5Catheter-based renal nerve ablation decreased renal norepinephrine spillover, reflecting efferent activity by 47%. 2 The mechanisms likely contribute to the blood pressure-lowering effect because efferent renal sympathetic nerves activate the renin-angiotensin system 6,7 and directly stimulate tubular sodium retention. 8,9 In addition, reduced afferent renal nerve traffic may have elicited a central nervous sympatholytic response. Indeed, massive reductions in muscle sympathetic nerve activity (MSNA) and systemic norepinephrine spillover have been reported in a single patient after renal nerve ablation.10 Similarly, removal of the diseased native kidney reduced MSNA in renal transplant recipients.11 These clinical observations translate the experimental finding that renal afferents convey signals to the brain, thus raising sympathetic activity and blood pressure 12,13 from animals to humans.
See Editorial Commentary, pp 1385-1386Abstract-Endovascular renal nerve ablation has been developed to treat resistant hypertension. In addition to lowering efferent renal sympathetic activation, the intervention may attenuate central sympathetic outflow through decreased renal afferent nerve traffic, as evidenced by a recent case report. We tested the hypothesis in 12 nonpreselected patients with difficult-to-control hypertension (aged 45-74 years) admitted for renal nerve ablation. All patients received ≥3 antihypertensive medications at full doses, including a diuretic. Electrocardiogram, respiration, brachial and finger arterial blood pressure, and muscle sympathetic nerve activity were recorded before and 3 to 6 months after renal nerve ablation. Heart rate and blood pressure variability were analyzed in the time and frequency domain. Pharmacological baroreflex slopes were determined using the modified Oxford bolus technique. Resting heart rate was 61±3 bpm before and 58±2 bpm after ablation (P=0.4). Supine blood pressure was 157±7/85±4 mm Hg before and 157±6/85±4 mm Hg after ablation (P=1.0). Renal nerve ablation did not change resting muscle sympathetic nerve activity (before, 34±2 bursts per minute; after, 32±3 bursts per minute P=0.6), heart rate variability, or blood pressure variability. Pharmacological baroreflex control of heart rate and muscle sympathetic nerve activity did not change. We conclude that reduced central sympathetic inhibition may be the exception rather than the rule after renal nerve ablation in unselected patients with difficult-to-control arterial hypertension. (Hypertension. 2012;60:1485-1490.) • Online Data Supplement