Role of fibrinogen and fibrin D-dimer in peripheral arterial disease

This thesis is composed of two studies. The principal aim of the first study, the Sites of Atheroma Study, was to determine whether plasma fibrinogen, fibrin D-dimer and other haemostatic factors (von Willebrand Factor and plasminogen activator inhibitor - type I) were related to the angiographic site and severity of atherosclerosis in the arteries of the lower limb. The principal aim of the second study, the Prognostic Study of Intermittent Claudication, was to determine whether plasma fibrinogen, fibrin D-dimer and other haemostatic factors (von Willebrand Factor and tissue plasminogen activator), were related to the future incidence of atherothrombotic events, and deterioration of peripheral arterial disease in subjects with intermittent claudication. The study samples in both studies consisted of men and women with ischaemic symptoms in the lower limb referred to the Peripheral Vascular Clinic, Royal Infirmary of Edinburgh. In the Sites of Atheroma Study, 192 patients referred for angiography were categorised by site and severity of peripheral atherosclerosis using the Bollinger angiographic scoring system. A clinical examination was conducted on each patient including the administration of a questionnaire and taking of a blood sample for the measurement of haemostatic factors. In the Prognostic Study, 607 patients with intermittent claudication who had had a comprehensive examination at baseline, including measurement of haemostatic factors, were followed up over six years to determine the incidence of fatal and non-fatal ischaemic heart disease and stroke and deterioration of peripheral arterial disease. Follow-up data were obtained from hospital records, general practitioners, self-administered questionnaires, the Information and Statistics division of the Common Services Agency and the Scottish National Health Service Central Registry. Results from the Sites of Atheroma Study indicated that 34 (17.7%) patients had predominantly aorto-iliac disease, 85 (44.3%) had femoro-popliteal disease and 73 (38.0%) had dual-site disease. There were no significant differences in the mean levels of the haemostatic factors between patients with disease affecting different sites. An independent relationship was found between nephelometric fibrinogen and between fibrin D-dimer and disease severity only in the femoro-popliteal arteries. On multiple regression, fibrinogen remained independently associated with disease severity in the femoro-popliteal arteries, when life-time smoking or current smoking were taken into account. There was no influence of current smoking on the association between fibrin D-dimer and disease severity but, on inclusion of life-time smoking, the association became non-significant. In the Prognostic Study of Intermittent Claudication, a total of 210 (34.6%) patients died during the six year follow-up period. Of these 90 (42.9%) died from ischaemic heart disease, 29 (13.8%) from stroke and 27 (12.9%) from other vascular causes, including cardiac arrhythmias and ruptured aneurysm. Ninety three (15.3%) patients had a non-fatal myocardial infarction and 79 (13.0%) had a fatal or non-fatal stroke. Forty five (7.4%) patients underwent investigations for peripheral arterial disease and 64 (10.5%) patients progressed to severe chronic leg ischaemia. A total of 203 (33.4%) patients did not have a vascular event or show any deterioration of limb ischaemia. Baseline median levels of plasma fibrinogen, fibrin D-dimer and von Willebrand Factor were significantly higher in patients who died from ischaemic heart disease compared to those who had no vascular events. Tissue plasminogen activator antigen levels were significantly elevated in patients who suffered a stroke. All the relationships between the haemostatic factors and vascular events became weaker and statistically non-significant in analysis adjusting for cardiovascular risk factors and baseline ischaemic heart disease. von Willebrand Factor levels were significantly raised in claudicants who developed severe chronic leg ischaemia (rest pain, ulceration and gangrene). In multivariate analyses adjusting for life-time smoking, fibrinogen became significantly associated with the risk of vascular intervention, and von Willebrand Factor was associated with the risk of severe chronic leg ischaemia. In conclusion, these results indicate that there may be a stronger relationship between chronic smoking and increased fibrin turnover than coagulation in symptomatic peripheral arterial disease. Increased coagulation and fibrinolytic activity may also contribute to thrombosis or progression of atherosclerosis in the coronary and cerebral arteries in claudicants. The effect that fibrinogen, fibrin D-dimer and other haemostatic factors may have on the progression of peripheral arterial disease was mostly independent of cigarette smoking