Estimation of Plasma Renin Activity on the Basis of Serum and Urinary Chloride Concentrations versus Sodium Concentrations.

Introduction: The present study examined the possible estimation of plasma renin activity (PRA) by serum and urinary concentrations of chloride versus sodium in acute and chronic heart failure (HF).

Methods: Data from 29 patients with acute HF (48% men; 80.3 ± 12 years) and 26 patients with recovery of HF after decongestive therapy (50% men; 81.2 ± 12 years) were analyzed. Blood and urine samples were obtained immediately before decongestive therapy in acute HF patients. Clinical tests included peripheral blood tests, serum and spot urinary electrolytes, and plasma neurohormones. Sodium- or chloride-related indices included serum ([sNa+] or [sCl-]) and urinary ([uNa+] or [uCl-]) concentrations, their differences, and their ratio. Linear regression analysis was used for correlation coefficients.

Results: PRA levels higher than the normal range were detected in only 5 (17%) of 29 patients with acute HF, but in as many as 11 (42%) of 26 patients with chronic HF. In the 29 patients with acute HF, all the chloride- and sodium-related indices except for [sNa+] were correlated with PRA: the [sCl-]/[uCl-] ratio was best correlated with PRA (R2 = 0.84, p < 0.0001) followed by the [sNa+]/[uNa+] ratio (R2 = 0.64, p < 0.0001). In the 26 patients with chronic HF, however, both the [sCl-] (R2 = 0.36, p = 0.001) and [sNa+] (R2 = 0.22, p = 0.016) were only weakly correlated with PRA.

Conclusion: In acute HF, chloride-related indices derived from serum and urinary concentrations were firmly associated with PRA or better than sodium-related indices. In chronic HF, either chloride- or sodium-related indices were not firmly associated with PRA, presumably due to influence of cardiovascular medication.