Sympathetic nerve traffic and blood pressure changes after bilateral renal denervation in resistant hypertension: a time-integrated analysis

Background. Renal denervation reduces blood pressure (BP) and sympathetic drive in experimental animal models, but the effect of this intervention on sympathetic activity in patients with treatment-resistant hypertension is still unclear. Methods. In an incident series of 29 patients with treatmentresistant hypertension, we performed serial measurements (n = 123) of muscle sympathetic nerve activity (MSNA, microneurography) and standardized BP measurements. Data were analysed by mixed linear modelling (MLM) and by regression analysis of time-integrated changes of both MSNA and synchronous, standardized (in-lab) BP measurements. Results. Bilateral renal denervation was accompanied by a marked reduction in MSNA (P = 0.01 by MLM), which was parallelled by a reduction in systolic (from 175 +/- 14 to 156 +/- 16mmHg) and, to a lesser extent, in diastolic (from96 +/- 12 to 87 +/- 6mmHg) BP over time. Neither systolic nor diastolic BP associated to a significant extent with corrected MSNA (MSNAC) in the MLM analysis (systolic BP versus MSNAC: beta = -0.08, P = 0.08; diastolic BP versus MSNAC: beta = -0.007, P = 0.75). However, the study of time-integrated changes in MSNA and BP showed a robust association between proportional changes in MSNA over time and simultaneous changes in systolic and diastolic BP (beta = 0.61, P < 0.001 and beta = 0.37 P < 0.05). Conclusions. Time-integrated changes in MSNAC and BP after bilateral renal denervation document a close link between the sympathetic activity and BP responses to this procedure. These findings further strengthen the relevance of the sympathetic nervous system both in the pathophysiology of resistant hypertension and in the BP-lowering effect of the procedure.