Venous and arterial thrombophilia.

BACKGROUND AND OBJECTIVE

The thrombophilic state may be defined as a condition which predisposes to thrombosis. It is well know that the pathogenesis of venous and arterial thrombosis may be different. However, such differences may be more apparent than real. In fact, both venous and arterial thrombosis may occur in any given patient with a thrombophilic state. The aim of this review is to critically analyze the thrombophilic state and define a rational approach to the patient with overt or suspected venous and/or arterial thrombosis.

EVIDENCE AND INFORMATION SOURCES

The material examined in the present review includes personal papers in this field, and articles and abstracts published in journals covered by the Science Citation Index.

STATE OF ART AND PERSPECTIVES

Both venous and arterial thrombosis may occur in thrombophilic states such as APC resistance, protein C or S defects, and antiphospholipid antibody syndrome. Venous thrombosis is surely more frequent than arterial thrombosis in such conditions but, fortunately, it is usually less severe. Antithrombin deficiency is almost exclusively associated with venous thrombosis. In foreseeing the occurrence of venous or arterial thrombosis in a given thrombophilic patient, one must explore the state of the vessels carefully. Often venous or arterial thrombosis occurs only because a vessel injury is present. Severely decreased blood flow, such as that seen in policythemia vera, may be responsible for arterial or venous thrombosis without any other predisposing cause. From a laboratory stand point there is no sure demonstration that some changes may indicate a more likely occurrence of arterial or venous thrombosis. The same alteration of one or more than one test may be accompanied by either arterial or venous thrombosis or both. One exception to this rule is represented by increased blood viscosity, which is usually associated with arterial thrombosis. The hypercoagulable or thrombophilic state is a single clinical entity that cannot be divided into arterial and venous thrombophilia, although the unfortunate outcome, namely thrombosis, tends to manifest itself in just one district. The preexisting condition of the vessels, together with sudden triggering factors, plays an important role in the transformation of the "sol" into the "gel" that is a thrombosis in any given district.