FIBRINOGEN AND CEREBROVASCULAR-DISEASE

The importance of fibrinogen has been identified in two prospective observational studies. Reactive elevations in fibrinogen levels that occur within hours of a major stroke invalidate most cross-sectional case-control studies evaluating fibrinogen as a risk factor. However, as no elevation is seen following fresh episodes of transient ischaemic attacks, reliable conclusions drawn from a case-control study using such patients support the findings of the prospective studies. The association is related to occlusive stroke, but the relationship with intracerebral haemorrhage is unclear. The relationship has been found to be independent of other haemostatic and haemorheological factors (e.g. von Willebrand factor, tissue plasminogen activator and packed cell volume). Adjustment for regression dilution bias would further strengthen the observed relationship. Therefore, after blood pressure, fibrinogen is the most important potentially treatable risk factor for ischaemic stroke. There are several mechanisms whereby fibrinogen could promote atherothromboembolism: thrombosis through a hypercoagulable state; the acceleration of atherosclerosis; or the reduction of blood flow due to high blood or plasma viscosity. The mechanism, however, is unlikely to be mediated through high blood viscosity per se as secondary erythrocytosis (another major determinant of blood viscosity) has not consistently been found to be a risk factor for stroke. Studies relating fibrinogen levels to the degree of carotid artery stenosis support the accelerating influence of fibrinogen on atherosclerosis. Fibrinogen should be considered a risk factor for ischaemic stroke and included in the assessment of individual risk factors. For stroke prevention, individuals with high fibrinogen values but no other risk factors should be considered for therapies to reduce the overall risk of future stroke, i.e. blood pressure reduction and antiplatelet therapy, as well as regular exercise, weight loss and possibly the adoption of a vegetarian diet.