Summary
The West of Scotland Coronary Prevention Study (WOSCOPS) showed that pravastatin reduced
the risk of coronary heart disease (CHD) events in 6,595 middle-aged hypercholesterolaemic
men aged 45–64 years without prior myocardial infarction followed for an average of
4.9 years. We hypothesised prospectively (a) that baseline levels of haemorheological
variables were related to baseline and incident CHD and to mortality; and (b) that
reduction in lipoproteins by pravastatin would lower plasma and blood viscosity, a
potential contributory mechanism to CHD events. We therefore studied plasma and blood
viscosity, fibrinogen, haematocrit, and blood cell counts at baseline and 1 year.
At baseline, plasma and blood viscosity were related to risk factors, CHD measures,
and claudication. On univariate analysis, baseline levels of all rheological variables
(except platelet count) were related to incident CHD; CHD mortality; and total mortality.
On multivariate analysis including 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 associated
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 viscosity (mean difference
0.06 mPa.s, p <0.001), but was not associated with significant changes in other rheological
variables. We therefore suggest that pravastatin therapy, which reduces elevated lipoproteins
in hypercholesterolaemic men, may lower risks of CHD and mortality partly by lowering
plasma and blood viscosity. Further studies are required to test this hypothesis.
Key words
Rheology - viscosity - coronary heart disease - lipoproteins - pravastatin
