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ISU Student Experience

Feline Aortic Thromboembolism

Written by: Natalie Hendriksenoutl • 2022 Scholar

History and Physical Exam

Chloe, a 9-year-old feline domestic short hair, presented to IVS as a triage. Chloe had started vocalizing loudly at around 6 pm, a few hours before she was brought in. About an hour before she was brought in, the owner noticed that she could not use both her hind limbs.

Upon physical exam, she had tachycardia (abnormally increased heart rate) and tachypnea (increased respiratory rate) with increased effort. Diffuse cachexia (weakness or
wasting of body muscle) and a tense and painful abdomen were also noted. The main concern from the physical exam was the bilateral hind limb lameness, absent femoral pulses, and both limbs cool to the touch.

After examination, it was determined that Chloe had an aortic thromboembolism, which is also known as a saddle thrombus.


A saddle thrombus is a smaller blood clot that usually breaks off from a larger blood clot found in the heart’s left atrium. This thrombus gets lodged in the trifurcation of the aorta, where it splits into the iliac arteries that supply both hind limbs. (Brooks, 2012) Once the clot is lodged, it cuts off blood supply to both hind limbs and is usually very painful. Thus, the
cats will loudly cry and vocalize.

Usually, 89% of cats with saddle thrombus usually have prior heart disease, the most common being hypertrophic cardiomyopathy. However, not all cats with heart disease will form thromboembolism. It is currently unknown how to predict which cats are more likely to form emboli. Most cats with heart disease had a saddle thrombus, the first sign
of heart disease. (Brooks, 2012)

Diagnosis and Tests

Usually, a physical exam is the main test needed to diagnose aortic thromboembolism. This is seen by observing weakness or paralysis in one to both hind limbs, decreased pulses in the hind limbs (specifically the femoral arteries), and cold and pale hind limb nailbeds and pads
due to decreased or absent blood circulation. (Weir and Downing)

Comprehensive blood work and chest radiographs can be done if the cat is stable enough. These tests will indicate toxins in the body, kidney function, body function, heart failure, or cancer. These tests may indicate why the clot occurred if it was due to heart disease, cancer, or no apparent reason. (Brooks, 2012)

Treatment and prognosis

Cats with aortic thromboembolism may benefit from some oxygen therapy. Usually, since cats with this issue have heart disease, it is best to keep them as stress-free as possible. In some cases, pain medication may be useful as well.

Surgical removal of the embolism is not recommended because of how small and delicate the cat’s vessels are, and heart disease patients are usually at high risk of undergoing surgery.
Clopidogrel is a drug that can be given during and after an episode. This drug works to stop platelets from clumping together, which then prevents a clot from forming.
The prognosis for this disorder is quite poor, and it may take days to weeks for recovery.

In addition, since cats with aortic thromboembolism have heart disease, there is a high possibility that another reoccurrence of blood clots. The prognosis is usually a few months with treatment and will require medication and frequent re-evaluations. (Weir and Downing)
In most cases, since many cats are brought at a later stage of the disorder, quite a bit of damage is already done. Most owners, 50-75%, who bring in their cats for this issue elect for humane euthanasia. (Brooks)

In Chloe’s case, the owners elected for humane euthanasia.


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