Atlas of pathophysiology, 2 Edition

Part II - Disorders

Cardiovascular disorders

Deep Vein Thrombosis

An acute condition characterized by inflammation and thrombus formation, deep vein thrombosis (DVT) mainly refers to thrombosis in the deep veins of the legs. Without treatment, this disorder is typically progressive and can lead to potentially lethal pulmonary embolism. DVT commonly begins with localized inflammation alone (phlebitis), which rapidly provokes thrombus formation. Rarely, venous thrombosis develops without associated inflammation of the vein.

Causes

·   Idiopathic

·   Endothelial damage

·   Accelerated blood clotting

·   Reduced blood flow, stasis

Predisposing risk factors

·   Prolonged bed rest

·   Trauma, especially hip fracture

·   Surgery, especially hip, knee, or gynecologic surgery

·   Childbirth

·   Hormonal contraceptives such as estrogens

·   Age over 40

·   Obesity

Pathophysiology

A thrombus forms when an alteration in the epithelial lining causes platelet aggregation and consequent fibrin entrapment of red and white blood cells and additional platelets. Thrombus formation is more rapid in areas where blood flow is slower, because contact between platelets increases and thrombin accumulates. The rapidly expanding thrombus initiates a chemical inflammatory process in the vessel epithelium, which leads to fibrosis (narrowing of the blood vessel). The enlarging clot may occlude the vessel lumen partially or totally, or it may detach and embolize to lodge elsewhere in the systemic circulation.

Signs and symptoms

·   Vary with site and length of the affected vein (may produce no symptoms)

·   Pain or tenderness

·   Fever, chills

·   Malaise

·   Edema and cyanosis of the affected arm or leg

·   Redness and warmth over the affected area

·   Palpable vein

·   Surface veins more visible

·   Lymphadenitis

Clinical Tip

Some patients may display signs of inflammation and, possibly, a positive Homans' sign (pain on dorsiflexion of the foot) during physical examination.

Diagnostic test results

·   Duplex Doppler ultrasonography reveals sluggish blood flow.

·   Impedance plethysmography shows a difference in blood pressure between the arms and the legs.

·   Impedance phlebography shows decreased blood flow.

·   Coagulation studies reveal an elevated prothrombin time in the presence of a hypercoagulable state.

Treatment

The goals of treatment are to control thrombus development, prevent complications, relieve pain, and prevent recurrence of the disorder. Treatment includes:

·   bed rest with elevation of the affected arm or leg

·   warm, moist soaks over the affected area

·   analgesics

·   antiembolism stockings

·   anticoagulants (initially, heparin; later, warfarin)

·   streptokinase

·   simple ligation to vein plication, or clipping

·   embolectomy and insertion of a vena caval umbrella or filter.

P.53

VENOUS THROMBUS

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