Overview of Aortic Thromboembolism (ATE) in Cats

Aortic thromboembolism, also referred to as saddle thrombus, is a common complication associated with all types of heart disease in the cat. A thrombosis is the formation of a blood clot. An embolism is when the clot lodges within a vessel. It is thought that clots form in one chamber of the left side of the diseased heart. Eventually, these clots break free and travel in the blood vessels until they become lodged or stuck.

Below is an overview of Aortic Thromboembolism in cats followed by detailed information about the diagnosis and treatment of this serious condition. 

The most common site for the clot to lodge is in the far part of the aorta, in the area between the rear legs. This cuts off the blood supply to both rear legs. A clot can also get stuck in the artery that supplies the front legs, kidneys or intestines or can clog an artery to the brain. Clots rarely lodge in veins since the right side of the heart is not commonly involved.

When a clot lodges, the cat can no longer use his rear legs and drags them. The cat usually becomes painful and begins crying. The rear feet are often cold to the touch and the pads of the feet blue in color, due to a lack of blood flow.

The vast majority of cats with saddle thrombus also have underlying heart disease that may not be apparent. Unfortunately, the stress and anxiety of the embolism may precipitate congestive heart failure.

What to Watch For

Sudden onset of dragging rear legs

Difficulty breathing

Crying

Panting or open mouth breathing

Diagnosis of Aortic Thromboembolism in Cats

Most cases of saddle thrombus are diagnosed based on the history and physical exam findings. A lack of pulses to the rear legs, cold paws and blue tinged footpads are highly suspicious of saddle thrombus. Other tests may be performed to determine if underlying heart disease is present and the severity.

Complete blood count

Biochemical profile

Chest X-rays

Ultrasound of the heart

Treatment of Aortic Thromboembolism (ATE) in Cats

Treatment will vary depending on the severity and location of the clot and the severity of the underlying heart disease.

Congestive heart failure is treated with:

Oxygen

Diuretics for fluid accumulation within the lungs

Heart medication

Nitroglycerine

Sometimes, medication is used to treat the clot. This may include:

Pain medication

Blood thinners

Aspirin

Home Care and Prevention

There is no home care for saddle thrombus. If you suspect your cat has saddle thrombus, he should be examined by your veterinarian immediately. Over 90 percent of cats with saddle thrombus also have underlying heart disease that often requires treatment.

Cats with known heart disease may be placed on aspirin therapy in an attempt to reduce the risk of developing saddle thrombus.

In-depth Information on Aortic Thromboembolism (ATE) in Cats

Aortic thromboembolism (saddle thrombus) is a relatively common complication associated with heart disease. The most common heart disease in cats is hypertrophic cardiomyopathy. The walls of the diseased heart allow the formation of clots in the left atrium, the upper chamber of the heart. These clots then become dislodged and travel down the aorta, the main vessel leaving the heart. Clots most often become lodged at the base of the aorta when it divides into the arteries that supply blood to the rear legs. This causes a sudden onset of inability to use the rear legs, dragging the rear legs and cold paws. Cats often howl and cry in pain.

Clots may also lodge anywhere in the body including the arteries to the kidneys, intestines, front arms or brain. If affecting the front arms, usually the right front arm is affected.

After the clot lodges in the vessel, it almost always dissolves on its own over time, although it may cause severe nerve and muscle damage. This damage may not be reversible. For this reason, it is recommended that your cat receive immediate treatment for saddle thrombus.

Following treatment, about 35 to 40 percent of cats are able to walk again, usually within three weeks of the episode. Unfortunately, a significant number of cats do not survive the heart failure that often accompanies saddle thrombus. Other cats may not survive the muscle and nerve damage that occurrs with the clot.

Cats that do survive an episode of saddle thrombus unfortunately have a 90 percent chance of recurrence within six months.

Other diseases may cause sudden onset of dragging rear legs. These include:

Intervertebral disk disease

Tumor of the spinal cord

Pelvic fracture

Traumatic injury

 

Diagnosis In-depth

Various tests should be performed to determine the extent of injury and heart disease. These tests include:

Complete blood count – A CBC is performed to determine the number of red blood cells, white blood cells and platelets. Often, this test is normal, but an elevated white blood cell count may be present.

Biochemical profile – A biochemical profile is done to determine if any organs are affected and this test can be used to support the diagnosis. Since the clot cuts off blood supply to the muscles, the enzymes secreted by damaged muscles are often significantly elevated. If the clot lodges in the artery to the kidney, kidney values are elevated. High potassium is also a common finding. Injured or inflamed muscles leak potassium, which is absorbed into the blood. This high potassium can be quite dangerous to the heart.

Chest radiograph – Chest X-rays are taken to determine the extent of the underlying heart disease and to determine if congestive heart failure is present. An enlarged heart may be present and the X-rays may show fluid accumulation.

Ultrasound – An ultrasound of the heart (echocardiogram) is performed to determine what type of heart disease is present and can also help determine if additional clots are present in the heart chambers.

Treatment In-depth

Treatment for saddle thrombus involves treating the underlying heart disease, treating congestive heart failure if present and trying to dissolve the clot.

Treatment for heart disease and/or congestive heart failure includes:

Oxygen therapy for cats with difficulty breathing

Diuretics, such as furosemide, to reduce the amount of fluid accumulation in the lungs

Nitroglycerine to dilate the blood vessels

Diltiazem or other heart medication to help with contractions of the heart

Treatment for saddle thrombus includes:

Analgesics – Pain medication, such as butorphanol or fentanyl. Many cats are quite painful in the early stages of saddle thrombus.

Sedatives – Sedation to help alleviate anxiety associated with saddle thrombus

Blood thinners – Heparin to reduce the ability of the blood to clot. The goal is to reduce the incidence of additional clots. Heparin does not dissolve a clot that has already formed. In the past, specific medication, such as streptokinase or tissue plasminogen activator (TPA) has been attempted. These medications can dissolve a clot but can be very dangerous. Over 50 percent of cats given these drugs may die because of the drug itself. And these drugs can worsen the existing heart disease. For these reasons, these medications are not recommended.

Aspirin – Aspirin is often recommended to reduce the chance of additional clots. Cats cannot tolerate aspirin as well as other animals and can be given only one baby aspirin every three days. Sometimes Coumadin is used but this must be closely monitored.

Follow-up Care for Cats with Aortic Thromboembolism

Following initial care, cats should be closely monitored for the next several weeks to determine response to therapy. Repeat X-ray, ultrasound and bloodwork can help guide long-term therapy. Cats should also be monitored for recurrence of thromboembolism, which occurs in up to 90 percent of cases within six months.