Long-Term Follow-Up of Baroreflex Activation Therapy in Resistant Hypertension

Renal Nerve Activity and Arterial Depressor Responses Induced by Neuromodulation of the Deep Peroneal Nerve in Spontaneously Hypertensive Rats

Hypertension is a main cause of death in the United States with more than 103 million adults affected. While pharmacological treatments are effective, blood pressure (BP) remains uncontrolled in 50–60% of resistant hypertensive subjects. Using a custom-wired miniature electrode, we previously reported that deep peroneal nerve stimulation (DPNS) elicited acute cardiovascular depressor responses in anesthetized spontaneously hypertensive rats (SHRs). Here, we further study this effect by implementing a wireless system and exploring different stimulation parameters to achieve a maximum depressor response. Our results indicate that DPNS consistently induces a reduction in BP and suggests that renal sympathetic nerve activity (RSNA) is altered by this bioelectronic treatment. To test the acute effect of DPNS in awake animals, we developed a novel miniaturized wireless microchannel electrode (w-μCE), with a Z-shaped microchannel through which the target nerves slide and lock into the recording/stimulation chamber. Animals implanted with w-μCE and BP telemetry systems for 3 weeks showed an average BP of 150 ± 14 mmHg, which was reduced significantly by an active DPNS session to 135 ± 8 mmHg (p < 0.04), but not in sham-treated animals. The depressor response in animals with an active w-μCE was progressively returned to baseline levels 14 min later (164 ± 26 mmHg). This depressor response was confirmed in restrained fully awake animals that received DPNS for 10 days, where tail-cuff BP measurements showed that systolic BP in SHR lowered 10% at 1 h and 16% 2 h after the DPNS when compared to the post-implantation baseline. Together, these results support the use of DPN neuromodulation as a possible strategy to lower BP in drug-resistant hypertension.

Magnetic stimulation of carotid sinus as a treatment for hypertension

Previously, we reported that magnetic stimulation of carotid sinus (MSCS) could lower arterial pressure in rabbits. In this randomized, sham-controlled pilot study, we evaluated the effects of MSCS on blood pressure in pre-hypertensive and hypertensive subjects. A total of 15 subjects with blood pressure higher than 130/80 mm Hg were randomized to receive sham or 1Hz MSCS. The changes of systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MAP) during treatment were compared between groups. The heart rate variability (HRV) and baroreflex sensitivity (BRS) before, during, and after treatments were analyzed. Reduction of SBP was significantly greater in subjects with MSCS than those with sham stimulation (6.6 ± 0.4 vs -2.5 ± 0.4 mm Hg, P < 0.001). Reduction of DBP was significantly greater in subjects with MSCS than those with sham stimulation (1.2 ± 0.2 vs -2.8 ± 0.2 mm Hg, P < 0.001). Reduction of MAP was significantly greater in subjects with MSCS than those with sham stimulation (1.4 ± 0.3 mm Hg vs -4.0 ± 0.3 mm Hg, P < 0.001). Reduction of HR was significantly greater in subjects with MSCS than those with sham stimulation (0.5 ± 0.5 vs -1.9 ± 0.3 beats/min, P = 0.002). BRS increased from 6.85 ± 0.77 to 8.79 ± 0.95 ms/mm Hg after MSCS compared with that at baseline (P = 0.027). Thus, MSCS can lower blood pressure and heart rate in pre-hypertensive and hypertensive subject, warranting further study for establishing MSCS as a treatment for hypertension.