Here’s something many cat owners don’t know about until they hear a heart-stopping scream from their cat — who suddenly can’t walk. It’s called an aortic thromboembolism (ATE), or “saddle thrombus,” and usually occurs in cats with heart disease — something else the owner may not know their cat has.
This is a serious condition in cats where a thrombus (blood clot) affects the blood flow to the hind legs of the cat. Typically, the blood clot forms in the heart and then moves down the aorta — the largest artery in the body, which provides blood to the abdomen and rear legs of the cat. The clots can also effect other organs, even the brain of the feline.
Cats with partial or total ATE usually are taken to the veterinarian because the cat is unable to use one or both the rear legs. Upon examination at the vet’s office, we often find rear legs that are cool to the touch (because of compromised blood flow), are desensitized, and that the cat may be unable to walk.
The nails and foot pads have a blue tinge, indicating poor oxygenation of the tissues, and the cat might be shocky. Using a stethoscope, the vet will often hear a heart murmur or abnormal heart signs. The onset of signs is usually very rapid (as in an hour ago, the cat was fine, now she can’t walk) and can include weakness, lameness, vocalization (from pain), and trouble breathing.
To diagnose, we usually take x-rays and find an enlarged heart. Special tests may be performed to check for blood flow through the aorta and into the ileac arteries of the rear legs.
What is the prognosis if a cat has aortic thromboembolism? Very poor. Even with aggressive, state-of-the-art veterinary care, data shows only 15-50 percent survive the initial clot event and very few survivors regain full use of the legs. Even worse, many of the cats who survive the initial event suffer another clot event within 6-12 months despite aggressive anti-clotting therapy.
How do veterinarians try and prevent ATE if we detect cardiomyopathy in a cat? In the past, we’ve used products such as aspirin or Plavix to prevent the occurrence of a blood clot. Results have been poor.
But there’s hope on the horizon! The Morris Animal Foundation funded a study at the University of Georgia that hypothesized that rivaroxaban (Xarelto), a commonly prescribed blood thinner in humans, could help prevent ATE in cats. In a study published in the Journal of Veterinary Emergency and Critical Care, the study authors reported that Xarelto was well tolerated by six health feline study participants and showed ant-clotting effects. These researchers are now recruiting cats with heart disease who have survived one episode of ATE to participate in a larger study.
It’s important to note this is just one example of a human drug that is being studied for off-label in pets. It is incredibly expensive to take a drug through FDA approval, and thus not cost effective for most animal health companies to develop products to treat conditions like this where most cat owners opt for euthanasia. But anyone who has lost a beloved pet to this painful nightmare will want to keep an eye out for future findings that could mean the difference between life and death.