Renal Sympathetic Hyperactivity in Hypertension: True or False?

Abstract

Increased renal norepinephrine spillover, observed by using isotope-dilution method, is thought to indicate renal sympathetic hyperactivity and to play a crucial role in hypertension. However, SYMPLICITY HTN-3 (Renal Denervation in Patients With Uncontrolled Hypertension), the first randomized sham-controlled trial, failed to show a benefit of renal denervation for resistant hypertension.1 This raises the issue of whether the sympathetic hyperactivity hypothesis is true. In a recent issue of Circulation Research , Grassi et al2 have emphasized the presence and importance of sympathetic hyperactivity in hypertension, primarily based on the results of isotope-dilution studies. However, the isotope-dilution method cannot exclude the involvement of intraorgan platelet release of norepinephrine. We would argue that platelet norepinephrine release, rather than sympathetic nervous system alterations, may be the cause of increased norepinephrine spillover in hypertension for …