Sustained Reduction of Cardiac Impedance and Preload in Congestive Heart Failure with the Antihypertensive Vasodilator Prazosin

To elucidate the hemodynamic effects of prazosin, an antihypertensive agent, in congestive heart failure, we studied 10 patients with ischemic cardiomyopathy and severe ventricular dysfunction. After an oral dose of 2 to 7 mg, heart rate was unchanged (P>0.05). One hour after prazosin administration, mean arterial pressure declined from 95 to 78 mm Hg (P<0.001); left ventricular filling pressure declined from 30 to 18 mm Hg (P<0.001), cardiac index increased from 2.1 to 2.9 liters per minute per square meter (P<0.001), and systemic vascular resistance fell from 2074 to 1156 dynes sec cm-5 (P<0.001). In both forearms vascular resistance and venous tone were reduced (86 to 48 mm Hg per ml per 100 g per minute, and 59 to 18 mm Hg per ml, respectively P<0.001). All responses persisted for at least six hours (P< 0.01). Prazosin benefits severe congestive heart failure by inducing a sustained fall of both cardiac preload and impedance. (N Engl J Med 297:303–307, 1977)