Saddle Thrombus in Cats
Saddle thrombus, or Aortic Thromboembolism (ATE), in cats is the term used when a blood clot gets lodged in the main artery in the body, the aorta. These clots can also get stuck in other arteries, but most commonly occur in the aorta in the back half of the body, affecting the legs. This is an acute and painful condition and is very distressing to the cat and owner to observe. Continue reading to learn more about ATE’s, causes, symptoms, and possible treatments.
What causes saddle thrombus in cats?
The most common cause of ATE is a heart disease called Hypertrophic Cardiomyopathy. In cats, their heart walls tend to enlarge inward giving less space for the blood to move through the heart. As the heart disease progresses, the smaller heart chamber (atrium) on the left side begins to enlarge since there is too much pressure in the heart. This enlarged chamber of the heart often accumulates blood that is not efficiently pumped out of the heart, causing a clot to form. Eventually, this large blood clot moves out of the atrium and into the arteries and aorta where it gets stuck again as the aorta gets smaller and divides.
Other possible causes of ATE include cancer, foreign bodies, and some are idiopathic, meaning we don’t know what caused the condition to develop.
Symptoms of Saddle Thrombus in Cats
Cats with a saddle thrombus will often have acute and severe pain, their muscles in the back legs may be hard to the touch, the paws and limbs are often cold or cool, and the paw pads may be pale in color. The cats will be unable to use their back legs well and may be dragging them and seem paralyzed. This may involve both or just one rear limb.
How can my vet diagnose saddle thrombus?
After your vet completes the physical exam, they may check for blood flow to the affected limbs with a Doppler blood pressure unit. If your vet cannot hear a pulse/beat in the affected limb, there is a complete blockage of blood supply to that area.
Your vet may also recommend radiographs (x-rays) of the chest to look for an enlarged left atrium (part of the heart).
An echocardiogram may also be recommended to screen for Hypertrophic Cardiomyopathy. Remember, in cats, the heart walls thicken inward so most of the heart will look normal on radiographs. The echo allows your vet to look inside the heart and confirm the walls are enlarging inward and may be able to see a large blood clot in the left atrium.
An abdominal ultrasound with Color Flow Doppler may also be recommended to see if the clot/reduced blood flow in the aorta can be detected.
My cat has been diagnosed with saddle thrombus. How can it be treated?
Some cats can break down the clot on their own over 2-3 days. Your cat will need strong pain control during this time to keep them as comfortable as possible. Your cat would likely remain in the hospital during this time so they can be monitored. Some cats develop heart failure and need treatments. Some cats need oxygen supplementation for the initial 24-48 hours.
Some cats with saddle thrombus improve with medications that inhibit platelet formation and blood thinners. Spontaneous bleeding, especially nose bleeds, can occur with these medications.
Unfortunately, most cats do not improve, even with aggressive treatments. And of those that do survive, many develop ATE’s again within a week. This risk is the highest for cats that do not continue treatment with blood thinners and anti-platelet medications at home.
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