Postural orthostatic tachycardia syndrome and the potential role of mast cell activation

Mast cell activation syndrome: Current understanding and research needs

Mast cell activation syndrome (MCAS) is a term applied to several clinical entities that have gained increased attention from patients and medical providers. Although several descriptive publications about MCAS exist, there are many gaps in knowledge, resulting in confusion about this clinical syndrome. Whether MCAS is a primary syndrome or exists as a constellation of symptoms in the context of known inflammatory, allergic, or clonal disorders associated with systemic mast cell activation is not well understood. More importantly, the underlying mechanisms and pathways that lead to mast cell activation in MCAS patients remain to be elucidated. Here we summarize the known literature, identify gaps in knowledge, and highlight research needs. Covered topics include contextualization of MCAS and MCAS-like endotypes and related diagnostic evaluations; mechanistic research; management of typical and refractory symptoms; and MCAS-specific education for patients and health care providers.

Non-invasive Vagus Nerve Simulation in Postural Orthostatic Tachycardia Syndrome

Postural orthostatic tachycardia syndrome (POTS) is a chronic debilitating condition of orthostatic intolerance, predominantly affecting young females. Other than postural tachycardia, symptoms of POTS include a spectrum of non-cardiac, systemic and neuropsychiatric features. Despite the availability of widespread pharmacological and non-pharmacological therapeutic options, the management of POTS remains challenging. Exaggerated parasympathetic withdrawal and sympathetic overdrive during postural stress are principal mechanisms of postural tachycardia in POTS. Non-invasive, transcutaneous, vagus nerve stimulation (tVNS) is known to restore sympathovagal balance and is emerging as a novel therapeutic strategy in cardiovascular conditions including arrhythmias and heart failure. Furthermore, tVNS also exerts immunomodulatory and anti-inflammatory effects. This review explores the effects of tVNS on the pathophysiology of POTS and its potential as an alternative non-pharmacological option in this condition.

Postural orthostatic tachycardia syndrome and post-acute COVID-19

While the acute illness of COVID-19 was the initial focus of concern, there are increasing reports of patients with chronic symptoms, known as long-COVID. Dysautonomia may be a possible post-acute neurological complication explaining the persistent symptoms observed in long COVID. Postural tachycardia syndrome (POTS), a form of dysautonomia characterized by sustained tachycardia and orthostatic intolerance, has been increasingly reported in patients after SARS-CoV-2 infection. In this context, this review aimed to report and discuss the available literature pertaining to post COVID-19 POTS.

Postural Orthostatic Tachycardia Syndrome as a Manifestation of Post-COVID-19 Syndrome

The pandemic of coronavirus infection, the complex and insufficiently studied mechanisms of which cause disorders in the functions of many organs and systems of the body, has led to the emergence of new problems that are far from being resolved. Researchers note the difficulty in predicting the course of the disease and outcome due to the detection of many symptoms that arose at the height of the disease and persisted for 3-6 months after recovery. The term "post-COVID-19syndrome" has appeared, reflecting the condition of a patient who has undergone COVID-19, with a negative PCR test, and with symptoms lasting more than 12 weeks from the onset of the disease, which cannot be explained by an alternative diagnosis. Postural orthostatic tachycardia as a manifestation of the post-COVID-19syndrome has been described in young women who have undergone coronavirus infection of varying severity. In the case of the development of the syndrome of postural orthostatic tachycardia, the quality of life deteriorates, and the ability to work of patients is limited. There is no evidence base for drug therapy of postural tachycardia syndrome, in most cases empirical drug and non-drug methods of treatment are used.

Observational case series of postural tachycardia syndrome (PoTS) in post-COVID-19 patients

There is emerging evidence that a proportion of patients who develop long (post)-COVID-19 have abnormalities in the regulation of their autonomic nervous system manifesting as postural tachycardia syndrome (PoTS). We report a series of 14 patients who developed symptoms and signs compatible with PoTS following clinically diagnosed COVID-19 infection. Their symptoms and clinical findings were consistent with those of patients with non-COVID-related PoTS. The authors recommend an active stand test for patients who present after COVID-19 infection with cardiovascular symptoms including chest pain, palpitations, lightheadedness and breathlessness that are worse with the upright posture. They further recommend training of clinicians and investment in health services to provide for the anticipated significant increase in patients presenting with PoTS and other forms of autonomic dysfunction due to the COVID-19 pandemic.

Post-HPV-Vaccination Mast Cell Activation Syndrome: Possible Vaccine-Triggered Escalation of Undiagnosed Pre-Existing Mast Cell Disease?

For nearly a decade, case reports and series have emerged regarding dysautonomias-particularly postural orthostatic tachycardia syndrome (POTS)-presenting soon after vaccination against human papilloma virus (HPV). We too have observed a number of such cases (all following vaccination with the Gardasil product), and have found several to have detectable mast cell activation syndrome (MCAS) as well as histories suggesting that MCAS was likely present long before vaccination. We detail 11 such cases here, posing a hypothesis that HPV vaccination (at least with the Gardasil product) may have triggered or exacerbated MCAS in teenagers previously not recognized to have it. Only recently recognized, MCAS is being increasingly appreciated as a prevalent and chronic multisystem disorder, often emerging early in life and presenting with inflammatory ± allergic phenomena following from known mast cell (MC) mediator effects. There is rising recognition, too, of associations of MCAS with central and peripheral neuropathic disorders, including autonomic disorders such as POTS. Given the recognized potential for many antigens to trigger a major and permanent escalation of baseline MC misbehavior in a given MCAS patient, we hypothesize that in our patients described herein, vaccination with Gardasil may have caused pre-existing (but not yet clinically recognized) MCAS to worsen to a clinically significantly degree, with the emergence of POTS and other issues. The recognition and management of MCAS prior to vaccinations in general may be a strategy worth investigating for reducing adverse events following HPV vaccinations and perhaps even other types of vaccinations.

Mast cell activation disease and immunoglobulin deficiency in patients with hypermobile Ehlers-Danlos syndrome/hypermobility spectrum disorder

Mast cell activation disease (MCAD) includes single organ disease such as asthma, urticaria, and gastroenteritis, as well as multiorgan system involvement such as mast cell activation syndrome and anaphylaxis. Reports link MCAD with hypermobile Ehlers-Danlos syndrome (hEDS), hypermobility spectrum disorder (HSD), and with primary immune deficiencies such as complement and immunoglobulin deficiencies (Ig Def). This study assesses the concurrence of these syndromes. We undertook a cohort analysis of patients seen in a community-based Allergy/Immunology clinic from 2015 to 2019. We searched for diagnostic codes for Ig Def disorders, hypermobility syndrome, hypermobile/Ehlers-Danlos syndrome, and MCADs. Of 974 patients with suspected MCAD, 449 (46%) had a diagnosis of MCAD; 496 (51%) of cases had a combination of at least two of hEDS/HSD, MCAD, and Ig Def. Ig Def was present in 417 (43%) of patients; 188 (19.3%) had hEDS/HSD with an Ig Def with or without MCAD and accounted for 45% of all the cases with Ig Def. Of 974 cases, 101 (10%) had hEDS/HSD and MCAD; 207 (21%) had Ig Def and MCAD; 7 (0.7%) had Ig Def and hEDS/HSD; and 181 (19%) had a combination of all three syndromes. Most patients (74%) with these comorbidities were female. The presence of MCAD and Ig Def should be explored in patients with hEDS/HSD. Identifying underlying contributors to recurrent/chronic inflammation and tissue injury is needed to tailor and personalize therapies. This, in turn, can reduce tissue damage, iatrogenic intervention, and optimize health outcomes.

Mast Cell Activation Syndrome: A Primer for the Gastroenterologist

Mast cell activation syndrome is thought to be a common, yet under-recognized, chronic multi-system disorder caused by inappropriate mast cell activation. Gastrointestinal symptoms are frequently reported by these patients and are often mistaken by physicians as functional gastrointestinal disorders. This syndrome can be diagnosed by the medical history and measurable biomarkers. Gastroenterologists manage diseases associated with active inflammatory cells including neutrophils, lymphocytes, macrophages, and eosinophils. The mast cell has only recently been recognized as a major player in our specialty. Gastrointestinal disorders from mast cell mediators often present with apparent irritable bowel syndrome, dyspepsia, chronic or cyclical nausea, and heartburn. Individuals with mast cell activation syndrome experience significant delays in diagnosis. The gastrointestinal symptoms are often refractory to symptom-targeted prescription medications. Beyond avoiding triggers, the best therapy is directed at modulating mast cell activation and the effects of the mediators. Many of these therapies are simple over-the-counter medications. In this article, we review mast cell function and dysfunction and the gastrointestinal symptoms, comorbid conditions, diagnosis, and management of mast cell activation syndrome. Gastroenterologists who become aware of this syndrome can dramatically improve the quality of life for their patients who previously have been labeled with a functional gastrointestinal disorder.

Observational case series describing features of cardiopulmonary exercise testing in Postural Tachycardia Syndrome (PoTS)

Postural Tachycardia Syndrome (PoTS) is a chronic condition often affecting multiple systems with varied presenting symptoms. Diagnosis is made by demonstrating cardiovascular criteria on standing along with clinical assessment. Cardiopulmonary exercise testing has been used to demonstrate and characterise the physiological response to exercise and the severity of the syndrome. Previous studies on exercise testing in these patients have focussed on cardiovascular changes alone. This series characterises the integrated cardiac and respiratory response to exercise seen with cardiopulmonary exercise testing. Our main findings show that peak oxygen uptake, work done and peak heart rate are significantly reduced from their respective predicted values in PoTS patients. However, despite this, most patients demonstrated a normal exercise capacity. Features of ventilatory inefficiency were also seen which suggest exercise capacity in these patients may be limited more by impaired ventilatory control such as dysfunctional breathing during exercise rather than by cardiovascular issues.

Joint Hypermobility Syndrome in Patients With Functional Dyspepsia

INTRODUCTION:

The pathophysiology underlying functional dyspepsia (FD) is multifactorial and focuses on gastric sensorimotor dysfunction. Recent studies demonstrated that joint hypermobility syndrome (JHS) is strongly associated with unexplained dyspeptic symptoms in patients attending gastrointestinal clinics. We aimed to study the relationship between symptoms, gastric sensorimotor function, and JHS in FD patients.

METHODS:

Tertiary care FD patients who underwent a gastric barostat study and a gastric emptying breath test with 13C-octanoic acid were recruited for assessment of JHS. The presence of JHS was evaluated by a 2-phase interview and clinical examination that included major and minor criteria of the Brighton classification.

RESULTS:

A total of 62 FD patients (68% women, age 44 ± 1.8 years, and body mass index: 21.7 ± 0.7 kg/m²) accepted to participate in the study. JHS was diagnosed in 55% of FD patients. Assessed symptom profiles during the visit did not differ between the groups. Delayed gastric emptying was not significantly more common in JHS group compared with non-JHS group (JHS group 32% vs non-JHS group 16%, P = 0.31). Prevalence of hypersensitivity to distention (JHS group 24% vs non-JHS group 29%, P = 0.76) and impaired gastric accommodation (JHS group 38% vs non-JHS group 42%, P = 0.79) was similar in patients with or without JHS. No correlations were found between the Beighton hypermobility score and gastric compliance (r = 0.09).

DISCUSSION:

A large subset of this study cohort of tertiary care FD patients has coexisting JHS. We did not identify any specific differences in gastric sensorimotor function between patients with and without JHS. Further prospective research will be required to elucidate the relationship between JHS, a multisystemic disorder with widespread manifestations, and FD symptoms.

Mechanisms and management of gastrointestinal symptoms in postural orthostatic tachycardia syndrome

Postural orthostatic tachycardia syndrome (POTS) is a disorder of orthostatic intolerance associated with many GI manifestations that can be broadly classified into two different categories: those present all the time (non-positional) and those that occur with orthostatic position change. There are also many conditions that can co-exist with POTS such as mast cell activation syndrome and the hypermobile form of Ehlers-Danlos syndrome (hEDS) that are also oftentimes associated with GI symptoms. In the current issue of Neurogastroenterology and Motility, Tai et al. explored the relationship between functional GI disorders among hEDS patients with and without concomitant POTS and showed that the hEDS-POTS cohort was more likely to have more than one GI organ involved compared to the cohort with hEDS alone, and certain GI symptoms were also more common in the hEDS-POTS cohort. In this review article, we will briefly review the literature surrounding putative mechanisms responsible for GI symptoms in POTS with an emphasis on the contributory role of concomitant hEDS and then discuss management strategies for GI symptoms in POTS.

Risk Factors for Orthostatic Hypertension in Children

OBJECTIVE

To investigate the risk factors for orthostatic hypertension in children.

STUDY DESIGN

Eighty children with orthostatic hypertension were enrolled in the group with orthostatic hypertension, and 51 healthy children served as the control group. Demographic characteristics, clinical history, daily water intake, nightly sleep duration, the results of the standing test, and complete blood count were recorded and compared between the 2 groups. The risk factors for pediatric orthostatic hypertension were determined by logistic regression analysis.

RESULTS

Body mass index and red blood cell distribution width were higher in the group with orthostatic hypertension than in healthy children, whereas daily water intake and sleep duration were lower. Logistic regression analyses showed that, if a child suffered from overweight, suffered from obesity, had a daily water intake of less than 800 mL, or had a red blood cell distribution width that was increased by 1%, the risk of orthostatic hypertension would be increased by 6.069 times (95% CI, 1.375-26.783; P < .05), 7.482 times (95% CI, 1.835-30.515; P < .01), 4.027 times (95% CI, 1.443-11.241; P < .01), or 4.008 times (95% CI, 1.698-9.461; P < .01), respectively. However, if the sleep duration was increased by 1 hour, the risk of developing orthostatic hypertension would be decreased by 74.3% (95% CI, 54.6%-85.4%, P < .01).

CONCLUSIONS

Increased body mass index, inadequate water intake and sleep duration, and elevated red blood cell distribution width were identified as risk factors for pediatric orthostatic hypertension.

Postural Tachycardia Syndrome in Children and Adolescents: Pathophysiology and Clinical Management

Postural tachycardia syndrome (POTS), characterized by chronic (≥6 months) orthostatic intolerance symptoms with a sustained and excessive heart rate increase while standing without postural hypotension, is common in children and adolescents. Despite the unclear pathogenesis of POTS, the present opinion is that POTS is a heterogeneous and multifactorial disorder that includes altered central blood volume, abnormal autonomic reflexes, "hyperadrenergic" status, damaged skeletal muscle pump activity, abnormal local vascular tension and vasoactive factor release, mast cell activation, iron insufficiency, and autoimmune dysfunction. A number of pediatric POTS patients are affected by more than one of these pathophysiological mechanisms. Therefore, individualized treatment strategies are initiated in the management of POTS, including basal non-pharmacological approaches (e.g., health education, the avoidance of triggers, exercise, or supplementation with water and salt) and special pharmacological therapies (e.g., oral rehydration salts, midodrine hydrochloride, and metoprolol). As such, the recent progress in the pathogenesis, management strategies, and therapeutic response predictors of pediatric POTS are reviewed here.

Frequency and severity of autonomic symptoms in idiopathic hypersomnia

STUDY OBJECTIVES

We aimed to quantify the symptoms of autonomic nervous system dysfunction in a large online cohort of patients with idiopathic hypersomnia, and to determine how the severity of these symptoms interacts with sleepiness, fatigue, and quality of life.

METHODS

One hundred thirty-eight patients with idiopathic hypersomnia and 81 age- and sex-matched controls were recruited through the website of the Hypersomnia Foundation, a US-based patient advocacy group. Twenty-four patients with confirmed idiopathic hypersomnia were selected by the study investigators as a comparison group. All participants completed a battery of online sleep, autonomic, and quality of life questionnaires including the composite autonomic symptom score-31 (COMPASS-31).

RESULTS

Online and confirmed patients reported significantly higher COMPASS-31 scores (median [interquartile range]) (43.6 [33.6-52.7] and 32.9 [21.7-46.8] vs 17.6 [11.7-27.9], P < .001), with the greatest symptom burden in the orthostatic and vasomotor domains. Online and confirmed patients reported more sleepiness (Epworth sleepiness scale), whereas only online patients reported more fatigue (Chalder fatigue scale). Both the Epworth sleepiness scale and Chalder fatigue scale positively correlated with COMPASS-31 scores. Patients reported lower quality of life as reflected by lower scores across all domains of the RAND 36-item health survey, which was negatively correlated with COMPASS-31 scores.

CONCLUSIONS

Symptoms of autonomic nervous system dysfunction are common in idiopathic hypersomnia. In addition, autonomic nervous system symptom burden was positively correlated with sleepiness and negatively correlated with quality of life.

Postural Orthostatic Tachycardia Syndrome: Mechanisms and New Therapies

Postural orthostatic tachycardia syndrome (POTS) is a clinically heterogeneous disorder with multiple contributing pathophysiologic mechanisms manifesting as symptoms of orthostatic intolerance in the setting of orthostatic tachycardia (increase in heart rate by at least 30 beats per minute upon assuming an upright position) without orthostatic hypotension. The three major pathophysiologic mechanisms include partial autonomic neuropathy, hypovolemia, and hyperadrenergic state. Patients often will exhibit overlapping characteristics from more than one of these mechanisms. The approach to the treatment of POTS centers on treating the underlying pathophysiologic mechanism. Stockings, abdominal binders, and vasoconstrictors are used to enhance venous return in partial neuropathic POTS. Exercise and volume expansion are the main treatment strategies for hypo-volemic POTS. For hyperadrenergic POTS, beta-blockers and avoidance of norepinephrine reuptake inhibitors is important. Attempts should be made to discern which pathophysiologic mechanism(s) may be afflicting patients so that treatment regimens can be individualized.

Restless legs syndrome is associated with mast cell activation syndrome

STUDY OBJECTIVES

Mast cell activation syndrome (MCAS) is an inflammatory and allergic disorder. We determined the prevalence of restless legs syndrome (RLS) in MCAS because each common syndrome may be inflammatory in nature and associated with dysautonomia.

METHODS

Individuals with MCAS were evaluated for RLS by two standard questionnaires. Prevalence comparisons included spouse control patients and two prevalence publications. MCAS diagnosis required mast cell (MC) symptoms in ≥ 2 organs plus ≥ 1 elevated MC mediators, improvement with MC therapy, and/or increased intestinal MC density. Clinical variables were studied.

RESULTS

There were 174 patients with MCAS (146 female, 28 male, mean age 44.8 years) and 85 spouse control patients (12 female, 73 male, mean age 50.9 years). Patients with MCAS as a whole had a higher prevalence of RLS (40.8%) than spouse control (12.9%) (P < .0001) Male patients with MCAS had a higher prevalence of RLS (32.1%) than male controls (12.3%, odds ratio [OR] 3.4, confidence interval [CI] 1.2-9.7, P = .025), American men (8.4%, OR 5.2, CI 2.2-12.0, P < .001), and French men (5.8%, OR 7.7, CI 3.4-17.1, P < .001). Female patients with MCAS also had a higher prevalence of RLS (42.5%) than female controls (16.7%) but this did not reach statistical significance perhaps because of the sample size of the female controls. However, female patients with MCAS had a statistically higher prevalence of RLS than American women (10.0%, OR 6.7, CI 4.5-9.7, P < .0001) and French women (10.8%, OR 6.1, CI 4.4-8.6, P < .0001).

CONCLUSIONS

RLS appears to be associated with MCAS. Effects of mast cell mediators, inflammation, immune mechanisms, dysautonomia, or hypoxia may theoretically activate RLS in MCAS.