Acute and Chronic Cardiocirculatory Effects of Oral Prazosin in Chronic Refractory Heart Failure

The acute hemodynamic effects of oral prazosin were investigated in 7 patients with chronic refractory heart failure. A single dose of 1 to 3mg prazosin produced a significant increase in cardiac index (+17.6%, p<0.01) associated with substantial decreases in pulmonary arterial diastolic pressure (-31.6%, p<0.02), systemic vascular resistance (-29.7%, p<0.01), and double product (-24.1%, p<0.02). Plasma renin activity was significantly elevated (+42.4%, p<0.02). These effects were found maximum at 2 hours and persisted for 8 hours.The chronic hemodynamic effects in 5 patients with chronic refractory heart failure were evaluated by administration of 1 to 2mg prazosin 3 times daily for 8 weeks, and ventricular function was assessed by echocardiography and carotid pulse recording. All the patients showed improvement in the clinical symptoms of heart failure. Peripheral venous pressure decreased slightly (-12.5%). ET/PEP increased (+24.5%) without any significant changes in EF and mVcf. Plasma renin activity also slightly increased (+17.8%).Thus, prazosin possesses sustained nitroprusside-like actions, and is effective in the management of chronic congestive heart failure refractory to conventional therapy. While, further investigation is necessary to define the effect of prazosin on plasma renin activity.