Blood rheology, cardiovascular risk factors, and cardiovascular disease: The West of Scotland Coronary Prevention Study

The West of Scotland Coronary Prevention Study (WOSCOPS) showed that pravas tatin reduced the risk of coronary heart disease (CHD) events in 6,595 midd le-aged hypercholesterolaemic men aged 45-64 years without prior myocardial infarction followed for an average of 4.9 years. We hypothesised prospecti vely (a) that baseline levels of haemorheological variables were related to baseline and incident CHD and to mortality; and (b) that reduction in lipo proteins by pravastatin would lower plasma and blood viscosity, a potential contributory mechanism to CHD events. We therefore studied plasma and bloo d viscosity, fibrinogen, haematocrit, and blood cell counts at baseline and 1 year. At baseline, plasma and blood viscosity were related to risk facto rs, CHD measures, and claudication. On univariate analysis, baseline levels of all rheological variables (except platelet count) were related to incid ent CHD; CHD mortality; and total mortality. On multivariate analysis inclu ding baseline CHD and risk factors, plasma and blood viscosity, haematocrit and white cell count each remained significantly associated with incident CHD; while fibrinogen remained an independent predictor of mortality (all p < 0.03). After one year, lipoprotein reduction by pravastatin was associat ed with significant reductions (about one quarter of a standard deviation) in plasma viscosity (mean difference 0.02 mPa.s, p < 0.001) and in blood vi scosity (mean difference 0.06 mPa.s, p < 0.001), but was not associated wit h significant changes in other rheological variables. We therefore suggest that pravastatin therapy, which reduces elevated lipoproteins in hyperchole sterolaemic men, may lower risks of CHD and mortality partly by lowering pl asma and blood viscosity. Further studies are required to test this hypothe sis.