Thromboembolism in Cats

Thromboembolism (thrombus formation) is a common and serious complication of myocardial disease in the cats.

Etiology

It is estimated that between 10% and 20% of cats with HCM will experience development of thrombi on the left side of the heart, which may dislodge and become trapped elsewhere in the arterial system.

Cats appear to have inherently high platelet reactivity, making clot formation a more likely sequel to endothelial damage and sluggish blood flow occurring with myocardial disease.

Pathophysiology

Emboli lodge as “saddle thrombi” in the distal aortic trifurcation, resulting in hindlimb pain and paresis. Rarely will a thrombus lodge at other arterial sites such as the renal artery, the coronary arteries, the cerebral arteries, or the mesenteric artery.

Clinical Signs

• Acute onset of rear leg pain and paresis accompanied by vocalisation
• Cold, bluish foot pads (decreased circulation)
• Lack of palpable pulses in rear limbs

Diagnosis

• Based on history and clinical signs
• Nonselective angiography

Treatment

The goal of treatment is to dissolve the thrombus and restore perfusion to the area. Several drugs have been tried with varying results. Tissue plasminogen activator (tPA) has shown some success, but it is expensive.

Heparin has also been used with some success. Low-dose aspirin therapy can be used prophylactically in cats with myocardial disease.

• TPA (Activase) serves as a fibrolysin resulting in the breakdown of clots already formed in the vasculature.
• Heparin acts on coagulation factors in both the intrinsic and extrinsic coagulation pathways, inhibits the formation of a stable clot.
• Prophylaxis by low dose aspirin.