Saddle Thrombus in Cats

feline arterial thromboembolism or saddle thrombus in cats
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A saddle thrombus is a sudden and serious condition caused by a blood clot. If it happens to your cat, it could cause severe pain, trouble breathing, and rear limb paralysis. Sadly, many cats will not survive a saddle thrombus. However, early detection and treatment can increase the odds of recovery.

What is Saddle Thrombus in Cats?

A saddle thrombus occurs when a blood clot becomes lodged in the base of the aorta where two large arteries branch off to each rear leg. This condition is sometimes called feline arterial thromboembolism or feline aortic thromboembolism.

The aorta is the main artery that carries oxygenated blood from the left ventricle of the heart to other parts of the body, including the rear limbs. The region where the arteries branch off to the rear legs is called the "saddle" due to its shape.

The term "thrombus" describes a large blood clot that forms in a blood vessel or the heart. An "embolus" is a small clot that breaks off of a thrombus and becomes lodged in a vessel. Together, these conditions are called "thromboembolism," which is obstruction of blood flow caused by an embolism from a blood clot.

Feline aortic thromboembolism (FATE) occurs when a blood clot develops in the heart, then part of that clot breaks off and becomes lodged in an artery, obstructing blood flow. The saddle region is a common area for clot obstruction. A saddle thrombus is a painful event that occurs suddenly and disrupts circulation to the rear part of the body. This is an emergency situation that can lead to death.

Symptoms of Saddle Thrombus in Cats

Signs of Saddle Thrombus in Cats

  • Sudden pain, often with vocalization
  • Rapid or labored breathing
  • Acute paralysis or partial paralysis of one or both rear limbs
  • One or both rear limbs is cooler than front limbs
  • Rear paw pads that appear blue, gray, or pale

Feline arterial thromboembolism happens suddenly, causing severe pain followed by abnormal breathing and rear limb paralysis or paresis (partial paralysis). Owners typically notice sudden vocalization and heavy breathing along with the inability to move the rear limbs properly. It may look as if the cat suddenly has a broken back. Upon further investigation, you may see that the paw pads are pale or bluish-gray in color and cold to the touch.

Bring your cat to the nearest open veterinarian if you notice any of these signs or any other sudden or serious signs of illness.

Causes of Saddle Thrombus in Cats

A saddle thrombus is caused by a blood clot that came from the atrium of the heart. Approximately 89% of cats with arterial thromboembolism have underlying heart disease.

Hypertrophic cardiomyopathy is the most common type of cardiac condition seen in cats and most often the reason for a saddle thrombus. HCM causes thickening of the heart muscle walls, impeding the heart's ability to properly pump blood.

Other cardiomyopathies, congenital heart disease, hyperthyroidism, and cancer may predispose a cat to arterial thromboembolism.

In rare cases, the underlying cause for the saddle thrombus cannot be determined.

Diagnosis and Treatment

Veterinarians can often make an initial diagnosis of saddle thrombus based on the physical exam findings. Cats with respiratory distress will need oxygen therapy and are quickly placed inside an oxygen cage. Pain medication is typically administered as soon as possible to offer the cat some relief.

At this stage, your vet will go over the initial findings with you and discuss your cat's prognosis. Your vet will discuss your cat's current status and help you decide if treatment should be continued.

Feline arterial thromboembolism can be difficult to treat. Sadly, saddle thrombus has a poor prognosis, especially if the signs are severe (low rectal temperature, slow heart rate, total loss of motor function). in addition, cats with existing heart disease have a high chance of recurring Euthanasia is sometimes the most humane option.

If treatment is continued, the cat will be admitted to the hospital for close monitoring and nursing care. The veterinary team will attempt to stabilize the cat with continued pain medication, symptomatic treatment, and, if necessary, oxygen therapy.

When the cat is stable enough for more tests, the vet will attempt to find and manage underlying heart disease. An echocardiogram will be necessary to visualize the heart. Thoracic radiographs (chest X-rays) may also be performed. Cardiac drugs may be started at this point.

Lab tests will be run to assess organ function, measure electrolytes, analyze blood cells, and evaluate blood clotting function. Intravenous fluid therapy may be necessary for cats with electrolyte imbalances or dehydration. This must be done very carefully in cats with heart disease.

Cats recovering from arterial thromboembolism are often treated with antithrombotic (anti-clotting) drugs such as clopidogrel or aspirin. These medications can help prevent future clots from forming. It is possible for the exiting clot to be resorbed and the cat may regain limb function. However, there is a high risk of new blood clots forming over the next few weeks to months.

Cats are monitored closely for several days in the hospital. They may receive physiotherapy, passive manipulation of the affected limbs to reduce muscle contraction and avoid limb deformity. Cats that survive to discharge will typically go home on medications and with instructions for at-home physiotherapy.

How to Prevent Saddle Thrombus in Cats

The best way to prevent feline arterial thromboembolism is to detect and treat heart disease. Routine wellness visits can enable your vet to detect a heart murmur or other signs of heart disease and treat your cat before something serious happens. Unfortunately, a saddle thrombus is often the first sign of heart disease seen in the cat. The cat may have seemed completely healthy before the event, including having normal heart sounds during physical examination.

If you are concerned about your cat's risk for heart disease, a cardiologist can do a complete cardiac workup that includes an echocardiogram. However, this is somewhat costly and not something most owners want to do unless heart disease is already suspected. Talk to your veterinarian to find a veterinary cardiologist near you.

Article Sources
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  2. “Feline Aortic Thromboembolism (FATE or Saddle Thrombus).” Vin.Com,