Chronic fatigue syndrome: illness severity, sedentary lifestyle, blood volume and evidence of diminished cardiac function. Clin Sci (Lond). 2010;118:125-135. [PMID: 19469714 DOI: 10.1042/cs20090055]

Association between chronic fatigue syndrome/myalgic encephalomyelitis and cardiovascular disease

Chronic fatigue syndrome or myalgic encephalomyelitis (CFS/ME) is a medical condition characterized by severe and prolonged fatigue that is not relieved by rest or attributed to any underlying medical or psychological condition. Individuals with CFS/ME are considered to have an increased risk of a wide range of comorbid conditions, including cardiovascular disease (CVD). The association between CFS/ME and CVD is not fully understood. To determine the prevalence of CFS/ME in a sample population and examine its association with CVD. Weighted sample size data of 114,834 was analyzed from the 2021-2022 national health interview survey (NHIS). Information on sociodemographic factors, CVD risk factors, and history of CFS/ME and CVD were collected. Multivariable logistic regression model was used to determine the association between CFS/ME and CVD, adjusting for traditional CVD risk factors (age, sex, race, hypertension, diabetes, dyslipidemia, smoking, and body mass index (BMI). Median age of participants was 53 years, and majority of participants were female (53.9%). Prevalence of CFS/ME was 1.2%. A history of CFS/ME was significantly associated with CVD (aOR 3.26, 95%CI 2.85, 3.72, p-value: <0.001) after adjusting for traditional CVD risk factors. A history of CFS/ME was independently associated with CVD after adjusting for traditional CVD risk factors. Patients with CFS/ME need close evaluation for CVD. Further studies are needed to better understand the relationship between CFS/ME and CVD.

Two Different Hemodynamic Responses in ME/CFS Patients with Postural Orthostatic Tachycardia Syndrome During Head-Up Tilt Testing

Introduction: While the diagnosis of postural orthostatic tachycardia syndrome (POTS) is based on heart rate (HR) and blood pressure (BP) criteria, the pathophysiology of POTS is not fully understood as multiple pathophysiological mechanisms have been recognized. Also, cardiac function, being dependent on preload, afterload, contractility, and HR, has not been properly studied. Preload and contractility changes can be inferred from stroke volume index (SVI) changes during a tilt test. Afterload plays a minor role in POTS as a normal BP response is a prerequisite for POTS. Therefore, we analyzed the HR-SVI relation during a tilt test in myalgic encephalomyelitis (ME/CFS) patients with POTS and compared the data with ME/CFS patients with a normal HR-BP response and with that of healthy controls (HC). Material and Methods: In ME/CFS patients with either POTS (n = 233) or a normal HR-BP response (n = 507) and healthy controls (n = 48), we measured SVI (by suprasternal echo), HR, and BP during the tilt. Results: In all ME/CFS patients, the decrease in SVI was larger compared to HC. In patients with a normal HR-BP response and in POTS patients with a HR increase between 30-39 bpm, there was an inverse relationship between the HR increase and SVI decrease during the tilt, compatible with increased venous pooling. In POTS patients with a HR increase ≥40 bpm, this inverse relation was lost, and SVI changes were significantly less compared to POTS patients with a HR increase between 30-39 bpm, suggestive of a hyperadrenergic response. Conclusions: In ME/CFS patients with POTS, two different hemodynamic profiles can be observed: in patients with a limited HR increase, mainly increased venous pooling is observed, while in patients with a large (≥ 40 bpm) HR increase the data are suggestive of a hyperadrenergic response. These two different profiles may have different therapeutic implications.

Analysis of the relationship between age-related erythrocyte dysfunction and fatigue

With the declining birth rates and aging societies in developed countries, the average age of the working population is increasing. Older people tend to get tired more easily, so prevention of fatigue is important to improve the quality of life for older workers. This study aimed to assess the mechanism of fatigue in older people, especially focused on relation between dysfunction of erythrocyte and fatigue. Total power (TP), which is the value of autonomic nerve activity, was measured as a value of fatigue and significantly decreased in workers with aging. As properties of senescent erythrocytes, the erythrocyte sedimentation rate and damaged erythrocytes population increased with aging and correlated with TP. These results suggested that the accumulation of damaged erythrocytes contributes to fatigue. Recent studies revealed that senescence-associated secretory phenotype (SASP), a phenomenon in which senescent cells secrete a variety of cytokines, affected hematopoiesis in bone marrow. We analyzed the effects of SASP factors on erythropoiesis and found that Interleukin -1α (IL-1α) suppressed erythrocyte differentiation of hematopoietic stem cells in vitro. We also showed that IL-1α levels in human blood and saliva increase with aging, suggesting the possibility that IL-1α level in saliva can be used to predict the decline in hematopoietic function.

Orthostatic chronotropic incompetence in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)

Background

Orthostatic intolerance (OI) is a core diagnostic criterion in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). The majority of ME/CFS patients have no evidence of hypotension or postural orthostatic tachycardia syndrome (POTS) during head-up tilt, but do show a significantly larger reduction in stroke volume index (SVI) when upright compared to controls. Theoretically a reduction in SVI should be accompanied by a compensatory increase in heart rate (HR). When there is an incomplete compensatory increase in HR, this is considered chronotropic incompetence. This study explored the relationship between HR and SVI to determine whether chronotropic incompetence was present during tilt testing in ME/CFS patients.

Methods

From a database of individuals who had undergone tilt testing with Doppler measurements for SVI both supine and end-tilt, we selected ME/CFS patients and healthy controls (HC) who had no evidence of POTS or hypotension during the test. To determine the relation between the HR increase and SVI decrease during the tilt test in patients, we calculated the 95% prediction intervals of this relation in HC. Chronotropic incompetence in patients was defined as a HR increase below the lower limit of the 95th % prediction interval of the HR increase in HC.

Results

We compared 362 ME/CFS patients with 52 HC. At end-tilt, tilt lasting for 15 (4) min, ME/CFS patients had a significantly lower SVI (22 (4) vs. 27 (4) ml/m²; p < 0.0001) and a higher HR (87 (11) vs. 78 (15) bpm; p < 0.0001) compared to HC. There was a similar relationship between HR and SVI between ME/CFS patients and HC in the supine position. During tilt ME/CFS patients had a lower HR for a given SVI; 37% had an inadequate HR increase. Chronotropic incompetence was more common in more severely affected ME/CFS patients.

Conclusion

These novel findings represent the first description of orthostatic chronotropic incompetence during tilt testing in ME/CFS patients.

Influence of end-tidal CO2 on cerebral blood flow during orthostatic stress in controls and adults with myalgic encephalomyelitis/chronic fatigue syndrome

Brain perfusion is sensitive to changes in CO2 levels (CO2 reactivity). Previously, we showed a pathological cerebral blood flow (CBF) reduction in the majority of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) patients during orthostatic stress. Limited data are available on the relation between CO2 and CBF changes in ME/CFS patients. Therefore, we studied this relation between ME/CFS patients and healthy controls (HC) during tilt testing. In this retrospective study, supine and end-tilt CBF, as measured by extracranial Doppler flow, were compared with PET CO2 data in female patients either with a normal heart rate and blood pressure (HR/BP) response or with postural orthostatic tachycardia syndrome (POTS), and in HC. Five hundred thirty-five female ME/CFS patients and 34 HC were included. Both in supine position and at end-tilt, there was a significant relation between CBF and PET CO2 in patients (p < 0.0001), without differences between patients with a normal HR/BP response and with POTS. The relations between the %CBF change and the PET CO2 reduction were both significant in patients and HC (p < 0.0001 and p = 0.0012, respectively). In a multiple regression analysis, the patient/HC status and PET CO2 predicted CBF. The contribution of the PET CO2 to CBF changes was limited, with low adjusted R2 values. In female ME/CFS patients, CO2 reactivity, as measured during orthostatic stress testing, is similar to that of HC and is independent of the type of hemodynamic abnormality. However, the influence of CO2 changes on CBF changes is modest in female ME/CFS patients.

Cardiovascular and haematological pathology in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS): A role for viruses

ME/CFS is a debilitating chronic condition that often develops after viral or bacterial infection. Insight from the study of Long COVID/Post Acute Sequelae of COVID-19 (PASC), the post-viral syndrome associated with SARS-CoV-2 infection, might prove to be useful for understanding pathophysiological mechanisms of ME/CFS. Disease presentation is similar between the two conditions, and a subset of Long COVID patients meet the diagnostic criteria for ME/CFS. Since Long COVID is characterized by significant vascular pathology - including endothelial dysfunction, coagulopathy, and vascular dysregulation - the question of whether or not the same biological abnormalities are of significance in ME/CFS arises. Cardiac abnormalities have for a while now been documented in ME/CFS cohorts, with recent studies demonstrating major deficits in cerebral blood flow, and hence vascular dysregulation. A growing body of research is demonstrating that ME/CFS is accompanied by platelet hyperactivation, anomalous clotting, a procoagulant phenotype, and endothelial dysfunction. Endothelial damage and dysregulated clotting can impair substance exchange between blood and tissues, and result in hypoperfusion, which may contribute to the manifestation of certain ME/CFS symptoms. Here we review the ME/CFS literature to summarize cardiovascular and haematological findings documented in patients with the condition, and, in this context, briefly discuss the potential role of previously-implicated pathogens. Overall, cardiac and haematological abnormalities are present within ME/CFS cohorts. While atherosclerotic heart disease is not significantly associated with ME/CFS, suboptimal cardiovascular function defined by reduced cardiac output, impaired cerebral blood flow, and vascular dysregulation are, and these abnormalities do not appear to be influenced by deconditioning. Rather, these cardiac abnormalities may result from dysfunction in the (autonomic) nervous system. Plenty of recently published studies are demonstrating significant platelet hyperactivity and endothelial dysfunction in ME/CFS, as well as anomalous clotting processes. It is of particular importance to determine to what extent these cardiovascular and haematological abnormalities contribute to symptom severity, and if these two systems can be targeted for therapeutic purposes. Viral reservoirs of herpesviruses exist in ME/CFS, and most likely contribute to cardiovascular and haematological dysfunction directly or indirectly. This review highlights the potential of studying cardiac functioning, the vasculature, and coagulation system in ME/CFS.

ME/CFS and Long COVID share similar symptoms and biological abnormalities: road map to the literature

Some patients remain unwell for months after "recovering" from acute COVID-19. They develop persistent fatigue, cognitive problems, headaches, disrupted sleep, myalgias and arthralgias, post-exertional malaise, orthostatic intolerance and other symptoms that greatly interfere with their ability to function and that can leave some people housebound and disabled. The illness (Long COVID) is similar to myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) as well as to persisting illnesses that can follow a wide variety of other infectious agents and following major traumatic injury. Together, these illnesses are projected to cost the U.S. trillions of dollars. In this review, we first compare the symptoms of ME/CFS and Long COVID, noting the considerable similarities and the few differences. We then compare in extensive detail the underlying pathophysiology of these two conditions, focusing on abnormalities of the central and autonomic nervous system, lungs, heart, vasculature, immune system, gut microbiome, energy metabolism and redox balance. This comparison highlights how strong the evidence is for each abnormality, in each illness, and helps to set priorities for future investigation. The review provides a current road map to the extensive literature on the underlying biology of both illnesses.

Orthostatic Intolerance after COVID-19 Infection: Is Disturbed Microcirculation of the Vasa Vasorum of Capacitance Vessels the Primary Defect?

Following COVID-19 infection, a substantial proportion of patients suffer from persistent symptoms known as Long COVID. Among the main symptoms are fatigue, cognitive dysfunction, muscle weakness and orthostatic intolerance (OI). These symptoms also occur in myalgic encephalomyelitis/chronic fatigue (ME/CFS). OI is highly prevalent in ME/CFS and develops early during or after acute COVID-19 infection. The causes for OI are unknown and autonomic dysfunction is hypothetically assumed to be the primary cause, presumably as a consequence of neuroinflammation. Here, we propose an alternative, primary vascular mechanism as the underlying cause of OI in Long COVID. We assume that the capacitance vessel system, which plays a key role in physiologic orthostatic regulation, becomes dysfunctional due to a disturbance of the microvessels and the vasa vasorum, which supply large parts of the wall of those large vessels. We assume that the known microcirculatory disturbance found after COVID-19 infection, resulting from endothelial dysfunction, microthrombus formation and rheological disturbances of blood cells (altered deformability), also affects the vasa vasorum to impair the function of the capacitance vessels. In an attempt to compensate for the vascular deficit, sympathetic activity overshoots to further worsen OI, resulting in a vicious circle that maintains OI. The resulting orthostatic stress, in turn, plays a key role in autonomic dysfunction and the pathophysiology of ME/CFS.

Ongoing Exercise Intolerance Following COVID-19: A Magnetic Resonance-Augmented Cardiopulmonary Exercise Test Study

Background Ongoing exercise intolerance of unclear cause following COVID-19 infection is well recognized but poorly understood. We investigated exercise capacity in patients previously hospitalized with COVID-19 with and without self-reported exercise intolerance using magnetic resonance-augmented cardiopulmonary exercise testing. Methods and Results Sixty subjects were enrolled in this single-center prospective observational case-control study, split into 3 equally sized groups: 2 groups of age-, sex-, and comorbidity-matched previously hospitalized patients following COVID-19 without clearly identifiable postviral complications and with either self-reported reduced (COVID_reduced) or fully recovered (COVID_normal) exercise capacity; a group of age- and sex-matched healthy controls. The COVID_reducedgroup had the lowest peak workload (79W [Interquartile range (IQR), 65-100] versus controls 104W [IQR, 86-148]; P=0.01) and shortest exercise duration (13.3±2.8 minutes versus controls 16.6±3.5 minutes; P=0.008), with no differences in these parameters between COVID_normal patients and controls. The COVID_reduced group had: (1) the lowest peak indexed oxygen uptake (14.9 mL/minper kg [IQR, 13.1-16.2]) versus controls (22.3 mL/min per kg [IQR, 16.9-27.6]; P=0.003) and COVID_normal patients (19.1 mL/min per kg [IQR, 15.4-23.7]; P=0.04); (2) the lowest peak indexed cardiac output (4.7±1.2 L/min per m²) versus controls (6.0±1.2 L/min per m²; P=0.004) and COVID_normal patients (5.7±1.5 L/min per m²; P=0.02), associated with lower indexed stroke volume (SVi:COVID_reduced 39±10 mL/min per m² versus COVID_normal 43±7 mL/min per m² versus controls 48±10 mL/min per m²; P=0.02). There were no differences in peak tissue oxygen extraction or biventricular ejection fractions between groups. There were no associations between COVID-19 illness severity and peak magnetic resonance-augmented cardiopulmonary exercise testing metrics. Peak indexed oxygen uptake, indexed cardiac output, and indexed stroke volume all correlated with duration from discharge to magnetic resonance-augmented cardiopulmonary exercise testing (P<0.05). Conclusions Magnetic resonance-augmented cardiopulmonary exercise testing suggests failure to augment stroke volume as a potential mechanism of exercise intolerance in previously hospitalized patients with COVID-19. This is unrelated to disease severity and, reassuringly, improves with time from acute illness.

Physiological assessment of orthostatic intolerance in chronic fatigue syndrome

BACKGROUND

Orthostatic intolerance-OI is common in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome-ME/CFS. We used a 10-min passive vertical lean test as orthostatic challenge-OC and measured changes in vitals and end tidal CO2 (eTCO2). An abnormal physiologic response to OC was identified in 60% of the 63 patients evaluated from one to three times over several years. Hypocapnia, either resting or induced by OC, was the most frequent abnormality, followed by postural orthostatic tachycardia.

OBJECTIVE

Evaluate the physiologic response of patients with ME/CFS to a standardized OC.

DESIGN

Respiratory and heart rate, blood pressure and eTCO2 were recorded twice at the end of 10-min supine rest and then every minute during the 10-min lean. Hypocapnia was eTCO2 ≤ 32 mmHg. Orthostatic tachycardia was heart rate increase ≥ 30 beats per minute compared with resting or ≥ 120 BPM. Orthostatic hypotension was decreased systolic pressure ≥ 20 mmHg from baseline. Tachypnea was respiratory rate of  ≥ 20 breaths per minute-either supine or leaning. Questionnaire data on symptom severity, quality of life and mood were collected at visit #2.

PATIENTS

63 consecutive patients fulfilling the 1994 case definition for CFS underwent lean testing at first visit and then annually at visit 2 (n = 48) and 3 (n = 29).

MEASURES

Supine hypocapnia; orthostatic tachycardia, hypocapnia or hypotension.

RESULTS

The majority of ME/CFS patients (60.3%, 38/63) had an abnormality detected during a lean test at any visit (51%, 50% and 45% at visits 1, 2 and 3, respectively). Hypocapnia at rest or induced by OC was more common and more likely to persist than postural orthostatic tachycardia. Anxiety scores did not differ between those with and without hypocapnia.

CONCLUSIONS

The 10-min lean test is useful in evaluation of OI in patients with ME/CFS. The most frequent abnormality, hypocapnia, would be missed without capnography.

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Essentials of Diagnosis and Management

Despite myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) affecting millions of people worldwide, many clinicians lack the knowledge to appropriately diagnose or manage ME/CFS. Unfortunately, clinical guidance has been scarce, obsolete, or potentially harmful. Consequently, up to 91% of patients in the United States remain undiagnosed, and those diagnosed often receive inappropriate treatment. These problems are of increasing importance because after acute COVID-19, a significant percentage of people remain ill for many months with an illness similar to ME/CFS. In 2015, the US National Academy of Medicine published new evidence-based clinical diagnostic criteria that have been adopted by the US Centers for Disease Control and Prevention. Furthermore, the United States and other governments as well as major health care organizations have recently withdrawn graded exercise and cognitive-behavioral therapy as the treatment of choice for patients with ME/CFS. Recently, 21 clinicians specializing in ME/CFS convened to discuss best clinical practices for adults affected by ME/CFS. This article summarizes their top recommendations for generalist and specialist health care providers based on recent scientific progress and decades of clinical experience. There are many steps that clinicians can take to improve the health, function, and quality of life of those with ME/CFS, including those in whom ME/CFS develops after COVID-19. Patients with a lingering illness that follows acute COVID-19 who do not fully meet criteria for ME/CFS may also benefit from these approaches.

Chronic Fatigue Syndrome and Cardiovascular Disease: JACC State-of-the-Art Review

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a medically unexplained illness characterized by severe fatigue limiting normal daily activities for at least 6 months accompanied by problems with unrefreshing sleep, exacerbation of symptoms following physical or mental efforts (postexertional malaise [PEM]), and either cognitive reports or physiological evidence of orthostatic intolerance in the form of either orthostatic tachycardia and/or hypocapnia. Although rarely considered to have cardiac dysfunction, ME/CFS patients frequently have reduced stroke volume with a significant inverse relation between cardiac output and PEM severity. Magnetic resonance imaging of ME/CFS patients compared with normal control subjects found significantly reduced stroke, end-systolic, and end-diastolic volumes together with reduced end-diastolic wall mass. Another cardiovascular abnormality is reduced nocturnal blood pressure assessed by 24-hour monitoring. Autonomic dysfunction is also frequently observed with postural orthostatic tachycardia and/or hypocapnia. Two consecutive cardiopulmonary stress tests may provide metabolic data substantiating PEM.

Radiation exposure and mitochondrial insufficiency in chronic fatigue and immune dysfunction syndrome

Chronic fatigue and Immune Dysfunction Syndrome (CFIDS) is a heterogeneous disease that may be promoted by various environmental stressors, including viral infection, toxin uptake, and ionizing radiation exposure. Previous studies have identified mitochondrial dysfunction in CFIDS patients, including modulation of mitochondrial respiratory chain activity, deletions in the mitochondrial genome, and upregulation of reactive oxygen species (ROS). This paper focuses on radiation effects and hypothesizes that CFIDS is primarily caused by stressor-induced mitochondrial metabolic insufficiency, which results in decreased energy production and anabolic metabolites required for normal cellular metabolism. Furthermore, tissues neighbouring or distant from directly perturbed tissues compensate for this dysfunction, which causes symptoms associated with CFIDS. This hypothesis is justified by reviewing the links between radiation exposure and CFIDS, cancer, immune dysfunction, and induction of oxidative stress. Moreover, the relevance of mitochondria in cellular responses to radiation and metabolism are discussed and putative mitochondrial biomarkers for CFIDS are introduced. Implications for diagnosis are then described, including a potential urine assay and PCR test for mitochondrial genome mutations. Finally, future research needs are offered with an emphasis on where rapid progress may be made to assist the afflicted.

The Role of Prevention in Reducing the Economic Impact of ME/CFS in Europe: A Report from the Socioeconomics Working Group of the European Network on ME/CFS (EUROMENE)

This report addresses the extent to which there may be scope for preventive programmes for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), and, if so, what economic benefits may accrue from the implementation of such programmes. We consider the economic case for prevention programmes, whether there is scope for preventive programmes for ME/CFS, and what are the health and economic benefits to be derived from the implementation of such programmes. We conclude that there is little scope for primary prevention programmes, given that ME/CFS is attributable to a combination of host and environmental risk factors, with host factors appearing to be most prominent, and that there are few identified modifiable risk factors that could be the focus of such programmes. The exception is in the use of agricultural chemicals, particularly organophosphates, where there is scope for intervention, and where Europe-wide programmes of health education to encourage safe use would be beneficial. There is a need for more research on risk factors for ME/CFS to establish a basis for the development of primary prevention programmes, particularly in respect of occupational risk factors. Secondary prevention offers the greatest scope for intervention, to minimise diagnostic delays associated with prolonged illness, increased severity, and increased costs.

Reductions in Cerebral Blood Flow Can Be Provoked by Sitting in Severe Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients

Introduction: In a large study with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) patients, we showed that 86% had symptoms of orthostatic intolerance in daily life and that 90% had an abnormal reduction in cerebral blood flow (CBF) during a standard tilt test. A standard head-up tilt test might not be tolerated by the most severely affected bed-ridden ME/CFS patients. Sitting upright is a milder orthostatic stress. The present study examined whether a sitting test, measuring cerebral blood flow by extracranial Doppler, would be sufficient to provoke abnormal reductions in cerebral blood flow in severe ME/CFS patients. Methods and results: 100 severe ME/CFS patients were studied, (88 females) and were compared with 15 healthy controls (HC) (13 females). CBF was measured first while seated for at least one hour, followed by a CBF measurement in the supine position. Fibromyalgia was present in 37 patients. Demographic data as well as supine heart rate and blood pressures were not different between ME/CFS patients and HC. Heart rate and blood pressure did not change significantly between supine and sitting both in patients and HC. Supine CBF was not different between patients and HC. In contrast, absolute CBF during sitting was lower in patients compared to HC: 474 (96) mL/min in patients and 627 (89) mL/min in HC; p < 0.0001. As a result, percent CBF reduction while seated was −24.5 (9.4)% in severe ME/CFS patients and −0.4 (1.2)% in HC (p < 0.0001). In the ten patients who had no orthostatic intolerance complaints in daily life, the CBF reduction was −2.7 (2.1)%, which was not significantly different from HC (p = 0.58). The remaining 90 patients with orthostatic intolerance complaints had a −26.9 (6.2)% CBF reduction. No difference in CBF parameters was found in patients with and without fibromyalgia. Patients with a previous diagnosis of postural orthostatic tachycardia syndrome (POTS) had a significantly larger CBF reduction compared with those without POTS: 28.8 (7.2)% vs. 22.3 (9.7)% (p = 0.0008). Conclusions: A sitting test in severe ME/CFS patients was sufficient to provoke a clinically and statistically significant mean CBF decline of 24.5%. Patients with a previous diagnosis of POTS had a larger CBF reduction while seated, compared to patients without POTS. The magnitude of these CBF reductions is similar to the results in less severely affected ME/CFS patients during head-up tilt, suggesting that a sitting test is adequate for the diagnosis of orthostatic intolerance in severely affected patients.

Paradigm shift to disequilibrium in the genesis of orthostatic intolerance in patients with myalgic encephalomyelitis and chronic fatigue syndrome

BACKGROUND

Orthostatic intolerance (OI) markedly impairs activities of daily living in patients with myalgic encephalomyelitis (ME) or chronic fatigue syndrome. OI is surmised to be a cardiovascular symptom correlated with cerebral hypo-perfusion and exaggerated sympathetic activation. Postural instability or disequilibrium may be part of the etiology of OI.

METHODS

The study comprised 72 patients with ME (18 men, 54 women; mean age, 37 ± 10 years) who underwent neurological examinations and the 10 min standing test. We quantified disequilibrium (instability upon standing with feet together and eyes shut), ability to complete the 10 min standing test, and postural orthostatic tachycardia (POT) during the test.

RESULTS

Disequilibrium was detected in 23/72 (32%) patients and POT in 16 (22%). Nineteen (26%) patients failed to complete the 10 min standing test; disequilibrium was significantly more common in the 19- patient subgroup than in the 53-patient test-completing subgroup (89% vs. 11%, p < 0.01). However, the rate of POT was not different between the groups (21% vs. 23%, p = 1.00). Compared with the 49 (68%) patients without disequilibrium, the 23 (32%) patients with disequilibrium were significantly more likely to have failed to complete the test (74% vs. 4%, p < 0.01). The rate of POT was comparable between the groups (23% vs. 22%, p = 1.00). Among patients with disequilibrium who failed to complete the 10 min standing test and had a previous record, 6/8 had completed the test 6-24 months earlier when all six had reported no disequilibrium.

CONCLUSION

Disequilibrium should be recognized as an important cause of OI in patients with ME.

Leveraging Prior Knowledge to Recover Characteristic Immune Regulatory Motifs in Gulf War Illness

Potentially linked to the basic physiology of stress response, Gulf War Illness (GWI) is a debilitating condition presenting with complex immune, endocrine and neurological symptoms. Here we interrogate the immune response to physiological stress by measuring 16 blood-borne immune markers at 8 time points before, during and after maximum exercise challenge in n = 12 GWI veterans and n = 11 healthy veteran controls deployed to the same theater. Immune markers were combined into functional sets and the dynamics of their joint expression described as classical rate equations. These empirical networks were further informed structurally by projection onto prior knowledge networks mined from the literature. Of the 49 literature-informed immune signaling interactions, 21 were found active in the combined exercise response data. However, only 4 signals were common to both subject groups while 7 were uniquely active in GWI and 10 uniquely active in healthy veterans. Feedforward mediation of IL-23 and IL-17 by IL-6 and IL-10 emerged as distinguishing control elements that were characteristically active in GWI versus healthy subjects. Simulated restructuring of the regulatory circuitry in GWI as a result of applying an IL-6 receptor antagonist in combination with either a Th1 (IL-2, IFNγ, and TNFα) or IL-23 receptor antagonist predicted a partial rescue of immune response elements previously associated with illness severity. Overall, results suggest that pharmacologically altering the topology of the immune response circuitry identified as active in GWI can inform on strategies that while not curative, may nonetheless deliver a reduction in symptom burden. A lasting and more complete remission in GWI may therefore require manipulation of a broader physiology, namely one that includes endocrine oversight of immune function.

A Unifying Hypothesis of the Pathophysiology of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): Recognitions from the finding of autoantibodies against ß2-adrenergic receptors

Myalgic Encephalomyelitis or Chronic Fatigue Syndrome (CFS/ME) is a complex and severely disabling disease with a prevalence of 0.3% and no approved treatment and therefore a very high medical need. Following an infectious onset patients suffer from severe central and muscle fatigue, chronic pain, cognitive impairment, and immune and autonomic dysfunction. Although the etiology of CFS/ME is not solved yet, there is numerous evidence for an autoantibody mediated dysregulation of the immune and autonomic nervous system. We found elevated ß2 adrenergic receptor (ß2AdR) and M3 acetylcholine receptor antibodies in a subset of CFS/ME patients. As both ß2AdR and M3 acetylcholine receptor are important vasodilators, we would expect their functional disturbance to result in vasoconstriction and hypoxemia. An impaired circulation and oxygen supply could result in many symptoms of ME/CFS. There are consistent reports of vascular dysfunction in ME/CFS. Muscular and cerebral hypoperfusion has been shown in ME/CFS in various studies and correlated with fatigue. Metabolic changes in ME/CFS are also in line with a concept of hypoxia and ischemia. Here we try to develop a unifying working concept for the complex pathomechanism of ME/CFS based on the presence of dysfunctional autoantibodies against ß2AdR and M3 acetylcholine receptor and extrapolate it to the pathophysiology of ME/CFS without an autoimmune pathogenesis.

Parasympathetic activity is reduced during slow-wave sleep, but not resting wakefulness, in patients with chronic fatigue syndrome

STUDY OBJECTIVES

Physiological dearousal characterized by an increase in parasympathetic nervous system activity is important for good-quality sleep. Previous research shows that nocturnal parasympathetic activity (reflected by heart rate variability [HRV]) is diminished in individuals with chronic fatigue syndrome (CFS), suggesting hypervigilant sleep. This study investigated differences in nocturnal autonomic activity across sleep stages and explored the association of parasympathetic activity with sleep quality and self-reported physical and psychological wellbeing in individuals with CFS.

METHODS

Twenty-four patients with medically diagnosed CFS, and 24 matched healthy control individuals participated. Electroencephalography and HRV were recorded during sleep in participants' homes using a minimally invasive ambulatory device. Questionnaires were used to measure self-reported wellbeing and sleep quality.

RESULTS

Sleep architecture in patients with CFS differed from that of control participants in slower sleep onset, more awakenings, and a larger proportion of time spent in slow-wave sleep (SWS). Linear mixed-model analyses controlling for age revealed that HRV reflecting parasympathetic activity (normalized high frequency power) was reduced in patients with CFS compared to control participants, particularly during deeper stages of sleep. Poorer self-reported wellbeing and sleep quality was associated with reduced parasympathetic signaling during deeper sleep, but not during wake before sleep, rapid eye movement sleep, or with the proportion of time spent in SWS.

CONCLUSIONS

Autonomic hypervigilance during the deeper, recuperative stages of sleep is associated with poor quality sleep and self-reported wellbeing. Causal links need to be confirmed but provide potential intervention opportunities for the core symptom of unrefreshing sleep in CFS.

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.

The etiologic relation between disequilibrium and orthostatic intolerance in patients with myalgic encephalomyelitis (chronic fatigue syndrome)

BACKGROUND

Orthostatic intolerance (OI) causes a marked reduction in the activities of daily living in patients with myalgic encephalomyelitis (ME) or chronic fatigue syndrome. Most symptoms of OI are thought to be related to cerebral hypo-perfusion and sympathetic activation. Because postural stability is an essential element of orthostatic tolerance, disequilibrium may be involved in the etiology of OI.

METHODS AND RESULTS

The study comprised 44 patients with ME (men, 11 and women, 33; mean age, 37±9 years), who underwent neurological examinations and 10-min standing and sitting tests. Symptoms of OI were detected in 40 (91%) patients and those of sitting intolerance were detected in 30 (68%). Among the 40 patients with OI, disequilibrium with instability on standing with their feet together and eyes shut, was detected in 13 (32.5%) patients and hemodynamic dysfunction during the standing test was detected in 19 (47.5%); both of these were detected in 7 (17.5%) patients. Compared with 31 patients without disequilibrium, 13 (30%) patients with disequilibrium more prevalently reported symptoms during both standing (100% vs. 87%, p=0.43) and sitting (92% vs. 58%, p=0.06) tests. Several (46% vs. 3%, p<0.01) patients failed to complete the 10-min standing test, and some (15% vs. 0%, p=0.15) failed to complete the 10-min sitting test. Among the seven patients with both hemodynamic dysfunction during the standing test and disequilibrium, three (43%) failed to complete the standing test. Among the 6 patients with disequilibrium only, 3 (50%) failed while among the 12 patients with hemodynamic dysfunction only, including 8 patients with postural orthostatic tachycardia, none (0%, p=0.02) failed.

CONCLUSIONS

Patients with ME and disequilibrium reported not only OI but also sitting intolerance. Disequilibrium should be recognized as an important cause of OI and appears to be a more influential cause for OI than postural orthostatic tachycardia in patients with ME.

Blood Volume Status in ME/CFS Correlates With the Presence or Absence of Orthostatic Symptoms: Preliminary Results

Introduction: Conflicting data have been published on the reduction of circulating blood volume in adults with Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). The aim of the present study was to compare blood volumes based on the presence or absence of orthostatic symptoms. Methods and results: Twenty consecutive adults with ME/CFS participated in the study. All underwent dual isotope blood volume measurement and were evaluated for a clinical suspicion of orthostatic intolerance (OI). The mean age was 34 (10) years, and median duration of disease was 7.5 (6-10) years. The mean (SD) absolute blood volume was 59 (8) ml/kg, a value -11 (7) ml/kg below the reference blood volume. Of the 12 patients, 4 had no OI and 8 had a clinical suspicion of OI. In 8 patients with OI, absolute blood volumes were significantly lower than for the 4 without OI (56 [2] vs. 66 [5]; p < 0.05) as were the differences between the measured and the reference blood volume (-14 [2]; vs. -4 [3]; p < 0.02). Conclusions: Adults with ME/CFS had a significantly lower blood volume if they had a clinical suspicion of OI compared to those without a clinical suspicion of OI, as well as a significantly lower blood volume compared to the expected value. The data suggest that accounting for symptoms of OI could enhance the detection of the subset with reduced blood volume.

Pediatric Disorders of Orthostatic Intolerance

Orthostatic intolerance (OI), having difficulty tolerating an upright posture because of symptoms or signs that abate when returned to supine, is common in pediatrics. For example, ∼40% of people faint during their lives, half of whom faint during adolescence, and the peak age for first faint is 15 years. Because of this, we describe the most common forms of OI in pediatrics and distinguish between chronic and acute OI. These common forms of OI include initial orthostatic hypotension (which is a frequently seen benign condition in youngsters), true orthostatic hypotension (both neurogenic and nonneurogenic), vasovagal syncope, and postural tachycardia syndrome. We also describe the influences of chronic bed rest and rapid weight loss as aggravating factors and causes of OI. Presenting signs and symptoms are discussed as well as patient evaluation and testing modalities. Putative causes of OI, such as gravitational and exercise deconditioning, immune-mediated disease, mast cell activation, and central hypovolemia, are described as well as frequent comorbidities, such as joint hypermobility, anxiety, and gastrointestinal issues. The medical management of OI is considered, which includes both nonpharmacologic and pharmacologic approaches. Finally, we discuss the prognosis and long-term implications of OI and indicate future directions for research and patient management.

Elevated brain natriuretic peptide levels in chronic fatigue syndrome associate with cardiac dysfunction: a case control study

Objectives

To explore levels of the brain natriuretic peptide (BNP) and how these associate with the cardiac abnormalities recently identified in chronic fatigue syndrome (CFS).

Methods

Cardiac magnetic resonance examinations were performed using 3T Philips Intera Achieva scanner (Best, Netherlands) in CFS (Fukuda) participants and sedentary controls matched group wise for age and sex. BNP was also measured by using an enzyme immunoassay in plasma from 42 patients with CFS and 10 controls.

Results

BNP levels were significantly higher in the CFS cohort compared with the matched controls (P=0.013). When we compared cardiac volumes (end-diastolic and end-systolic) between those with high BNP levels (BNP >400 pg/mL) and low BNP (<400 pg/mL), there were significantly lower cardiac volumes in those with the higher BNP levels in both end-systolic and end-diastolic volumes (P=0.05). There were no relationships between fatigue severity, length of disease and BNP levels (P=0.2) suggesting that our findings are unlikely to be related to deconditioning.

Conclusion

This study confirms an association between reduced cardiac volumes and BNP in CFS. Lack of relationship between length of disease suggests that findings are not secondary to deconditioning. Further studies are needed to explore the utility of BNP to act as a stratification paradigm in CFS that directs targeted treatments.

Trail registration number

Registered with NIHR Portfolio CLRN ID 97805.

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.

Mortality in Patients with Myalgic Encephalomyelitis and Chronic Fatigue Syndrome

BACKGROUND

There is a dearth of research examining mortality in individuals with myalgic encephalomyelitis (ME) and chronic fatigue syndrome (CFS). Some studies suggest there is an elevated risk of suicide and earlier mortality compared to national norms. However, findings are inconsistent as other researchers have not found significant increases in all-cause mortality for patients.

OBJECTIVE

This study sought to determine if patients with ME or CFS are reportedly dying earlier than the overall population from the same cause.

METHODS

Family, friends, and caregivers of deceased individuals with ME or CFS were recruited through social media, patient newsletters, emails, and advocate websites. This study analyzed data including cause and age of death for 56 individuals identified as having ME or CFS.

RESULTS

The findings suggest patients in this sample are at a significantly increased risk of earlier all-cause (M = 55.9 years) and cardiovascular-related (M = 58.8 years) mortality, and they had a directionally lower mean age of death for suicide (M = 41.3 years) and cancer (M =66.3 years) compared to the overall U.S. population [M = 73.5 (all-cause), 77.7 (cardiovascular), 47.4 (suicide), and 71.1 (cancer) years of age].

CONCLUSIONS

The results suggest there is an increase in risk for earlier mortality in patients with ME and CFS. Due to the small sample size and over-representation of severely ill patients, the findings should be replicated to determine if the directional differences for suicide and cancer mortality are significantly different from the overall U.S. population.

Fatigue and fluid hydration status in multiple sclerosis: A hypothesis

BACKGROUND

Fatigue is a prevalent and functionally disabling symptom for individuals living with multiple sclerosis (MS) which is poorly understood and multifactorial in etiology. Bladder dysfunction is another common MS symptom which limits social engagement and quality of life. To manage bladder issues, individuals with MS tend to limit their fluid intake, which may contribute to a low-hydration (LoH) state and fatigue.

OBJECTIVE

To evaluate the relationship between patient-reported MS fatigue, bladder dysfunction, and hydration status.

METHODS

We performed a prospective cross-sectional study in 50 women with MS. Participants submitted a random urine sample and completed several fatigue-related surveys. Using a urine specific gravity (USG) threshold of 1.015, we classified MS subjects into two groups: high-hydration (HiH) and LoH states.

RESULTS

LoH status was more common in MS subjects with bladder dysfunction. Statistically significant differences in self-reported Fatigue Performance Scale were observed between HiH and LoH subjects (p = 0.022). USG was significantly correlated with fatigue as measured by the MS Fatigue Severity Scale (FSS) score (r = 0.328, p = 0.020).

CONCLUSION

Hydration status correlates with self-reported fatigue, with lower fatigue scores found in those with HiH status (USG < 1.015).

Reduced cardiac volumes in chronic fatigue syndrome associate with plasma volume but not length of disease: a cohort study

Objectives

To explore potential mechanisms that underpin the cardiac abnormalities seen in chronic fatigue syndrome (CFS) using non-invasive cardiac impedance, red cell mass and plasma volume measurements.

Methods

Cardiac MR (MR) examinations were performed using 3 T Philips Intera Achieva scanner (Best, NL) in participants with CFS (Fukuda; n=47) and matched case-by-case controls. Total volume (TV), red cell volume (RCV) and plasma volume (PV) measurements were performed (41 CFS and 10 controls) using the indicator dilution technique using simultaneous 51-chromium labelling of red blood cells and 125-iodine labelling of serum albumin.

Results

The CFS group length of history (mean±SD) was 14±10 years. Patients with CFS had significantly reduced end-systolic and end-diastolic volumes together with reduced end-diastolic wall masses (all p<0.0001). Mean±SD RCV was 1565±443 mL with 26/41 (63%) having values below 95% of expected. PV was 2659±529 mL with 13/41 (32%) <95% expected. There were strong positive correlations between TV, RCV and PV and cardiac end-diastolic wall mass (all p<0.0001; r²=0.5). Increasing fatigue severity correlated negatively with lower PV (p=0.04; r²=0.2). There were no relationships between any MR or volume measurements and length of history, suggesting that deconditioning was unlikely to be the cause of these abnormalities.

Conclusions

This study confirms an association between reduced cardiac volumes and blood volume in CFS. Lack of relationship between length of disease, cardiac and plasma volumes suggests findings are not secondary to deconditioning. The relationship between plasma volume and severity of fatigue symptoms suggests a potential therapeutic target in CFS.

Autonomic correlations with MRI are abnormal in the brainstem vasomotor centre in Chronic Fatigue Syndrome

Autonomic changes are often associated with the chronic fatigue syndrome (CFS), but their pathogenetic role is unclear and brain imaging investigations are lacking. The vasomotor centre and, through it, nuclei in the midbrain and hypothalamus play a key role in autonomic nervous system regulation of steady state blood pressure (BP) and heart rate (HR). In this exploratory cross-sectional study, BP and HR, as indicators of autonomic function, were correlated with volumetric and T1- and T2-weighted spin-echo (T1w and T2w) brain MRI in 25 CFS subjects and 25 normal controls (NC). Steady state BP (systolic, diastolic and pulse pressure) and HR in two postures were extracted from 24 h blood pressure monitoring. We performed (1) MRI versus autonomic score interaction-with-group regressions to detect locations where regression slopes differed in the CFS and NC groups (collectively indicating abnormality in CFS), and (2) MRI regressions in the CFS and NC groups alone to detect additional locations with abnormal correlations in CFS. Significant CFS regressions were repeated controlling for anxiety and depression (A&D). Abnormal regressions were detected in nuclei of the brainstem vasomotor centre, midbrain reticular formation and hypothalamus, but also in limbic nuclei involved in stress responses and in prefrontal white matter. Group comparisons of CFS and NC did not find MRI differences in these locations. We propose therefore that these regulatory nuclei are functioning correctly, but that two-way communication between them is impaired in CFS and this affects signalling to/from peripheral effectors/sensors, culminating in inverted or magnified correlations. This single explanation for the diverse abnormal correlations detected here consolidates the conclusion for a brainstem/midbrain nerve conduction deficit inferred earlier (Barnden et al., 2015). Strong correlations were also detected in isolated NC regressions.

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For the first time in CFS, we performed MRI regressions with steady state BP and HR.

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Vasomotor centre, midbrain and hypothalamus correlations were abnormal in CFS.

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MRI group comparisons between CFS and controls detected no differences.

•

Regulatory nuclei and peripheral effectors/sensors appear to function correctly.

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Signalling between brainstem/midbrain regulatory nuclei appears to be impaired.

Variability of postural orthostatic tachycardia in patients with myalgic encephalomyelitis and orthostatic intolerance

Central nervous system dysfunction with myalgic encephalomyelitis (ME) has been suggested as the main cause of chronic fatigue syndrome. Fluctuation of the symptom severity and hierarchy is a characteristic feature in ME patients. The characteristics of the sympathetic activation may differ between the "good days" and "bad days" in them. Twenty-four ME patients with orthostatic intolerance underwent a conventional 10-min active standing test and echocardiography both on a "good day" and a "bad day", defined according to the severity of their symptoms. The mean heart rate at rest was significantly higher on the "bad days" than on the "good days". During the standing test on a "bad day", 5 patients (21 %) failed to maintain an upright posture for 10 min, whereas on a "good day" all the 24 patients maintained it. Postural orthostatic tachycardia (POT) (increase in heart rate ≥30 beats/min) or severe POT (heart rate ≥120 beats/min) was observed on the "bad days" in 10 patients (43 %) who did not suffer from the severe tachycardia on the "good days", suggesting the exaggerated sympathetic nervous activation. In contrast, POT did not occur or severe POT was attenuated on the "bad days" in 5 patients (21 %) who developed POT or severe POT on the "good days", suggesting the impaired sympathetic activation. Echocardiography revealed significantly lower mean values of both the left ventricular end-diastolic diameter and stroke volume index on the "bad days" compared with the "good days". In conclusion, in ME patients with orthostatic intolerance, the exaggerated activation of the sympathetic nervous system while standing appears to switch to the impaired sympathetic activation after the system is loaded with the additional accentuated stimuli associated with the preload reduction.

Accurate diagnosis of myalgic encephalomyelitis and chronic fatigue syndrome based upon objective test methods for characteristic symptoms

Although myalgic encephalomyelitis (ME) and chronic fatigue syndrome (CFS) are considered to be synonymous, the definitional criteria for ME and CFS define two distinct, partially overlapping, clinical entities. ME, whether defined by the original criteria or by the recently proposed criteria, is not equivalent to CFS, let alone a severe variant of incapacitating chronic fatigue. Distinctive features of ME are: muscle weakness and easy muscle fatigability, cognitive impairment, circulatory deficits, a marked variability of the symptoms in presence and severity, but above all, post-exertional “malaise”: a (delayed) prolonged aggravation of symptoms after a minor exertion. In contrast, CFS is primarily defined by (unexplained) chronic fatigue, which should be accompanied by four out of a list of 8 symptoms, e.g., headaches. Due to the subjective nature of several symptoms of ME and CFS, researchers and clinicians have questioned the physiological origin of these symptoms and qualified ME and CFS as functional somatic syndromes. However, various characteristic symptoms, e.g., post-exertional “malaise” and muscle weakness, can be assessed objectively using well-accepted methods, e.g., cardiopulmonary exercise tests and cognitive tests. The objective measures acquired by these methods should be used to accurately diagnose patients, to evaluate the severity and impact of the illness objectively and to assess the positive and negative effects of proposed therapies impartially.

Metabolism in chronic fatigue syndrome

Chronic fatigue syndrome (CFS) is a poorly understood condition that presents as long-term physical and mental fatigue with associated symptoms of pain and sensitivity across a broad range of systems in the body. The poor understanding of the disorder comes from the varying clinical diagnostic definitions as well as the broad array of body systems from which its symptoms present. Studies on metabolism and CFS suggest irregularities in energy metabolism, amino acid metabolism, nucleotide metabolism, nitrogen metabolism, hormone metabolism, and oxidative stress metabolism. The overwhelming body of evidence suggests an oxidative environment with the minimal utilization of mitochondria for efficient energy production. This is coupled with a reduced excretion of amino acids and nitrogen in general. Metabolomics is a developing field that studies metabolism within a living system under varying conditions of stimuli. Through its development, there has been the optimisation of techniques to do large-scale hypothesis-generating untargeted studies as well as hypothesis-testing targeted studies. These techniques are introduced and show an important future direction for research into complex illnesses such as CFS.

High flow variant postural orthostatic tachycardia syndrome amplifies the cardiac output response to exercise in adolescents

Postural orthostatic tachycardia syndrome (POTS) is characterized by chronic fatigue and dizziness and affected individuals by definition have orthostatic intolerance and tachycardia. There is considerable overlap of symptoms in patients with POTS and chronic fatigue syndrome (CFS), prompting speculation that POTS is akin to a deconditioned state. We previously showed that adolescents with postural orthostatic tachycardia syndrome (POTS) have excessive heart rate (HR) during, and slower HR recovery after, exercise – hallmarks of deconditioning. We also noted exaggerated cardiac output during exercise which led us to hypothesize that tachycardia could be a manifestation of a high output state rather than a consequence of deconditioning. We audited records of adolescents presenting with long‐standing history of any mix of fatigue, dizziness, nausea, who underwent both head‐up tilt table test and maximal exercise testing with measurement of cardiac output at rest plus 2–3 levels of exercise, and determined the cardiac output () versus oxygen uptake () relationship. Subjects with chronic fatigue were diagnosed with POTS if their HR rose ≥40 beat·min⁻¹ with head‐up tilt. Among 107 POTS patients the distribution of slopes for the , relationship was skewed toward higher slopes but showed two peaks with a split at ~7.0 L·min⁻¹ per L·min⁻¹, designated as normal (5.08 ± 1.17, N = 66) and hyperkinetic (8.99 ± 1.31, N = 41) subgroups. In contrast, cardiac output rose appropriately with in 141 patients with chronic fatigue but without POTS, exhibiting a normal distribution and an average slope of 6.10 ± 2.09 L·min⁻¹ per L·min⁻¹. Mean arterial blood pressure and pulse pressure from rest to exercise rose similarly in both groups. We conclude that 40% of POTS adolescents demonstrate a hyperkinetic circulation during exercise. We attribute this to failure of normal regional vasoconstriction during exercise, such that patients must increase flow through an inappropriately vasodilated systemic circulation to maintain perfusion pressure.

e12122

Forty percent of postural orthostatic tachycardia syndrome (POTS) adolescents who, by definition have abnormal sympathetic control of HR and BP, demonstrate a hyperkinetic circulation during exercise. We attribute this to failure of normal regional vasoconstriction during exercise, such that patients must increase flow through an inappropriately vasodilated systemic circulation to maintain perfusion pressure.

Color distribution differences in the tongue in sleep disorder

Introduction. According to traditional East Asian medicine (TEAM) theory, the tongue represents conditions of qi and blood. In the present study, the relationship between the tongue and the qi and blood in conditions with no apparent disease was investigated. Methods. A total of 454 elderly people with no apparent disease were recruited. Two Korean oriental medicine doctors classified subjects into a normal group (n = 402) and a sleep disorder group (n = 52). Three to five weeks after the experiment, 153 subjects were rerecruited for a second experiment. Two-dimensional color histograms, whose seven variables represent the color distribution in Commission Internationale de l'Éclairage 1976 (L∗, a∗, b∗) color space, were produced from tongue images. Results. The color of the tongue body in the sleep disorder group appeared paler than that in the normal group, and the tongue coating in the normal group was less widely distributed compared with that in the sleep disorder group. The differences in tongue color between the normal at first experiment and sleep disorder at second experiment conditions were similar to the differences between the normal and the sleep disorder groups. Conclusions. The tongue states in the sleep disorder group indicate a qi and blood deficiency according to TEAM theory.

Cardiac dysfunction and orthostatic intolerance in patients with myalgic encephalomyelitis and a small left ventricle

The etiology of chronic fatigue syndrome (CFS) is unknown. Myalgic encephalomyelitis (ME) has been recently postulated to be the cause of CFS. Orthostatic intolerance (OI) has been known as an important symptom in predicting quality of life in CFS patients. Cardiac function may be impaired in patients with ME. The presence or absence of OI was determined both symptomatically and by using a 10-min stand-up test in 40 ME patients. Left ventricular (LV) dimensions and function were determined echocardiographically in the ME patients compared to 40 control subjects. OI was noted in 35 (97%) of the 36 ME patients who could stand up quickly. The mean values for the cardiothoracic ratio, systemic systolic and diastolic pressures, LV end-diastolic diameter (EDD), LV end-systolic diameter, stroke volume index, cardiac index and LV mass index were all significantly smaller in the ME group than in the controls. Both a small LVEDD (<40 mm, 45 vs. 3%) and a low cardiac index (<2 l/ min/mm2, 53 vs. 8%) were significantly more common in the ME group than in the controls. Both heart rate and LV ejection fraction were similar between the groups. In conclusion, a small LV size with a low cardiac output was common in ME patients, in whom OI was extremely common. Cardiac dysfunction with a small heart appears to be related to the symptoms of ME.

Comorbidity of postural orthostatic tachycardia syndrome and chronic fatigue syndrome in an Australian cohort

OBJECTIVE

Patients with chronic fatigue syndrome (CFS) are frequently diagnosed with comorbid postural orthostatic tachycardia syndrome (POTS), suggesting a shared pathogenesis. The aim of this study was to examine the relationship between demographic characteristics, autonomic functioning and fatigue levels amongst CFS patients with and without comorbid POTS.

DESIGN AND SETTING

All patients presenting to the CFS Discovery Clinic between 2009 and 2012 completed a 20-min standing task as part of their initial assessment. Heart rate and pulse pressure were recorded at baseline, at 2-min intervals poststanding, at the end of the task and following a recovery period. Average heart rate and pulse pressure variability were calculated from this data. Age, gender, length of illness and self-reported fatigue scores were also recorded. POTS patients were diagnosed by an orthostatic increase in heart rate >30 beats per min, concomitant symptoms of orthostatic intolerance and no orthostatic hypotension. Differences in autonomic functioning between POTS and CFS patients were compared using independent samples t-tests, whilst logistic and linear regressions were performed to examine the contribution of autonomic functioning to task completion and perceived fatigue, respectively.

RESULTS

Comorbidity of CFS and POTS (CFS-POTS) was observed in 11% (33/306) of patients. CFS-POTS patients were significantly younger (P < 0.001), had a shorter length of illness (P = 0.034), experienced greater task difficulty (P = 0.002) and were able to stand for significantly shorter periods compared to the CFS-only patients (P < 0.001). CFS-POTS patients experienced significantly lower baseline diastolic blood pressure (P = 0.002), significantly higher heart rate and lower pulse pressures at each standing measurement. Early heart rate changes (P = 0.002) and overall heart rate change (P < 0.001) were significant predictors of completion status, whereas heart rate variability (P < 0.001) and female gender (P < 0.001) were significant predictors of increased perceived task difficulty.

CONCLUSIONS

Haemodynamic and demographic differences between CFS-POTS and CFS-only patients suggest that the former group reflects a distinct subgroup of the CFS population. The findings highlight the utility of screening younger patients with fatigue for POTS, and identified heart rate variability as an important marker of fatigue for CFS patients in general.

The status of and future research into Myalgic Encephalomyelitis and Chronic Fatigue Syndrome: the need of accurate diagnosis, objective assessment, and acknowledging biological and clinical subgroups

Although Myalgic Encephalomyelitis (ME) and Chronic Fatigue Syndrome (CFS) are used interchangeably, the diagnostic criteria define two distinct clinical entities. Cognitive impairment, (muscle) weakness, circulatory disturbances, marked variability of symptoms, and, above all, post-exertional malaise: a long-lasting increase of symptoms after a minor exertion, are distinctive symptoms of ME. This latter phenomenon separates ME, a neuro-immune illness, from chronic fatigue (syndrome), other disorders and deconditioning. The introduction of the label, but more importantly the diagnostic criteria for CFS have generated much confusion, mostly because chronic fatigue is a subjective and ambiguous notion. CFS was redefined in 1994 into unexplained (persistent or relapsing) chronic fatigue, accompanied by at least four out of eight symptoms, e.g., headaches and unrefreshing sleep. Most of the research into ME and/or CFS in the last decades was based upon the multivalent CFS criteria, which define a heterogeneous patient group. Due to the fact that fatigue and other symptoms are non-discriminative, subjective experiences, research has been hampered. Various authors have questioned the physiological nature of the symptoms and qualified ME/CFS as somatization. However, various typical symptoms can be assessed objectively using standardized methods. Despite subjective and unclear criteria and measures, research has observed specific abnormalities in ME/CFS repetitively, e.g., immunological abnormalities, oxidative and nitrosative stress, neurological anomalies, circulatory deficits and mitochondrial dysfunction. However, to improve future research standards and patient care, it is crucial that patients with post-exertional malaise (ME) and patients without this odd phenomenon are acknowledged as separate clinical entities that the diagnosis of ME and CFS in research and clinical practice is based upon accurate criteria and an objective assessment of characteristic symptoms, as much as possible that well-defined clinical and biological subgroups of ME and CFS patients are investigated in more detail, and that patients are monitored before, during and after interventions with objective measures and biomarkers.

The effect of fatigue and fibromyalgia on sexual dysfunction in women with chronic fatigue syndrome

Sexual dysfunction in patients with chronic fatigue syndrome is attracting growing interest but, to date, few studies have analyzed it. For this reason, the authors evaluated sexual dysfunction in women with chronic fatigue syndrome (using the Golombok Rust Inventory of Sexual Satisfaction) and explore correlations with fatigue and other symptoms. Sexual dysfunction was greater in patients with chronic fatigue syndrome (n = 615) with a higher number of cognitive, neurological, and neurovegetative symptoms, concomitant fibromyalgia, Sjögren's syndrome, or myofascial pain syndrome, and more intense fatigue (p <.05).

Discriminative validity of metabolic and workload measurements for identifying people with chronic fatigue syndrome

BACKGROUND

Reduced functional capacity and postexertion fatigue after physical activity are hallmark symptoms of chronic fatigue syndrome (CFS) and may even qualify for biomarker status. That these symptoms are often delayed may explain the equivocal results for clinical cardiopulmonary exercise testing in people with CFS. Test reproducibility in people who are healthy is well documented. Test reproducibility may not be achievable in people with CFS because of delayed symptoms.

OBJECTIVE

The objective of this study was to determine the discriminative validity of objective measurements obtained during cardiopulmonary exercise testing to distinguish participants with CFS from participants who did not have a disability but were sedentary.

DESIGN

A prospective cohort study was conducted.

METHODS

Gas exchange data, workloads, and related physiological parameters were compared in 51 participants with CFS and 10 control participants, all women, for 2 maximal exercise tests separated by 24 hours.

RESULTS

Multivariate analysis showed no significant differences between control participants and participants with CFS for test 1. However, for test 2, participants with CFS achieved significantly lower values for oxygen consumption and workload at peak exercise and at the ventilatory or anaerobic threshold. Follow-up classification analysis differentiated between groups with an overall accuracy of 95.1%.

LIMITATIONS

Only individuals with CFS who were able to undergo exercise testing were included in this study. Individuals who were unable to meet the criteria for maximal effort during both tests, were unable to complete the 2-day protocol, or displayed overt cardiovascular abnormalities were excluded from the analysis.

CONCLUSIONS

The lack of any significant differences between groups for the first exercise test would appear to support a deconditioning hypothesis for CFS symptoms. However, the results from the second test indicated the presence of CFS-related postexertion fatigue. It might be concluded that a single exercise test is insufficient to reliably demonstrate functional impairment in people with CFS. A second test might be necessary to document the atypical recovery response and protracted fatigue possibly unique to CFS, which can severely limit productivity in the home and workplace.

Multiscale analysis of heart rate variability in non-stationary environments

Heart rate variability (HRV) is highly non-stationary, even if no perturbing influences can be identified during the recording of the data. The non-stationarity becomes more profound when HRV data are measured in intrinsically non-stationary environments, such as social stress. In general, HRV data measured in such situations are more difficult to analyze than those measured in constant environments. In this paper, we analyze HRV data measured during a social stress test using two multiscale approaches, the adaptive fractal analysis (AFA) and scale-dependent Lyapunov exponent (SDLE), for the purpose of uncovering differences in HRV between chronic fatigue syndrome (CFS) patients and their matched-controls. CFS is a debilitating, heterogeneous illness with no known biomarker. HRV has shown some promise recently as a non-invasive measure of subtle physiological disturbances and trauma that are otherwise difficult to assess. If the HRV in persons with CFS are significantly different from their healthy controls, then certain cardiac irregularities may constitute good candidate biomarkers for CFS. Our multiscale analyses show that there are notable differences in HRV between CFS and their matched controls before a social stress test, but these differences seem to diminish during the test. These analyses illustrate that the two employed multiscale approaches could be useful for the analysis of HRV measured in various environments, both stationary and non-stationary.

Peripheral and central mechanisms of fatigue in inflammatory and noninflammatory rheumatic diseases

Fatigue is a common symptom in a large number of medical and psychological disorders, including many rheumatologic illnesses. A frequent question for health care providers is related to whether reported fatigue is "in the mind" or "in the body"-that is, central or peripheral. If fatigue occurs at rest without any exertion, this suggests psychological or central origins. If patients relate their fatigue mostly to physical activities, including exercise, their symptoms can be considered peripheral. However, most syndromes of fatigue seem to depend on both peripheral and central mechanisms. Sometimes, muscle biopsy with histochemistry may be necessary for the appropriate tissue diagnosis, whereas serological tests generally provide little reliable information about the origin of muscle fatigue. Muscle function and peripheral fatigue can be quantified by contractile force and action potential measurements, whereas validated questionnaires are frequently used for assessment of mental fatigue. Fatigue is a hallmark of many rheumatologic conditions, including fibromyalgia, myalgic encephalitis/chronic fatigue syndrome, rheumatoid arthritis, systemic lupus, Sjogren's syndrome, and ankylosing spondylitis. Whereas many studies have focused on disease activity as a correlate to these patients' fatigue, it has become apparent that other factors, including negative affect and pain, are some of the most powerful predictors for fatigue. Conversely, sleep problems, including insomnia, seem to be less important for fatigue. There are several effective treatment strategies available for fatigued patients with rheumatologic disorders, including pharmacological and nonpharmacological therapies.

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.

Altered immune pathway activity under exercise challenge in Gulf War Illness: an exploratory analysis

Though potentially linked to the basic physiology of stress response we still have no clear understanding of Gulf War Illness (GWI), a debilitating illness presenting with a complex constellation of immune, endocrine and neurological symptoms. Here we compared male GWI (n=20) with healthy veterans (n=22) and subjects with chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) (n=7). Blood was drawn during a Graded eXercise Test (GXT) prior to exercise, at peak effort (VO2 max) and 4-h post exercise. Affymetrix HG U133 plus 2.0 microarray gene expression profiling in peripheral blood mononuclear cells (PBMCs) was used to estimate activation of over 500 documented pathways. This was cast against ELISA-based measurement of 16 cytokines in plasma and flow cytometric assessment of lymphocyte populations and cytotoxicity. A 2-way ANOVA corrected for multiple comparisons (q statistic <0.05) indicated significant increases in neuroendocrine-immune signaling and inflammatory activity in GWI, with decreased apoptotic signaling. Conversely, cell cycle progression and immune signaling were broadly subdued in CFS. Partial correlation networks linking pathways with symptom severity via changes in immune cell abundance, function and signaling were constructed. Central to these were changes in IL-10 and CD2+ cell abundance and their link to two pathway clusters. The first consisted of pathways supporting neuronal development and migration whereas the second was related to androgen-mediated activation of NF-κB. These exploratory results suggest an over-expression of known exercise response mechanisms as well as illness-specific changes that may involve an overlapping stress-potentiated neuro-inflammatory response.