Catheter-Based Renal Nerve Ablation and Centrally Generated Sympathetic Activity in Difficult-to-Control Hypertensive Patients

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.