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Arterial Thromboembolism in Cats

General Information

Arterial thromboembolism is a disorder of the heart and blood of cats. It is one of several complications that occur in cats with heart damage. Blood clots (thrombi) may occur within the heart and travel through the bloodstream until they become lodged. A common site for a clot to lodge is toward the rear of the body, where the aorta divides to supply blood to the rear legs. The blood supply to one or both legs can be greatly reduced by a lodged clot, depending on where the clot is. Rear-leg lameness, pain and cool rear legs are common signs.

Important Points in Treatment

1. Initial treatment is aimed at improving circulation to the rear limbs. Blood tests and radiographs (x-rays) are used to assess and monitor the disorder during treatment.

2. If the condition fails to improve, surgical removal of the blood clot is necessary. This requires general anesthesia.

3. The condition is very serious and the prognosis (medical forecast) is guarded. Your doctor will discuss the disease and the surgery to assist you in your decision.

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Understanding Your Pet's Diagnosis

Aortic Thromboembolism

What is aortic thromboembolism?

Aortic thromboembolism results when a blood clot (thrombus) is thrown into the aorta (the major blood vessel of the body). The blood clot generally forms in the left atrium (one of the chambers of the heart). It is dislodged and moves through the left ventricle and into the aorta. At some point, the thrombus lodges in the aorta or arteries coming off of the aorta. The size of the blood clot determines where it stops. Once the thrombus has lodged in the aorta or artery, it causes severe blood and oxygen loss to the tissues served by that blood vessel. When the clot moves through the circulation, it is known as an "embolus." Aortic thromboembolism may be the first sign of heart disease in cats. It is one of the most devastating complications associated with heart disease in cats. Aortic thromboembolism occurs rarely in dogs.

What causes aortic thromboembolism?

The cause of aortic thromboembolism has not been determined. Aortic thromboembolism is associated with disease of the heart muscle. A theory is that abnormal blood flow and an increased likelihood of producing blood clots leads to the formation of a clot or thrombus in the left atrium.

What are the signs of aortic thromboembolism?

The signs of aortic thromboembolism depend upon the location of the blood clot. Sudden onset of paralysis or weakness and pain are the most common initial signs. The animal may be lame or walk in an abnormal manner. Usually the paralysis or weakness is in the rear legs; however, it sometimes only occurs in one front leg. The nail beds and footpads may be pale or bluish. Rapid breathing and difficulty in breathing are common. The animal will be anxious and will vocalize (meow or bark).

How is aortic thromboembolism diagnosed?

Aortic thromboembolism is diagnosed upon a good medical history and thorough physical examination. A diagnostic work-up will be done. Complete blood counts (CBCs) and blood chemistries may indicate blood abnormalities. Blood clotting (coagulation) studies are done but typically do not reveal significant defects; however, the information is needed to manage anticoagulant medication. Radiographs (X-rays) of the heart and lungs may indicate an enlarged heart or fluid in the lungs. An echocardiogram (graphic recording of the position and motion of the heart) and electrocardiogram (ECG or EKG, an electrical analysis of the heart) are helpful in assessing the heart. Occasionally, abdominal ultrasound may demonstrate a blood clot (thrombus) in the aorta. Special contrast X-rays (such as angiography, where contrast dye is injected into the circulation) also may be needed.

How is aortic thromboembolism treated?

Aortic thromboembolism is a serious condition. Initially, pets should be hospitalized for treatment. Activity is restricted and the pet is kept quiet and calm. Most of these animals have poor appetites and must be coaxed to eat with any type of tasty diet. Medication to prevent blood clots (anticoagulant medication) is the treatment of choice. Initially it is given intravenously (through a vein). Anticoagulant medication to be given by mouth (oral) is available. The anticoagulant medications have no effect on the established clot; however, they prevent further formation of clots. Aspirin may be beneficial during and after an episode of thromboembolism and may be prescribed. Cats are sensitive to aspirin, so the dose is low; the veterinarian will determine the dose. Other medications are given for pain and for anxiety. Most animals that survive will be on some type of long-term anticoagulant therapy; they will require frequent reevaluations and an indoor lifestyle.

So-called "clot buster" drugs are used in human medicine. These drugs actually break up the established clot. Unfortunately, these drugs are very expensive and have potential side effects. They are used rarely in veterinary medicine.

What is the prognosis for animals with aortic thromboembolism?

The prognosis (outcome) for animals with aortic thromboembolism usually is grave. Most cats that survive will form new clots. However, cats that survive an initial episode often recover complete function of their legs. Full recovery of function takes days to weeks. Long-term survival for cats varies between two months to several years; however, the average length of survival is about 11 months with treatment. Survival information for dogs is limited due to the infrequent occurrence of aortic thromboembolism.

The information on this page was obtained from the site www.vetmedcenter.com