The microvascular pathophysiology of chronic venous insufficiency.

Severe chronic venous insufficiency (CVI) demonstrates as chronic, hard-to-heal wounds of the lower extremity. The wound is the result of poor skin perfusion due to a complex series of pathologic events, often initiated by a deep vein thrombosis (DVT). As years pass, the DVT causes venous valvular damage and incompetence. The calf muscle pump fails to augment venous return, and venous blood pressure is chronically elevated upon standing. Mechanisms that normally prevent the transmission of venous hypertension back upstream to the dermal microcirculation are lost. Early dermal microvascular responses include increased fluid filtration and edema. An inflammatory response induces white cell activation and adhesion. It is thought that activated white cells are trapped in dermal capillaries and increase microvascular permeability. Plasma proteins leak into the tissue space, increasing the edema. Ischemic damage to the epidermis leads to epithelial cell necrosis and ulceration. The ulcer is often slow to heal, due to inadequate perfusion and delivery of substrates required for proper wound healing. Current treatments aim to improve calf pump function, reduce edema, improve perfusion, and enhance wound healing.