The relationship between cardiovagal baroreflex and cerebral autoregulation in postural orthostatic tachycardia disorder using advanced cross-correlation function.

Postural orthostatic tachycardia syndrome (POTS) presents excessive orthostatic tachycardia and orthostatic intolerance. POTS is a common and therapeutically challenging condition affecting numerous people worldwide. As many disease entities can be confused with POTS, it becomes critical to identify this syndrome. Moreover, unbalanced autonomic nervous activity can induce cardiovascular diseases and influence the bio-feedback mechanism: Baroreflex (BR) and cerebral autoregulation (CA). BR and CA are important bio-mechanisms that maintain a stable circulatory system via the autonomic nervous system. Therefore, an impaired autonomic nervous system would lead to imbalanced BRS and CA. Consequently, we propose an advanced cross-correlation function (ACCF) time-domain approach to analyze baroreflex and cerebral autoregulation using physiological signals. This study assesses relation changes in BR and CA using ACCF in POTS for early clinical detection and diagnosis. The ACCF analysis results has thresholds that reveal that the BR of healthy and POTS groups present significantly different maximum CCF values (p < 0.05). The complete CCF index shows that the BR phase changes significantly into phase lag in the POTS group. Although CA analysis using the maximum CCF index was mildly weak, it did not differ in the POTS group. Thus, POTS only affects BR. An increasing sympathetic activity might induce an unbalanced baroreflex effect and increase cerebral vasomotor tone with CA. Maximum CCF value correlation coefficients between BR and CA indicated positive in POTS groups and negative in the healthy group. It could be speculated that the sympathetic nervous system compensates to improve BR function, which remains CA function. The advantage of this ACCF algorithm is that it helps observe BR and CA for early detection.

Palmitoylation regulates norepinephrine transporter uptake, surface localization, and total expression with pathogenic implications in postural orthostatic tachycardia syndrome.

Postural orthostatic tachycardia syndrome (POTS) is an adrenergic signaling disorder characterized by excessive plasma norepinephrine, postural tachycardia, and syncope. The norepinephrine transporter (NET) modulates adrenergic homeostasis via the reuptake of extracellular catecholamines and is implicated in the pathogenesis of adrenergic and neurological disorders. In this study, we reveal NET is palmitoylated in male Sprague-Dawley rats and Lilly Laboratory Cell Porcine Kidney (LLC-PK1) cells. S-palmitoylation, or the addition of a 16-carbon saturated fatty acid, is a reversible post-translational modification responsible for the regulation of numerous biological mechanisms. We found that LLC-PK1 NET is dynamically palmitoylated, and that inhibition with the palmitoyl acyltransferase (DHHC) inhibitor, 2-bromopalmitate (2BP) results in decreased NET palmitoylation within 90 min of treatment. This result was followed closely by a reduction in transport capacity, cell surface, and total cellular NET expression after 120 min of treatment. Increasing 2BP concentrations and treatment time revealed a nearly complete loss of total NET protein. Co-expression with individual DHHCs revealed a single DHHC enzyme, DHHC1, promoted wild-type (WT) hNET palmitoylation and elevated NET protein levels. The POTS-associated NET mutant, A457P, exhibits dramatically decreased transport capacity and cell surface levels which we have confirmed in the current study. In an attempt to recover A457P NET expression, we co-expressed the A457P variant with DHHC1 to drive expression as seen with the WT protein but instead saw an increase in NET N-terminal immuno-detectable forms and fragments. Elimination of a potential palmitoylation site at cysteine 44 in the N-terminal tail of hNET resulted in a low expression phenotype mimicking the A457P hNET variant. Further investigation of A457P NET palmitoylation and surface expression is necessary, but our preliminary novel findings reveal palmitoylation as a mechanism of NET regulation and suggest that dysregulation of this process may contribute to the pathogenesis of adrenergic disorders like POTS.

The Prevalence of Anxiety and Depression in Children With Postural Orthostatic Tachycardia Syndrome (POTS): A Retrospective Study.

INTRODUCTION: Postural orthostatic tachycardia syndrome (POTS) is a chronic form of orthostatic intolerance characterized by various symptoms such as dizziness, lightheadedness, and increased heart rate. Conflicting reports exist regarding the prevalence of anxiety and depression in adults with POTS, while data on pediatric POTS remains scarce. METHOD: A retrospective analysis of pediatric patients aged 11-17 years with POTS, who underwent autonomic testing at Nemours Children's Hospital in Orlando, Florida, was conducted. The patients were screened for anxiety, using the Severity Measure for Generalized Anxiety Disorder-Child Age 11-17 years (GAD-7) questionnaire, and depression, using PHQ-9 Modified for Adolescence (PHQ-A) for depression. The prevalence rates of anxiety and depression in the study cohort were compared to historical data from similar age groups in the existing literature. The study was approved by the Nemours Children's Hospital Institutional Review Board. RESULTS: The cohort comprised 27 children with POTS (26 females, age 15.8±1.6 years). Overall, 74% exhibited moderate-to-severe anxiety, depression, or both, with 44% having comorbid anxiety and depression. In total, 4/27 (14%) had pure depression and 4/27 (14%) had pure anxiety. Six patients had no depression or anxiety. On average, POTS symptoms began 1.9±1.3 years before diagnosis. Eleven patients took stable doses of psychotropic medications. After a follow-up period of 5.1±1.7 months of POTS therapy, seven patients had follow-up questionnaires. In 4/7 patients, the depression severity improved, and in 3/7 patients, the anxiety severity improved. Patients were not actively treated for depression and anxiety during this time. CONCLUSION: Anxiety and depression are prevalent among pediatric patients with POTS. While preliminary data suggests POTS therapy may alleviate these psychological symptoms, further longitudinal studies are warranted to explore the therapeutic impact in greater detail.

Complication Avoidance in Chiari Malformation Surgery.

Posterior fossa decompression for symptomatic Chiari malformation is an effective and frequently performed procedure, but it does carry risks of significant complications including cerebrospinal fluid leak and craniocervical instability. Patients sometimes do not improve or worsen after decompression, which may discourage neurosurgeons from performing Chiari decompression surgery. In this chapter, management strategies and surgical approaches are discussed that minimize the risks of complications and maximize favorable outcomes in Chiari malformation surgery.

Reduced Stroke Volume and Brain Perfusion Drive Postural Hyperventilation in Postural Orthostatic Tachycardia Syndrome.

Postural hyperventilation has been implicated as a cause of postural orthostatic tachycardia syndrome (POTS), yet the precise mechanisms underlying the heightened breathing response remain unclear. This study challenges current hypotheses by revealing that exaggerated peripheral chemoreceptor activity is not the primary driver of postural hyperventilation. Instead, significant contributions from reduced stroke volume and compromised brain perfusion during orthostatic stress were identified. These findings shed light on our understanding of POTS pathophysiology, emphasizing the critical roles of systemic hemodynamic status. Further research should explore interventions targeting stroke volume and brain perfusion for more effective clinical management of POTS.

An overview of Ehlers Danlos syndrome and the link between postural orthostatic tachycardia syndrome and gastrointestinal symptoms with a focus on gastroparesis.

There has been an increasingly reported association between Ehlers-Danlos syndrome (EDS), postural orthostatic tachycardia syndrome (POTS) and gastrointestinal disorders. EDS is a hereditary connective tissue disorder which may manifest as a spectrum of symptoms stemming from collagen defects. The prevalence of EDS is estimated to affect 1 in 5000 individuals which underscores its clinical significance. Notably the hypermobile form (hEDS) accounts for the majority of cases. POTS is characterized by orthostatic intolerance with an increase in heart rate on standing in the absence of hypotension. This condition predominantly affects women between 15 and 45 years of age. Gastrointestinal symptoms in the form of reflux, bloating and abdominal pain significant impact this population. Gastroparesis is a chronic disorder involving symptoms of delayed gastric emptying and may be closely associated with hEDS and POTS, and may be underreported. Autonomic dysfunction associated with hEDS has been proposed as the likely mechanism underlying POTS and gastrointestinal dysfunction though a clear pathophysiological process has not been established.

Long COVID and hypermobility spectrum disorders have shared pathophysiology.

Hypermobility spectrum disorders (HSD) and hypermobile Ehlers-Danlos syndrome (hEDS) are the most common joint hypermobility conditions encountered by physicians, with hypermobile and classical EDS accounting for >90% of all cases. Hypermobility has been detected in up to 30-57% of patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), fibromyalgia, postural orthostatic tachycardia syndrome (POTS), and long COVID (LC) compared to the general population. Extrapulmonary symptoms, including musculoskeletal pain, dysautonomia disorders, cognitive disorders, and fatigue, are seen in both LC and HSD. Additionally, ME/CFS has overlapping symptoms with those seen in HSD. Mast cell activation and degranulation occurring in both LC and ME/CFS may result in hyperinflammation and damage to connective tissue in these patients, thereby inducing hypermobility. Persistent inflammation may result in the development or worsening of HSD. Hence, screening for hypermobility and other related conditions including fibromyalgia, POTS, ME/CFS, chronic pain conditions, joint pain, and myalgia is essential for individuals experiencing LC. Pharmacological treatments should be symptom-focused and geared to a patient's presentation. Paced exercise, massage, yoga, and meditation may also provide benefits.

Improving quality in adult long covid services: Findings from the LOCOMOTION quality improvement collaborative.

The protracted form of COVID-19 known as 'long covid' was first described in 2020. Its symptoms, course and prognosis vary widely; some patients have a multi-system, disabling and prolonged illness. In 2021, ring-fenced funding was provided to establish 90 long covid clinics in England; some clinics were also established in Scotland and Wales. The NIHR-funded LOCOMOTION project implemented a UK-wide quality improvement collaborative involving ten of these clinics, which ran from 2021 to 2023. At regular online meetings held approximately 8-weekly, participants prioritised topics, discussed research evidence and guidelines, and presented exemplar case histories and clinic audits. A patient advisory group also held a priority-setting exercise, participated in quality meetings and undertook a service evaluation audit. The goal of successive quality improvement cycles aimed at changing practice to align with evidence was sometimes hard to achieve because definitive evidence did not yet exist in this new condition; many patients had comorbidities; and clinics were practically constrained in various ways. Nevertheless, much progress was made and a series of 'best practice' guides was produced, covering general assessment and management; breathing difficulties; orthostatic tachycardia and other autonomic symptoms; fatigue and cognitive impairment; and vocational rehabilitation. This paper summarises key findings with the frontline clinician in mind.

Hyperadrenergic Postural Tachycardia Syndrome: Clinical Biomarkers and Response to Guanfacine.

BACKGROUND: A subset of patients with postural tachycardia syndrome (POTS) are thought to have a primary hyperadrenergic cause. We assessed clinical biomarkers to identify those that would benefit from sympatholytic therapy. METHODS: We measured sympathetic function (supine muscle sympathetic nerve activity, upright plasma norepinephrine, and blood pressure responses to the Valsalva maneuver) in 28 patients with POTS (phenotyping cohort) to identify clinical biomarkers that are associated with responsiveness to the central sympatholytic guanfacine in a separate uncontrolled treatment cohort of 38 patients that had received guanfacine clinically for suspected hyperadrenergic POTS (HyperPOTS). RESULTS: In the phenotyping cohort, an increase in diastolic blood pressure (DBP) >17 mm Hg during late phase 2 of the Valsalva maneuver identified patients with the highest quartile of resting muscle sympathetic nerve activity (HyperPOTS) with 71% sensitivity and 85% specificity. In the treatment cohort, patients with HyperPOTS, identified by this clinical biomarker, more often reported clinical improvement (85% versus 44% in nonhyperadrenergic; P=0.016), had better orthostatic tolerance (∆Orthostatic Hypotension Daily Activities Scale: -1.9±0.9 versus 0.1±0.5; P=0.032), and reported less chronic fatigue (∆PROMIS Fatigue Short Form 7a: -12.9±2.7 versus -2.2±2.2; P=0.005) in response to guanfacine. CONCLUSIONS: These results are consistent with the concept that POTS is caused by a central sympathetic activation in a subset of patients, which can be identified clinically by an exaggerated DBP increase during phase 2 of the Valsalva maneuver and improved by central sympatholytic therapy. These results support further clinical trials to determine the safety and efficacy of guanfacine in patients with POTS enriched for the presence of this clinical biomarker.

The Suggested Relationships Between Common GI Symptoms and Joint Hypermobility, POTS, and MCAS.

An increasing number of reports suggest an association between a newly recognized disease cluster and significant and often disabling gastrointestinal (GI) symptoms. This cluster is composed of diagnoses of hypermobility spectrum disorders (HSDs) such as joint hypermobility and hypermobile variant Ehlers-Danlos syndrome (hEDS), postural orthostatic tachycardia syndrome (POTS), and mast cell activation syndrome (MCAS). The diagnosis of these entities remains a challenge, as the pathophysiology of each has not been completely elucidated and the diagnostic criteria continue to evolve. This article describes a cohort of young adult females who shared similar GI symptoms, with intractable nausea and vomiting being most prominent and gastroesophageal reflux disease and constipation also occurring. Most strikingly, these females also exhibited or reported a history of HSD, hEDS, POTS, and/or MCAS. The clinical course of their GI symptoms was remarkable for considerable challenges in management, and artificial nutritional support proved necessary for some. This article describes the clinical features and outcomes of their GI manifestations, examines how these manifestations might be linked to their systemic syndromes, and discusses whether a shared pathophysiology exists. Pending the definition of a common thread between these conditions, this article seeks to raise awareness of their clinical definitions and foster research that will hopefully improve outcomes for these patients.

Postural Orthostatic Tachycardia Syndrome Associated with COVID-19: A Narrative Review.

Postural orthostatic tachycardia syndrome (POTS) is a complex condition marked by an atypical autonomic response to standing, leading to orthostatic intolerance and significant tachycardia without accompanying hypotension. In recent studies, a considerable number of individuals recovering from COVID-19 have been reported to experience POTS within 6 to 8 months post-infection. Key symptoms of POTS include fatigue, difficulty with orthostatic tolerance, tachycardia, and cognitive challenges. The underlying causes of POTS following COVID-19 remain unknown, with various theories proposed such as renin-angiotensin-aldosterone system (RAAS) dysregulation, hyperadrenergic reaction, and direct viral infection. Healthcare professionals should be vigilant for POTS in patients who have recovered from COVID-19 and are experiencing signs of autonomic dysfunction and use diagnostic procedures such as the tilt-up table test for confirmation. COVID-19-related POTS should be approached with a holistic strategy. Although many patients show improvement with initial non-drug treatments, for subjects who do not respond and exhibit more severe symptoms, medication-based therapies may be necessary. The current understanding of COVID-19-related POTS is limited, underscoring the need for more research to increase knowledge and enhance treatment approaches.

Evaluation of the relationship between mast cell activation and postural orthostatic tachycardia syndrome in children and adolescents.

OBJECTIVE: Postural orthostatic tachycardia syndrome (POTS) is one of the orthostatic intolerance syndromes that are common in young adolescents and impair quality of life. POTS is a multi-systemic disease. Many mechanisms have been defined in POTS etiology, such as autonomic denervation, hypovolemia, hyperadrenergic stimulation, low condition, and hypervigilance. Recently, mast cell activation (MCA) has also been on the agenda in etiology. There are few studies in the literature on the relationship between MCA and POTS in adulthood. However, data on children and adolescents is limited. In light of this information, we aimed to evaluate the relationship between POTS and MCA by measuring serum tryptase levels, a specific marker for MCA. METHODS: This prospective study included patients who were admitted to Kocaeli University Faculty of Medicine Hospital Pediatric Cardiology outpatient clinic for syncope-presyncope between November 2018 and August 2019. Patients who underwent the TILT-table test were enrolled in the study. Patients with structural heart disease or chronic heart disease were not included in this study. Serum tryptase levels were obtained from all patients before the TILT-table test, and serum tryptase levels were re-studied after the test was terminated in patients with positive TILT-table tests for POTS. Patients diagnosed with POTS were classified as Group 1, and other patients were classified as Group 2. RESULTS: Twenty-eight of the 58 patients included in the study (mean: 14.4±2.0 years; 38 girls, 20 boys) were diagnosed with POTS. The remaining 30 patients were diagnosed with vasovagal syncope and included in Group 2. The increase in mean heart rate during the test was 38±6 beats/min and 47.05%±15.65% in patients with POTS. Basal serum tryptase levels were not different between groups (3.2±1.3 ng/ml and 3.84±1.78 ng/ml, respectively; p=0.129), while serum tryptase levels (both baseline and after 45-60 min of the TILT-table test) were higher in patients presenting with symptoms related to MCA compared to others. CONCLUSION: In the literature, MCA was considered to be one of the mechanisms leading to POTS. Although other mechanisms, such as neuropathic and hypovolemic POTS, may be active in the patients, the symptoms of MCA in these patients should be routinely questioned.

Orthostatic Intolerance in Children With Long COVID Utilizing a 10-Minute Passive Standing Test.

Despite there being a wide variety of symptoms reported in pediatric long COVID, one condition that has become increasingly recognized is orthostatic intolerance (OI), which can cause significant morbidity, limiting activities of daily living. This study examines rates of OI in 92 children with long COVID who underwent a bedside passive standing test in a pediatric post-COVID-19 rehabilitation clinic. Seventy-one percent met criteria for an orthostatic condition, including postural orthostatic tachycardia syndrome (POTS), orthostatic tachycardia (OT), classic orthostatic hypotension (OH), delayed OH, and orthostatic hypertension. Our findings suggest that OI is common in pediatric long COVID, necessitating appropriate clinical screening and treatment.

Nonpelvic comorbid symptoms of 45 patients with pain of pelvic venous origin, before and after treatment.

OBJECTIVE: To report the prevalence and severity of nonpelvic symptoms for patients with venous-origin chronic pelvic pain (VO-CPP) and to describe outcomes after pelvic vein stenting and embolization. METHODS: We retrospectively reviewed outcomes of 45 women with VO-CPP who underwent treatment with iliac vein stenting and/or embolization. Patients completed symptom-severity questionnaires before and after treatment that assessed for pelvic pain, and multiple other symptoms, including brain fog, anxiety, depression, musculoskeletal pain, fatigue, migraines and more. RESULTS: Patient age ranged from 18 to 65 years. The prevalence of common symptoms was as follows: migraines, 69%; brain fog, 76%; anxiety attacks, 58%; excess sweating, 64%; hip pain, 73%; diarrhea, 62%; constipation, 76%; and abdominal bloating, 82%. After treatment, most symptom scores improved by more than 50%; exceptions were excessive sweating (41% improvement) and bloating (47% improvement). Prevalence of individual symptoms that bundle into POTS ranged from 29% to 76%, where symptom improvement ranged from 23% to 59% after treatment. Overlapping individual symptoms characteristic of fibromyalgia and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) were present in 64% to 82% of patients and all improved by 49% to 63% after treatment. CONCLUSIONS: Pelvic venous flow abnormality is linked causally to a spectrum of interrelated symptoms, of which many can be bundled into named syndromes of unknown cause. With catheter- based treatment of pelvic venous pooling, nonpelvic symptom and syndrome scores improved.

Suspected Diphtheria Toxoid and Tetanus Toxoid (dTdap) Booster Vaccine-Induced Postural Orthostatic Tachycardia Syndrome (POTS).

We describe a case of a 40-year-old South Asian woman who presented with symptoms suggestive of postural orthostatic tachycardia syndrome (POTS) following a diphtheria toxoid and tetanus toxoid (dTdap) booster vaccination administered one week prior. The patient's POTS responded favorably to treatment with low-dose fludrocortisone and ivabradine. Clinicians should maintain a high index of suspicion for POTS as a possible vaccine adverse event (VAE) post-dTdap booster inoculation and be aware of appropriate management strategies.

Elevated total serum IgM predicts the presence of antiphospholipid antibodies in dysautonomia patients.

Dysautonomia is an abnormal clinical state with multiple etiologies, including autoimmunity. Antiphospholipid antibodies (aPL) are among the autoantibodies that have been associated with autonomic dysfunction. We have observed that an elevated total serum IgM appears to be associated with the presence of aPL in dysautonomia patients. This is a retrospective study analyzing the clinical characteristics of 45 consecutive patients with cardiac autonomic dysfunction and a persistently elevated total serum IgM. 93% of patients were female with a mean age of 32.7 years. Most patients had severely disabling disease, with a mean Karnofsky-like functional ability score of 42% (normal 100%). 93% of patients tested persistently positive for one or more aPL and all patients tested persistently positive for aPL and/or Sjogren's antibodies. No patient had lupus specific antibodies. One third of patients experienced one or more thrombotic events and 58% of patients attempting pregnancy experienced pregnancy morbidity. Lastly, 78% of aPL-positive patients treated with antithrombotic therapy experienced 50 to 100% improvement in one or more symptoms (e.g., migraine, cognitive dysfunction) recognized to be responsive to antithrombotic therapy in a subset of aPL-positive patients and 73% of patients treated with and tolerating immune modulatory therapy experienced a positive response. We propose total serum IgM as a reliable and inexpensive test that can be used to identify dysautonomia patients at risk for persistent aPL-positivity. These patients are important to identify as they have a significant risk for thrombosis and pregnancy morbidity and often experience significant symptomatic improvement with antithrombotic therapy and/or immune modulatory therapy.