[Rheology and coronary heart disease]

More than 25 years ago it was demonstrated that an improvement in various parameters of blood flow in patients who have an hyperviscosity syndrome improves coronary blood flow. Hyperfibrinogenemia with resulting increase in plasma viscosity and erythrocyte aggregation has been demonstrated in patients with coronary heart disease. Poiseuille's law, which describes the interaction between vascular resistance, vessel geometry and blood viscosity, indicates--when applied to coronary artery disease--that an increase in the viscosity of blood, especially of plasma, can in the poststenotic microcirculation be a flow-limiting factor and a critical determinant of oxygen supply to myocardium that is at risk of ischaemia. An increased concentration of fibrinogen, which is the substance that causes the increase in plasma viscosity, has been shown to correlate prospectively with the risk of serious cardiovascular events. Patients with multiple-vessel coronary heart disease and treatment-refractory angina pectoris have clearly increased fibrinogen values. Chronic intermittent urokinase administrations--given with the aim of achieving fibrinogenolysis of the elevated fibrinogen concentration at a dose of 500 000 IU urokinase three times weekly -improves the rheological parameters and achieves an impressive decrease in symptoms. It is thus important in clinical practice to take into account that patients with atherosclerosis and a fibrinogen concentration of more than 300 mg may develop perfusion disorders and worsening of their symptoms.