 A reduced release of endothelium derived relaxing factor (EDRF) causes a decrease in the stimulation of guanylate cyclase and cyclic GMP (cGMP) levels fall in vascular smooth muscle.This impairs relaxation in the vasculature and is a part of the vicious cycle of CHF.Patients with CHF have a down-regulation of their β-1 adrenergic receptors which alters their ability to activate intracellular adenylate cyclase which catalyzes cAMP formation.