By Dr. Becker
Saddle thrombus is a quirky name for a very serious medical condition that occurs in cats, and much less often in dogs. The disorder is also called aortic thromboembolism, as well as feline aortic thromboembolism (FATE).
The condition occurs in pets with heart disease and affects as many as 25 percent of cats with hypertrophic cardiomyopathy, which is a common feline heart condition. FATE usually occurs without warning and can be the first and only sign of heart disease in some cats.
In dogs, additional causes of saddle thrombus include hyperadrenocorticism (Cushing's disease), protein-losing nephropathy (a kidney issue), and sepsis, which is a full-body infection.
An aortic thromboembolism is a blood clot that forms in the heart. A part of the clot dislodges and travels through the aorta. The aorta is the largest artery in the body. It originates in the heart and runs down the entire length of the back.
In the lower abdomen, the aorta splits into two arteries to supply the back legs. That split, where the aorta becomes the left and right iliac arteries, is called the saddle. Eventually, the dislodged blood clot gets stuck, often in the wedge at the top of the saddle, hence the name, saddle thrombus.
Symptoms of Saddle Thrombus
Signs of an aortic thromboembolism in kitties depends on which blood vessels are blocked and whether the blockage is partial or total. If the clot moves past the saddle and enters into just one iliac artery, only that hind leg will be involved. If it sits right at the split, both hind legs will be involved.
When blood circulation is blocked at the saddle, the rear legs grow cold and hard as the muscles and nerves swell due to lack of oxygen and nutrients. The animal may drag one or both legs, cry out or even scream in pain, and may pant or have open-mouthed breathing as well.
The nails and pads of the back feet may appear bluish in color due to lack of oxygen, and the cat may show signs of shock. Sudden paralysis is also a common symptom with this condition.
Diagnosing Saddle Thrombus
The onset of saddle thrombus symptoms is usually very rapid and is a serious medical emergency. If you suspect your pet is showing signs of the condition, seek emergency veterinary care immediately.
Your veterinarian can often detect a heart murmur or abnormal heart sounds, and certain signs of heart failure may already be present. In FATE patients, the rectal temperature is usually low. The lower the temperature, the more serious the condition.
Diagnostic tests typically performed include a complete blood count (CBC) to check for anemia, infection, and blood clotting factors; a biochemistry profile to check organ function; and chest x-rays to assess the size of the heart and the state of the lungs.
An echocardiogram will evaluate heart function and the degree of heart disease present, and a Doppler ultrasound is the method used to confirm a lack of blood flow to the rear limbs.
A pet with saddle thrombus is usually in shock and may already be in heart failure, so the situation is life-threatening even with immediate veterinary care.
Even when heart failure or shock are not present or can be controlled, the pet still has heart disease and a blood clot in the left side of the heart that could dislodge another embolism at any time.
Sadly, about a quarter of cat owners ultimately decide to euthanize their pet due to the extreme pain the animal is in, the potential for recurrence of the condition, and the need for long-term management of heart disease even in cases in which the pet survives the initial crisis.
For owners who choose to treat the condition, the goal of blood clot management is to address the pain, provide supportive care in the form of fluid therapy, and treat circulatory shock. The pet must be on cage rest and a great deal of nursing care will be required to keep the paralyzed patient clean and comfortable.
An alternative and very encouraging treatment for FATE is medicinal leeching. Israeli veterinarian Dr. Sagiv Ben-Yakir has achieved about a 90 percent success rate in returning cats with FATE to a normal life using leech therapy.
In addition to clot management, the underlying heart disease must be addressed. I recommend that all cats who have survived an episode of saddle thrombus be placed on life-long ubiquinol supplementation (ubiquinol is the reduced form of CoQ10).
Prevention of the formation of additional clots is also important. I recommend a supplement called nattokinase for this purpose.
Most cats who survive a FATE episode regain normal limb function within a few months. However, they typically require a great deal of nursing care until they’re once again mobile. Recurrences of aortic thromboembolism are common, typically within a year or two of the first episode. Partnering with an integrative veterinarian using holistic preventive strategies is a really good idea.