Thromboembolism

Thromboembolism is the technical term for a blood clot that forms a blockage somewhere in the vascular system. In cats, this condition is usually secondary to underlying heart disease. Large clots form in a chamber of a diseased heart, and it is theorized that a piece breaks off and leaves the heart. The main blood vessel coming from the heart is the aorta, and often the clots will get lodged where the vessel narrows. The most common site at which a clot will become lodged is where te vessels that supply the hind legs branch off from the aorta. This causes a blockage of blood flow to the affected area, which in turn can cause partial or complete paralysis of the legs, cold limbs, and vocalization due to pain. When the rear legs are affected, the condition is also termed saddle thrombus.

Although the paralysis is usually the most noticeable and dramatic symptom, it is often merely a complication of the more serious illness, heart disease. This may not be as apparent, but may manifest other symptoms such as panting, bluish mucous membranes, and distress. This is a life-threatening situation that may indicate fluid in the lungs and requires immediate medical attention.

Treatment

As with any animal with trouble breathing, oxygen is immediately administered. The main types of drugs usually given are: Anticoagulants, or blood thinners, such as heparin or aspirin, to help prevent further clots; analgesics, to relieve pain and anxiety often present, and once heart disease is diagnosed, heart medications. Diuretics such as Lasix may also be given to help drain fluid from the lungs, and sodium bicarbonate if metabolic acidosis is suspected. IV Fluids are not given until the lung congestion is controlled.

Prognosis

The expected prognosis for the devastating condition is generally poor. Long-term therapy for the thromboembolism may be a secondary concern. In one study, about 60-70% of cats undergoing therapy, unfortunately, did not survive, or were euthanized, due to the underlying heart disease. Most of those that survive the initial episode typically recover function of their legs, but neurologic deficits may persist. Functional restoration of the affected limbs may take days to weeks, and long-term prognosis varies between 2 months to several years; the average is approximately 11 months with treatment.