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Efficacy of Electrical Baroreflex Activation Is Independent of Peripheral Chemoreceptor Modulation.

ABSTRACT: Arterial baroreflex activation through electrical carotid sinus stimulation has been developed for the treatment of resistant hypertension. Previous studies suggested that the peripheral chemoreflex is tonically active in hypertensive patients and may inhibit baroreflex responses. We hypothesized that peripheral chemoreflex activation attenuates baroreflex efficacy evoked by electrical carotid sinus stimulation. We screened 35 patients with an implanted electrical carotid sinus stimulator. Of those, 11 patients with consistent acute depressor response were selected (7 men/4 women, age: 67±8 years, body mass index: 31.6±5.2 kg/m², 6±2 antihypertensive drug classes). We assessed responses to electrical baroreflex stimulation during normoxia, isocapnic hypoxia (SpO₂: 79.0±1.5%), and hyperoxia (40% end-tidal O₂ fraction) by measuring heart rate, blood pressure, ventilation, oxygen saturation, end-tidal CO₂ and O₂ fractions, and muscle sympathetic nerve activity. During normoxia, baroreflex activation reduced systolic blood pressure from 164±27 to 151±25 mm Hg (mean±SD, P<0.001), heart rate from 64±13 to 61±13 bpm (P=0.002), and muscle sympathetic nerve activity from 42±12 to 36±12 bursts/min (P=0.004). Hypoxia increased systolic blood pressure 8±12 mm Hg (P=0.057), heart rate 10±6 bpm (P<0.001), muscle sympathetic nerve activity 7±7 bursts/min (P=0.031), and ventilation 10±7 L/min (P=0.002). However, responses to electrical carotid sinus stimulation did not differ between hypoxic and hyperoxic conditions: systolic blood pressure: -15±7 versus -14±8 mm Hg (P=0.938), heart rate: -2±3 versus -2±2 bpm (P=0.701), and muscle sympathetic nerve activity: -6±4 versus -4±3 bursts/min (P=0.531). We conclude that moderate peripheral chemoreflex activation does not attenuate acute responses to electrical baroreflex activation therapy in patients with resistant hypertension. These patients provided insight into human baroreflex-chemoreflex interactions that could not be gained otherwise.

SUBMITTER: Heusser K

PROVIDER: S-EPMC7158700 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Efficacy of Electrical Baroreflex Activation Is Independent of Peripheral Chemoreceptor Modulation.

Heusser Karsten K Thöne Arvo A Lipp Axel A Menne Jan J Beige Joachim J Reuter Hannes H Hoffmann Fabian F Halbach Marcel M Eckert Siegfried S Wallbach Manuel M Koziolek Michael M Haarmann Helge H Joyner Michael J MJ Paton Julian F R JFR Diedrich André A Haller Hermann H Jordan Jens J Tank Jens J

Hypertension (Dallas, Tex. : 1979) 20191202 1

Arterial baroreflex activation through electrical carotid sinus stimulation has been developed for the treatment of resistant hypertension. Previous studies suggested that the peripheral chemoreflex is tonically active in hypertensive patients and may inhibit baroreflex responses. We hypothesized that peripheral chemoreflex activation attenuates baroreflex efficacy evoked by electrical carotid sinus stimulation. We screened 35 patients with an implanted electrical carotid sinus stimulator. Of th ...[more]

PMID: 31786986

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Project description:BackgroundThe mechanisms of intradialytic increases in blood pressure are not well defined. The present study was undertaken to assess the role of autonomic nervous system activation during intradialytic hypertensive episodes.Methodology/principal findingsContinuous interbeat intervals (IBI) and systolic blood pressure (SBP) were monitored during hemodialysis in 108 chronic patients. Intradialytic hypertensive episodes defined as a period of at least 10 mmHg increase in SBP between the beginning and the end of a dialysis session or hypertension resistant to ultrafiltration occurring during or immediately after the dialysis procedure, were detected in 62 out of 113 hemodialysis sessions. SBP variability, IBI variability and baroreceptor sensitivity (BRS) in the low (LF) and high (HF) frequency ranges were assessed using the complex demodulation technique (CDM). Intradialytic hypertensive episodes were associated with an increased (n = 45) or decreased (n = 17) heart rate. The maximal blood pressure was similar in both groups. In patients with increased heart rate the increase in blood pressure was associated with marked increases in SBP and IBI variability, with suppressed BRS indices and enhanced sympatho-vagal balance. In contrast, in those with decreased heart rate, there were no significant changes in the above parameters. End-of-dialysis blood pressure in all sessions associated with hypertensive episode was significantly higher than in those without such episodes. In logistic regression analysis, predialysis BRS in the low frequency range was found to be the main predictor of intradialytic hypertension.Conclusion/significanceOur data point to sympathetic overactivity with feed-forward blood pressure enhancement as an important mechanism of intradialytic hypertension in a significant proportion of patients. The triggers of increased sympathetic activity during hemodialysis remain to be determined. Intradialytic hypertensive episodes are associated with higher end-of-dialysis blood pressure, suggesting that intradialytic hypertension may play a role in generation of interdialytic hypertension.

Project description:IntroductionBrain computer interface-based action observation (BCI-AO) is a promising technique in detecting the user's cortical state of visual attention and providing feedback to assist rehabilitation. Peripheral nerve electrical stimulation (PES) is a conventional method used to enhance outcomes in upper extremity function by increasing activation in the motor cortex. In this study, we examined the effects of different pairings of peripheral nerve electrical stimulation (PES) during BCI-AO tasks and their impact on corticospinal plasticity.Materials and methodsOur innovative BCI-AO interventions decoded user's attentive watching during task completion. This process involved providing rewarding visual cues while simultaneously activating afferent pathways through PES. Fifteen stroke patients were included in the analysis. All patients underwent a 15 min BCI-AO program under four different experimental conditions: BCI-AO without PES, BCI-AO with continuous PES, BCI-AO with triggered PES, and BCI-AO with reverse PES application. PES was applied at the ulnar nerve of the wrist at an intensity equivalent to 120% of the sensory threshold and a frequency of 50 Hz. The experiment was conducted randomly at least 3 days apart. To assess corticospinal and peripheral nerve excitability, we compared pre and post-task (post 0, post 20 min) parameters of motor evoked potential and F waves under the four conditions in the muscle of the affected hand.ResultsThe findings indicated that corticospinal excitability in the affected hemisphere was higher when PES was synchronously applied with AO training, using BCI during a state of attentive watching. In contrast, there was no effect on corticospinal activation when PES was applied continuously or in the reverse manner. This paradigm promoted corticospinal plasticity for up to 20 min after task completion. Importantly, the effect was more evident in patients over 65 years of age.ConclusionThe results showed that task-driven corticospinal plasticity was higher when PES was applied synchronously with a highly attentive brain state during the action observation task, compared to continuous or asynchronous application. This study provides insight into how optimized BCI technologies dependent on brain state used in conjunction with other rehabilitation training could enhance treatment-induced neural plasticity.

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Efficacy of Electrical Baroreflex Activation Is Independent of Peripheral Chemoreceptor Modulation.

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Efficacy of Electrical Baroreflex Activation Is Independent of Peripheral Chemoreceptor Modulation.

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