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 greater than 0.05). One hour after prazosin administration, mean arterial pressure declined from 95 to 78 mm Hg (P less than 0.001); left ventricular filling pressure declined from 30 to 18 mm Hg (P less than 0.001), cardiac index increased from 2.1 to 2.9 liters per minutes per square meter (P less than 0.001), and systemic vascular resistance fell from 2074 to 1156 dynes sec cm-5 (P less than 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 less than 0.001]). All responses persisted for a least six hours (P less than 0.01). Prazosin benefits severe congestive heart failure by inducing a sustained fall of both cardiac preload and impedance.