Autonomic uprising: the tilt table test in autonomic medicine

TRANSCENDENT (Transforming Research by Assessing Neuroinformatics across the Spectrum of Concussion by Embedding iNterdisciplinary Data-collection to Enable Novel Treatments): protocol for a prospective observational cohort study of concussion patients with embedded comparative effectiveness research within a network of learning health system concussion clinics in Canada

INTRODUCTION

Concussion affects over 400 000 Canadians annually, with a range of causes and impacts on health-related quality of life. Research to date has disproportionately focused on athletes, military personnel and level I trauma centre patients, and may not be applicable to the broader community. The TRANSCENDENT Concussion Research Program aims to address patient- and clinician-identified research priorities, through the integration of clinical data from patients of all ages and injury mechanisms, patient-reported outcomes and objective biomarkers across factors of intersectionality. Seeking guidance from our Community Advisory Committee will ensure meaningful patient partnership and research findings that are relevant to the wider concussion community.

METHODS AND ANALYSIS

This prospective observational cohort study will recruit 5500 participants over 5 years from three 360 Concussion Care clinic locations across Ontario, Canada, with a subset of participants enrolling in specific objective assessments including testing of autonomic function, exercise tolerance, vision, advanced neuroimaging and fluid biomarkers. Analysis will be predicated on pre-specified research questions, and data shared with the Ontario Brain Institute's Brain-CODE database. This work will represent one of the largest concussion databases to date, and by sharing it, we will advance the field of concussion and prevent siloing within brain health research.

ETHICS AND DISSEMINATION

This study was approved by the Children's Hospital of Eastern Ontario Research Ethics Board and preregistered on OSF (25 June 2024); https://doi.org/10.17605/OSF.IO/HYDZC. Dissemination of findings will be multifaceted, including conference presentations, peer-reviewed publications and sharing of adapted materials (eg, videos, infographics, plain language summaries) with community groups and key knowledge users.

Physiological and clinical comparison of active stand and head-up tilt tests in Postural Orthostatic Tachycardia Syndrome (POTS)

Head-up tilt (HUT) and active stand tests (AST) are used in the diagnosis of Postural Orthostatic Tachycardia Syndrome (POTS), but their relative diagnostic accuracy is unclear. This necessitates a direct comparison under standardized conditions. We aimed to compare the hemodynamic responses and diagnostic accuracy of AST vs. HUT in POTS. To address this, patients with POTS (n = 60) completed a 10-min AST followed by HUT on the same day. Beat-to-beat hemodynamics were recorded during 10-min supine baselines and each test. Delta values were calculated for each test (upright 1-min averages minus baseline average). Δ[heart rate] increased significantly over time (1_Min: 28 bpm to 10_Min: 40 bpm; PTime < 0.001), and was greater for HUT (33 bpm vs. 37 bpm; PASTvHUT = 0.01), with significant Time x Condition interaction (38 bpm vs. 42 bpm at10min; PINT < 0.001). Δ[stroke volume] declined over time (1_Min: -18 ml to 10_Min: -32 ml); PTime < 0.001), with no significant test or interaction effects (PASTvHUT = 0.36; PINT = 0.21). Δ[SBP] decreased (1_Min: -0.3 mmHg to 10_Min: -5.7 mmHg); PTime < 0.001) over time, with no test or interaction effects. Fewer patients met POTS heart rate criteria during the AST (AST: 74 % vs. HUT: 98 %; p < 0.001). Lowering the threshold to 27 bpm for AST narrowed the gap but was still significantly higher for HUT (AST: 83 % vs HUT: 98 %; p = 0.02). Orthostatic tachycardia differs between AST and HUT in patients with POTS. The proportion of patients with POTS meeting the heart rate diagnostic criteria differs significantly between AST and HUT, a discrepancy that can be mitigated by lowering the heart rate threshold for the AST.

Comparison of the head-up tilt test and the 10-minute NASA lean test for assessing blood pressure and heart rate responses in young individuals with postacute COVID-19 syndrome

BACKGROUND

Individuals with postacute COVID-19 syndrome (PACS) typically exhibit abnormal hemodynamic responses during upright positioning, including orthostatic hypotension and postural orthostatic tachycardia syndrome. The 10-minute NASA lean test (NLT) has been suggested for this condition. However, no comparative study with the head-up tilt table test (HUTT) has been conducted. This study aimed to compare blood pressure and heart rate responses during the 10-minute duration of NLT and HUTT.

METHODS

Eighty young individuals (aged 22.0 ± 3.1 years) with PACS underwent both tests, with a 30-minute interval between tests. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were measured every minute, and the differences between supine and upright positions were analyzed.

RESULTS

There were no significant differences in SBP changes between HUTT and NLT (-7.8 ± 6.2 vs. -7.1 ± 7.5 mmHg) with a mean difference of -0.7 ± 9.0 mmHg. However, DBP changes were significantly lower in HUTT compared to NLT (-0.9 ± 6.4 vs. 1.5 ± 6.9 mmHg for NLT) with a mean difference of -2.4 ± 7.1 mmHg. Maximal HR was significantly lower in HUTT compared to NLT (92.0 ± 11.4 vs. 96.2 ± 10.8 bpm for NLT) with a mean difference of -4.2 ± 6.9 bpm. Additionally, HR changes were significantly lower in HUTT compared to NLT (21.5 ± 8.1 vs. 27.0 ± 9.0 bpm) with a mean difference of -5.4 ± 6.4 bpm.

CONCLUSION

The NLT demonstrated comparability with the HUTT in detecting SBP changes. However, clinical applications should consider differences in measuring DBP and HR changes.

Effect of Protein Supplementation on Orthostatic Hypotension in Older Adult Patients with Heart Failure

Purpose: Heart failure (HF) impairs physical performance and increases the incidence of orthostatic hypotension (OH). Individuals with OH have a higher risk of falls, which are a major source of morbidity and mortality in older adults. Dietary protein supplementation can improve physical performance in healthy older adult individuals; however, its effect on OH in older adult patients with HF is unknown. Methods: Twenty-one older adult patients with mild-to-moderate HF were randomized to placebo or protein supplementation. Dietary protein was supplemented with whey protein so the total protein intake for each participant was 1.2 g/kg bodyweight/day, plus 1 g/day of the amino acid l-carnitine for 16 weeks. Susceptibility to OH was assessed using a head-up tilt test, blood markers, and a functional test (6 min walk) at baseline and 16 weeks. Results: There were no differences in tilt test responses or 6 min walk test (6MWT) distances. The protein-supplement group had a significant increase in 6MWT pulse pressures post-walk after 16 weeks of treatment as compared to placebo. However, the tachycardia observed at baseline after 6MWT in the protein group was not seen at the end of the study. There was also a trend towards lower levels of brain naturetic peptide (proBNP) in the protein group vs. placebo at 16 weeks. Conclusions: The improved pulse-pressure response to exertion and positive trends in proBNP in this pilot study suggest that dietary supplementation may improve cardiovascular function and general health in individuals with HF and that larger future studies are justifiable.

Haemodynamic Patterns in Reflex Syncope: Insights from Head-Up Tilt Tests in Adults and Children

Introduction: Vasovagal syncope is a prevalent condition marked by transient loss of consciousness due to abrupt decreases in systemic blood pressure and/or heart rate. Despite its clinical impact, the underlying haemodynamic mechanisms remain poorly defined, and data on age-related differences are limited and sometimes contradictory. Objectives: This study aimed to characterise haemodynamic adaptation patterns during a head-up tilt (HUT) test in adult (≥18 years) and paediatric (<18 years) patients with recurrent reflex syncope, compared with healthy adult controls. We sought to identify distinct temporal haemodynamic signatures and clarify potential age-related differences in syncope mechanisms. Methods: In this prospective observational study, participants underwent continuous beat-to-beat monitoring of cardiac output (CO), stroke volume (SV), heart rate (HR), and total peripheral resistance (TPR) during HUT. Linear mixed-effects models were used to examine time-by-group interactions, and post-hoc analyses were adjusted for multiple comparisons. Effect sizes and confidence intervals (CIs) were reported to quantify the magnitude of differences. Results: A total of 187 fainters (paediatric n = 81, adult n = 106) and 108 non-fainters (including 30 healthy controls) were studied. Compared to adult fainters, paediatric fainters showed a 24% larger decline in CO from baseline (mean difference of 1.1 L/min [95% CI: 0.5-1.7], p = 0.003) and a 15-20 bpm higher peak HR (p = 0.001) during presyncope. Both subgroups experienced significant drops in TPR, which were more pronounced in paediatric fainters (effect size = 0.27, 95% CI: 0.12-0.42). Non-fainters (including controls) maintained relatively stable haemodynamics, with no significant decrease in CO or TPR (p > 0.05). Age-related comparisons indicated a heavier reliance on HR modulation in paediatric fainters, leading to an earlier transition from compensated to pre-syncopal states. Conclusions: These findings demonstrate that paediatric fainters exhibit more abrupt decreases in CO and TPR than adults, alongside higher HR responses during orthostatic stress. Targeted interventions that address this heightened chronotropic dependency-such as tilt-training protocols or strategies to improve venous return-may be particularly beneficial in younger patients. An age-specific approach to diagnosis and management could improve risk stratification, minimise recurrent episodes, and enhance patient outcomes.

Parasympathetic Dysfunction Prevails in GBA1-Associated Parkinson's Disease

BACKGROUND

The role played by sympathetic and parasympathetic autonomic branches in patients with Parkinson's disease carrying variants in the GBA1 gene (GBA-PD) is still elusive.

OBJECTIVES

To characterize cardiovascular autonomic function in GBA-PD and I-PD patients with early and mid-stage disease.

METHODS

These assessments were performed: cardiovascular autonomic tests, analysis of heart rate and blood pressure variability, cardiac noradrenergic imaging. The frequency and severity of autonomic symptoms were comparatively assessed with the SCOPA-AUT questionnaire.

RESULTS

Compared to the I-PD cohort, GBA-PD patients displayed an increased burden of autonomic symptoms. Autonomic tests revealed worse parasympathetic scores in GBA-PD while sympathetic indexes and the degree of cardiac sympathetic binding were comparable in the two groups. Heart rate variability indexes also revealed lower vagal modulation in the GBA-PD group.

CONCLUSIONS

The cardiovascular autonomic profile in GBA PD is characterized by a prominent cardiovagal dysfunction compared to I-PD.

Identification of small fiber neuropathy in neuronal intranuclear inclusion disease: A clinicopathological study

INTRODUCTION

Neuronal intranuclear inclusion disease (NIID) manifests as dementia combined with other neurological symptoms. However, small fiber neuropathy (SFN) and pathology remain unknown in NIID.

METHODS

A total of 294 subjects, including patients with NIID, Parkinson's disease, Alzheimer's disease, diabetic peripheral neuropathy, and healthy controls (HCs), were included. Clinical scales, sensory and autonomic function testing, and skin biopsy were performed.

RESULTS

NIID patients had more severe sensory and autonomic dysfunction than other groups. Substantial reductions in intraepidermal, sweat gland, and pilomotor nerve fiber densities were observed in NIID patients, with a non-length dependent pattern. Detailed analysis revealed marked reductions in noradrenergic, cholinergic, peptidergic, and regenerative nerve fibers. Small fiber densities showed high diagnostic accuracy in distinguishing NIID from HCs and other diseases.

DISCUSSION

This study is the first to reveal wide and severe loss of small fibers in NIID, suggesting the involvement of SFN in the pathogenesis of NIID.

HIGHLIGHTS

Our study is the first to identify wide and severe non-length dependent small fiber neuropathy in neuronal intranuclear inclusion disease (NIID) patients. Approximately 50% of NIID patients exhibited pure small fiber neuropathy without large fiber or mixed neuropathy. NIID patients showed a significant reduction in noradrenergic, cholinergic, peptidergic, and regenerative fiber innervation. Small fiber densities, especially intraepidermal nerve fiber density, demonstrated high diagnostic accuracy in distinguishing NIID patients from healthy controls and other disease groups. Findings suggest that small fiber neuropathy may play a role in the pathogenesis of NIID.

Autonomic assessment at the intersection of psychosocial and gastrointestinal health

BACKGROUND

Wearable technology is increasingly used in clinical practice and research to monitor functional gastrointestinal symptoms and mental health.

AIMS

This article explores the potential of wearable sensors to enhance the understanding of the autonomic nervous system (ANS), particularly its role in linking psychological and gastrointestinal function. The ANS, facilitates brain-gut communication and is responsive to psychosocial conditions. It is implicated in disorders related to psychological stress and gut-brain interaction. Wearable technology enables tracking of the ANS in daily life, offering complementary and alternative methods from traditional lab-based measures. This review places focus on autonomic metrics such as respiratory sinus arrhythmia, vagal efficiency, and electrodermal activity as well as self-reports of autonomic symptoms.

DISCUSSION

Potential applications include use of wearable sensors for tracking autonomic activity in disorder of gut-brain interaction such as cyclic vomiting syndrome, in which ANS dysregulation may be triggered by psychosocial factors. Considerations for data interpretation and contextualization are addressed, acknowledging challenges such as situational confounders of ANS activity and accuracy of wearable devices.

Cardiovascular Autonomic Dysfunction Before and After Chemotherapy in Cancer Patients

Complications that occur during cancer therapy have emerged as a major contributor to the poor quality of life experienced by cancer patients as they live longer due to improved treatments. Many studies have investigated chemotherapy-induced peripheral neuropathy, but few have investigated the autonomic nervous system. Cardiovascular autonomic dysfunction (CAD) contributes to the distressing symptoms experienced by cancer patients, and it is also related to poor treatment outcomes. CAD has a multifactorial etiology in patients with cancer: it can be caused by the cancer itself, chemotherapy or radiation therapy, or other comorbidities. Its symptoms are nonspecific, and they include orthostatic hypotension, resting tachycardia, dizziness, chest tightness, and exertional dyspnea. It is important to suspect CAD and perform therapeutic interventions in a clinical context, because a patient who is more frail is less like to endure the treatment process. The quality of life of patients receiving active cancer treatments can be improved by evaluating the risk of CAD before and after chemotherapy, and combining both nonpharmacological and pharmacological management. Here we review the prevalence, pathogenesis, diagnosis, and treatment of CAD, which is the most common and a sometimes serious symptom in cancer patients.

Frequency and severity of autonomic dysfunction assessed by objective hemodynamic responses and patient-reported symptoms in individuals with myasthenia gravis

Introduction

Myasthenia gravis (MG), a rare autoimmune disorder, poses diagnostic and management challenges, with increasing incidence in Europe and significant impact on patient quality of life. Despite prevalent autonomic symptoms, comprehensive assessments integrating subjective and objective measures are lacking. We aimed to investigate the prevalence and severity of autonomic dysfunction in patients with MG and healthy controls (HCs).

Materials and methods

We used beat-to-beat hemodynamic responses during standardized autonomic function tests (AFTs) and the Composite Autonomic Symptom Score 31 (COMPASS-31) questionnaire. Study participants including, 53 patients with MG and 30 age- and sex matched HCs underwent standardized cardiovascular AFTs and completed the COMPASS-31 questionnaire. Patients were categorized into Non-CAN and CAN groups based on their Cardiovascular Autonomic Neuropathy (CAN) status, as evaluated using the Composite Autonomic Scoring Scale (CASS). During the AFTs, cardiovascular parameters including heart rate, systolic blood pressure (BP), diastolic BP, mean BP, stroke volume (SV), cardiac output (CO), and total peripheral resistance (TPR) were measured.

Results

Twenty patients with MG (38%) exhibited mild CAN (CASS ≥2) with a median total CASS score of 1.00 and CASS 0.00 in HCs. Adrenergic impairment was observed in 27 patients (52%), with 13 patients (24.5%) exhibiting longer pressure recovery time after Valsalva maneuver (VM). Cardiovagal impairment was evident in 71% of patients, with abnormal results observed in 39.6% for the deep breathing test and 56.6% for the VM. CAN MG showed worse scores than HCs for the total COMPASS-31 (p < 0.001), orthostatic (OI) (p < 0.001), secretomotor (p = 0.004), and pupillomotor domains (p = 0.004). Total COMPASS-31 and OI scores were correlated with worse disease outcomes (disease duration, severity), hemodynamic parameter changes (SV, CO, TPR) during phase II late of VM, and with changes (Δtilt-supine) in Δsystolic BP, Δdiastolic BP, Δmean BP, ΔTPR during head-up-tilt test, but not with CASS score.

Conclusion

Our findings demonstrate mild cardiovascular autonomic impairment in adrenergic and cardiovagal domains in patients with MG. Additionally, patient-reported autonomic symptoms correlated with hemodynamic changes during AFTs and worse disease outcomes and not with the grade of autonomic abnormalities. Incorporating beat-to-beat hemodynamics during AFTs may offer further insights for characterizing orthostatic intolerance symptoms in MG group.

Tilt Table Testing

This Diagnostic Test Interpretation uses a patient case to illustrate tilt table testing, useful for evaluating patients with syncope of unknown cause or postural orthostatic tachycardia syndrome (POTS).

Adult vasovagal syncope with abdominal pain diagnosed by head-up tilt combined with transcranial doppler: a preliminary study

BACKGROUND

Syncope is a common condition that increases the risk of injury and reduces the quality of life. Abdominal pain as a precursor to vasovagal syncope (VVS) in adults is rarely reported and is often misdiagnosed.​.

METHODS

We present three adult patients with VVS and presyncopal abdominal pain diagnosed by synchronous multimodal detection (transcranial Doppler [TCD] with head-up tilt [HUT]) and discuss the relevant literature.

RESULTS

Case 1: A 52-year-old man presented with recurrent decreased consciousness preceded by six months of abdominal pain. Physical examinations were unremarkable. Dynamic electrocardiography, echocardiography, head and neck computed tomography angiography, magnetic resonance imaging (MRI), and video electroencephalogram showed no abnormalities. Case 2: A 57-year-old woman presented with recurrent syncope for 30 + years, accompanied by abdominal pain. Physical examination, electroencephalography, and MRI showed no abnormalities. Echocardiography showed large right-to-left shunts. Case 3: A 30-year-old woman presented with recurrent syncope for 10 + years, with abdominal pain as a precursor. Physical examination, laboratory analysis, head computed tomography, electrocardiography, and echocardiography showed no abnormalities. Syncope secondary to abdominal pain was reproduced during HUT. Further, HUT revealed vasovagal syncope, and synchronous TCD showed decreased cerebral blood flow; the final diagnosis was VVS in all cases.

CONCLUSIONS

Abdominal pain may be a precursor of VVS in adults, and our findings enrich the clinical phenotypic spectrum of VVS. Prompt recognition of syncopal precursors is important to prevent incidents and assist in treatment decision-making. Abdominal pain in VVS may be a sign of sympathetic overdrive. Synchronous multimodal detection can help in diagnosing VVS and understanding hemodynamic mechanisms.

Functional and 123I-MIBG scintigraphy assessment of cardiac adrenergic dysfunction in diabetes

OBJECTIVES

To assess the agreement between clinical cardiovascular adrenergic function and cardiac adrenergic innervation in type 2 diabetes patients (T2D).

METHODS

Thirty-three patients with T2D were investigated bimodally through (1) a standardized clinical cardiovascular adrenergic assessment, evaluating adequacy of blood pressure responses to the Valsalva maneuver and (2) 123I-meta-iodobenzylguanidine (MIBG) scintigraphy assessing myocardial adrenergic innervation measured as early and delayed heart heart/mediastinum (H/M) ratio, and washout rate (WR).

RESULTS

T2D patients had significantly lower early and delayed H/M-ratios, and lower WR, compared to laboratory specific reference values. Thirteen patients had an abnormal adrenergic composite autonomic severity score (CASS > 0). Patients with abnormal CASS scores had significantly higher early H/M ratios (1.76 [1.66-1.88] vs. 1.57 [1.49-1.63], p < 0.001), higher delayed H/M ratios (1.64 [1.51:1.73] vs. 1.51 [1.40:1.61] (p = 0.02)), and lower WR (-0.13(0.10) vs -0.05(0.07), p = 0.01). Lower Total Recovery and shorter Pressure Recovery Time responses from the Valsalva maneuver was significantly correlated to lower H/M early (r = 0.55, p = 0.001 and r = 0.5, p = 0.003, respectively) and lower WR for Total Recovery (r = -0.44, p = 0.01).

CONCLUSION

The present study found impairment of sympathetic innervation in T2D patients based on parameters derived from MIBG cardiac scintigraphy (low early H/M, delayed H/M, and WR). These results confirm prior studies. We found a mechanistically inverted relationship with favourable adrenergic cardiovascular responses being significantly associated unfavourable MIBG indices for H/M early and delayed. This paradoxical relationship needs to be further explored but could indicate adrenergic hypersensitivity in cardiac sympathetic denervated T2D patients.

Deep vein thrombosis and its risk factors in neurodegenerative diseases: A markedly higher incidence in Parkinson's disease

BACKGROUND

Information on the incidence and risk factors of deep vein thrombosis (DVT) in neurodegenerative diseases is limited. We aimed to determine the incidence of DVT among neurodegenerative disorders (amyotrophic lateral sclerosis [ALS], Parkinson's disease [PD], multiple system atrophy [MSA], and progressive supranuclear palsy [PSP]-corticobasal syndrome [CBS]) and the risk factors for the development of DVT.

METHODS

Overall, 229 hospitalized patients with neurodegenerative diseases (65 patients with ALS, 61 with PD, 53 with MSA, and 50 with PSP-CBS) were included in this study. D-dimer value and ultrasonography of the leg vein were assessed to determine the presence or absence of leg DVT. We compared the DVT incidence among each disease group. To identify the risk factors for DVT, a multivariate analysis was performed.

RESULTS

Of 229 patients, 34 had leg DVT; the incidence was significantly higher in patients with PD (38%) than in those with ALS (2%), MSA (5%), or PSP-CBS (4%). Patients with DVT were older, had a smaller waist circumference, had a longer disease duration, and had a high blood pressure (BP) variability. Multivariate analysis revealed that a PD diagnosis and female sex, with a high BP variability were predictive of leg DVT.

CONCLUSIONS

Among the neurodegenerative diseases, the DVT incidence was markedly higher in PD than in ALS, MSA, and PSP-CBS. Several risk factors have been identified in patients with leg DVT. Recognition of these risk factors will improve patient care and guide the appropriate use of anticoagulants.

Tilt-evoked, breathing-driven blood pressure oscillations: Independence from baroreflex-sympathoneural function

PURPOSE

Orthostasis increases the variability of continuously recorded blood pressure (BP). Low-frequency (LF) BP oscillations (Mayer waves) in this setting are related to the vascular-sympathetic baroreflex. Mechanisms of increased high-frequency (HF) BP oscillations at the periodicity of respiration during orthostasis have received less research attention. A previously reported patient with post-neurosurgical orthostatic hypotension (OH) and vascular-sympathetic baroreflex failure had large tilt-evoked, breathing-driven BP oscillations, suggesting that such oscillations can occur independently of vascular-sympathetic baroreflex modulation. In the present study we assessed effects of orthostasis on BP variability in the frequency domain in patient cohorts with or without OH.

METHODS

Power spectral analysis of systolic BP variability was conducted on recordings from 73 research participants, 42 with neurogenic OH [13 pure autonomic failure, 14 Parkinson's disease (PD) with OH, 12 parkinsonian multiple system atrophy, and 3 status post-brainstem neurosurgery] and 31 without OH (control group of 16 healthy volunteers and 15 patients with PD lacking OH), before, during, and after 5' of head-up tilt at 90 degrees from horizontal. The data were log transformed for statistical testing.

RESULTS

Across all subjects, head-up tilting increased HF power of systolic BP variability (p = 0.001), without a difference between the neurogenic OH and control groups. LF power during orthostasis was higher in the control than in the OH groups (p = 0.009).

CONCLUSIONS

The results of this observational cohort study confirm those based on our case report and lead us to propose that even in the setting of vascular-sympathetic baroreflex failure orthostasis increases HF power of BP variability.

Possible Role of Fibrinaloid Microclots in Postural Orthostatic Tachycardia Syndrome (POTS): Focus on Long COVID

Postural orthostatic tachycardia syndrome (POTS) is a common accompaniment of a variety of chronic, inflammatory diseases, including long COVID, as are small, insoluble, 'fibrinaloid' microclots. We here develop the argument, with accompanying evidence, that fibrinaloid microclots, through their ability to block the flow of blood through microcapillaries and thus cause tissue hypoxia, are not simply correlated with but in fact, by preceding it, may be a chief intermediary cause of POTS, in which tachycardia is simply the body's exaggerated 'physiological' response to hypoxia. Similar reasoning accounts for the symptoms bundled under the term 'fatigue'. Amyloids are known to be membrane disruptors, and when their targets are nerve membranes, this can explain neurotoxicity and hence the autonomic nervous system dysfunction that contributes to POTS. Taken together as a system view, we indicate that fibrinaloid microclots can serve to link POTS and fatigue in long COVID in a manner that is at once both mechanistic and explanatory. This has clear implications for the treatment of such diseases.

Comparisons of heart rate variability responses to head-up tilt with and without abdominal and lower-extremity compression in healthy young individuals: a randomized crossover study

Introduction: Abdominal and lower-extremity compression techniques can help reduce orthostatic heart rate increases. However, the effects of body compression on the cardiac autonomic systems, which control heart rate, remain unclear. The primary objective of this study was to compare heart rate variability, a reflection of cardiac autonomic regulation, during a head-up tilt test with and without abdominal and lower-extremity compression in healthy young individuals. The secondary objective was to conduct a subgroup analysis, considering participant sex, and compare heart rate and heart rate variability responses to head-up tilt with and without compression therapy. Methods: In a randomized crossover design, 39 healthy volunteers (20 females, aged 20.9 ± 1.2 years) underwent two head-up tilt tests with and without abdominal and lower-extremity compression. Heart rate and heart rate variability parameters were measured during the head-up tilt tests, including the Stress Index, root mean square of successive differences between adjacent R-R intervals, low- and high-frequency components, and low-to-high frequency ratio. Results: Abdominal and lower-extremity compression reduced the orthostatic increase in heart rate (p < 0.001). The tilt-induced changes in heart rate variability parameters, except for the low-frequency component, were smaller in the compression condition than in the no-compression condition (p < 0.001). These results were consistent regardless of sex. Additionally, multiple regression analysis with potentially confounding variables revealed that the compression-induced reduction in Stress Index during the head-up tilt position was a significant independent variable for the compression-induced reduction in heart rate in the head-up tilt position (coefficient = 0.411, p = 0.025). Conclusion: Comparative analyses revealed that abdominal and lower-extremity compression has a notable impact on the compensatory sympathetic activation and vagal withdrawal typically observed during orthostasis, resulting in a reduction of the increase in heart rate. Furthermore, this decrease in heart rate was primarily attributed to the attenuation of cardiac sympathetic activity associated with compression. Our findings could contribute to the appropriate application of compression therapy for preventing orthostatic tachycardia. This study is registered with UMIN000045179.

Cardiac noradrenergic deficiency revealed by 18F-dopamine positron emission tomography identifies preclinical central Lewy body diseases

BACKGROUND

In Lewy body diseases (LBDs) Parkinson disease (PD), and dementia with Lewy bodies (DLB), by the time parkinsonism or cognitive dysfunction manifests clinically, substantial neurodegeneration has already occurred. Biomarkers are needed to identify central LBDs in a preclinical phase, when neurorescue strategies might forestall symptomatic disease. This phase may involve catecholamine deficiency in the autonomic nervous system. We analyzed data from the prospective, observational, long-term PDRisk study to assess the predictive value of low versus normal cardiac 18F-dopamine positron emission tomography (PET), an index of myocardial content of the sympathetic neurotransmitter norepinephrine, in at-risk individuals.

METHODS

Participants self-reported risk factor information (genetics, olfactory dysfunction, dream enactment behavior, and orthostatic intolerance or hypotension) at a protocol-specific website. Thirty-four with 3 or more confirmed risk factors underwent serial cardiac 18F-dopamine PET at 1.5-year intervals for up to 7.5 years or until PD was diagnosed.

RESULTS

Nine participants had low initial myocardial 18F-dopamine-derived radioactivity (<6,000 nCi-kg/cc-mCi) and 25 had normal radioactivity. At 7 years of follow-up, 8 of 9 with low initial radioactivity and 1 of 11 with normal radioactivity were diagnosed with a central LBD (LBD+) (P = 0.0009 by Fisher's exact test). Conversely, all 9 LBD+ participants had low 18F-dopamine-derived radioactivity before or at the time of diagnosis of a central LBD, whereas among 25 participants without a central LBD only 1 (4%) had persistently low radioactivity (P < 0.0001 by Fisher's exact test).

CONCLUSION

Cardiac 18F-dopamine PET highly efficiently distinguishes at-risk individuals who are diagnosed subsequently with a central LBD from those who are not.

TRIAL REGISTRATION

CLINICALTRIALS

gov NCT00775853.

FUNDING

Division of Intramural Research, NIH, NINDS.

Impact of daily artificial gravity on autonomic cardiovascular control following 60-day head-down tilt bed rest

Impaired cardiovascular autonomic control following space flight or immobilization may limit the ability to cope with additional hemodynamic stimuli. Head-down tilt bedrest is an established terrestrial analog for space flight and offers the opportunity to test potential countermeasures for autonomic cardiovascular deconditioning. Previous studies revealed a possible benefit of daily artificial gravity on cardiovascular autonomic control following head-down tilt bedrest, but there is a need for efficiency in a long-term study before an artificial gravity facility would be brought to space. We hypothesized that artificial gravity through short-arm centrifugation attenuates functional adaptions of autonomic function during head-down tilt bed rest. 24 healthy persons (8 women, 33.4 ± 9.3 years, 24.3 ± 2.1 kg/m2) participated in the 60-day head-down tilt bed rest (AGBRESA) study. They were assigned to three groups, 30 min/day continuous, or 6(5 min intermittent short-arm centrifugation, or a control group. We assessed autonomic cardiovascular control in the supine position and in 5 minutes 80° head-up tilt position before and immediately after bed rest. We computed heart rate variability (HRV) in the time (rmssd) and frequency domain, blood pressure variability, and baroreflex sensitivity (BRS). RR interval corrected rmssd was reduced supine (p = 0.0358) and during HUT (p = 0.0161). Heart rate variability in the high-frequency band (hf-RRI; p = 0.0004) and BRS (p < 0.0001) decreased, whereas blood pressure variability in the low-frequency band (lf-SBP, p = 0.0008) increased following bedrest in all groups. We did not detect significant interactions between bedrest and interventions. We conclude that up to daily 30 min of artificial gravity on a short-arm centrifuge with 1Gz at the center of mass do not suffice to prevent changes in autonomic cardiovascular control following 60-day of 6° head-down tilt bed rest. Clinical Trial Registration: https://drks.de/search/en/trial/DRKS00015677, identifier, DRKS00015677.

Neuro-Cardiovascular Responses to Sympathetic Stimulation in Fighter Pilots

INTRODUCTION: The chronic effects of regular exposure to high acceleration levels (G-force) on the neuro-cardiovascular system are unclear. We compared the mean arterial pressure (MAP) and cardiac autonomic modulation between nonpilots (NP) vs. military fighter (FP) and transport (TP) pilots. Additionally, we correlated the cardiac autonomic indices with the cardiorespiratory fitness and flight experience of FP.METHODS: A total of 21 FP, 8 TP, and 20 NP performed a tilt test (TT), during which beat-to-beat blood pressure and heart rate were recorded.RESULTS: No difference was detected between groups for changes in MAP and heart rate variability indices during the TT. However, the analysis of areas under the curves showed a greater increase in MAP in FP vs. TP and NP. Conversely, there was a greater decrease in indices reflecting vagal modulation in TP vs. FP and NP (rMSSD, pNN50, and SDNN), and a greater increase in heart rate and sympathovagal balance in TP vs. other groups (LF/HF). The maximal oxygen uptake was strongly correlated with the vagal reserve in FP (r = -0.74). Moreover, the total flying hours of FP were positively correlated with resting HFnu (r = 0.47) and inversely correlated with resting LFnu (r = -0.55) and LF/HF (r = -0.46).CONCLUSION: FP had a higher pressor response to TT than TP and NP. Vagal withdrawal and sympathovagal increase induced by TT in FP were similar vs. NP and attenuated vs. TP. Greater cardiorespiratory fitness and accumulated flying hours in FP seemed to favor lower sympathetic and greater vagal modulation at rest.dos Santos Rangel MV, de Sá GB, Farinatti P, Borges JP. Neuro-cardiovascular responses to sympathetic stimulation in fighter pilots. Aerosp Med Hum Perform. 2023; 94(10):761-769.

Clinical and Autonomic Profile, and Modified Calgary Score for Children and Adolescents with Presumed Vasovagal Syncope Submitted to the Tilt Test

BACKGROUND

In the pediatric population, syncope is mainly from vasovagal (VVS) origin. Its evaluation must be done by clinical methods, and the tilt test (TT) can contribute to the diagnosis.

OBJECTIVES

To analyze the clinical profile, Calgary and modified Calgary scores, response to TT and heart rate variability (HRV) of patients aged ≤ 18 years with presumed VVS. To compare the variables between patients with positive and negative responses to TT.

METHOD

Observational and prospective study, with 73 patients aged between 6 and 18 years, submitted to clinical evaluation and calculation of scores without previous knowledge of the TT. It was done at 70º under monitoring for HRV analysis. P-value < 0.05 was the statistical significance criterion.

RESULTS

Median age was 14.0 years; 52% of participants were female, 72 had Calgary ≥ -2 (mean 1.80), and 69 had modified Calgary ≥ -3 (mean 1.38). Prodromes were observed in 59 patients, recurrence in 50 and trauma in 19. The response to TT was positive in 54 participants (49 vasovagal, with 39 vasodepressor responses), with an increase in the low frequency (LF) component and a decrease in the high frequency (HF) component (p < 0,0001). In the supine position, LF was 33.6 in females and 47.4 in normalized units for males (p = 0.02). When applying the operating characteristic curve for positive TT, there was no statistical significance for HRV and scores.

CONCLUSION

Most children and adolescents with a presumed diagnosis of VVS presented a typical clinical scenario, with a Calgary score ≥ -2, and a predominant vasodepressor response to TT. Greater sympathetic activation was observed in the supine position in males. Calgary scores and sympathetic activation did not predict the response to TT.

Interaction of large artery stiffness and baroreceptor function explored through multiple measurement techniques - a pilot study

Baroreceptors, sensors that play a role in controlling arterial blood pressure (BP), are mechanical stretch receptors located in the aortic arch and carotid sinuses. Factors affecting the degree of stretch in the vessel wall with BP, such as increased arterial stiffness, may compromise baroreceptor sensitivity (BRS) to BP changes. Yet, evidence of this is scattered, as both baroreceptor sensitivity (BRS) and arterial stiffness are calculated variables with multiple methodological approaches. This pilot study (n=10) investigates the correlation of arterial stiffness and BRS using multiple BRS calculation techniques (spectral and sequence methodologies at aortic and finger sites) and arterial stiffness measurement [carotid-femoral pulse wave velocity (cfPWV), carotid compliance and distensibility]. BRS was assessed under resting BP conditions and during BP altered by maneuvers (0.1 Hz controlled breathing and leg ischemia). Magnitude of arterial stiffness - BRS correlation was positive for carotid distensibility and compliance, and negative for cfPWV, supporting the theory. A sample size of 100 participants (not rounded - exact figure by power calculation) would be required to confirm or reject all permutations of correlation between BRS by multiple calculation methods and large artery stiffness by PWV and compliance/distensibility measures.

Use of Valsalva Maneuver to Detect Late-Onset Delayed Orthostatic Hypotension

BACKGROUND

Standard autonomic testing includes a 10-minute head-up tilt table test to detect orthostatic hypotension. Although this test can detect delayed orthostatic hypotension (dOH) between 3 and 10 minutes of standing, it cannot detect late-onset dOH after 10 minutes of standing.

METHODS

To determine whether Valsalva maneuver responses can identify patients who would require prolonged head-up tilt table test to diagnose late-onset dOH; patients with immediate orthostatic hypotension (onset <3 minutes; n=176), early-onset dOH (onset between 3 and 10 minutes; n=68), and late-onset dOH (onset >10 minutes; n=32) were retrospectively compared with controls (n=114) with normal head-up tilt table test and composite autonomic scoring scale score of 0.

RESULTS

Changes in baseline systolic blood pressure at late phase 2 (∆SBPVM2), heart rate difference between baseline and phase 3 (∆HRVM3), and Valsalva ratio were lower and pressure recovery time (PRT) at phase 4 was longer in late-onset dOH patients than in controls. Differences in PRT and ∆HRVM3 remained significant after correcting for age. A PRT ≥2.14 s and ∆HRVM3 ≤15 bpm distinguished late-onset dOH from age- and sex-matched controls. Patients with longer PRT (relative risk ratio, 2.189 [1.579-3.036]) and lower ∆HRVM3 (relative risk ratio, 0.897 [0.847-0.951]) were more likely to have late-onset dOH. Patients with longer PRT (relative risk ratio, 1.075 [1.012-1.133]) were more likely to have early-onset than late-onset dOH.

CONCLUSIONS

Long PRT and short ∆HRVM3 can help to identify patients who require prolonged head-up tilt table test to diagnose late-onset dOH.

How to explore and explain autonomic changes in multiple sclerosis

Autonomic dysfunction (AD) in people with MS (pwMS) is a frequent finding. This narrative review will present an overview of central neural mechanisms involved in the control of cardiovascular and thermoregulatory systems, and methods of autonomic nervous system testing will be discussed thereafter. Since the need for standardization of autonomic nervous system (ANS) testing, we will focus on the standard battery of tests (blood pressure and heart rate response to Valsalva maneuver and head-up tilt, and heart rate response to deep breathing test plus one of the tests for sudomotor function), which can detect ANS pathology in the majority of pwMS. The review will briefly discuss the other types of AD in pwMS and the use of appropriate tests. While performing ANS testing in pwMS one has to consider the multiple sclerosis phenotypes, disease duration, and its activity, the degree of clinical disability of patients included in the study, and the disease-modifying therapies taken, as these factors may have a great influence on the results of ANS testing. In other words, detailed patient characteristics presentation and patient stratification are beneficial when reporting results of ANS testing in pwMS.

Cardiac Vagal Regulation Is Impeded in Children With Cyclic Vomiting Syndrome

INTRODUCTION

The pathophysiology underlying cyclic vomiting syndrome (CVS) remains undefined. Scant data and distinct clinical features point to altered autonomic nervous system function. Autonomic signaling can be noninvasively assessed through cardiac indices of parasympathetic vagal regulation, which is reduced in children with disorders of gut-brain interaction. We aimed to examine dynamic cardiac vagal regulation in children with CVS compared with that in healthy controls (HC).

METHODS

A total of 31 children with CVS evaluated in a tertiary care CVS center and 66 HC (ages 8-18 years) underwent cardiac autonomic function assessment. Electrocardiogram recordings were conducted during 3-minute sit/stand/sit posture challenges. The electrocardiogram-derived variables heart period, respiratory sinus arrhythmia (RSA), and vagal efficiency (VE) were analyzed using linear regression and mixed-effects modeling.

RESULTS

After exclusion of medication confounders, 23 patients with CVS were included in analyses. Both groups were comparable in age, gender, and body mass index. Compared with HC, children with CVS had shorter heart period (standardized mean difference range: 1.15-1.22, all P values < 0.05) and lower RSA (SMD range: 0.66-0.88, all P values < 0.05). Patients with CVS had significantly lower VE during the entire course of posture shifts, compared with HC ( B = -19.87, SE = 6.95, t = -2.86, P = 0.005, SMD = 0.76).

DISCUSSION

Children with CVS have suboptimal parasympathetic autonomic regulation compared with HC, indexed by reduced RSA and VE, even during their interepisodic well phase. Abnormal vagal modulation may underlie CVS pathophysiology, comorbidities, and triggers. Assessing VE during posture stressors could inform therapeutic interventions.

Baroreflex-sympathoneural dysfunction characterizes at-risk individuals with preclinical central Lewy body diseases

PURPOSE

In central Lewy body diseases (LBDs) such as Parkinson's disease (PD) and dementia with Lewy bodies (DLB), by the time parkinsonism or cognitive dysfunction becomes manifest, substantial central neurodegeneration has already occurred. Cardiovascular autonomic biomarkers might detect preclinical central LBDs in at-risk individuals, enabling possibly effective disease-modifying treatment.

METHODS

In the prospective, longitudinal PDRisk study, 59 participants provided information about family history of PD, olfactory dysfunction, dream enactment behavior, and orthostatic intolerance or hypotension at a protocol-specific website and were screened as outpatients. Thirty-four had three or more confirmed risk factors and were followed until PD was diagnosed or up to 7.5 years. Dependent measures included assessments of baroreflex-sympathoneural function, via the blood pressure recovery time (PRT) after release of the Valsalva maneuver and baroreflex areas; and baroreflex-cardiovagal function, via heart rate variability in the time and frequency domains and Valsalva baroslopes. Data were compared from groups with or without a subsequent diagnosis of a central LBD (LBD+, N = 9; LBD-, N = 25) and PDRisk participants with fewer than three confirmed risk factors (PDRisk-, N = 25).

RESULTS

The LBD+ group had larger orthostatic falls in systolic blood pressure than did the LBD- and PDRisk- groups (p < 0.0001 each). The LBD+ group had increased PRTs (p = 0.0114 versus LBD-, p = 0.0094 versus PDRisk-) and baroreflex areas after the Valsalva maneuver (p = 0.0225 versus LBD-, p = 0.0028 versus PDRisk-), whereas the groups did not differ in indices of baroreflex-cardiovagal function.

CONCLUSION

Orthostatic hypotension and baroreflex-sympathoneural dysfunction characterize at-risk individuals who go on to be diagnosed with a central LBD during longitudinal follow-up.

A Review on Autonomic Functional Assessment in Diabetic Patients

In today's world, science has progressed significantly, yet most people are still unaware of diabetes. Lack of obesity, physical work, and lifestyle changes are the main factors. Diabetes is becoming more common all around the globe. Type 2 diabetes may go unnoticed for years, resulting in serious consequences and high healthcare expenses. The goal of this study is to look at a wide range of studies in which the autonomic function of diabetic people has been studied with the help of various autonomic function tests (AFTs). AFT is a non-invasive approach to assessing patients for testing sympathetic and parasympathetic responses to stimuli. AFT findings give us comprehensive knowledge of the autonomic physiology reactions in normal and in autonomic diseases like diabetes. This review will concentrate on AFTs that are scientifically valid, trustworthy, and clinically beneficial, according to experts.

Transient asystole associated with vasovagal reflex in an oral surgery patient: A case report

The perioperative cardiac events may be brought about by a relative imbalance of autonomic activities due to excessive psychological and physical stress. The present case study focuses on the asystole that can occur as a serious cardiac adverse event associated with vasovagal reflex likely to be triggered by venipuncture for securing an intravenous line during dental care. In addition, we describe and discuss herein the management of intravenous sedation for a dental phobic patient who experienced the vasovagal reflex involved in an unexpected transient asystole. The patient with vasovagal reflex episodes in daily life, who had no past medical history relevant to cardiovascular disorders, was scheduled for dental extraction under intravenous sedation. Immediately after peripheral intravenous catheterization, she complained of discomfort and nausea, and a II-lead electrocardiogram revealed asystole following bradycardia associated with vasovagal reflex. Oxygenation and intravenous fluid loading in the supine position with elevation of the lower extremities restored sinus rhythm and normal hemodynamics without the intervention of cardiopulmonary resuscitation. With administration of intravenous atropine and betamethasone as premedication, she was uneventfully treated in stress-free psychosomatic conditions under optimal sedation with midazolam without any signs of cardiovascular disorders. After administration of flumazenil, the patient satisfactorily recovered from sedation without re-sedation. The present case suggests that an asystole associated with vasovagal reflex can be triggered by venipuncture for intravenous catheterization during dental anxiety likely to affect the imbalance between sympathetic and parasympathetic activities.

Blood pressure reduction cut-points for orthostatic hypotension in stroke survivors using a sit-up test: a multicentre cross-sectional study

OBJECTIVE

The sit-up test is used to assess orthostatic hypotension in stroke survivors who cannot stand independently without using a tilt table. However, no study has identified the optimal cut-points for orthostatic hypotension using the test. Therefore, this study aimed to examine the decrease in SBP and DBP during the sit-up test to detect orthostatic hypotension in individuals with stroke.

METHODS

Thirty-eight individuals with stroke, recruited from three convalescent rehabilitation hospitals, underwent the sit-up and head-up tilt tests. Systolic and diastolic orthostatic hypotension was defined as a decrease of at least 20 and 10 mmHg in the SBP and DBP, respectively, during the head-up tilt test. The receiver operator characteristic curve with the Youden Index was used to identify the optimal cut-points.

RESULTS

Eight and three participants showed systolic and diastolic orthostatic hypotension, respectively. The optimal cut-points for orthostatic hypotension using the sit-up test were a decrease of 10 mmHg in SBP [sensitivity = 87.5% (95% confidence interval: 47.4-99.7), specificity = 96.7% (82.8-99.9)] and 5 mmHg in DBP [sensitivity = 100.0% (29.2-100.0), specificity = 88.6% (73.3-96.8)].

CONCLUSION

Compared with the conventional cut-points, smaller cut-points of a decrease in SBP and DBP may be better to identify orthostatic hypotension in individuals with stroke using the sit-up test. The findings of this study may provide valuable information for the clinical application of the sit-up test.

Preferential impairment of parasympathetic autonomic function in type 2 diabetes

OBJECTIVE

Cardiovascular autonomic neuropathy is a known complication in type 2 diabetes (T2D). However, the extent of sympathetic dysfunction and its relation to blood pressure (BP) dysregulation is insufficiently studied. We therefore assessed the cardiovascular sympathetic function using a standardized autonomic test-battery.

RESEARCH DESIGN AND METHODS

Forty T2D patients (mean age and duration of diabetes ±SD, 65.5 ± 7.3 and 9.5 ± 4.2 years) and 40 age- and gender-matched controls were examined through autonomic testing, assessing cardiovascular responses to deep breathing, Valsalva maneuver and tilt-table testing. Additionally, 24-hour oscillometric BP and self-reported autonomic symptoms on COMPASS-31 questionnaire was recorded.

RESULTS

Patients with T2D had reduced parasympathetic activity with reduced deep breathing inspiratory:expiratory-ratio (median [IQR] T2D 1.11 [1.08-1.18] vs. controls 1.18 [1.11-1.25] (p = 0.01)), and reduced heart rate variability (p < 0.05). We found no differences in cardiovascular sympathetic function measured through BP responses during the Valsalva maneuver (p > 0.05). 24-hour-BP detected reduced night-time systolic BP drop in T2D (9.8 % ± 8.8 vs. controls 15.8 % ± 7.7 (p < 0.01)) with more patients having reverse dipping. Patients with T2D reported more symptoms of orthostatic intolerance on the COMPASS-31 (p = 0.04).

CONCLUSIONS

Patients with T2D showed reduced parasympathetic activity but preserved short-term cardiovascular sympathetic function, compared to controls, indicating autonomic dysfunction with predominantly parasympathetic impairment. Despite this, T2D patients reported more symptoms of orthostatic intolerance in COMPASS-31 and had reduced nocturnal BP dipping, indicating that these are not a consequence of cardiovascular sympathetic dysfunction.

Effects of 24-h acute total sleep deprivation on physiological coupling in healthy young adults

Sleep deprivation is associated with dysregulation of the autonomic nervous system, adverse cardiovascular events, cognitive and complex motor performance impairment. Less is known about the effects of acute total sleep deprivation (ATSD) on physiological coupling. We aimed to determine the effects of 24-h ATSD on the physiological coupling between complex subsystems by evaluating the cardiorespiratory, cardiovascular and cortico-cardiac interactions. This study enrolled 38 young healthy participants aged 23.2 ± 2.4 years. Multiple synchronous physiological signals including electrocardiography, photoplethysmography, bio-electrical impedance, electroencephalography, and continuous hemodynamic data, were performed over a baseline night after regular sleep and after a night with 24-h ATSD in the supine position. The magnitude squared coherence, phase synchronization index, and heartbeat evoked potential amplitudes, were obtained from 10-min synchronous physiological recordings to estimate the coupling strength between two time series. Parameters of hemodynamic characteristics and heart rate variability were also calculated to quantify autonomic regulation. Results indicated that the magnitude squared coherence (0.38 ± 0.17 vs. 0.29 ± 0.12, p = 0.015) between respiration and heart rate variability along with the magnitude squared coherence (0.36 ± 0.18 vs. 0.27 ± 0.13, p = 0.012) between respiration and pulse transit time were significantly decreased after 24-h ATSD. There were no significant differences (all p > 0.05) in phase synchronization indices, heartbeat evoked potential amplitudes as well as other analyzed measurements between baseline and 24-h ATSD states. We conclude that exposure to 24-h ATSD appears to weaken the cardiorespiratory and respiratory-cardiovascular coupling strength of young healthy adults. These findings suggest that physiological coupling analysis may serve as a complementary approach for characterizing and understanding the complex effects of sleep deprivation.

The Cardiac Autonomic Response Recovery to the Modified Tilt Test in Children Post Moderate-Severe Traumatic Brain Injury

OBJECTIVE

To assess the recovery of the cardiac autonomic control system (CACS) response to the modified tilt-test during rehabilitation, in children post moderate-severe TBI at the subacute phase post-injury.

METHOD

Thirty-seven children aged 6-18 years, 14-162 days post moderate-severe TBI, participated in the study. The assessment included CACS values evaluation (heart rate (HR), heart rate variability (HRV) and blood pressure) during the modified tilt-test: five minutes lying supine and five minutes passive standing. Re-assessment was performed after eight weeks of rehabilitation.

RESULTS

In both assessments, only four children reported symptoms associated with orthostatic intolerance during the modified tilt-test. No change was found over time in the HR and HRV values at rest. In response to the modified tilt-test, the systolic blood pressure showed change over time, with a significant interaction effect (p=0.04); while in the first assessment the SBP values showed a hypertension trend in the second assessment the SBP values showed a hypotension trend.

CONCLUSIONS

Children post moderate-severe TBI at the sub-acute phase post-injury, have a better systolic blood pressure response during the modified tilt-test after eight weeks of individually tailored rehabilitation program, despite no change in the CACS values at rest.

CLINICAL TRIAL GOV. NUMBER

NCT03215082.

Orthostatic intolerance: a handicap of aging or physical deconditioning?

Despite several studies that have been investigated physical inactivity and age-related effects on orthostatic tolerance, impaired hemodynamics and postural balance responses to orthostatic stress are incorrectly attributed to aging or sedentarism alone. The isolated effects from aging and sedentarism should be investigated through comparative studies between senior athletes and age-matched controls, and physical activity assessments on aging follow-up studies. On the other hand, bed rest and space flight studies mimic accelerated physical inactivity or disuse, which is not the same physiological decline provoked by aging alone. Thus, the elementary question is: could orthostatic intolerance be attributed to aging or physical inactivity? The main purpose of this review is to provide an overview of possible mechanisms underlying orthostatic tolerance contrasting the paradigm of aging and/or physical inactivity. The key points of this review are the following: (1) to counterpoint all relevant literature on physiological aspects of orthostatic tolerance; (2) to explore the mechanistic aspects underneath the cerebrovascular, cardiorespiratory, and postural determinants of orthostatic tolerance; and (3) examine non-pharmacological interventions with the potential to counterbalance the physical inactivity and aging effects. To date, the orthostatic intolerance cannot be attributed exclusively with aging since physical inactivity plays an important role in postural balance, neurovascular and cardiorespiratory responses to orthostatic stress. These physiological determinates should be interpreted within an integrative approach of orthostatic tolerance, that considers the interdependence between physiological systems in a closed-loop model. Based on this multisystem approach, acute and chronic countermeasures may combat aging and sedentarism effects on orthostatic tolerance.

The Gut Microbiota and Short-Chain Fatty Acids Profile in Postural Orthostatic Tachycardia Syndrome

Postural orthostatic tachycardia syndrome (POTS) is a devastating chronic form of orthostatic intolerance associated with excessive heart rate increase without hypotension during upright posture. POTS patients exhibit increased circulating norepinephrine levels with exaggerated sympathetic nervous system response upon standing. Emerging evidence suggests a role for the gut microbiome in cardiovascular disorders. However, the etiology of POTS and whether the gut microbiome plays a role are not fully elucidated. We assessed whether the gut microbiome and fecal short-chain fatty acids were different in POTS patients (N = 25) compared to healthy control (N = 23) women. Patients underwent hemodynamic measurements while supine and upon standing. Fecal samples were collected and analyzed using shotgun sequencing and Liquid Chromatography-High Resolution Mass Spectrometry and dietary habits were measured with a fitness application. We found that POTS patients in the standing position had higher circulating norepinephrine and epinephrine levels and increased heart rate. There were no differences in diet composition between groups. Of note dietary salt intake was also similar despite the fact that these patients are advised to consume a high salt diet. Alpha and beta diversity were similar between groups. We observed no differences in bacteria at the phylum levels or Firmicutes to Bacteroidetes ratio. We found no significant differences at the genus level, but observed trends in certain bacteria. Lachnoclostridium genus were higher in POTS when compared to the control group. On the other hand, Coprococcus and Coprobacter, were lower in POTS patients compared to controls. Although our KEGG metabolic pathways indicated differences related to short-chain fatty acids (SCFAs), we found that both POTS patients and healthy controls had similar levels of SCFAs. These results suggest POTs per se may have limited effects on gut microbiota composition and derived SCFAs. Further studies are needed to assess the role of the alterations observed at the genus level.

Worsening Postural Tachycardia Syndrome Is Associated With Increased Glucose-Dependent Insulinotropic Polypeptide Secretion

BACKGROUND

Postural tachycardia syndrome (POTS) is characterized by excessive upright tachycardia and disabling presyncopal symptoms, which are exacerbated after consuming a high-carbohydrate meal; it is unknown, however, what is the precise underlying mechanism. We seek to investigate the effect of glucose intake on orthostatic hemodynamic changes and gastrointestinal hormone secretion in POTS.

METHODS

Prospective, case-control study, 12 women with POTS who reported a postprandial worsening of their POTS symptoms and 13 age-matched female controls received 75-g oral glucose and 20 mg/kg acetaminophen to assess nutrient absorption. Hemodynamic, gastrointestinal hormone and acetaminophen levels were measured for up to 120 minutes postingestion while supine and standing.

RESULTS

Patients with POTS had significant orthostatic tachycardia, 48.7±11.2 versus 23.3±8.1 bpm, P=0.012 and elevated upright norepinephrine levels, 835.2±368.4 versus 356.9±156.7 pg/mL, P=0.004. After oral glucose, upright heart rate significantly increased in POTS, 21.2±11.9% versus 6.0±19.9%, P=0.033 with a concomitant decline in upright stroke volume, -10.3±11.90% versus 3.3±13.7%, P=0.027; total peripheral resistance, blood pressure and cardiac output remained unaltered. Acetaminophen rate of appearance was similar between groups (P=0.707), indicating comparable nutrient absorption rates. POTS had increased plasma levels of C-peptide (P=0.001), GIP (glucose-dependent insulinotropic polypeptide; P=0.001), peptide YY (P=0.016), and pancreatic polypeptide (P=0.04) following glucose consumption, but only GIP had a time-dependent association with the worsening upright tachycardia and stroke volume fall.

CONCLUSIONS

The glucose-induced worsening orthostatic tachycardia in POTS was associated with a decline in SV; these changes occurred while GIP, a splanchnic vasodilator, was maximally elevated.

Comparison of the sit-up test and head-up tilt test for assessing blood pressure and hemodynamic responses in healthy young individuals

OBJECTIVE

The sit-up test is used to assess orthostatic hypotension, without the use of a tilt table, in populations who are unable to stand. The primary objective of this study was to determine the differences in blood pressure and hemodynamic responses between the sit-up and head-up tilt tests. The secondary objective was to determine the hemodynamic responses related to changes in blood pressure during each test.

METHODS

Nineteen healthy volunteers (nine males, aged 24.3 ± 2.4 years) underwent the sit-up and head-up tilt tests. Systolic and diastolic blood pressure, heart rate, stroke volume, cardiac output, and total peripheral resistance were measured.

RESULTS

The increase in systolic blood pressure (15 ± 9 vs. 8 ± 8 mmHg) was greater, while the increase in heart rate (8 ± 5 vs. 12 ± 8 bpm) and reduction in stroke volume (-17 ± 10 vs. -21 ± 10 ml) were smaller during the sit-up test than during the head-up tilt test (P < 0.05). Additionally, the increases in blood pressure variables were significantly associated with the increase in total peripheral resistance (P < 0.05), but not with changes in other hemodynamic variables in both tests.

CONCLUSION

Although the magnitudes of changes in systolic blood pressure, heart rate, and stroke volume differed between the tests, the hemodynamic variable related to changes in blood pressure was the same for both tests. These results may contribute to the clinical application of the sit-up test for identifying the presence and hemodynamic mechanisms of orthostatic hypotension.

Oral and intravenous hydration in the treatment of orthostatic hypotension and postural tachycardia syndrome

Hydration with water and salt is the mainstay of treatment for autonomic nervous system disorders that impair orthostatic tolerance. The goal is to expand intravascular volume to compensate for the downward displacement of blood volume that occurs when standing and thereby sustain cerebral perfusion and restore quality of life. Despite strong consensus recommendations for salt supplementation as standard treatment of these disorders, published evidence of benefit is relatively weak, and no randomized clinical trials have occurred. This review summarizes the physiological rationale for hydration and evaluates the literature on oral and intravenous hydration in the treatment of neurogenic orthostatic hypotension, postural tachycardia syndrome, and recurrent vasovagal syncope. We conclude that oral salt replacement is indicated for treatment of neurogenic orthostatic hypotension because these patients have excessive renal sodium excretion, and for treatment of chronic orthostatic intolerance because these patients are often hypovolemic. As not all patients are able to tolerate sufficient oral hydration, there is also a role for intravenous volume-loading in severe cases of postural tachycardia syndrome. We offer guidance, based on review of the literature and the clinical judgment of a cardiologist and neurologist with experience treating autonomic disorders, regarding the option of ongoing intravenous hydration for treatment of severe, refractory cases of postural tachycardia syndrome.

Cardiovascular Response to Posture Changes: Multiscale Modeling and in vivo Validation During Head-Up Tilt

In spite of cardiovascular system (CVS) response to posture changes have been widely studied, a number of mechanisms and their interplay in regulating central blood pressure and organs perfusion upon orthostatic stress are not yet clear. We propose a novel multiscale 1D-0D mathematical model of the human CVS to investigate the effects of passive (i.e., through head-up tilt without muscular intervention) posture changes. The model includes the main short-term regulation mechanisms and is carefully validated against literature data and in vivo measures here carried out. The model is used to study the transient and steady-state response of the CVS to tilting, the effects of the tilting rate, and the differences between tilt-up and tilt-down. Passive upright tilt led to an increase of mean arterial pressure and heart rate, and a decrease of stroke volume and cardiac output, in agreement with literature data and present in vivo experiments. Pressure and flow rate waveform analysis along the arterial tree together with mechano-energetic and oxygen consumption parameters highlighted that the whole system approaches a less stressed condition at passive upright posture than supine, with a slight unbalance of the energy supply-demand ratio. The transient dynamics is not symmetric in tilt-up and tilt-down testing, and is non-linearly affected by the tilting rate, with stronger under- and overshoots of the hemodynamic parameters as the duration of tilt is reduced. By enriching the CVS response to posture changes, the present modeling approach shows promise in a number of applications, ranging from autonomic system disorders to spaceflight deconditioning.

Clinical Features of Patients Undergoing the Head-Up Tilt Test and Its Safety and Efficacy in Diagnosing Vasovagal Syncope in 4,873 Patients

Background: The head-up tilt test (HUTT) is a useful diagnostic tool in patients with suspected vasovagal syncope (VVS).

Objectives: We aimed to investigate the direct drug-potentiated HUTT in patients with recurrent syncope or precursor syncope and to assess the diagnostic value of the direct drug-potentiated HUTT.

Methods: The medical history and direct drug-potentiated HUTT records of patients who complained of syncope or precursor syncope and who visited The Xianyang Central Hospital from January 2016 to December 2020 were retrospectively reviewed.

Results: A total of 4,873 patients (age = 43.8 ± 17.6 years; male = 2,064 [42.4%]) were enrolled in our study. Overall, 2,343 (48.1%) showed positive responses as follows: 1,260 (25.9%) with the mixed type, 34 (0.7%) with the cardioinhibitory type, 580 (11.9%) with the vasodepressor type, 179 (3.7%) with postural tachycardia syndrome (POTS), and 290 (6.0%) with orthostatic hypotension (OH). The study showed that prior to syncope or near-syncope symptoms, patients first presented an increase in heart rate (HR), followed by decreases in blood pressure (BP) and HR successively. Among the patients in the syncope group, the sensitivity of the HUTT was 65.9%, which was significantly higher than a sensitivity of 44.8% for patients in the non-syncope group (P < 0.01). The sensitivity of the HUTT was higher for females than males in both the syncope group (52.6% in males and 77.9% in females, P < 0.01) and the non-syncope group (36.5% in males and 50.6% in females, P < 0.01). Within the four age groups (<20, 21–40, 41–60, and >60 years old), the sensitivities were 74.7%, 67.7%, 45.6%, and 31.2%, respectively. And all gender, age and symptom (whether suffered from a syncope or not) significantly affected the positive responses of HUTT. There were two adverse events and no deaths during the HUTT in this study.

Conclusion: The direct drug-potentiated HUTT is a safe and highly sensitive tool with which to diagnose VVS. Patients with precursor syncope symptoms without syncope should undergo a HUTT, especially young females presenting with weakness and sweating, which can decrease the probability of a misdiagnosis or a missed diagnosis.

Parkinson's disease outside the brain: targeting the autonomic nervous system

Patients with Parkinson's disease present with signs and symptoms of dysregulation of the peripheral autonomic nervous system that can even precede motor deficits. This dysregulation might reflect early pathology and therefore could be targeted for the development of prodromal or diagnostic biomarkers. Only a few objective clinical tests assess disease progression and are used to evaluate the entire spectrum of autonomic dysregulation in patients with Parkinson's disease. However, results from epidemiological studies and findings from new animal models suggest that the dysfunctional autonomic nervous system is a probable route by which Parkinson's disease pathology can spread both to and from the CNS. The autonomic innervation of the gut, heart, and skin is affected by α-synuclein pathology in the early stages of the disease and might initiate α-synuclein spread via the autonomic connectome to the CNS. The development of easy-to-use and reliable clinical tests of autonomic nervous system function seems crucial for early diagnosis, and for developing strategies to stop or prevent neurodegeneration in Parkinson's disease.

Comparison of the Active Sitting Test and Head-Up Tilt Test for Diagnosis of Postural Tachycardia Syndrome in Children and Adolescents

Objectives: We aimed to compare the hemodynamic responses to the active sitting test with the passive head-up tilt test (HUTT) in children and adolescents with postural tachycardia syndrome (POTS). We hypothesized that sitting tachycardia was also present in POTS patients during sitting. Materials and methods: We tested 30 POTS patients and 31 control subjects (mean age = 12 years, range = 9-16 years) who underwent both active sitting test and HUTT successively. We measured the heart rate (HR) and blood pressure (BP) during each test. Results: For both POTS patients and control subjects, the HUTT produced significantly larger HR and BP increases from 3 to 10 min of postural change than did the sitting test. Moreover, POTS patients with excessive orthostatic tachycardia during the HUTT also had significantly larger increases in HR at all test intervals during the sitting test than did the control subjects. A maximum increase in HR ≥ 22 bpm within 10 min of the sitting test was likely suggested to predict orthostatic tachycardia, yielding a sensitivity and specificity of 83.3 and 83.9%, respectively. Only six of 30 POTS patients (20%) reached the 40-bpm criterion during the sitting test, and no one complained of sitting intolerance symptoms. Conclusions: We have shown that POTS patients also have sitting tachycardia when changing from a supine position to a sitting position. We believe that the active sitting test is a reasonable alternative maneuver in assessing POTS in population groups that cannot tolerate the standing test or HUTT.

The impact of atrial mechanical function on age-dependent presentation of neurocardiogenic syncope

Background

The contribution of atrial and ventricular function in neurocardiogenic syncope (NCS) pathophysiology is elusive.

Hypothesis

We assessed the influence of echocardiographic properties to the age of presentation and NCS recurrences.

Methods

We assigned 124 patients with symptoms suggesting NCS, to those with syncope initiation at age <35 (group A, n = 56) and >35 years (group B, n = 68). Echocardiographic indices were measured before head‐up tilt test (HUTT).

Results

A total of 55 had positive HUTT (44%) with a trend favoring group A (p = .08). Group A exhibited lower left atrial (LA) volume index (17 ± 6 vs. 22 ± 11 ml/m², p = .015), higher LA ejection fraction (69 ± 10 vs. 63 ± 11%, p = .008), LA peak strain (reservoir phase 41 ± 13 vs. 31 ± 14%, p = .001, contraction phase 27 ± 11 vs. 15 ± 10%, p < .001) and LA peak strain rate (reservoir phase 1.83 ± 1.04 vs. 1.36 ± 0.96 1/s, p = .012, conduit phase 2.36 ± 1.25 vs. 1.36 ± 0.78 1/s, p = .001). Group A showed smaller minimum right atrial (RA) volume, better RA systolic function, superior left ventricular diastolic indices, and lower filling pressures. Group A patients were more likely to have >3 recurrences (82.0% vs. 50.1%, p < .05).

Conclusions

Patients with younger age of NCS onset and more syncopal recurrences manifest smaller LA and RA dimensions with distinct patterns of systolic and diastolic function and better LA reservoir and contraction properties. These findings may indicate an increased susceptibility to preload reduction, thereby triggering the NCS mechanism.

Reduction in Pulse Pressure during Standing Can Distinguish Neurogenic Orthostatic Hypotension

Background: We investigated whether changes in the pulse pressure (PP) reduction ratio during the head-up tilt test (HUTT) can aid in distinguishing neurogenic orthostatic hypotension (OH) from non-neurogenic OH. Methods: We enrolled consecutive patients with NOH and non-neurogenic OH between January 2015 and October 2018. We compared the Valsalva ratio, the presence or absence of late phase II and IV overshoot, the pressure recovery time, and the PP reduction ratio during HUTT between the two OH groups. Results: The expiratory–inspiratory (E:I) ratio and Valsalva ratio were significantly decreased in the NOH group (p = 0.026, p < 0.001, respectively). The absence of late phase II and phase IV overshoot was more frequent in the NOH group than in the non-neurogenic OH group (p = 0.001, p < 0.001, respectively). The pressure recovery time was significantly prolonged in the NOH group (p < 0.001), which exhibited increases in the PP reduction ratio (1—minimal PP/baseline PP) during the HUTT (p < 0.001). We calculated the cutoff point for the PP reduction ratio during HUTT, which exhibited an area under the receiver operating characteristic curve of 0.766 (0.659–0.840, 95% confidence interval). The cutoff value for the PP reduction ratio during HUTT (0.571) exhibited sensitivity of 0.879 and specificity of 0.516. Conclusions: Increases in the PP reduction ratio during HUTT may be a meaningful NOH laboratory marker.

Back somersault-induced atrioventricular nodal reentrant tachycardia - A case of a 15-year-old promising gymnast

A male 15-year-old promising gymnast suffered palpitations, which emerged only after landing a round-off back somersault. The performance induced an attack of regular narrow QRS complex tachycardia that was highly reproducible. Not a single element of the performance, but a whole sequence of round-off back somersault was required to induce the attack. An electrophysiologic study revealed an intra-nodal dual pathway causing atrioventricular nodal reentrant tachycardia (AVNRT). A complication of a tiny atrial septal defect (ASD) was incidentally detected, thus we initially suspected a causal relation of ASD as the platypnea-orthodeoxia syndrome. However, it was denied as the major mechanism of attack because of a very faint shunt flow and no-induction of hypoxemia during a round-off back somersault. The major triggering mechanisms of a whole sequence of round-off back somersaults were speculated to be related to transient atrial overload and autonomic imbalance induced by a swift postural-axial change together with an intense Valsalva maneuver with the maximal level of breath holding. The AVNRT attack was successfully treated by radiofrequency catheter ablation and has never recurred even by a whole sequence of round-off back somersaults. Currently he is a healthy and active gymnast with no symptoms. <Learning objective: The individual trigger of an atrioventricular nodal reentrant tachycardia (AVNRT) attack varies. The unique and sole trigger of the attack in the present gymnast case was a whole sequence of round-off back somersaults. A swift postural-axial change together with an intense Valsalva maneuver with the maximal level of breath holding increased the atrial overload with stretching the atrial wall, which might have induced atrial extrasystole and played a trigger role initiating the AVNRT attack.>.

From Provider to Advocate: The Complexities of Traumatic Brain Injury Prompt the Evolution of Provider Engagement

Treating a patient with traumatic brain injury requires an interdisciplinary approach because of the pervasive, profound and protean manifestations of this condition. In this review, key aspects of the medical history and review of systems will be described in order to highlight how the role of any provider must evolve to become a better patient advocate. Although this review is written from the vantage point of a vision care provider, it is hoped that patients, caregivers and providers will recognize the need for a team approach.

Recommendations for tilt table testing and other provocative cardiovascular autonomic tests in conditions that may cause transient loss of consciousness : Consensus statement of the European Federation of Autonomic Societies (EFAS) endorsed by the American Autonomic Society (AAS) and the European Academy of Neurology (EAN)

An expert committee was formed to reach consensus on the use of tilt table testing (TTT) in the diagnosis of disorders that may cause transient loss of consciousness (TLOC) and to outline when other provocative cardiovascular autonomic tests are needed. While TTT adds to history taking, it cannot be a substitute for it. An abnormal TTT result is most meaningful if the provoked event is recognised by patients or eyewitnesses as similar to spontaneous events. The minimum requirements to perform TTT are a tilt table, a continuous beat-to-beat blood pressure monitor, at least one ECG lead, protocols for the indications stated below and trained staff. This basic equipment lends itself to the performance of (1) additional provocation tests, such as the active standing test, carotid sinus massage and autonomic function tests; (2) additional measurements, such as video, EEG, transcranial Doppler, NIRS, end-tidal CO2 or neuro-endocrine tests; and (3) tailor-made provocation procedures in those with a specific and consistent trigger of TLOC. TTT and other provocative cardiovascular autonomic tests are indicated if the initial evaluation does not yield a definite or highly likely diagnosis, but raises a suspicion of (1) reflex syncope, (2) the three forms of orthostatic hypotension (OH), i.e. initial, classic and delayed OH, as well as delayed orthostatic blood pressure recovery, (3) postural orthostatic tachycardia syndrome or (4) psychogenic pseudosyncope. A therapeutic indication for TTT is to teach patients with reflex syncope and OH to recognise hypotensive symptoms and to perform physical counter manoeuvres.