[Short- and medium-term hemodynamic effects of prazosin in chronic refractory cardiac failure]

The hemodynamic effects of prazosin, a post-synaptic alpha blocker, were studied in 10 patients with chronic stable cardiac failure, in Classes III and IV of the NYHA classification, resistant to digitalis and diuretic therapy. The measurements of pressure and cardiac output were carried out by right heart catheterisation and thermodilution. The administration of the first dose (1 to 3 mg) led to a 38% reduction in mean right atrial pressure, a 22% reduction in mean pulmonary artery pressure, a 22 ù reduction of wedge pulmonary artery pressure and a 15% reduction of systemic vascular resistance. The systolic index rose by 20%, systemic blood pressure and heart rate remained unchanged. After 7 days, treatment with 3 to 12 ng/day of prazosin mean right atrial pressure had fallen by 54%, mean pulmonary artery pressure by 37%, and wedge pulmonary artery pressure by 48%. The systolic index increased by 27%. The blood pressure was unchanged, but the heart rate decreased by 10%. The patients lost an average of 2,7 Kg in weight. These results show that in the short term, prazosin had a mixed vasodilator effect on both arteries and veins. In the medium term the arterial vasodilator action appears to be significantly smaller but remains detectable with doses greater than 8 mg/day, whilst the venous vasodilator effect persists, unchanged.