Glossary
Arterial thromboembolism
A blood clot that lodges in an artery, most often cutting off blood to a cat's back legs and causing sudden pain and paralysis.
Also called: ATE, saddle thrombus, blood clot in cats, cat blood clot
Arterial thromboembolism, or ATE, occurs when a clot forms, usually inside an enlarged heart chamber, travels with the blood and blocks an artery. The most common site is the point where the main artery splits to supply the hind legs, which is why the condition is also called a saddle thrombus. Most cats affected have underlying heart disease, often hypertrophic cardiomyopathy, which may not have been diagnosed beforehand.
The onset is sudden and dramatic. A cat may cry out in pain, drag or be unable to use one or both back legs, and have cold, pale or bluish paw pads and no pulse in the legs. Many cats also breathe fast or pant with an open mouth, because of heart failure. Signs can look like a spinal injury.
This is an emergency. Take the cat to a vet or emergency hospital straight away and handle it gently. Treatment aims to manage pain, support the heart and breathing, and prevent new clots, and some cats regain use of their legs over days to weeks. The outlook is guarded, and clots often return. Some owners choose hospice care or euthanasia when a cat is in great pain. Ask your vet to explain the likely outcome for your cat.
Last reviewed November 7, 2026