Case 21 — Text

Text from “Small Animal Cardiovascular Medicine”

Systemic Arterial Thromboembolism

Systemic arterial thromboembolism (STE) is a relatively common and usually very serious sequel to feline cardiac disease. Over 90% of cases in veterinary small animal practice are in cats with cardiac disease, the vast majority having left atrial enlargement on echocardiography. The left atrium is usually the site of thrombus formation. STE is a common complication of hypertrophic cardiomyopathy and the unclassified or restrictive forms of feline cardiac disease.

Most cats (~90%) with STE have the thromboembolus lodged at the terminal abdominal aorta (aortic trifurcation), commonly called a saddle thromboembolus. This produces acute caudal limb paresis/paralysis and pain with loss of femoral pulses and pale or cyanotic pads (pain, paralysis, pulselessness, and pallor). Some cats have smaller thromboemboli in one femoral artery, a brachial artery, or another smaller artery. Occasionally, a very large thromboembolus lodges more proximally, causing acute renal failure or sudden death.

Pathophysiology

A thrombus is an aggregation of platelets and fibrin with entrapped blood cells. Systemic arterial thromboembolism occurs when a thrombus forms in the left heart and then breaks loose to travel to a distal region of the systemic circulation. Reasons for intravascular thrombus formation include sluggish blood flow, endothelial damage, and increased blood coagulability. The left atrium is usually enlarged in cats with STE, causing decreased flow velocity that promotes red cell aggregation and thrombus formation, most commonly in the left auricle.

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