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Medical Hypotheses Jan 2020The carotid sinus is a dilated area at the base of the internal carotid artery of humans and is located immediately superior to the bifurcation of the internal and...
The carotid sinus is a dilated area at the base of the internal carotid artery of humans and is located immediately superior to the bifurcation of the internal and external carotid arteries. It is widely accepted, in the fields of medicine and physiology, to function as a baroreceptor in its central control role. This paper presents a hypothesis challenging this paradigm - that the carotid sinus functions by detecting oscillations at the vessel wall which result from shear stress due to vortical flow. This is contrary to conventional thinking which presumes that the carotid sinus responds to blood pressure or wall pressure. Our hypothesis is based on anatomy, physiology and physical properties of fluid which make the sinus the area of highest vorticity. Utilizing magnetic resonance angiograms of undiseased carotid vessels, we computed the oscillatory shear index (OSI) via a computational fluid dynamics simulation of flow. This region of highest OSI coincides with the area where the nerve to the carotid sinus lies within the vessel wall. Accordingly, the hypothesis is that the carotid sinus acts as a mechanotransducer of wall shear stress oscillation and not as a baroreceptor.
Topics: Baroreflex; Carotid Artery, External; Carotid Artery, Internal; Carotid Sinus; Computer Simulation; Hemorheology; Humans; Magnetic Resonance Angiography; Mechanotransduction, Cellular; Models, Cardiovascular; Pressoreceptors; Stress, Mechanical
PubMed: 31726427
DOI: 10.1016/j.mehy.2019.109441 -
Trends in Cardiovascular Medicine Oct 2020Atrial fibrillation (AF) is a rapidly growing clinical problem in routine practice, both for cardiologists as well as general practitioners. Current therapies aimed at... (Review)
Review
Atrial fibrillation (AF) is a rapidly growing clinical problem in routine practice, both for cardiologists as well as general practitioners. Current therapies aimed at the management of AF include anti-arrhythmic drug therapy and catheter ablation. These therapies have a number of limitations and risks, and have disappointing long-term efficacy in maintaining sinus rhythm and improving hard clinical outcomes. Because of this, there is growing interest in pursuing alternative management strategies in patients with AF. This review seeks to highlight emerging AF therapies, with a specific focus on several modalities aimed at modulation of the autonomic nervous system. These therapies have shown promise in early pre-clinical and clinical trials, and represent exciting alternatives to standard AF treatment.
Topics: Animals; Atrial Fibrillation; Autonomic Nervous System; Baroreflex; Heart Atria; Heart Rate; Humans; Kidney; Magnetic Field Therapy; Pressoreceptors; Recovery of Function; Renal Artery; Sympathectomy; Treatment Outcome; Vagus Nerve Stimulation
PubMed: 31708408
DOI: 10.1016/j.tcm.2019.10.009 -
BioMed Research International 2019Professional athlete training is significantly different from recreational physical activity, and sustained, repetitive exposure to over-strenuous and intensive training...
INTRODUCTION
Professional athlete training is significantly different from recreational physical activity, and sustained, repetitive exposure to over-strenuous and intensive training may result in critical changes of most systems and organs in a sportsman's body.
AIM
The assessment of the influence of multiannual strength-endurance training on the autonomic nervous system (ANS) and cardiovascular system (CVS) among the rowers of Polish national team.
MATERIALS AND METHODS
20 rowers, aged 20-30, seniors of Polish national team were qualified into the study. The functional examination of ANS was conducted by means of Task Force® Monitor system. The assessed parameters included hemodynamic parameters, heart rate, and blood pressure variability and reflexes sensitivity of baroreceptors. In order to examine and compare the reaction of autonomic nervous system the subjects underwent a tilt test.
RESULTS
In the study group, significantly higher levels of sBP (129.3 ± 12.2 vs 118.3 ± 8.4, = 0.0030), SI (59.9 ± 8.8 vs 41.2 ± 6.8, > 0.001), CI (3.2 ± 0.5 vs 2.4 ± 0.4, > 0.001), and significantly lower levels of HR (54.2 ± 5.3 vs 60.1 ± 5.7, = 0.0034) and TPRI (2333.3 ± 389.9 vs 2950.2 ± 604.2, = 0.0012) compared to the control group, were found. After the tilt test the levels of HR ( = 0.0005) and TPRI ( = 0.0128) were significantly higher but SI ( > 0.001) and CI ( = 0.0006) were significantly lower in the study group compared to the control.
CONCLUSIONS
Multiannual strength-endurance training connected with rowing activities substantially modulates the activity of cardiovascular and autonomic nervous system, influences the volumetric workload of the heart and structural changes, and increases the sensitivity of reflexes of arterial baroreceptors.
Topics: Adult; Autonomic Nervous System; Blood Pressure; Blood Pressure Determination; Cardiovascular System; Endurance Training; Heart; Heart Rate; Hemodynamics; Humans; Male; Physical Endurance; Poland; Pressoreceptors; Resistance Training; Water Sports; Young Adult
PubMed: 31662977
DOI: 10.1155/2019/3989304 -
Hypertension (Dallas, Tex. : 1979) Dec 2019We investigated the impact of hypertension on circulatory responses to exercise and the role of the exercise pressor reflex in determining the cardiovascular...
We investigated the impact of hypertension on circulatory responses to exercise and the role of the exercise pressor reflex in determining the cardiovascular abnormalities characterizing patients with hypertension. After a 7-day drug washout, 8 hypertensive (mean arterial pressure [MAP] 130±4 mm Hg; 65±3 years) and 8 normotensive (MAP 117±2 mm Hg; 65±2 years) individuals performed single-leg knee-extensor exercise (7 W, 15 W, 50%, 80%-W) under control conditions and with lumbar intrathecal fentanyl impairing feedback from µ-opioid receptor-sensitive leg muscle afferents. Femoral artery blood flow (Q), MAP (femoral artery), leg vascular conductance, and changes in cardiac output were continuously measured. While the increase in MAP from rest to control exercise was significantly greater in hypertension compared with normotension, the exercise-induced increase in cardiac output was comparable between groups, and Q and leg vascular conductance responses were ≈18% and ≈32% lower in the hypertensive patients (<0.05). The blockade-induced decreases in MAP were significantly larger during exercise in hypertensive (≈11 mm Hg) compared with normotensive (≈6 mm Hg). Afferent blockade attenuated the central hemodynamic response to exercise similarly in both groups resulting in a ≈15% lower cardiac output at each workload. With no effect in normotensive, afferent blockade significantly raised the peripheral hemodynamic response to exercise in hypertensive, resulting in ≈14% and ≈23% higher Q and leg vascular conductance during exercise. Finally, Q and MAP during fentanyl-exercise in hypertensive were comparable to that of normotensive under control conditions (>0.2). These findings suggest that exercise pressor reflex abnormalities largely account for the exaggerated MAP response and the impaired peripheral hemodynamics during exercise in hypertension.
Topics: Aged; Arterial Pressure; Blood Flow Velocity; Blood Pressure Determination; Cardiovascular Abnormalities; Case-Control Studies; Exercise; Female; Hemodynamics; Humans; Hypertension; Male; Middle Aged; Muscle Contraction; Pressoreceptors; Reference Values; Regional Blood Flow; Severity of Illness Index; Stroke Volume
PubMed: 31607174
DOI: 10.1161/HYPERTENSIONAHA.119.13366 -
BMC Cardiovascular Disorders Sep 2019Remote ischemic conditioning (RIC) is a procedure applied in a limb for triggering endogenous protective pathways in distant organs, namely brain or heart. The...
BACKGROUND
Remote ischemic conditioning (RIC) is a procedure applied in a limb for triggering endogenous protective pathways in distant organs, namely brain or heart. The underlying mechanisms of RIC are still not fully understood, and it is hypothesized they are mediated either by humoral factors, immune cells and/or the autonomic nervous system. Herein, heart rate variability (HRV) was used to evaluate the electrophysiological processes occurring in the heart during RIC and, in turn to assess the role of autonomic nervous system.
METHODS
Healthy subjects were submitted to RIC protocol and electrocardiography (ECG) was used to evaluate HRV, by assessing the variability of time intervals between two consecutive heart beats. This is a pilot study based on the analysis of 18 ECG from healthy subjects submitted to RIC. HRV was characterized in three domains (time, frequency and non-linear features) that can be correlated with the autonomic nervous system function.
RESULTS
RIC procedure increased significantly the non-linear parameter SD2, which is associated with long term HRV. This effect was observed in all subjects and in the senior (> 60 years-old) subset analysis. SD2 increase suggests an activation of both parasympathetic and sympathetic nervous system, namely via fast vagal response (parasympathetic) and the slow sympathetic response to the baroreceptors stimulation.
CONCLUSIONS
RIC procedure modulates both parasympathetic and sympathetic autonomic nervous system. Furthermore, this modulation is more pronounced in the senior subset of subjects. Therefore, the autonomic nervous system regulation could be one of the mechanisms for RIC therapeutic effectiveness.
Topics: Adult; Aged; Autonomic Nervous System; Baroreflex; Electrocardiography; Female; Healthy Volunteers; Heart; Heart Rate; Humans; Ischemic Preconditioning; Male; Middle Aged; Pilot Projects; Pressoreceptors; Regional Blood Flow; Time Factors; Upper Extremity
PubMed: 31500561
DOI: 10.1186/s12872-019-1181-5 -
Neurogastroenterology and Motility Dec 2019Different physical exercise interventions for pain and other related symptoms largely follow non-personalized guidelines and show a high degree of variability in... (Comparative Study)
Comparative Study Randomized Controlled Trial
BACKGROUND
Different physical exercise interventions for pain and other related symptoms largely follow non-personalized guidelines and show a high degree of variability in outcome. These interventions are considered to have different pathways toward improvement in autonomic regulation of energy metabolism. The current pilot study was conducted to assess the predictive value of individual cardiovascular (CV) activity markers at rest to predict clinical outcomes for two popular exercise-based interventions (walking and yoga) in patients with Irritable Bowel Syndrome (IBS).
METHODS
Twenty-seven adult participants with IBS were randomly assigned to a 16-biweekly Iyengar yoga or walking program. They completed pre- and post-treatment assessments on IBS symptom severity, affective and somatic complaints, and various measures of resting autonomic function including blood pressure (BP), heart rate and its variability, baroreceptor sensitivity (BRS) to activations and inhibitions with gains of brady- and tachycardiac baro-responses, and BP start points for these spontaneous baroreflexes.
RESULTS
Pretreatment BRS was differentially related to clinical response for the treatment groups. Specifically, a significant decrease in pain severity was found in response to yoga for those participants who had lower resting BRS to activations, but decreased pain severity was associated with higher resting BRS for those in the walking group. The effect was not related to affective symptom relief. Other CV measures showed similar associations with clinical outcomes for both groups.
CONCLUSIONS
The data suggest therefore that CV based phenotypes may be useful in personalizing clinical interventions for IBS. They may also point to autonomic mechanisms that are targets for such interventions.
Topics: Abdominal Pain; Adolescent; Adult; Aged; Baroreflex; Chronic Pain; Exercise Therapy; Female; Heart Rate; Humans; Irritable Bowel Syndrome; Life Style; Male; Middle Aged; Pain Management; Phenotype; Pilot Projects; Precision Medicine; Pressoreceptors; Rest; Socioeconomic Factors; Treatment Outcome; Visceral Pain; Walking; Yoga; Young Adult
PubMed: 31429514
DOI: 10.1111/nmo.13710 -
Journal of Anatomy Nov 2019The glossopharyngeal nerve, via the carotid sinus nerve (CSN), presents baroreceptors from the internal carotid artery (ICA) and chemoreceptors from the carotid body....
The glossopharyngeal nerve, via the carotid sinus nerve (CSN), presents baroreceptors from the internal carotid artery (ICA) and chemoreceptors from the carotid body. Although neurons in the nodose ganglion were labelled after injecting tracer into the carotid body, the vagal pathway to these baro- and chemoreceptors has not been identified. Neither has the glossopharyngeal intracranial afferent/sensory pathway that connects to the brainstem been defined. We investigated both of these issues in male Sprague-Dawley rats (n = 40) by injecting neural tracer wheat germ agglutinin-horseradish peroxidase into: (i) the peripheral glossopharyngeal or vagal nerve trunk with or without the intracranial glossopharyngeal rootlet being rhizotomized; or (ii) the nucleus of the solitary tract right after dorsal and ventral intracranial glossopharyngeal rootlets were dissected. By examining whole-mount tissues and brainstem sections, we verified that only the most rostral rootlet connects to the glossopharyngeal nerve and usually four caudal rootlets connect to the vagus nerve. Furthermore, vagal branches may: (i) join the CSN originating from the pharyngeal nerve base, caudal nodose ganglion, and rostral or caudal superior laryngeal nerve; or (ii) connect directly to nerve endings in the middle segment of the ICA or to chemoreceptors in the carotid body. The aortic depressor nerve always presents and bifurcates from either the rostral or the caudal part of the superior laryngeal nerve. The vagus nerve seemingly provides redundant carotid baro- and chemoreceptors to work with the glossopharyngeal nerve. These innervations confer more extensive roles on the vagus nerve in regulating body energy that is supplied by the cardiovascular, pulmonary and digestive systems.
Topics: Animals; Carotid Artery, Internal; Carotid Body; Chemoreceptor Cells; Male; Neuronal Tract-Tracers; Pressoreceptors; Rats; Rats, Sprague-Dawley; Vagus Nerve
PubMed: 31347697
DOI: 10.1111/joa.13054 -
Journal of Neurophysiology Sep 2019Baroreceptors play a pivotal role in the regulation of blood pressure through moment to moment sensing of arterial blood pressure and providing information to the...
Baroreceptors play a pivotal role in the regulation of blood pressure through moment to moment sensing of arterial blood pressure and providing information to the central nervous system to make autonomic adjustments to maintain appropriate tissue perfusion. A recent publication by Zeng and colleagues (Zeng WZ, Marshall KL, Min S, Daou I, Chapleau MW, Abboud FM, Liberles SD, 362: 464-467, 2018) suggests the mechanosensitive ion channels Piezo1 and Piezo2 represent the cellular mechanism by which baroreceptor nerve endings sense changes in arterial blood pressure. However, before Piezo1 and Piezo2 are accepted as the sensor of baroreceptors, the question must be asked of what criteria are necessary to establish this and how well the report of Zeng and colleagues (Zeng WZ, Marshall KL, Min S, Daou I, Chapleau MW, Abboud FM, Liberles SD, 362: 464-467, 2018) satisfies these criteria. We briefly review baroreceptor function, outline criteria that a putative neuronal sensor of blood pressure must satisfy, and discuss whether the recent findings of Zeng and colleagues suitably meet these criteria. Despite the provocative hypothesis, there are significant concerns regarding the evidence supporting a role of Piezo1/Piezo2 in arterial baroreceptor function.
Topics: Animals; Autonomic Nervous System; Baroreflex; Blood Pressure; Humans; Ion Channels; Pressoreceptors
PubMed: 31314636
DOI: 10.1152/jn.00315.2019 -
Experimental Physiology Sep 2019What is the central question of this study? The traditional surgical approach for sino-aortic denervation in rats leads to simultaneous carotid baroreceptor and...
NEW FINDINGS
What is the central question of this study? The traditional surgical approach for sino-aortic denervation in rats leads to simultaneous carotid baroreceptor and chemoreceptor deactivation, which does not permit their individual study in different situations. What is the main finding and its importance? We have described a new surgical approach capable of selective denervation of the arterial (aortic and carotid) baroreceptors, keeping the carotid bodies (chemoreceptors) intact. It is understood that this technique might be a useful tool for investigating the relative role of the baro- and chemoreceptors in several physiological and pathophysiological conditions.
ABSTRACT
Studies have demonstrated that the traditional surgical approach for sino-aortic denervation in rats leads to simultaneous carotid baroreceptor and chemoreceptor deactivation. The present study reports a new surgical approach to denervate the aortic and the carotid baroreceptors selectively, keeping the carotid bodies (peripheral chemoreceptors) intact. Wistar rats were subjected to specific aortic and carotid baroreceptor denervation (BAROS-X) or sham surgery (SHAM). Baroreflex activation was achieved by i.v. administration of phenylephrine, whereas peripheral chemoreflex activation was produced by i.v. administration of potassium cyanide. The SHAM and BAROS-X rats displayed significant hypertensive responses to phenylephrine administration. However, the reflex bradycardia following the hypertensive response caused by phenylephrine was remarkable in SHAM, but not significant in the BAROS-X animals, confirming the efficacy of the surgical procedure to abolish the baroreflex. In addition, the baroreflex activation elicited by phenylephrine increased carotid sinus nerve activity only in SHAM, but not in the BAROS-X animals, providing support to the notion that the baroreceptor afferents were absent. Instead, the classical peripheral chemoreflex hypertensive and bradycardic responses to potassium cyanide were similar in both groups, suggesting that the carotid body chemoreceptors were preserved after BAROS-X. In summary, we describe a new surgical approach in which only the baroreceptors are eliminated, while the carotid chemoreceptors are preserved. Therefore, it is understood that this procedure is potentially a useful tool for examining the relative roles of the arterial baroreceptors versus the chemoreceptors in several pathophysiological conditions, for instance, arterial hypertension and heart failure.
Topics: Animals; Aorta; Arteries; Baroreflex; Blood Pressure; Carotid Body; Chemoreceptor Cells; Denervation; Heart Rate; Hypertension; Male; Phenylephrine; Pressoreceptors; Rats; Rats, Wistar
PubMed: 31161612
DOI: 10.1113/EP087764 -
BioMed Research International 2019Reduced baroreflex sensitivity (BRS) has been reported in patients with acute cardiovascular events. We tested the hypothesis that BRS varies in different subtypes of...
BACKGROUND
Reduced baroreflex sensitivity (BRS) has been reported in patients with acute cardiovascular events. We tested the hypothesis that BRS varies in different subtypes of acute ischemic stroke (AIS) and that BRS is a predictor of clinical outcomes.
METHODS
We examined autonomic parameters in 34 patients with AIS, including the small deep hemisphere infarction, the large hemisphere infarction, and the brainstem infarction groups on Day 1, Day 7, and Day 30 after AIS. Autonomic parameters were also evaluated in 18 age- and sex-matched healthy volunteers as a control group. The clinical outcomes were analyzed using the modified Rankin scale at 30 days after stroke.
RESULTS
The BRS, Valsalva ratio, and heart rate response to deep breathing (HR-DB) were significantly lower in patients after AIS on admission than in controls (<0.01). The frequency domain of HRV (LF/HF ratio) was significantly increased in patients after AIS compared to controls (<0.05). BRS was significantly reduced in patients with large hemisphere infarction or brainstem infarction compared to patients with small deep hemisphere infarction on Day 1 after AIS (<0.01). Stepwise logistic regression showed that the levels of BRS and NIHSS are prognostic factors of 1-month outcomes in patients with AIS.
CONCLUSION
Beside NIHSS score on admission, BRS is a potential prognostic factor of 1-month outcomes in patients with AIS. Patients with large hemisphere infarction or brainstem infarction have more blunting BRS than do those with lacunar infarction, which provides some insight into which patients may be expected to have a poor outcome.
Topics: Aged; Case-Control Studies; Female; Humans; Male; Middle Aged; Pressoreceptors; Prognosis; Stroke; Time Factors; Treatment Outcome
PubMed: 31139650
DOI: 10.1155/2019/7614828