Thromboembolism pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Pathophysiology

The formation of a thrombus is usually caused by the top three causes, known as (Virchow's triad): (Classically, thrombosis is caused by abnormalities in one or more of the following)

• The composition of the blood (hypercoagulability)
• Quality of the vessel wall (endothelial cell injury)
• Nature of the blood flow (hemostasis)

To elaborate, the pathogenesis includes:

• an injury to the vessel's wall (such as by trauma, infection, or turbulent flow at bifurcations);
• by the slowing or stagnation of blood flow past the point of injury (which may occur after long periods of sedentary behavior (for example, sitting on a long airplane flight);
• by a blood state of hypercoagulability (caused for example, by genetic deficiencies or autoimmune disorders).

High altitude has also been known to induce thrombosis . Occasionally, abnormalities in coagulation are to blame. Intravascular coagulation follows, forming a structureless mass of red blood cells, leukocytes, and fibrin.

Pathological Findings

Images courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology

A 67-year-old male was hospitalized because of extensive atherosclerotic cardiovascular disease. Following surgery, during which diseased portions of the femoral arteries were bypassed, he developed massive pulmonary embolism and expired. At autopsy, thrombi were found in the femoral and iliac veins, as well as in the larger pulmonary arteries.

This is a gross photograph of a cut section of lung demonstrating thromboemboli in the pulmonary arteries (arrows).

This is a gross photograph of the heart with the main pulmonary artery opened. Note the thromboembolus filling the pulmonary artery (arrows).

This is a gross photograph of portions of muscle from the legs including sections of leg veins. Note that the leg veins contain thrombus (arrows).

Thromboembolism: Testes

This is a gross photograph of an infarcted testis. Because of the anatomy of the blood supply to the testis, torsion or the blood vessels often leads to venous occlusion (due to compression of the thin walled veins) but not arterial occlusion. Thus, blood still flows into the testis but it can’t get out! This leads to hypoxia and eventually to hemorrhagic necrosis.

Thromboembolism: Bowel Infarction

This is a gross photograph of an opened abdomen at autopsy demonstrating loops of infarcted bowel (arrow). Vascular occlusion can lead to ischemic necrosis of the bowel. In this case, a section of bowel herniated through a fibrous connective tissue band and was strangulated, leading to ischemic necrosis.

Coronary Thrombosis

Images courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology

This is a gross photograph of thrombosed coronary artery (arrows).

Artificial Heart Valve Thrombosis

Artificial heart valve thrombosis: Gross, aortic valve prosthesis with acute thrombus, ventricular view

Mitral valve prosthesis with thrombosis: Gross, natural color, view from the left atrium, thrombus around rim of caged ball prosthesis.

Sources of Systemic Embolism

• Left ventricular thrombus
• Left atrial thrombus
• Pelvic veins or lower extremity thrombus
• Native cardiac valves
• Prosthetic cardiac valves
• Cardiac tumors
• Aortic aneurysm
• Invasive manipulations
• Left ventricular aneurysm