DECREASED BLOOD-VISCOSITY AND SERUM LEVELS OF ERYTHROPOIETIN AFTER ANTIHYPERTENSIVE TREATMENT WITH AMLODIPINE OR METOPROLOL - RESULTS OF A CROSS-OVER STUDY

The increased viscosity of blood of hypertensive patients can be assum ed to be a risk factor for the development of cardiovascular diseases. The aim of the present study was to elucidate whether anti-hypertensi ve treatment has any impact on blood theology. Twenty patients with pr eviously untreated hypertension who consecutively attended our outpati ent hypertension clinic were included in this prospective, open, cross -over study. The patients were randomly selected to treatment with aml odipine or metoprolol. The antihypertensive therapy was switched after 4 months. Haemorheological and haemodynamic variables were measured w ith rotational viscometry and impedance cardiography, respectively. Fi fteen and 16 patients could be evaluated after amlodipine or metoprolo l treatment respectively. The mean blood pressure (BP) decreased from 159 +/- 22/105 +/- 7 to 139 +/- 21/91 +/- 6 mm Hg on amlodipine and fr om 162 +/- 22/104 +/- 5 to 145 +/- 24/90 +/- 8 mm Hg on metoprolol the rapy. After amlodipine treatment, the total peripheral resistance inde x decreased whereas metoprolol treatment was accompanied by a decrease in the cardiac index. Decreases in whole blood viscosity, haematocrit and serum erythropoietin were found after amlodipine as well as metop rolol treatment. After amlodipine the plasma viscosity decreased and t he erythrocyte deformability increased in the majority of patients. Pl asma fibrinogen decreased after metoprolol treatment. Despite the diff erences in haemodynamic mechanisms underlying the decrease in BP, amlo dipine and metoprolol exert beneficial effects on blood viscosity. Hae modilution and a decrease in serum erythropoietin may be factors under lying this decrease in blood viscosity.