Early impairment of renal hemodynamic reserve in patients with asymptomatic heart failure is restored by angiotensin II antagonism

Background-The early/asymptomatic stages of heart failure (HF) are characte rized by sodium retention secondary to derangement of sodium reabsorption a t the proximal nephron level. Because this phenomenon is reversed by ACE in hibition, abnormalities of renal sodium handling may depend on intrarenal c hanges of angiotensin II (AII)/nitric oxide (NO) levels. Renal hemodynamic reserve (ie, the glomerular vasodilatory response to amino acid infusion) h as been proposed as a reliable test to assess in vivo AII/NO balance. Methods and Results-In this study, the effects of 6 weeks of treatment with 5 mg/d of enalapril or with 50 mg/d of losartan on systemic hemodynamics a nd renal function were assessed, at baseline and after amino acid infusion (AA), in patients with mild HF (NYHA class I) and in healthy volunteers. Un treated HF patients showed a basal renal function comparable to that of hea lthy subjects. After AA, glomerular filtration rate and renal plasma flow s ignificantly increased in healthy subjects (+29.0% and +30.4%, respectively ), whereas no vasodilatory response was observed in HF. Although they did n ot affect basal renal hemodynamics, both enalapril and losartan restored a normal response to AA in HF patients. Blood pressure and heart rate were co mparable in HF subjects and healthy subjects at baseline and were not modif ied by either treatment. Left ventricular ejection fraction was depressed i n HF but did not change after either drug. Urinary excretions of cGMP and n itrate (indexes of NO activity in the kidney), comparable in healthy subjec ts and in HF patients, were unchanged by either enalapril or losartan and d id not correlate with renal reserve. Conclusions-(1) Renal functional reserve is absent in patients with early/a symptomatic HF and normal renal function and (2) both enalapril and losarta n restore a normal vasodilatory response to AA in these patients without af fecting basal systemic and renal hemodynamics. These data suggest a major r ole of AII in the development of early abnormalities in patients with HF.