% of treated cats survived to be discharged from the hospital.  

• The median hospitalization time was 2 days.  

• The median survival time of cats that did not present in heart failure was 223 days.  

• The median survival time of cats that did present in heart failure was 77 days.  

• Of cats who used aspirin as their main clot prevention drug after discharge, 25% of them had at least one more FATE episode at some point (usually in 6-12 months).  

• Occasionally a cat would lose tissue from loss of blood supply or even require limb amputation but these turn out to be exceptions to the rule. Most cats recover normal limb function after their FATE episode. 

 

Expect limb function to begin to improve after 2 to 3 weeks. The cat may require a great deal of nursing care until he is able to walk.