Association of plasma fibrinogen levels with coronary artery disease, smoking and inflammatory markers.

The plasma level of fibrinogen is associated with the risk of ischaemic heart disease (IHD) and the severity of atherosclerosis. It has been suggested that an increased plasma level of fibrinogen is a coronary risk indicator because it reflects the inflammatory condition of the vascular wall. An inflamed vascular wall may increase the production of the cytokines interleukin 6 (IL6), interleukin 1-beta (IL1-beta), and tumour necrosis factor alpha(TNF-alpha), which have a major role in the regulation of synthesis in the liver of acute phase proteins, including fibrinogen. Smoking has also been reported to increase the levels of fibrinogen and C-reactive protein (CRP). This may indicate that smoking induces an inflammatory reaction, probably of the pulmonary bronchi and alveolae. Therefore, we anticipated that with both types of inflammation the levels of acute phase proteins and cytokines would be related. We have investigated the contribution of inflammation to the plasma levels of fibrinogen in 34 patients with severe coronary artery disease (CAD) and 30 healthy controls comparable for age and smoking habits. We did not find a parallel in the effects of smoking and ischaemic heart disease on the plasma levels of fibrinogen, CRP, IL6, IL1-beta and TNF-alpha. Cardiovascular disease had its most important effect on the plasma fibrinogen level, while smoking appeared to increase the CRP levels, while both CAD and smoking seemed to affect the IL6 levels. Our results indicate that both smoking and CAD induce an inflammatory condition but that the increase of plasma levels of different inflammatory markers is complex. Although the acute phase reaction is the main regulatory mechanism of fibrinogen, the increase of fibrinogen in our group of CAD patients could not be fully explained by increased inflammation.