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Client Library Article
SADDLE THROMBUS
| Feline Aortic Aneurism=
Saddle Thrombus |
| Saddle thrombus formation is a serious complication of
feline heart disease (particularly hypertrophic
cardiomyopathy) where blood clots tend to form in the atria due to abnormal
blood flow. When part or all of the clot breaks off, it travels through the
heart and down the aorta where if large enough it will become lodged at the
end of the aorta where the vessel separates to go down each hind leg. If the
blockage is complete, the entire blood supply to the hind legs is cut off
and the cat becomes paralyzed in the hind end shortly after. With partial
blockages, the pulses are very weak due to decreased blood flow, but pain
and paralysis are still evident. An analogy would be if you were traveling
down a two lane highway and your car takes up all two lanes. Suddenly, the
highway splits into two one lane roads and your car can’t fit into either so
it stops there blocking all other cars in back from gaining access to either
one lane roads. An estimated 10-20 % of cats with cardiomyopathy will
develop a saddle thrombus. |
| Symptoms |
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History of heart disease
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Acute onset hind limb paralysis
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Very painful hind end- initially
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Loss of deep pain to hind legs as paralysis sets in
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Cold hind legs
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Weak / no pulses in hind legs
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Blue (cyanotic) nail beds
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Panting,
resp distress
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Concurrent congestive heart failure
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| Diagnosis |
| Based on history, and physical exam. The veterinarian
will feel for pulses in the hind legs and check the nail beds. In a
cat with a saddle thrombus, the nail beds are purple or blue because the
circulation has been cut off and the oxygen used up. The cat is often very painful
initially, but as paralysis ensues, they loose all pain sensation to the
limb. Approximately 50% of cats presented with a saddle thrombus are also in
congestive heart failure- possibly triggered from the stress of throwing the
clot or vice versa. A radiograph can quickly assess the heart and
lungs and eliminate spinal trauma as a cause of
the pain and paralysis- when owners suspect the cat was hit by a vehicle.
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| Treatment |
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Treatment is based on supportive care, and trying
to restore circulation to the hind limbs. Cats are supported with IV
fluids, pain medication and heparin to prevent further clot formation.
Cats with no pulses and suspected complete blockage can be treated with
either streptokinase or tissue plasminogen activator (TPA)- both are drugs which
help dissolve the clot thus returning or improving hind limb circulation.
However, reperfusion injury can be a life threatening complication when
using TPA and streptokinase. Cats with concurrent congestive heart
failure are treated accordingly with oxygen, nitroglycerine, and diuretics.
In cats whose heart disease has gone undetected, an echocardiogram should be
performed to assess the type and degree of heart disease and the cat should
be started immediately on cardiac medication
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| Prognosis |
| Cats with a saddle thrombus generally carry a poor
prognosis for long term survival due to the underlying heart disease.
The prognosis with saddle thrombus resolution varies, with a better
prognosis for cats with a partial obstruction than those with a complete
obstruction. Using streptokinase or TPA yields better results than heparin
and acepromazine alone. The most critical period is the first 48 hours
where acute death is common. If the clot has resolved in three days
and the hind limbs are cold with no circulation, it is recommended to
euthanize the cat before gangrene sets in. |
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