Feline Aortic Thromboembolism

Feline aortic thromboembolism, also called “saddle” thrombus or FATE, is a difficult and frustrating disease for the patient, the owner, as well as for the veterinarian. This disease, or rather clotting problem, occurs 99% of the time as a secondary complication to feline heart disease.

Feline aortic thromboembolism strikes cats that seem completely normal to their owners. Since the symptoms are acute and so severe, most of the time owners think that some type of trauma has happened.

Clinical symptoms of feline aortic thromboembolism vary somewhat from cat to cat; however, the overall appearance and temperament of the animals are very similar. Affected cats vocalize loudly, are weak and uncoordinated or paralyzed in the rear legs, and are restless. On closer examination, the hind limbs may feel cool and the footpads and nail beds are blue.

A thorough physical examination is necessary to diagnose aortic thromboembolism. Blood tests, x-rays and cardiac ultrasound are useful in diagnosing the underlying heart condition as well as eliminating other diseases. Feline aortic thromboembolism is very often associated with hypertrophic cardiomyopathy, the most common type of heart disease found in cats.

Cats with heart disease often have enlarged left atrium. The enlarged atrium causes blood flow to stagnate, thereby activating the clotting mechanism. A piece of this clot can break off, travel through the aorta and lodge in smaller arteries. The most common site for embolization is where the caudal aorta braches to form the 2 lilac arteries. Each iliac artery is responsible for delivering blood to its respective hind leg. Other areas where embolization occurs include (but not limited to) the renal arteries (causing acute renal failure) and cerebral arteries (causing seizures).

There are surgical and medical options for treating cats with feline aortic thromboembolism. Surgery is very risky and involves removing the clot. Prior to surgery, angiography is necessary to localize it. Surgery should be considered a last ditch effort because even if the clot were located and removed, there is a good chance that the animal would die from underlying heart disease.

Medical treatments for feline aortic thromboembolism include “clot busters” (such as streptokinase and tissue plasminogen activator) and anticoagulants (such as heparin). Major risks are involved with the administration of both medications.

Most cats that fall victim to feline aortic thromboembolism are managed conservatively, focusing on nursing care and pain suppression. Eventually, the clot may dissolve and some usage may return to the hind limbs; however, none of this is certain. The most frustrating problem is that even if the cat regains some hind limb usage, the underlying heart disease must still be considered.
The prognosis for cats with feline aortic thromboembolism is very poor to guard. 30% of affected cats die of heart failure or complications due to the clot; 30 % are euthanized due to the status of the patient and about 35% survive the initial episode. For the 35% that survive, there is a very large risk of clot formation occurring in the near future.

Prevention of future clotting episodes – The two most common medication used to prevent feline aortic thromboembolism are aspirin and heparin. The efficacy of these treatments is questionable and does not appear to reduce the chance of clot formation. Warfarin has also been used but it difficult to regulate and bleeding problems are common. At this time, heparin for several days after the initial clotting episode and long-term aspirin is the most commonly prescribed treatment for cats at high risk for clotting.

Due to the nature of this disease and the poor prognosis, euthanasia is considered to be an ethical and humane option. Owners that opt for treatment need to recognize that long-term aggressive care is necessary and that chances for recovery are not guaranteed.