EFFECTS OF ATRIAL-NATRIURETIC-PEPTIDE ON LEFT-VENTRICULAR FUNCTION INHYPERTENSION

Atrial natriuretic peptide (ANP) has natriuretic and vasodilator actio ns that lower arterial pressure and may be beneficial to hypertensive patients. To assess the effects of ANP on left ventricular function in patients with hypertension, we compared it with the pure vasodilator nitroprusside. Simultaneous left ventricular micromanometer pressure a nd radionuclide volume were obtained at baseline, during nitroprusside infusion, during a second baseline period, and during ANP infusion in 10 patients with hypertension. Mean arterial pressure fell during ANP and nitroprusside. Heart rate and plasma norepinephrine levels increa sed by similar amounts during the two agents, whereas cardiac index an d stroke volume index were unchanged during both. Peak positive left v entricular dP/dt fell similarly during ANP and nitroprusside, but left ventricular dP/dt at a developed pressure of 40 mm Hg, a less load-de pendent index of contractility, was unchanged during both. The relatio n between end-systolic pressure and volume during ANP infusion was not shifted leftward or rightward from that during nitroprusside infusion , indicating no inotropic effect. Both ANP and nitroprusside shortened the time constant of isovolumic relaxation calculated by the logarith mic method but did not change the time constant calculated by the deri vative method. Peak filling rate was unchanged from baseline during bo th agents. ANP did not shift the end-diastolic pressure-volume point a way from the relation constructed from baseline and nitroprusside poin ts. We conclude that ANP has no direct effect on myocardial contractil e or diastolic function in patients with hypertension.