THE USE of vasodilators as adjunctive therapy for congestive heart failure was first popularized over ten years ago by the work of Parmley, Chatterjee, Cohn, and Franciosa, although occasional clinical investigative reports using vasodilators date back to the 1950s and even earlier. Physicians have had considerable experience with vasodilators, yet important questions remain unanswered regarding the ultimate role of this therapeutic approach to the failing heart. This review will focus on the present status of the currently available vasodilators (nitrates, hydralazine hydrochloride, prazosin hydrochloride, and captopril) in the management of chronic congestive heart failure.
THE CONCEPT OF VASODILATOR THERAPY Afterload or Impedance Reduction
Afterload, a term derived from isolated cardiac muscle experiments, is best defined as the forces opposing left ventricular fiber shortening during ejection. Impedance, a term preferred by many investigators, is the instantaneous resistance to flow to the contracting left ventricle and is equivalent to instantaneous left ventricular