Effect of baroreflex activation therapy on renal sodium excretion in patients with resistant hypertension.

OBJECTIVE: Activation of the sympathetic nervous system increases sodium retention in resistant hypertension. Baroreflex activation therapy (BAT) is an interventional method to reduce sympathetic overactivity in patients with resistant hypertension. This study aimed to assess the effect of BAT on urinary sodium excretion.
METHODS: From 2012 to 2015, consecutive patients with resistant hypertension and blood pressure (BP) above target despite polypharmacy strategies were consecutively included in this observational study. BAT was provided with the individual adaption of programmed parameters over the first months. 24-h urinary sodium excretion (UNa) was estimated at baseline and after 6 months using the Kawasaki formula in patients undergoing BAT. Additionally, the fractional sodium excretion, plasma renin activity, and aldosterone levels were assessed.
RESULTS: Forty-two patients completed the 6-month follow-up period. Office systolic and ambulatory 24-h systolic BP at baseline were 169 ± 27 mmHg and 148 ± 16 mmHg despite a median intake of 7(3-9) antihypertensive drugs. After 6 months of BAT, systolic office BP decreased to 150 ± 29 mmHg (p < 0.01), 24-h systolic BP to 142 ± 22 mmHg (p = 0.04) and 24-h UNa increased by 37% compared to baseline (128 ± 66 vs. 155 ± 83 mmol/day, p < 0.01). These findings were accompanied by a significant increase in fractional sodium excretion (0.74% [0.43-1.47] to 0.92% [0.61-1.92]; p = 0.02). However, in contrast to the significant BP reduction, eGFR, plasma sodium, renin activity and aldosterone levels did not change during BAT. The increase in sodium excretion was correlated with the change in eGFR (r = 0.371; p = 0.015).
CONCLUSION: The present study revealed a significant increase of estimated 24-h UNa which may contribute to the long-term BP-lowering effects of this interventional method.