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Saddle Thrombus In A Cat
Also called a blood clot or Aortic Thromboembolism

The patient, a 10 year old domestic male neutered cat, was presented with a rapidly developing lameness of the rear legs, extreme pain, hyperventilation and vocalization.  Since the onset was spontaneous, unexpected and without any environmental stress or injury and since the cat's owners indicated that there was no injury or stress to the spinal column, a tentative diagnosis of Saddle Thrombus in the cat's descending aorta was made.  

Examination revealed a patient in extreme distress with rapid breathing, rapid heart rate, poor support ability in the rear legs and a lack of a femoral pulse in either rear leg.  The onset of signs began thirty minutes prior to presentation.  A diagnosis of AORTIC SADDLE THROMBOSIS was made and the extreme nature and severity of the situation was discussed quickly with the owners.  Since the onset of signs was so recent and the owners were intent on helping their cat as much as possible, the patient was immediately anesthetized and surgery was begun to remove the clot.  

The prognosis with these patients is very guarded due to the fact that there can be permanent muscle and nerve damage due to ischemia (lack of blood flow).  Every case is different... some extreme cases will display clots extending from the heart and continuing the entire length of the aorta.  Obviously, these cases seldom end successfully.  In this patient's case the quick presentation to surgery played a role in improving the cat's chance for success with the saddle thrombus surgery. The belief is that these clots form in the left atrium of the cat and are most common in cats that have preexisting cardiac pathology such as an enlarged heart, cardiomyopathy of the heart walls or valvular disorders.  When the thrombus breaks loose from the left auricle of the heart it is sent to and then ejected from the left ventricle and then down the aorta where the thrombus lodges at the branching anatomy of the femoral arteries.

This patient received anti-coagulant, corticosteroids, i.v. fluids and an antibiotic as soon as the i.v. line was inserted.  It was anesthetized with an injectable anesthetic and maintained through an endotracheal tube on Isoflurane gas anesthetic.

The photos below were taken during the surgery which lasted about 45 minutes.  Post operative medications were continued and pain suppressants administered.  The day after the surgery the cat was comfortable, eating and drinking and was purring when attended.  It was able to support weight on both rear legs and was able to walk and was interested in its surroundings.  Anticoagulation therapy will be given life-long in an attempt to prevent additional clotting episodes.  This patient has hyperthyroidism, which may have affected the heart muscle, but has been treated for hyperthyroidism and has responded well to therapy for over a year.  The hyperthyroidism may be a predisposing factor with this patient.

NOTE:  Many veterinarians believe these patients, when presented, should be euthanized immediately to alleviate the cat's extreme panic and pain.  Furthermore, it is believed that the survival rate for these patients is very low and that surgery will be unsuccessful.  This approach may be indicated for cats that display a saddle thrombus signs for extended periods or where the patient is in poor physical condition from other pathology.  In this case, however, the time of onset was just minutes prior to a diagnosis being made and the veterinarian and the cat's owners agreed that an attempt to save the kitty's life made more sense than simply giving up.  A euthanized cat has zero chance for recovery.  Perhaps more of these cases should be given at least a chance for recovery rather than immediate euthanasia.  Each case should be evaluated on an individual basis since no two cases of Saddle Thrombus are alike.

To see a larger, clear image of a Saddle Thrombus Surgery click on each image.
The surgical site for a saddle thrombus is in the lower midline abdomen of a cat. The femoral arteries run just under the skin along the inner thigh.  In this patient, no pulse was evident and the limbs were cool.	In this view the aorta is located and the blood clot is discovered occluding blood flow to the femoral arteries.  In some patients the clot will continue down the femoral arteries.	A thin rubber strip is used as a tourniquet to inhibit hemorrhage when the aorta is incised to  extract the clot.  In this view it is being passed beneath the aorta.
A small incision is made directly over the clot which can be seen escaping from the aortic artery.  The clot (thrombus) may extend back as far as the heart.	A forceps is used to grasp the blood clot and the saddle thrombus is extracted from the vessel.  The area inside the aorta is inspected and flushed.	Preliminary sutures are placed to close the incision.  The tourniquet is released to check for bleeding.  At this stage, more sutures are needed.
A closer view of the aortic closure.  More sutures were needed to prevent bleeding through the incision.  Anticoagulants actually work against the surgeon at this point but are required to prevent additional clots from forming.	Additional sutures and compression was required to eliminate bleeding from the descending aortic artery.  Notice to the left of the sutures the femoral arteries are now properly filled with circulating blood.	Lots of visitors for this lucky cat! To see more photos of the cat two days post-op and at suture removal ten days post operatively, go here.

The cause of aortic thromboembolism in the cat is thought to be due to slowly circulating blood in what is called the auricular appendage of the left atrium of the heart.  This blind end allows stasis of blood and eventual clot formation.  If a large clot dislodges it often will be trapped far down the aorta at the branching of the vessel into the femoral arteries.  The longer the thrombus obstructs the blood flow the more tissue damage occurs.  Immediate surgery may be very beneficial, as in the case presented here.  The longer the patient suffers with oxygen deprivation of the tissues nourished by the femoral arteries the less beneficial surgery becomes.  These clots may develop again in the future so most cats surviving an episode of Saddle Thrombus do best if placed on long term anticoagulation therapy.

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