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It usually comes on suddenly: Your cat begins to howl or pant and can’t seem to move one or both of his back legs. Although there can be a number of causes, one of the most common and painful in cats is a saddle thrombus. In this case, a thrombus, or a blood clot, lodges at the aortic bifurcation (where the vessel splits into the two arteries that supply the rear limbs), blocking or compromising the blood flow to the rear legs.
Because this condition is extremely painful and potentially life threatening, it’s critical to see a veterinarian immediately.
In cats, primary heart disease often leads to the formation of a blood clot in the heart. A chamber of the heart, usually the left atrium, becomes enlarged, slowing the flow of blood. As the blood pools, a clot forms, which can then travel through the bloodstream until it becomes lodged in a vessel, obstructing blood flow.
A very common location for a clot to become lodged is the aortic bifurcation, but other possible locations include arteries in the kidneys, abdominal tissue, front limbs, lungs or brain.
Signs include significant crying or yowling secondary to pain, an inability to move the rear limbs, rear limbs that are cool to the touch and a bluish tint to the skin around the nails and pale foot pads on the rear paws. Because there can be other painful causes for an inability to move the rear limbs, such as a fractured spine or pelvis, it's best to minimize moving or manipulating your cat. Gently wrap your cat in a soft blanket, keeping your hands away from his mouth to avoid inadvertent bites, and proceed to your veterinarian or an emergency veterinary clinic immediately.
A diagnosis of saddle thrombus is typically confirmed based on clinical signs and physical examination. Typically, the veterinarian will note an absence of pulses in the major arteries inside the thighs. Diagnostics such as an echocardiogram (cardiac ultrasound) of the heart, an ultrasound of the pelvic aorta or comparing blood pressures between the front limbs and hind limbs can also provide additional confirmatory evidence.
Unfortunately, this condition carries a guarded prognosis. Once a cat experiences a blood clot, it’s common for another clot to form within the next several months. Even if a cat survives the initial event, his survival time is frequently limited due to underlying heart disease.
Medical management can be initiated to help treat your cat’s pain and prevent another clot from occurring. However, if the blood flow obstruction is extreme, it’s possible your pet’s pain can’t be controlled. What’s more, in cases of advanced heart disease, the stress of the event can cause a significant decline in your pet’s heart condition, leading to death. Many owners elect humane euthanasia as the kindest option for a cat who experiences a saddle thrombus.
If treatment for a saddle thrombus is pursued, initial steps include pain management and potentially sedation to help relieve your cat’s discomfort and stress.
Your cat’s heart disease should be stabilized and appropriate management started for the underlying cardiac condition. Typically, this entails heart medications, but if the heart condition has progressed to congestive heart failure (evidenced by fluid buildup in the lungs), more aggressive treatments may be required, including oxygen therapy and administration of additional medications.
In addition, anticoagulant therapy may be started to help prevent another blood clot from forming. Thrombolytic therapy, or drugs to break down the current blood clot, may be considered, but additional studies are required to determine if this therapy is truly effective. Over time, the body can form an alternate route for blood flow around the obstructed blood vessels and the blood clot naturally breaks down.
If you have any concerns about your cat being at risk for this condition, be sure to talk with your veterinarian.
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