Neurally mediated hypotension and autonomic dysfunction measured by heart rate variability during head-up tilt testing in children with chronic fatigue syndrome

Phenylephrine alters phase synchronization between cerebral blood velocity and blood pressure in ME/CFS with orthostatic intolerance

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) with orthostatic intolerance (OI) is characterized by neurocognitive deficits perhaps related to upright hypocapnia and loss of cerebral autoregulation (CA). We performed N-back neurocognition testing and calculated the phase synchronization index (PhSI) between arterial pressure (AP) and cerebral blood velocity (CBV) as a time-dependent measurement of cerebral autoregulation in 11 control (mean age = 24.1 yr) and 15 patients with ME/CFS (mean age = 21.8 yr). All patients with ME/CFS had postural tachycardia syndrome (POTS). A 10-min 60° head-up tilt (HUT) significantly increased heart rate (109.4 ± 3.9 vs. 77.2 ± 1.6 beats/min, P < 0.05) and respiratory rate (20.9 ± 1.7 vs. 14.2 ± 1.2 breaths/min, P < 0.05) and decreased end-tidal CO2 (ETCO2; 33.9 ± 1.1 vs. 42.8 ± 1.2 Torr, P < 0.05) in ME/CFS versus control. In ME/CFS, HUT significantly decreased CBV compared with control (-22.5% vs. -8.7%, P < 0.005). To mitigate the orthostatic CBV reduction, we administered supplemental CO2, phenylephrine, and acetazolamide and performed N-back testing supine and during HUT. Only phenylephrine corrected the orthostatic decrease in neurocognition by reverting % correct n = 4 N-back during HUT in ME/CFS similar to control (ME/CFS = 38.5 ± 5.5 vs. ME/CFS + PE= 65.6 ± 5.7 vs. Control 56.9 ± 7.5). HUT in ME/CFS resulted in increased PhSI values indicating decreased CA. Although CO2 and acetazolamide had no effect on PhSI in ME/CFS, phenylephrine caused a significant reduction in PhSI (ME/CFS = 0.80 ± 0.03 vs. ME/CFS + PE= 0.69 ± 0.04, P < 0.05) and improved cerebral autoregulation. Thus, PE improved neurocognitive function in patients with ME/CFS, perhaps related to improved neurovascular coupling, cerebral autoregulation, and maintenance of CBV.NEW & NOTEWORTHY We evaluated cognitive function before and after CO2, acetazolamide, and phenylephrine, which mitigate orthostatic reductions in cerebral blood velocity. Neither CO2 nor acetazolamide affected N-back testing (% correct answers) during an orthostatic challenge. Only phenylephrine improved upright N-back performance in ME/CFS, as it both blocked hyperventilation and increased CO2 significantly compared with those untreated. And only phenylephrine resulted in improved PSI values in both ME/CFS and control while upright, suggesting improved cerebral autoregulation.

Evidence of altered cardiac autonomic regulation in myalgic encephalomyelitis/chronic fatigue syndrome: A systematic review and meta-analysis

BACKGROUND

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a complex condition with no reliable diagnostic biomarkers. Studies have shown evidence of autonomic dysfunction in patients with ME/CFS, but results have been equivocal. Heart rate (HR) parameters can reflect changes in autonomic function in healthy individuals; however, this has not been thoroughly evaluated in ME/CFS.

METHODS

A systematic database search for case-control literature was performed. Meta-analysis was performed to determine differences in HR parameters between ME/CFS patients and controls.

RESULTS

Sixty-four articles were included in the systematic review. HR parameters assessed in ME/CFS patients and controls were grouped into ten categories: resting HR (RHR), maximal HR (HRmax), HR during submaximal exercise, HR response to head-up tilt testing (HRtilt), resting HR variability (HRVrest), HR variability during head-up tilt testing (HRVtilt), orthostatic HR response (HROR), HR during mental task(s) (HRmentaltask), daily average HR (HRdailyaverage), and HR recovery (HRR) Meta-analysis revealed RHR (MD ± 95% CI = 4.14 ± 1.38, P < .001), HRtilt (SMD ± 95% CI = 0.92 ± 0.24, P < .001), HROR (0.50 ± 0.27, P < .001), and the ratio of low frequency power to high frequency power of HRVrest (0.39 ± 0.22, P < .001) were higher in ME/CFS patients compared to controls, while HRmax (MD ± 95% CI = -13.81 ± 4.15, P < .001), HR at anaerobic threshold (SMD ± 95% CI = -0.44 ± 0.30, P = 0.005) and the high frequency portion of HRVrest (-0.34 ± 0.22, P = .002) were lower in ME/CFS patients.

CONCLUSIONS

The differences in HR parameters identified by the meta-analysis indicate that ME/CFS patients have altered autonomic cardiac regulation when compared to healthy controls. These alterations in HR parameters may be symptomatic of the condition.

Wired for Threat: Clinical Features of Nervous System Dysregulation in 80 Children

BACKGROUND

The negative effect of perceived stress on health has become a cultural epidemic. Despite many health implications, the clinical impact of stress on the nervous system is not well understood. This case series describes the symptom profiles of 80 children with nervous system dysregulation attributed to maladaptive neuroendocrine responses to stress.

METHODS

We reviewed of 80 children with nervous system dysregulation identified from a single, tertiary care pediatric neurology clinic. Included patients were between five and 17 years of age, with unexplained medical symptoms lasting three months or longer affecting at least four of six neurological domains: (1) somatization, (2) executive function, (3) autonomic function, (4) digestion, (5) sleep, and (6) emotional regulation. Medical symptoms, diagnoses, and detailed social histories were collected.

RESULTS

Of 80 children, 57 were female (71%), 57 were Caucasian (71%), with median age of 14 years. Symptoms had a mean duration of 32 months, and included: 100% somatic symptoms, 100% emotional dysregulation, 92.5% disrupted sleep, 82.5% autonomic dysregulation, 75% executive dysfunction, and 66% digestive problems. Overall, 94% reported chronic or traumatic stressors; adverse childhood experiences were present in 65%.

CONCLUSIONS

Perceived stress impacts many functions of the neuroendocrine system through experience-dependent plasticity, resulting in a constellation of symptoms and functional impairments we describe as nervous system dysregulation. The pathophysiology of these symptoms involves dysregulation of subcortical, hormonal, and autonomic circuits, which remain largely untested. Recognition and understanding of maladaptive neurophysiology in stress-related symptoms has important implications for diagnosis, treatment, and advances in health research.

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Diagnosis and Management in Young People: A Primer

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex disease that affects children and adolescents as well as adults. The etiology has not been established. While many pediatricians and other health-care providers are aware of ME/CFS, they often lack essential knowledge that is necessary for diagnosis and treatment. Many young patients experience symptoms for years before receiving a diagnosis. This primer, written by the International Writing Group for Pediatric ME/CFS, provides information necessary to understand, diagnose, and manage the symptoms of ME/CFS in children and adolescents. ME/CFS is characterized by overwhelming fatigue with a substantial loss of physical and mental stamina. Cardinal features are malaise and a worsening of symptoms following minimal physical or mental exertion. These post-exertional symptoms can persist for hours, days, or weeks and are not relieved by rest or sleep. Other symptoms include cognitive problems, unrefreshing or disturbed sleep, generalized or localized pain, lightheadedness, and additional symptoms in multiple organ systems. While some young patients can attend school, on a full or part-time basis, many others are wheelchair dependent, housebound, or bedbound. Prevalence estimates for pediatric ME/CFS vary from 0.1 to 0.5%. Because there is no diagnostic test for ME/CFS, diagnosis is purely clinical, based on the history and the exclusion of other fatiguing illnesses by physical examination and medical testing. Co-existing medical conditions including orthostatic intolerance (OI) are common. Successful management is based on determining the optimum balance of rest and activity to help prevent post-exertional symptom worsening. Medications are helpful to treat pain, insomnia, OI and other symptoms. The published literature on ME/CFS and specifically that describing the diagnosis and management of pediatric ME/CFS is very limited. Where published studies are lacking, recommendations are based on the clinical observations and practices of the authors.

Effects of low-dose clonidine on cardiovascular and autonomic variables in adolescents with chronic fatigue: a randomized controlled trial

Background

Chronic Fatigue Syndrome (CFS) is a common and disabling condition in adolescence with few treatment options. A central feature of CFS is orthostatic intolerance and abnormal autonomic cardiovascular control characterized by sympathetic predominance. We hypothesized that symptoms as well as the underlying pathophysiology might improve by treatment with the alpha_2A–adrenoceptor agonist clonidine.

Methods

A total of 176 adolescent CFS patients (12–18 years) were assessed for eligibility at a single referral center recruiting nation-wide. Patients were randomized 1:1 by a computer system and started treatment with clonidine capsules (25 μg or 50 μg twice daily, respectively, for body weight below/above 35 kg) or placebo capsules for 9 weeks. Double-blinding was provided. Data were collected from March 2010 until October 2012 as part of The Norwegian Study of Chronic Fatigue Syndrome in Adolescents: Pathophysiology and Intervention Trial (NorCAPITAL). Effect of clonidine intervention was assessed by general linear models in intention-to-treat analyses, including baseline values as covariates in the model.

Results

A total of 120 patients (clonidine group n = 60, placebo group n = 60) were enrolled and started treatment. There were 14 drop-outs (5 in the clonidine group, 9 in the placebo group) during the intervention period. At 8 weeks, the clonidine group had lower plasma norepinephrine (difference = 205 pmol/L, p = 0.05) and urine norepinephrine/creatinine ratio (difference = 3.9 nmol/mmol, p = 0.002). During supine rest, the clonidine group had higher heart rate variability in the low-frequency range (LF-HRV, absolute units) (ratio = 1.4, p = 0.007) as well as higher standard deviation of all RR-intervals (SDNN) (difference = 12.0 ms, p = 0.05); during 20° head-up tilt there were no statistical differences in any cardiovascular variable. Symptoms of orthostatic intolerance did not change during the intervention period.

Conclusions

Low-dose clonidine reduces catecholamine levels in adolescent CFS, but the effects on autonomic cardiovascular control are sparse. Clonidine does not improve symptoms of orthostatic intolerance.

Trial registration

Clinical Trials ID: NCT01040429, date of registration 12/28/2009.

Cerebral blood flow during HUTT in young patients with orthostatic intolerance

PURPOSE

To investigate patterns of change in cerebral perfusion during head-up tilt testing (HUTT) in children and young adults with autonomic dysfunction.

METHODS

We utilized near-infrared spectroscopy (NIRS) to estimate bilateral cerebral perfusion patterns during HUTT in 71 adolescents and young adults with a diagnosis of autonomic dysfunction. In addition, we used transthoracic impedance to measure cardiac stroke volume and thus infer autonomic tone, heart rate, and blood pressure during the test. Cerebral blood-flow wave-patterns were then visually analyzed and associated with clinical symptoms and measures of cardiovascular and autonomic function.

RESULTS

Visual analysis of contour changes in head NIRS values during phases of HUTT revealed variable patterns of cerebral blood flow, some specifically associated with severe symptomatology (i.e., syncope). We also observed an inequality in blood flow of the cerebral hemispheres in many patients. Finally, we observed changes in cardiac stroke volume during HUTT, as previously reported, that related to changes in head NIRS.

CONCLUSION

These results confirm a decrease in cerebral blood flow during HUTT as assessed by head NIRS in patients with autonomic dysfunction. Specifically, we have profiled the cerebral blood flow contours throughout the phases of HUTT, which add insight into the clinical spectrum of the disorder and may correlate with clinical severity.

Biogenic amine metabolism in juvenile neurocardiogenic syncope with dysautonomia

OBJECTIVE

Biogenic amine brain levels and their cerebral metabolism are frequently studied by quantitation of biogenic amine metabolites in cerebrospinal fluid (CSF) compared to age-matched controls. There is a paucity of studies in adolescents and young adults investigating the potential role of disordered cerebral biogenic amine metabolism in young patients who have dysautonomia based on abnormal head-up tilt table (HUTT).

METHODS

In a cohort of juvenile patients with neurocardiogenic syncope and dysautonomia documented by abnormal HUTT, biogenic amine metabolites of dopamine and serotonin were quantitated in 18 patients (15 females). HUTT testing is an effective clinical method to evaluate posturally induced physiological events in patients suspected of neurocardiogenic syncope with dysautonomia.

RESULTS

Levels of the dopamine metabolite (homovanillic acid: HVA) and/or the serotonin metabolite (5-hydroxyindoleacetic acid: 5HIAA) were significantly reduced in 13 patients compared to age-matched controls.

INTERPRETATION

Peripheral biogenic amines and their metabolites have been extensively studied in adults with dysautonomia due to various neurodegenerative disorders (Parkinson disease, multiple system atrophy, primary autonomic failure). Our findings indicate that more than two-thirds of this cohort of young patients with dysautonomia of variable severity have a defect in cerebral biogenic amines, particularly in dopamine and serotonin metabolism.

Phenylephrine alteration of cerebral blood flow during orthostasis: effect on n-back performance in chronic fatigue syndrome

Chronic fatigue syndrome (CFS) with orthostatic intolerance is characterized by neurocognitive deficits and impaired working memory, concentration, and information processing. In CFS, upright tilting [head-up tilt (HUT)] caused decreased cerebral blood flow velocity (CBFv) related to hyperventilation/hypocapnia and impaired cerebral autoregulation; increasing orthostatic stress resulted in decreased neurocognition. We loaded the baroreflex with phenylephrine to prevent hyperventilation and performed n-back neurocognition testing in 11 control subjects and 15 CFS patients. HUT caused a significant increase in heart rate (109.4 ± 3.9 vs. 77.2 ± 1.6 beats/min, P < 0.05) and respiratory rate (20.9 ± 1.7 vs. 14.2 ± 1.2 breaths/min, P < 0.05) and decrease in end-tidal CO2 (ETCO2; 42.8 ± 1.2 vs. 33.9 ± 1.1 Torr, P < 0.05) in CFS vs. control. HUT caused CBFv to decrease 8.7% in control subjects but fell 22.5% in CFS. In CFS, phenylephrine prevented the HUT-induced hyperventilation/hypocapnia and the significant drop in CBFv with HUT (-8.1% vs. -22.5% untreated). There was no difference in control subject n-back normalized response time (nRT) comparing supine to HUT (106.1 ± 6.9 vs. 97.6 ± 7.1 ms at n = 4), and no difference comparing control to CFS while supine (97.1 ± 7.1 vs 96.5 ± 3.9 ms at n = 4). However, HUT of CFS subjects caused a significant increase in nRT (148.0 ± 9.3 vs. 96.4 ± 6.0 ms at n = 4) compared with supine. Phenylephrine significantly reduced the HUT-induced increase in nRT in CFS to levels similar to supine (114.6 ± 7.1 vs. 114.6 ± 9.3 ms at n = 4). Compared with control subjects, CFS subjects are more sensitive both to orthostatic challenge and to baroreflex/chemoreflex-mediated interventions. Increasing blood pressure with phenylephrine can alter CBFv. In CFS subjects, mitigation of the HUT-induced CBFv decrease with phenylephrine has a beneficial effect on n-back outcome.

Postural orthostatic tachycardia syndrome (POTS) and vitamin B12 deficiency in adolescents

OBJECTIVE

Vitamin B12 is involved in the production of adrenaline from noradrenaline. It is the cofactor involved in catecholamine degradation and plays a role in myelin synthesis. The current study aimed to investigate the association between vitamin B12 levels and postural orthostatic tachycardia syndrome (POTS) during adolescence when accelerated myelin synthesis increases the vitamin B12 need.

METHODS

One hundred twenty-five patients (mean age 11.1 ± 2.3 years; 60% female) reporting short-term loss of consciousness and diagnosed with vasovagal syncope based on anamnesis with a normal distribution and 50 control subjects (mean age 10.94 ± 2.5 years, 62% female) were included in this study. Serum vitamin B12, folic acid, and ferritin levels were measured prospectively in addition to other tests. We defined vitamin B12 deficiency as a serum level <300 pg/mL.(1-4) RESULTS: Vitamin B12 levels were significantly lower in the patient group compared with the control group (47.2% vs 18%, P < .001). In the patient group, children with the POTS pattern had significantly lower vitamin B12 levels compared with children without the POTS response (P = .03).

CONCLUSIONS

Vitamin B12 deficiency in patients with POTS may lead to sympathetic nervous system baroreceptor dysfunction.

Autonomic response to a visceral stressor is dysregulated in irritable bowel syndrome and correlates with duration of disease

BACKGROUND

Previous studies reported altered autonomic nervous system (ANS) responses in irritable bowel syndrome (IBS) at baseline and to colonic balloon distension. This study examined heart rate variability (HRV) and plasma catecholamines as an index of ANS responsiveness in IBS during flexible sigmoidoscopy (FS) and explored associations of HRV with clinical measures.

METHODS

Rome III-positive IBS patients and healthy controls completed questionnaires measuring gastrointestinal and psychological symptoms. Heart rate variability measures were calculated using electrocardiogram (ECG) data at rest and during FS. Plasma catecholamines were measured before and after the FS. Linear mixed effects models were used to compare HRV with IBS status and IBS duration across six time points. Significance was assessed at the 0.05 level.

KEY RESULTS

Thirty-six IBS patients (53% F, mean age 37.89) and 31 controls (58% F, mean age 37.26) participated. After adjusting for age, sex, body mass index, and current anxiety symptoms, IBS patients had a non-significant lower cardiovagal tone (P = 0.436) and higher cardiosympathetic balance (P = 0.316) at rest. During FS, controls showed a transient increase in cardiosympathetic balance and decrease in cardiovagal tone. However, IBS patients had significantly less cardiosympathetic and cardiovagal responsiveness both leading up to (P = 0.003, P = 0.005) and following (P = 0.001) this stimulus. Those with longer duration of disease had less cardiosympathetic (P = 0.014) and cardiovagal (P = 0.009) responsiveness than those with shorter duration. No differences in catecholamines between IBS and controls were found.

CONCLUSIONS & INFERENCES

Irritable bowel syndrome demonstrated dysregulated ANS responses to a visceral stressor which could be related to disease duration. Therefore, autonomic dysregulation is an objective physiologic correlate of IBS.

Myalgic encephalomyelitis/chronic fatigue syndrome and encephalomyelitis disseminata/multiple sclerosis show remarkable levels of similarity in phenomenology and neuroimmune characteristics

BACKGROUND

'Encephalomyelitis disseminata' (multiple sclerosis) and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) are both classified as diseases of the central nervous system by the World Health Organization. This review aims to compare the phenomenological and neuroimmune characteristics of MS with those of ME/CFS.

DISCUSSION

There are remarkable phenomenological and neuroimmune overlaps between both disorders. Patients with ME/CFS and MS both experience severe levels of disabling fatigue and a worsening of symptoms following exercise and resort to energy conservation strategies in an attempt to meet the energy demands of day-to-day living. Debilitating autonomic symptoms, diminished cardiac responses to exercise, orthostatic intolerance and postural hypotension are experienced by patients with both illnesses. Both disorders show a relapsing-remitting or progressive course, while infections and psychosocial stress play a large part in worsening of fatigue symptoms. Activated immunoinflammatory, oxidative and nitrosative (O+NS) pathways and autoimmunity occur in both illnesses. The consequences of O+NS damage to self-epitopes is evidenced by the almost bewildering and almost identical array of autoantibodies formed against damaged epitopes seen in both illnesses. Mitochondrial dysfunctions, including lowered levels of ATP, decreased phosphocreatine synthesis and impaired oxidative phosphorylation, are heavily involved in the pathophysiology of both MS and ME/CFS. The findings produced by neuroimaging techniques are quite similar in both illnesses and show decreased cerebral blood flow, atrophy, gray matter reduction, white matter hyperintensities, increased cerebral lactate and choline signaling and lowered acetyl-aspartate levels.

SUMMARY

This review shows that there are neuroimmune similarities between MS and ME/CFS. This further substantiates the view that ME/CFS is a neuroimmune illness and that patients with MS are immunologically primed to develop symptoms of ME/CFS.

Neuromuscular strain as a contributor to cognitive and other symptoms in chronic fatigue syndrome: hypothesis and conceptual model

Individuals with chronic fatigue syndrome (CFS) have heightened sensitivity and increased symptoms following various physiologic challenges, such as orthostatic stress, physical exercise, and cognitive challenges. Similar heightened sensitivity to the same stressors in fibromyalgia (FM) has led investigators to propose that these findings reflect a state of central sensitivity. A large body of evidence supports the concept of central sensitivity in FM. A more modest literature provides partial support for this model in CFS, particularly with regard to pain. Nonetheless, fatigue and cognitive dysfunction have not been explained by the central sensitivity data thus far. Peripheral factors have attracted attention recently as contributors to central sensitivity. Work by Brieg, Sunderland, and others has emphasized the ability of the nervous system to undergo accommodative changes in length in response to the range of limb and trunk movements carried out during daily activity. If that ability to elongate is impaired—due to movement restrictions in tissues adjacent to nerves, or due to swelling or adhesions within the nerve itself—the result is an increase in mechanical tension within the nerve. This adverse neural tension, also termed neurodynamic dysfunction, is thought to contribute to pain and other symptoms through a variety of mechanisms. These include mechanical sensitization and altered nociceptive signaling, altered proprioception, adverse patterns of muscle recruitment and force of muscle contraction, reduced intra-neural blood flow, and release of inflammatory neuropeptides. Because it is not possible to differentiate completely between adverse neural tension and strain in muscles, fascia, and other soft tissues, we use the more general term “neuromuscular strain.” In our clinical work, we have found that neuromuscular restrictions are common in CFS, and that many symptoms of CFS can be reproduced by selectively adding neuromuscular strain during the examination. In this paper we submit that neuromuscular strain is a previously unappreciated peripheral source of sensitizing input to the nervous system, and that it contributes to the pathogenesis of CFS symptoms, including cognitive dysfunction.

Clinical characteristics of a novel subgroup of chronic fatigue syndrome patients with postural orthostatic tachycardia syndrome

OBJECTIVES

A significant proportion of patients with chronic fatigue syndrome (CFS) also have postural orthostatic tachycardia syndrome (POTS). We aimed to characterize these patients and differentiate them from CFS patients without POTS in terms of clinical and autonomic features.

METHODS

A total of 179 patients with CFS (1994 Centers for Disease Control and Prevention criteria) attending one of the largest Department of Health-funded CFS clinical services were included in this study. Outcome measures were as follows: (i) symptom assessment tools including the fatigue impact scale, Chalder fatigue scale, Epworth sleepiness scale (ESS), orthostatic grading scale (OGS) and hospital anxiety and depression scale (HADS-A and -D, respectively), (ii) autonomic function analysis including heart rate variability and (iii) haemodynamic responses including left ventricular ejection time and systolic blood pressure drop upon standing.

RESULTS

CFS patients with POTS (13%, n = 24) were younger (29 ± 12 vs. 42 ± 13 years, P < 0.0001), less fatigued (Chalder fatigue scale, 8 ± 4 vs. 10 ± 2, P = 0.002), less depressed (HADS-D, 6 ± 4 vs. 9 ± 4, P = 0.01) and had reduced daytime hypersomnolence (ESS, 7 ± 6 vs. 10 ± 5, P = 0.02), compared with patients without POTS. In addition, they exhibited greater orthostatic intolerance (OGS, 11 ± 5; P < 0.0001) and autonomic dysfunction. A combined clinical assessment tool of ESS ≤9 and OGS ≥9 identifies accurately CFS patients with POTS with 100% positive and negative predictive values.

CONCLUSIONS

The presence of POTS marks a distinct clinical group of CFS patents, with phenotypic features differentiating them from those without POTS. A combination of validated clinical assessment tools can determine which CFS patients have POTS with a high degree of accuracy, and thus potentially identify those who require further investigation and consideration for therapy to control heart rate.

Impaired blood pressure variability in chronic fatigue syndrome--a potential biomarker

INTRODUCTION

Autonomic dysfunction is common in chronic fatigue syndrome (CFS). This study set out to derive an autonomic biomarker using a comprehensive assessment of heart rate and blood pressure variability.

METHODS

Heart rate and non-invasive continuous blood pressure measurements (task force monitor) at rest and on standing were performed in CFS (Fukuda n = 68) and matched controls (n = 68) to derive high frequency (HF; parasympathetic) and low frequency (LF; sympathetic) heart rate variability (HRV), systolic (SBPV) and diastolic (DBPV) blood pressure variability. Variables of significance were combined using receiver operator curves to explore the diagnostic utility of parameters particularly at rest.

RESULTS

At rest, LF-HRV (sympathetic) was significantly increased in CFS compared to controls, while parasympathetic markers were significantly reduced (P = 0.006). Total DBP spectral power was increased (P = 0.0003) across all domains, with a shift towards sympathetic and away from parasympathetic SBPV (P = 0.05). On standing, overall SBPV response was significantly reduced with reductions in both sympathetic and parasympathetic components of SBPV (all P < 0.0001). Change in LF-DBP and relative balance of LF/HF DBP on standing differed between CFS and controls (P < 0.0001). Using the 85% sensitivity levels, we determined a threshold for three chosen resting BPV parameters of LF DBP >3.185, rest HF DBP >0.86, rest total DBP >7.05. Achieving all of these differentiated between CFS and controls with 77% sensitivity and 53% specificity.

CONCLUSION

This study has shown that there are objectively measured abnormalities of blood pressure variability in CFS and that these abnormalities have the potential to be a bedside diagnostic tool.

Two types of orthostatic dysregulation assessed by diameter of inferior vena cava

AIMS

Orthostatic dysregulation (OD) is common in adolescents. This study was conducted to evaluate the usefulness of the measurement of the diameter of the inferior vena cava (IVC) for objective assessment of patients with OD.

METHODS

Twenty children with OD (median 14 years, range 9-15 years) and 23 age-matched healthy children (median 12 years, range 10-15 years) were enrolled. A diameter of IVC was measured by an abdominal echogram before and after a head-up tilt table testing (HUT). Changes in IVC was assessed by an arbitrary parameter, collapse index (CI) as the following equation: [(maximal IVC diameter in the supine position - maximal IVC diameter in the standing position)/(maximal IVC diameter in the supine position)]× 100. CI was evaluated 4 weeks after treatment with an adrenergic agent.

RESULTS

Children with OD demonstrated either higher CI or lower CI compared to that in control children: CI was more than 50 (range 50-71) in 12 patients with OD while that was equal to or less than 0 (range -225 to 0) in eight out of 20 patients. In contrast, CI was between 0 and 50 (range 1-26) in 23 healthy children. Pharmacological treatment induced the normalization in the CI in both higher and lower CI group.

CONCLUSION

OD can be classified into two subtypes: by HUT, one is characterized by an increase of IVC diameter while another is characterized by its decrease. Measurement of IVC diameter by HUT is useful to understand the pathophysiology and to assess the efficacy of treatment.

Neuroendocrine and immune contributors to fatigue

Central fatigue, a persistent and subjective sense of tiredness, generally correlates poorly with traditional markers of disease. It is frequently associated with psychosocial factors, such as depression, sleep disorder, anxiety, and coping style, which suggest that dysregulation of the body's stress systems may serve as an underlying mechanism in the maintenance of chronic fatigue (CF). This article addresses the endocrine, neural, and immune factors that contribute to fatigue and describes research regarding the role of these factors in chronic fatigue syndrome as a model for addressing the biology of CF. In general, hypoactivity of the hypothalamic-pituitary-adrenal axis, autonomic nervous system alterations characterized by sympathetic overactivity and low vagal tone, as well as immune abnormalities, may contribute to the expression of CF. Noninvasive methods for evaluating endocrine, neural, and immune function are also discussed. Simultaneous evaluation of neuroendocrine and immune systems with noninvasive techniques will help elucidate the underlying interactions of these systems, their role in disease susceptibility, and progression of stress-related disorders.

Abnormalities in pH handling by peripheral muscle and potential regulation by the autonomic nervous system in chronic fatigue syndrome

OBJECTIVES

To examine muscle acid handling following exercise in chronic fatigue syndrome (CFS/ME) and the relationship with autonomic dysfunction.

DESIGN

Observational study.

SETTING

Regional fatigue service. SUBJECTS & INTERVENTIONS: Chronic fatigue syndrome (n = 16) and age and sex matched normal controls (n = 8) underwent phosphorus magnetic resonance spectroscopy (MRS) to evaluate pH handling during exercise. Subjects performed plantar flexion at fixed 35% load maximum voluntary contraction. Heart rate variability was performed during 10 min supine rest using digital photophlethysmography as a measure of autonomic function.

RESULTS

Compared to normal controls, the CFS/ME group had significant suppression of proton efflux both immediately postexercise (CFS: 1.1 +/- 0.5 mmol L(-1) min(-1) vs. normal: 3.6 +/- 1.5 mmol L(-1) min(-1), P < 0.001) and maximally (CFS: 2.7 +/- 3.4 mmol L(-1) min(-1) vs. control: 3.8 +/- 1.6 mmol L(-1) min(-1), P < 0.05). Furthermore, the time taken to reach maximum proton efflux was significantly prolonged in patients (CFS: 25.6 +/- 36.1 s vs. normal: 3.8 +/- 5.2 s, P < 0.05). In controls the rate of maximum proton efflux showed a strong inverse correlation with nadir muscle pH following exercise (r(2) = 0.6; P < 0.01). In CFS patients, in contrast, this significant normal relationship was lost (r(2) = 0.003; P = ns). In normal individuals, the maximum proton efflux following exercise were closely correlated with total heart rate variability (r(2) = 0.7; P = 0.007) this relationship was lost in CFS/ME patients (r(2) < 0.001; P = ns).

CONCLUSION

Patients with CFS/ME have abnormalities in recovery of intramuscular pH following standardised exercise degree of which is related to autonomic dysfunction. This study identifies a novel biological abnormality in patients with CFS/ME which is potentially open to modification.

Executive functions, self-regulation, and chronic pain: a review

BACKGROUND

Chronic pain conditions are complicated and challenging to live with. Capacity to adjust to such conditions may depend on the ability to self-regulate, that is, the ability to alter thoughts, feelings, and behaviors. Self-regulation appears to rely on executive cognitive functions, and the current review, therefore, sought to draw attention to the impact of self-regulatory capacity and executive functions on chronic pain.

DISCUSSION

Chronic pain conditions present with complex interactions of cognitive, emotional, behavioral, and physiological components for which self-regulatory ability is crucial. The ability to self-regulate varies, and self-regulatory strength appears to be a limited resource that can be fatigued. The many challenges of chronic pain conditions could, therefore, tax self-regulatory strength, leading to self-regulatory deficits.

CONCLUSION

The current review proposes a relationship among pain, self-regulatory capacity, self-regulatory demands, executive functions, and self-regulatory fatigue, suggesting that executive functions and self-regulatory deficits are indeed part of the etiology and maintenance of chronic pain conditions.

Japanese clinical guidelines for juvenile orthostatic dysregulation version 1

This clinical practice guideline provides recommendations for the assessment, diagnosis and treatment of school-aged children and juveniles with orthostatic dysregulation (OD), usually named orthostatic intolerance in USA and Europe. This guideline is intended for use by primary care clinicians working in primary care settings. The guideline contains the following recommendations for diagnosis of OD: (i) initial evaluation composed of including and excluding criteria, the assessment of no evidence of other disease including cardiac disease and so on; (ii) a new orthostatic test to determine four different subsets: instantaneous orthostatic hypotension, postural tachycardia syndrome, neurally mediated syncope and delayed orthostatic hypotension; (iii) evaluation of severity; and (iv) judgment of psychosocial background with the use of rating scales. The guideline also contains the following recommendations for treatment of OD on the basis of the result of an orthostatic test in addition to psychosocial assessment: (i) guidance and education for parents and children; (ii) non-pharmacological treatments; (iii) contact with school personnel; (iv) use of adrenoceptor stimulants and other medications; (v) strategies of psychosocial intervention; and (vi) psychotherapy. This clinical practice guideline is not intended as a sole source of guidance in the evaluation of children with OD. Rather, it is designed to assist primary care clinicians by providing a framework for decision making of diagnosis and treatments.

Postural orthostatic tachycardia syndrome is an under-recognized condition in chronic fatigue syndrome

BACKGROUND

It has been suggested that postural orthostatic tachycardia syndrome (POTS) be considered in the differential diagnosis of those with chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME). Currently, measurement of haemodynamic response to standing is not recommended in the UK NICE CFS/ME guidelines.

OBJECTIVES

To determine prevalence of POTS in patients with CFS/ME.

DESIGN

Observational cohort study.

METHODS

Fifty-nine patients with CFS/ME (Fukuda criteria) and 52 age- and sex-matched controls underwent formal autonomic assessment in the cardiovascular laboratory with continuous heart rate and beat-to-beat blood pressure measurement (Task Force, CNSystems, Graz Austria). Haemodynamic responses to standing over 2 min were measured. POTS was defined as symptoms of orthostatic intolerance associated with an increase in heart rate from the supine to upright position of >30 beats per minute or to a heart rate of >120 beats per minute on standing.

RESULTS

Maximum heart rate on standing was significantly higher in the CFS/ME group compared with controls (106 +/- 20 vs. 98 +/- 13; P = 0.02). Of the CFS/ME group, 27% (16/59) had POTS compared with 9% (5) in the control population (P = 0.006). This difference was predominantly related to the increased proportion of those in the CFS/ME group whose heart rate increased to >120 beats per minute on standing (P = 0.0002). Increasing fatigue was associated with increase in heart rate (P = 0.04; r(2) = 0.1).

CONCLUSION

POTS is a frequent finding in patients with CFS/ME. We suggest that clinical evaluation of patients with CFS/ME should include response to standing. Studies are needed to determine the optimum intervention strategy to manage POTS in those with CFS/ME.

Prefrontal cortex oxygenation during incremental exercise in chronic fatigue syndrome

This study examined the effects of maximal incremental exercise on cerebral oxygenation in chronic fatigue syndrome (CFS) subjects. Furthermore, we tested the hypothesis that CFS subjects have a reduced oxygen delivery to the brain during exercise. Six female CFS and eight control (CON) subjects (similar in height, weight, body mass index and physical activity level) performed an incremental cycle ergometer test to exhaustion, while changes in cerebral oxy-haemoglobin (HbO2), deoxy-haemoglobin (HHb), total blood volume (tHb = HbO2 + HHb) and O2 saturation [tissue oxygenation index (TOI), %)] was monitored in the left prefrontal lobe using a near-infrared spectrophotometer. Heart rate (HR) and rating of perceived exertion (RPE) were recorded at each workload throughout the test. Predicted VO2peak in CFS (1331 +/- 377 ml) subjects was significantly (P < or = 0.05) lower than the CON group (1990 +/- 332 ml), and CFS subjects achieved volitional exhaustion significantly faster (CFS: 351 +/- 224 s; CON: 715 +/- 176 s) at a lower power output (CFS: 100 +/- 39 W; CON: 163 +/- 34 W). CFS subjects also exhibited a significantly lower maximum HR (CFS: 154 +/- 13 bpm; CON: 186 +/- 11 bpm) and consistently reported a higher RPE at the same absolute workload when compared with CON subjects. Prefrontal cortex HbO2, HHb and tHb were significantly lower at maximal exercise in CFS versus CON, as was TOI during exercise and recovery. The CFS subjects exhibited significant exercise intolerance and reduced prefrontal oxygenation and tHb response when compared with CON subjects. These data suggest that the altered cerebral oxygenation and blood volume may contribute to the reduced exercise load in CFS, and supports the contention that CFS, in part, is mediated centrally.

Enhanced vagal withdrawal during mild orthostatic stress in adolescents with chronic fatigue

BACKGROUND

Hemodynamic abnormalities have been documented in the chronic fatigue syndrome (CFS), indicating functional disturbances of the autonomic nervous system responsible for cardiovascular regulation. The aim of this study was to investigate autonomic heart rate control during mild orthostatic stress in adolescents with CFS.

METHODS

A total of 14 CFS patients and 56 healthy controls having equal distribution of age and gender underwent lower body negative pressure (LBNP) of horizontal line 20 mmHg. The RR interval (RRI) was recorded continuously, and spectral power densities were computed in the low-frequency (LF) band (0.04-0.15 Hz) and the high-frequency (HF) band (0.15-0.50 Hz) from segments of 120-second length, using an autoregressive algorithm. In addition, the time-domain indices SDNN, pNN50, and r-MSSD were computed.

RESULTS

At rest, CFS had lower RRI than controls (P < 0.05), but indices of variability were similar in the two groups. During LBNP, compared to controls, CFS patients had lower normalized and absolute HF power and r-MSSD (P < 0.05), and higher RRI (P < 0.001), normalized LF power and LF/HF (P < 0.05).

CONCLUSIONS

During mild orthostatic stress, adolescents with CFS appear to have enhanced vagal withdrawal, leading to a sympathetic predominance of heart rate control compared to controls. Possible underlying mechanisms include hypovolemia and abnormalities of reflex mechanisms.

A matched case control study of orthostatic intolerance in children/adolescents with chronic fatigue syndrome

This study aimed to define cardiovascular and heart rate variability (HRV) changes following head-up tilt (HUT) in children/adolescents with chronic fatigue syndrome (CFS) in comparison to age- and gender-matched controls. Twenty-six children/adolescents with CFS (11-19 y) and controls underwent 70-degree HUT for a maximum of 30 min, but returned to horizontal earlier at the participant's request with symptoms of orthostatic intolerance (OI) that included lightheadedness. Using electrocardiography and beat-beat finger blood pressure, a positive tilt was defined as OI with 1) neurally mediated hypotension (NMH); bradycardia (HR <75% of baseline), and hypotension [systolic pressure (SysP) drops >25 mm Hg)] or 2) postural orthostatic tachycardia syndrome (POTS); HR increase >30 bpm, or HR >120 bpm (with/without hypotension). Thirteen CFS and five controls exhibited OI generating a sensitivity and specificity for HUT of 50.0% and 80.8%, respectively. POTS without hypotension occurred in seven CFS subjects but no controls. POTS with hypotension and NMH occurred in both. Predominant sympathetic components to HRV on HUT were measured in CFS tilt-positive subjects. In conclusion, CFS subjects were more susceptible to OI than controls, the cardiovascular response predominantly manifest as POTS without hypotension, a response unique to CFS suggesting further investigation is warranted with respect to the pathophysiologic mechanisms involved.

Sympathetic predominance of cardiovascular regulation during mild orthostatic stress in adolescents with chronic fatigue

Haemodynamic abnormalities have been documented in the chronic fatigue syndrome (CFS), indicating functional disturbances of the autonomic nervous system responsible for cardiovascular control. This study was designed to explore the pathophysiology in adolescent CFS-patients by analysing RR-interval (RRI) variability and diastolic blood pressure (DBP) variability during mild orthostatic stress, using an algorithm which accounts for non-stationary biosignals. A total of 27 adolescents with CFS and 33 healthy control subjects having equal age- and sex distribution underwent 15 min of 20 degrees head-up tilt (HUT). The spectral power densities of RRI and DBP were computed in the low-frequency (LF) band (0.04-0.15 Hz) and the high-frequency (HF) band (0.15-0.4 Hz) using an adaptive autoregressive algorithm to obtain a time-varying spectrum. RMSSD, a time domain index of RRI variability, was also computed. At rest, all indices of variability were similar in the two groups. During tilt, CFS patients had a larger increase in the LF/HF ratio (P<or=0.001) and normalized LF power of RRI (P<or=0.01), and a larger decrease in normalized HF power (P<or=0.01) of RRI than controls. CFS patients also had trends towards a larger decrease in absolute HF power of RRI and a larger increase in normalized LF power of DBP. These findings suggest that adolescents with CFS have sympathetic predominance of cardiovascular regulation during very mild orthostatic stress. Possible underlying mechanisms are moderate hypovolemia, abnormalities of reflex control or physical de-conditioning.

Higher heart rate and reduced heart rate variability persist during sleep in chronic fatigue syndrome: a population-based study

Autonomic nervous system (ANS) dysfunction has been suggested in patients with chronic fatigue syndrome (CFS). In this study, we sought to determine whether increased heart rate (HR) and reduced heart rate variability (HRV) parameters observed in CFS patients during wakefulness persist during sleep. To this end, we compared heart rate (HR) and HRV as indicators of ANS function in CFS subjects and non-fatigued (NF) controls in a population-based, case-control study. Thirty subjects with CFS and 38 NF controls, matched for age-, sex- and body mass index, were eligible for analysis. Main outcome measures included mean RR interval (RRI), HR, and HRV parameters derived from overnight ECG. Plasma aldosterone and norepinephrine levels, medicines with cardiovascular effect, and reported physical activity were examined as covariates. General Linear Models were used to assess significance of associations and adjust for potential confounders. Compared to controls, CFS cases had significantly higher mean HR (71.4 vs 64.8 bpm), with a shorter mean RRI [840.4 (85.3) vs 925.4(97.8) ms] (p<0.0004, each), and reduced low frequency (LF), very low frequency (VLF), and total power (TP) of HRV (p<0.02, all). CFS cases had significantly lower plasma aldosterone (p<0.05), and tended to have higher plasma norepinephrine levels. HR correlated weakly with plasma norepinephrine (r=0.23, p=0.05) and moderately with vitality and fatigue scores (r=-0.49 and 0.46, respectively, p<0.0001). Limitation in moderate physical activity was strongly associated with increased HR and decreased HRV. Nevertheless, among 42 subjects with similar physical activity limitations, CFS cases still had higher HR (71.8 bpm) than respective controls (64.9 bpm), p=0.023, suggesting that reduced physical activity could not fully explain CFS-associated differences in HR and HRV. After adjusting for potential confounders case-control differences in HR and TP remained significant (p<0.05).

CONCLUSION

the presence of increased HR and reduced HRV in CFS during sleep coupled with higher norepinephrine levels and lower plasma aldosterone suggest a state of sympathetic ANS predominance and neuroendocrine alterations. Future research on the underlying pathophysiologic mechanisms of the association is needed.

A measure of heart rate variability is sensitive to orthostatic challenge in women with chronic fatigue syndrome

The use of symptoms generated by head up tilt (HUT) is not a useful tool in identifying chronic fatigue syndrome (CFS). We investigated whether heart rate variability (HRV) assessed early during HUT might be useful. A sample of 46 female subjects (24 with CFS and 22 sedentary, age-matched healthy controls; CON) who had exhibited no difference in time to syncope during tilt was examined for HRV responses to 10 min of 70 degrees HUT after 5 min of baseline in the supine position. HRV data were analyzed by the method of coarse graining spectral analysis. Variables compared between groups included mean and standard deviation (SD(RRI)) of RR intervals (RRI), amplitudes of low- (A(LF); 0.04-0.15 Hz) and high-frequency (A(HF); >0.15 Hz) harmonic as well as aperiodic, fractal (A(FR); 1/f(beta)) spectral components, the spectral exponent beta, and the difference in these values between baseline and HUT for each subject. In the supine baseline, only mean RRI was significantly (P < 0.01) lower in CFS than in CON. During HUT, however, mean RRI (P < 0.01), SD(RRI) (P < 0.01), A(HF) (P < 0.05), and A(FR) (P < 0.01) were significantly lower in CFS than in CON. When the difference in values between baseline and HUT for each subject was examined, only the difference for A(FR) (deltaA(FR)) was significantly (P < 0.01) lower in CFS than in CON, suggesting that A(FR)is a disease-specific response of HRV to HUT. When a cut-off level was set to deltaA(FR) = -2.7 msec, the sensitivity and the specificity in differentiating CFS from controls were 90% and 72%, respectively. The data suggest that a decrease in aperiodic fractal component of HRV in response to HUT can be used to differentiate patients with CFS from CON.

Joint hypermobility is more common in children with chronic fatigue syndrome than in healthy controls

OBJECTIVE

To determine whether children with chronic fatigue syndrome (CFS) have a higher prevalence of joint hypermobility than gender-matched controls.

STUDY DESIGN

Matched case-control study comparing the Beighton joint hypermobility scores in 58 consecutive children with CFS (incident cases) with 58 otherwise healthy controls referred to a dermatology clinic for evaluation of common skin problems. A second group of 58 patients previously diagnosed with CFS (prevalent cases) was matched by gender to the incident cases to evaluate temporal changes in referral patterns.

RESULTS

Of the 58 patients in each group, 71% were female. The median Beighton scores were higher in incident CFS cases than in healthy controls (4 vs 1, P <.001). More incident CFS cases had Beighton scores >/=4 (consistent with joint hypermobility), 60% versus 24%, P <.0001. Incident and prevalent CFS cases had similar Beighton scores. The odds ratio for hypermobility in all patients with CFS versus healthy controls was 3.5 (P <.001; 95% CI, 1.6-7.5).

CONCLUSIONS

Joint hypermobility is more common in patients with CFS than in otherwise healthy children with common skin disorders. The etiologic significance of the observed association remains to be defined.

Peripheral vestibular dysfunction in chronic fatigue syndrome

OBJECTIVE

To report left-sided peripheral vestibular failure as the cause of dizziness in a 12-year-old boy diagnosed as having chronic fatigue syndrome (CFS).

DESIGN

Retrospective case report with review of literature and discussion.

SETTING

Tertiary children's hospital.

CONCLUSION

We recommend proper vestibular assessment for CFS patients presenting with dizziness, as effective treatment for peripheral vestibular disorder exists in the form of balance rehabilitation exercises.

Pooling in chronic orthostatic intolerance: arterial vasoconstrictive but not venous compliance defects

BACKGROUND

Orthostatic intolerance is characterized by postural tachycardia syndrome (POTS) with exaggerated tachycardia, orthostatic symptoms, and "pooling" (which comprises acrocyanosis and dependent edema when upright). My colleagues and I tested the hypothesis that pooling results from increased venous compliance in POTS patients.

METHODS AND RESULTS

Fifteen patients aged 13 to 19 years were compared with 11 healthy, age-matched controls. The POTS group was divided into patients with high venous pressure (P(v)>20 mm Hg) and normal P(v) on the basis of resting supine P(v) obtained in previous work. Subjects were studied using strain gauge plethysmography to measure blood flow, P(v), and the venous compliance volume-pressure relation while supine and during incremental head-up tilt testing at -10 degrees, 0 degrees, 20 degrees, and 35 degrees. Volume-pressure relations of controls and POTS patients with normal P(v) and high P(v) were not different and were unchanged by orthostasis. Supine leg peripheral resistance was greater than control resistance in patients with high P(v) (54+/-9 versus 30+/-6 mm Hg x mL(-1) x 100 mL(-1) x min(-1)) and less than control resistance in patients with normal P(v) (17+/-2 mm Hg x mL(-1) x 100 mL(-1) x min(-1)). On upright tilt, resistance decreased in high P(v) to approximate resistance in normal P(v). Resistance in controls increased throughout tilt. Leg P(v) increased in patients with normal P(v) and in controls but remained unchanged in the high P(v) group.

CONCLUSIONS

The findings suggest that pooling in POTS is due to blunted arterial vasoconstriction, which produces passive redistribution of blood within peripheral venous capacitance beds. Venous compliance in POTS is similar to that in control subjects.

Impaired postural cerebral hemodynamics in young patients with chronic fatigue with and without orthostatic intolerance

OBJECTIVES

To measure postural changes in cerebral hemodynamics in young patients with chronic fatigue with and without orthostatic intolerance.

STUDY DESIGN

We studied 28 patients (age, 10 to 22 years) and 20 healthy control subjects (age, 6 to 27 years). Cerebral oxygenated hemoglobin (oxy-Hb) and deoxygenated Hb were noninvasively and continuously measured with near infrared spectroscopy during active standing. Beat-to-beat arterial pressure was monitored by Finapres.

RESULTS

Orthostatic intolerance determined by cardiovascular responses to standing was observed in 16 of 28 patients: instantaneous orthostatic hypotension in 8, delayed orthostatic hypotension in 2, and postural orthostatic tachycardia in 6. A rapid recovery of oxy-Hb by near infrared spectroscopy at the onset of active standing was not found in 15 of 16 patients with chronic fatigue and orthostatic intolerance and in 6 of 12 patients with chronic fatigue without orthostatic intolerance but only in 2 of 20 control subjects. Thirteen of 16 patients with orthostatic intolerance showed prolonged reduction in oxy-Hb during standing.

CONCLUSIONS

Impaired cerebral hemodynamics in patients with chronic fatigue syndrome and postural orthostatic tachycardia suggest a link between impaired cerebral oxygenation and chronic fatigue. However, this cannot explain the symptoms in patients meeting the criteria of chronic fatigue without orthostatic intolerance.

Neuroendocrine mechanisms in fibromyalgia-chronic fatigue

Fibromyalgia and chronic fatigue syndrome are poorly understood disorders that share similar demographic and clinical characteristics. Because of the clinical similarities between both disorders it was suggested that they share a common pathophysiological mechanism, namely, central nervous system dysfunction. This chapter presents data demonstrating neurohormonal abnormalities, abnormal pain processing and autonomic nervous system dysfunction in fibromyalgia and chronic fatigue syndrome. The possible contribution of the central nervous system dysfunction to the development and symptomatology of these conditions is discussed. The chapter concludes by reviewing the effect of current treatments and emerging therapeutic modalities in fibromyalgia and chronic fatigue syndrome.

The relation between lower limb pooling and blood flow during orthostasis in the postural orthostatic tachycardia syndrome of adolescents

OBJECTIVES

Postural orthostatic tachycardia syndrome (POTS) is characterized by symptoms of lightheadedness, fatigue, and signs of edema, acrocyanosis, and exaggerated tachycardia within 10 minutes of upright posture. Our objective was to determine how vascular properties contribute to the pathophysiology of POTS in adolescents.

STUDY DESIGN

We compared 11 patients aged 13 to 18 years with 8 members of a control group, recording continuous heart rate and blood pressure and using strain-gauge plethysmography to measure forearm and calf blood flow and to estimate venous pressure while the subjects were supine. Calf blood flow and size change were measured during 70 degrees head-up tilt.

RESULTS

Resting calf venous pressure was higher in the POTS group compared with the control group. Resting resistance was decreased in both the forearm (15 +/- 2 vs 30 +/- 4) and calf (27 +/- 2 vs 42 +/- 5) in the POTS group. Calf blood flow 60 seconds after tilt increased from 1.9 +/- 0.4 mL/100 mL/min to 6.6 +/- 2.3 mL/100 mL/min in the POTS group but only by half in the control group. Flow remained elevated in the POTS group but decreased to 70% baseline in the control group. Calf volume increased twice as much in the POTS group compared with the control group over a shorter time (13 vs 30 minutes).

CONCLUSIONS

Lower resistance at baseline reflects a defect in arterial vasoconstriction in POTS, further exacerbated during upright posture.

Role of impaired lower-limb venous innervation in the pathogenesis of the chronic fatigue syndrome

BACKGROUND

In patients with acute orthostatic hypotension, there is excessive pooling of blood in the legs, which may result from the strikingly subnormal compliance that is demonstrable in the pedal veins during norepinephrine infusion. The common occurrence of delayed orthostatic hypotension and/or tachycardia in the chronic fatigue syndrome (CFS) led to the present studies of foot vein compliance in CFS patients with a linear variable differential transformer.

METHODS

Seven patients with CFS were compared with 7 age- and gender matched healthy control subjects in their blood pressure, heart-rate, and plasma norepinephrine responses to prolonged standing and in measurements of their foot vein contractile responses to intravenous norepinephrine infusions with the linear variable differential transformer.

RESULTS

Excessive, delayed (usually after 10 min) orthostatic reductions in systolic and diastolic blood pressure (P < 0.01) and inconsistently excessive increases in heart rate were found in the CFS patients, in whom venous compliance in response to infused norepinephrine was significantly reduced (P < 0.05).

CONCLUSIONS

In these patients with CFS, delayed orthostatic hypotension was clearly demonstrable, and, as in previously reported patients with orthostatic hypotension of acute onset, this was associated with reduced pedal vein compliance during norepinephrine infusion, implying impaired sympathetic innervation of foot veins. The rapid symptomatic improvement demonstrated in previous studies of CFS patients during correction of orthostatic venous pooling by inflation of military antishock trousers (MAST) to 35 mm Hg may suggest that excessive lower body venous pooling, perhaps by reducing cerebral perfusion, is involved in the orthostatic component of fatigue in these patients.

Vascular perturbations in the chronic orthostatic intolerance of the postural orthostatic tachycardia syndrome

Chronic orthostatic intolerance is often related to the postural orthostatic tachycardia syndrome (POTS). POTS is characterized by upright tachycardia. Understanding of its pathophysiology remains incomplete, but edema and acrocyanosis of the lower extremities occur frequently. To determine how arterial and venous vascular properties account for these findings, we compared 13 patients aged 13-18 yr with 10 normal controls. Heart rate and blood pressure were continuously recorded, and strain-gauge plethysmography was used to measure forearm and calf blood flow, venous compliance, and microvascular filtration while the subject was supine and to measure calf blood flow and calf size change during head-up tilt. Resting venous pressure was higher in POTS compared with control (16 vs. 10 mmHg), which gave the appearance of decreased compliance in these patients. The threshold for edema formation decreased in POTS patients compared with controls (8.3 vs. 16.3 mmHg). With tilt, early calf blood flow increased in POTS patients (from 3.4 +/- 0.9 to 12.6 +/- 2.3 ml. 100 ml(-1). min(-1)) but did not increase in controls. Calf volume increased twice as much in POTS patients compared with controls over a shorter time of orthostasis. The data suggest that resting venous pressure is higher and the threshold for edema is lower in POTS patients compared with controls. Such findings make the POTS patients particularly vulnerable for edema fluid collection. This may signify a redistribution of blood to the lower extremities even while supine, accounting for tachycardia through vagal withdrawal.

Autonomic nervous system dysfunction in adolescents with postural orthostatic tachycardia syndrome and chronic fatigue syndrome is characterized by attenuated vagal baroreflex and potentiated sympathetic vasomotion

The objective was to determine the nature of autonomic and vasomotor changes in adolescent patients with orthostatic tachycardia associated with the chronic fatigue syndrome (CFS) and the postural orthostatic tachycardia syndrome (POTS). Continuous electrocardiography and arterial tonometry was used to investigate the heart rate and blood pressure responses before and 3-5 min after head-up tilt in 22 adolescents with POTS and 14 adolescents with CFS, compared with control subjects comprising 10 healthy adolescents and 20 patients with simple faint. Heart rate and blood pressure variability, determined baroreceptor function using transfer function analysis, and measured cardiac vagal and adrenergic autonomic responses were calculated using timed breathing and the quantitative Valsalva maneuver. Two of 10 healthy controls and 14 of 20 simple faint patients experienced vasovagal syncope during head-up tilt. By design, all CFS and POTS patients experienced orthostatic tachycardia, often associated with hypotension. R-R interval and heart rate variability were decreased in CFS and POTS patients compared with control subjects and remained decreased with head-up tilt. Low-frequency (0.05-0.15 Hz) blood pressure variability reflecting vasomotion was increased in CFS and POTS patients compared with control subjects and increased further with head-up tilt. This was associated with depressed baroreflex transfer indicating baroreceptor attenuation through defective vagal efferent response. Only the sympathetic response remained. Heart rate variability declined progressively from normal healthy control subjects through syncope to POTS to CFS patients. Timed breathing and Valsalva maneuver were most often normal in CFS and POTS patients, although abnormalities in select individuals were found. Heart rate and blood pressure regulation in POTS and CFS patients are similar and indicate attenuated efferent vagal baroreflex associated with increased vasomotor tone. Loss of beat-to-beat heart rate control may contribute to a destabilized blood pressure resulting in orthostatic intolerance. The dysautonomia of orthostatic intolerance in POTS and in chronic fatigue are similar.

The roles of orthostatic hypotension, orthostatic tachycardia, and subnormal erythrocyte volume in the pathogenesis of the chronic fatigue syndrome

BACKGROUND

Orthostatic hypotension during upright tilt is an important physical disorder in patients with chronic fatigue syndrome. We have tested its occurrence during prolonged standing, whether it is correctable, and whether reduced circulating erythrocyte volume is present.

METHODS

Fifteen patients were randomly selected from a large population of patients with chronic fatigue syndrome, studied, and observed for several years (by DSB). Blood pressure (BP) and heart rate (HR) measured with Dinamap every minute for 30 minutes supine and 60 minutes standing were compared with these findings in 15 healthy age- and gender-matched control subjects and later during lower body compression with military antishock trousers (MAST). Plasma catecholamines and circulating erythrocyte and plasma volumes were also measured by isotopic dilution methods.

RESULTS

Abnormal findings in the patients included excessive orthostatic reductions in systolic (P < 0.001) and diastolic BP (P < 0.001) and excessive orthostatic tachycardia (P < 0.01), together with presyncopal symptoms in 11 of the 15 patients and in none of the control subjects after standing for 60 min. Lower body compression with the MAST restored all orthostatic measurements to normal and overcame presyncopal symptoms within 10 min. Circulating erythrocyte but not plasma volumes were subnormal in the 12 women (P < 0.01) and plasma norepinephrine concentration rose excessively after standing for 10 min.

CONCLUSION

Delayed orthostatic hypotension and/or tachycardia caused by excessive gravitational venous pooling, which is correctable with external lower-body compression, together with subnormal circulating erythrocyte volume, are very frequent, although not invariably demonstrable, findings in moderate to severe chronic fatigue syndrome. When present, they may be involved in its pathogenesis.

Fibromyalgia, chronic fatigue syndrome, and myofascial pain syndrome

Fibromyalgia and widespread pain were common in Gulf War veterans with unexplained illness referred to a rheumatology clinic. Increased tenderness was demonstrated in the postmenstrual phase of the cycle compared with the intermenstrual phase in normally cycling women but not in users of oral contraceptives. Patients with fibromyalgia had high levels of symptoms that have been used to define silicone implant-associated syndrome. Tender points were found to be a common transient finding associated with acute infectious mononucleosis, but fibromyalgia was an unusual long-term outcome. The common association of fibromyalgia with other rheumatic and systemic illnesses was further explored. A preliminary study revealed a possible linkage of fibromyalgia to the HLA region. Patients with fibromyalgia were found to have an impaired ability to activate the hypothalamic pituitary portion of the hypothalamic pituitary adrenal axis as well as the sympathoadrenal system, leading to reduced corticotropin and epinephrine response to hypoglycemia. Much interest has been expressed in the literature on the possible role of autonomic dysfunction in the development or exacerbation of fatigue and other symptoms in chronic fatigue syndrome. Mycoplasma genus and mycoplasma fermentans were detected by polymerase chain reaction in patients with chronic fatigue syndrome. It was reported that myofascial temporomandibular disorder does not run in families. No major therapeutic trials in fibromyalgia, chronic fatigue syndrome, or myofascial pain syndrome were reported over the past year. The effectiveness of cognitive behavioral therapy and behavior therapy for chronic pain in adults was emphasized. A favorable outcome of fibromyalgia and chronic fatigue syndrome in children and adolescents was reported.

Intravenous cannulation of adolescents does not affect the modulation of autonomic tone assessed by heart rate and blood pressure variability

Invasive arterial monitoring alters autonomic tone. The effects of intravenous (i.v.) insertion are less clear. The author assessed the effects of i.v. insertion on autonomic activity in patients aged 11 to 19 years prior to head-up tilt by measuring heart rate, blood pressure, heart rate variability, blood pressure variability, and baroreceptor gain before and after i.v. insertion with continuous electrocardiography and arterial tonometry in patients with orthostatic tachycardia syndrome (OTS, N = 21), in patients who experienced simple fainting (N = 14), and in normal control subjects (N = 6). Five-minute samples were collected after 30 minutes supine. Fifteen minutes after i.v. insertion, data were collected again. These 5-minute samples were also collected in a separate control population without i.v. insertion after 30 minutes supine and again 30 minutes later. This population included 12 patients with OTS, 13 patients who experienced simple fainting, and 6 normal control subjects. Heart rate variability included the mean RR, the standard deviation of the RR interval (SDNN), and the root mean square of successive RR differences (RMSSD). Autoregressive spectral modeling was used. Low-frequency power (LFP, 0.04-0.15 Hz), high-frequency power (HFP, 0.15-0.40 Hz), and total power (TP, 0.01-0.40 Hz) were compared. Blood pressure variability included standard deviation of systolic blood pressure, LFP, and HFP. Baroreceptor gain at low frequency and high frequency was calculated from cross-spectral transfer function magnitudes when coherence was greater than 0.5. In patients with OTS, RR (790 +/- 50 msec), SDNN (54 +/- 6 msec), RMSSD (55 +/- 5 msec), LFP (422 +/- 200 ms2/Hz), HFP (846 +/- 400 ms2/Hz), and TP (1550 +/- 320 ms2/Hz) were less than in patients who experienced simple fainting (RR, 940 +/- 50 msec; SDNN, 84 +/- 10 msec; RMSSD, 91 +/- 7 msec; LFP, 880 +/- 342 ms2/Hz; HFP, 1720 +/- 210 ms2/Hz; and TP, 3228 +/- 490 ms2/Hz) or normal control subjects (RR, 920 +/- 30 msec; SDNN, 110 +/- 29 msec; RMSSD, 120 +/- 16 msec; LFP, 1600 +/- 331 ms2/Hz; HFP, 2700 +/- 526 ms2/Hz; and TP, 5400 +/- 1017 ms2/Hz). Blood pressure and blood pressure variability were not different in any group. Standard deviation, LFP, and HFP were, respectively, 5.24 +/- 0.8 mm Hg, 1.2 +/- 0.2, and 1.5 +/- 0.3 for patients with OTS; 4.6 +/- 0.4 mm Hg, 1.2 +/- 0.2, and 1.4 +/- 0.3 for patients who experienced simple fainting; and 5.55 +/- 1.0 mm Hg, 1.4 +/- 0.2, and 1.6 +/- 0.3 for normal control subjects. Baroreceptor gain at low frequency and high frequency in patients with OTS (16 +/- 4 msec/mm Hg, 17 +/- 5) was comparable to that in patients who experienced simple fainting (33 +/- 4, 32 +/- 3) and that in normal control subjects (31 +/- 8, 37 +/- 9). Heart rate variability differed between patients with OTS and patients who experienced simple fainting or normal control subjects, and blood pressure and blood pressure variability were not different, but no parameter changed after i.v. insertion. There were no differences from the groups that did not receive i.v. insertions. Data suggest, at most, a limited effect of i.v. insertion on autonomic function in adolescents.

Autonomic function in patients with chronic fatigue syndrome

Subtle signs of autonomic dysfunction and orthostatic intolerance have been reported in patients with chronic fatigue syndrome (CFS). To assess cardiovascular autonomic function noninvasively in an unselected group of patients with CFS, we examined responsiveness to several cardiovascular reflex tests in 37 CFS patients and 38 healthy control subjects. Blood pressure and heart rate (HR) were recorded continuously by a Finapres device before and during forced breathing, standing up, Valsalva maneuver, and sustained handgrip exercise (HG). In addition, a mental arithmetic test was carried out and questionnaires to assess the severity of CFS symptoms were completed. At rest, there were no significant differences in blood pressure or in HR between the two groups. The in- and expiratory difference in HR tended to be lower in CFS patients (28.4 +/- 10.5 beats) than in healthy controls (32.2 +/- 9.5) (p = 0.11). The maximal increase in HR during standing up was not significantly different between the CFS group (37.6 +/-8.9 beats) and the control group (40.2 +/- 8.9 beats). There were no significant differences between both groups with regard to the Valsalva ratio, but the systolic and diastolic blood pressure responses were significantly larger in CFS patients, despite the fact that many CFS patients were not able to sustain the Valsalva maneuver. The HR response to MA was significantly less in the CFS group (22.6 +/- 9.9) than in the control group (29.5 +/- 16.7) (p < 0.05), suggesting impaired cardiac sympathetic responsiveness to mental stress. The lower HR responses could not be explained by the level of concentration in the CFS group. During HG exercise, the hemodynamic responses were lower in the CFS group than in the control group, but this might be attributed to the lower level of muscle exertion in CFS patients. There were no significant differences between CFS patients with and without symptoms of autonomic dysfunction regarding the hemodynamic responses to the cardiovascular reflex tests. The findings of the study suggest that there are no gross alterations in cardiovascular autonomic function in patients with CFS.

Instantaneous orthostatic hypotension in children and adolescents: a new entity of orthostatic intolerance

We are the first to report clinical characteristics and circulatory and catecholamine responses to postural change in 44 children with instantaneous orthostatic hypotension (INOH). The symptoms include chronic fatigue, orthostatic dizziness, weakness, sleep disturbance, syncope or near syncope, headache, and loss of appetite. We divided the patients into two groups: group I (30 patients) had either a recovery time for mean arterial pressure of >25 s or a recovery time of >20 s with a 60% or greater decrease in mean arterial pressure at the initial decrease; group II (14 patients) had a prolonged reduction in systolic arterial pressure of > 15% during the later stage of standing (3-7 min) in addition to the criteria for group I. INOH was characterized by a marked reduction in blood pressure at the initial decrease (mean, -55/-27 mm Hg systolic/diastolic). Delayed recovery time of >60 s was found in 21 of 44 patients and orthostatic tachycardia (>35 beats per minute) in 20 of 44. Plasma noradrenaline responses were significantly lower in group I and II than in controls at 1 min of standing and were lower in group II at 5 min of standing. These results suggest that mechanisms responsible for INOH may depend on insufficient sympathetic activation during standing, possibly due to centrally mediated sympathetic inhibition, thus causing impairment of quality of life including school absenteeism. INOH is an important pathologic condition in children with complaints of orthostatic intolerance and can be an unrecognized cause of chronic fatigue. This condition can be identified by using a noninvasive beat-to-beat continuous blood pressure monitoring system.

Patterns of orthostatic intolerance: the orthostatic tachycardia syndrome and adolescent chronic fatigue

OBJECTIVES

To describe the orthostatic tachycardia syndrome (OTS) in adolescents, similarities to and differences from chronic fatigue syndrome (CFS), and patterns of orthostatic intolerance during head-up tilt (HUT).

STUDY DESIGN

Using electrocardiography and arterial tonometry, we investigated the heart rate and blood pressure responses during HUT in 20 adolescents with OTS compared with 25 adolescents with CFS, 13 healthy control subjects, and 20 patients with simple faint.

RESULTS

Of the control subjects, 4 of 13 experienced typical vasovagal faints with an abrupt fall in blood pressure and heart rate, and 14 of 20 patients with simple faint experienced similar HUT responses. All patients with CFS (25/25) experienced severe orthostatic symptoms with syncope in 2 of 25, early orthostatic tachycardia during HUT in 16 of 23 (13/16 hypotensive), and delayed orthostatic tachycardia in 7 of 23 (6/7 hypotensive). Acrocyanosis and edema occurred in 18 of 25. Early orthostatic tachycardia occurred in 10 of 20 patients with OTS. Of these, 9 of 10 were hypotensive, but hypotension was delayed in 4 of 9. Delayed tachycardia occurred in 10 of 20 (all hypotensive). Acrocyanosis and edema occurred in most patients with CFS, fewer patients with OTS, and in one patient with simple faint. Orthostatic symptoms were similar but more severe in patients with CFS compared with patients with OTS.

CONCLUSIONS

Symptoms and patterns of orthostatic heart rate and blood pressure change in OTS overlap strongly with those of CFS. Orthostatic intolerance in OTS may represent an attenuated form of chronic fatigue pathophysiology.