Aortic Thromboembolism in Dogs

What is aortic thromboembolism?

Aortic thromboembolism (ATE) is a potentially devastating condition. The aorta is the main artery of the body and carries oxygenated blood from the heart out to the rest of the body.

The word thromboembolism combines the words thrombus and embolism. A thrombus is a blood clot that occurs inside a blood vessel, and the word embolism indicates that the clot has traveled through a blood vessel to a location distant from where it formed.

An aortic thromboembolism results when a blood clot is dislodged and travels through the aorta, becoming lodged in a distant location. This clot causes severely reduced blood flow to the tissues receiving blood from that section of the aorta, leading to decreased oxygen in the tissues.

How does aortic thromboembolism happen?

Aortic thromboembolism is a rare occurrence in dogs.

Aortic thromboembolism can be associated with several problems, such as endocarditis (inflammation of the valves of the heart), sepsis (a body-wide generalized infection), hyperadrenocorticism (increased levels of steroid hormones produced by the adrenal glands associated with Cushing’s Disease), cancer, immune-mediated blood disorders, increased protein loss through diseased kidneys or gastrointestinal tract, or trauma. In some dogs, no underlying reason can be found. Unlike cats, heart disease in dogs is not often associated with aortic thromboembolism.

What are the signs of aortic thromboembolism?

The most common clinical signs of aortic thromboembolism are sudden paralysis and pain, usually in the rear legs, although weakness and lameness may be seen. If the rear limbs are affected, there may be decreased or absent pulses in the femoral arteries of the rear legs. The dog may also experience a lower-than-normal body temperature. An ultrasound may be performed to visualize the clot in the aorta.

How is aortic thromboembolism treated?

Initially, dogs may need to be treated in hospital, because they may have serious co-existent problems, such as those outlined above. They may also be experiencing considerable pain and distress.

Aspirin, and a similar drug called clopidogrel (brand name Plavix®), is theoretically beneficial during and after an episode of aortic thromboembolism but should be used only under the direct supervision of your veterinarian. These drugs prevent platelets (blood cells that assist with blood clotting) from activating to clump together and form a clot while flowing through the blood vessels.

Likewise, another anti-clotting medication called warfarin (brand name Coumadin®) has been tried as a treatment. This medication, however, requires very careful monitoring of blood clotting measurements, and the drug itself often interacts with other medications. Medications to break up the clot have been tried but must be started right away and should only be attempted at specialized referral centers as rates of complications are high.

Finally, the dog’s underlying disease(s) should be treated as appropriate for the type and severity of the disease.

Is any monitoring required? What is the expected outlook?

Blood work should be monitored to manage potential complications from anti-clotting therapies. Also, diagnostic imaging (such as ultrasound to look for clots in the aorta) may need to be performed or repeated.

The expected course of this disorder is days to weeks for full recovery, but the prognosis in general is poor. Long-term survival time varies between one month to several years with the average being a few months with treatment.