Hypercoagulable states.

Abstract

A prethrombotic or hypercoagulable state is one in which the hemostatic balance is disturbed, with increasing procoagulant activity or decreasing activity of intrinsic anticoagulant properties. A basic problem in the study of hypercoagulable states is that it cannot be determined with certainty whether changes in hemostatic variables are causative or consequences of thromboses that have already occurred. This chapter discusses the ways in which various physiologic and pathologic states may be associated with alterations in hemostatic systems and, by weighting the balance in favor of readier coagulability, may predispose to thrombosis. Physiologic conditions discussed include stress, cold, pregnancy, oral contraceptives (OCs), aging, and smoking. It is noted that major alterations in blood coagulability, rheology, and flow during pregnancy combine to increase the risk of thrombosis, especially venous. The risk that venous thromboembolism will occur is increased 10-fold in OC users. The increased risk may be related to alterations in hemostatic variables that occur gradually over the 1st year of use, with no further subsequent increase. At present, no individual laboratory test is capable of identifying patients at risk of thrombosis, but a number of variables in combination (e.g., obesity, age, presence of varocose veins, euglobulin lysis time, level of fibrinogen degradation products) may provide a useful indication. In the absence of reliable predictive indicators, assessment and management efforts should be directed in 3 ways. 1st, simple tests should be undertaken in all individuals in whom thromboembolism has occurred to diagnose treatable predisposing factors. 2nd, efforts should be directed toward refining a safe, effective prophylactic regimen. 3rd, a few selected patients (e.g., those who have their 1st thrombotic episode before age 30 years) should be investigated in greater detail.