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 3 mg prazosin produced a significant increase in cardiac index (+17.6%, p less than 0.01) associated with substantial decreases in pulmonary arterial diastolic pressure (-31.6%, p less than 0.02), systemic vascular resistance (-29.7%, p less than 0.01), and double product (-24.1%, p less than 0.02). Plasma renin activity was significantly elevated (+42.4%, p less than 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 2 mg 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.