Postural Orthostatic Tachycardia Syndrome (POTS): A critical assessment

Cardiovascular autonomic dysfunction in post-COVID-19 syndrome: a major health-care burden

Cardiovascular autonomic dysfunction (CVAD) is a malfunction of the cardiovascular system caused by deranged autonomic control of circulatory homeostasis. CVAD is an important component of post-COVID-19 syndrome, also termed long COVID, and might affect one-third of highly symptomatic patients with COVID-19. The effects of CVAD can be seen at both the whole-body level, with impairment of heart rate and blood pressure control, and in specific body regions, typically manifesting as microvascular dysfunction. Many severely affected patients with long COVID meet the diagnostic criteria for two common presentations of CVAD: postural orthostatic tachycardia syndrome and inappropriate sinus tachycardia. CVAD can also manifest as disorders associated with hypotension, such as orthostatic or postprandial hypotension, and recurrent reflex syncope. Advances in research, accelerated by the COVID-19 pandemic, have identified new potential pathophysiological mechanisms, diagnostic methods and therapeutic targets in CVAD. For clinicians who daily see patients with CVAD, knowledge of its symptomatology, detection and appropriate management is more important than ever. In this Review, we define CVAD and its major forms that are encountered in post-COVID-19 syndrome, describe possible CVAD aetiologies, and discuss how CVAD, as a component of post-COVID-19 syndrome, can be diagnosed and managed. Moreover, we outline directions for future research to discover more efficient ways to cope with this prevalent and long-lasting condition.

Small fiber neuropathy in children, adolescents, and young adults with chronic orthostatic intolerance and postural orthostatic tachycardia syndrome: A retrospective study

PURPOSE

To determine in children, adolescent and young adult (CAYA) patients presenting with Orthostatic Intolerance (OI) or Postural Orthostatic Tachycardia Syndrome (POTS) associated with the additional symptoms of neuropathic discomfort (pain, paresthesia and/or allodynia): 1) the incidence of small fiber neuropathy, and 2) assess if there was serologic evidence for an underlying inflammatory or autoimmune state.

METHODS

A cohort of 109 CAYA patients with the above symptoms underwent epidermal skin biopsy for nerve fiber density. Blood biomarkers for inflammation were tested (CRP, ESR, ANA, complement (C3), thyroid function testing with antibodies (thyroid peroxidase antibody and thyroglobulin antibody), and cytokine panel 13). Patients completed a Quality of Health questionnaire. Statistical analysis was performed using Wilcoxon rank sum tests.

RESULTS

In CAYA patients with OI or POTS and neuropathic symptoms, skin biopsy for small fiber neuropathy was abnormal in 53 %. The sample population was predominantly female and Caucasian with moderately decreased perceived quality of health. OI /POTS patients with small fiber neuropathy had a 3-fold probability of having a positive ANA or anti-thyroid antibody, suggesting an underlying autoimmune or inflammatory process.

CONCLUSION

Our data suggest a link between OI and POTS and small fiber neuropathy. Small fiber neuropathy was found by skin biopsy in over half of the patients tested. OI and Postural orthostatic tachycardia patients with small fiber neuropathy expressed multiple markers suggesting an underlying autoimmune or inflammatory process. Future research will be done to evaluate the symptomatic implication of SFN and whether immune or pharmacologic manipulation can alter patient symptoms.

Post-COVID postural orthostatic tachycardia syndrome (POTS): a new phenomenon

Background

The impact of COVID-19 has been far-reaching, and the field of neurology is no exception. Due to the long-hauler effect, a variety of chronic health consequences have occurred for some post-COVID patients. A subset of these long-hauler patients experienced symptoms of autonomic dysfunction and tested positive for postural orthostatic tachycardia syndrome (POTS) via autonomic testing.

Methods

We conducted a chart review of a convenience sample from patients seen by neurologists at our tertiary care center for suspicion of post-COVID POTS. Patients included in our study had clearly defined POTS based on clinical criteria and positive tilt table test, were 81.25% female, and had an average age of approximately 36. Out of 16 patients, 12 had a confirmed positive COVID test result, with the remaining 4 having strong clinical suspicion for COVID infection. Our analysis examined the most bothersome 3 symptoms affecting each patient per the neurologist's note at their initial visit for post-COVID POTS, clinical presentation, comorbidities, neurological exam findings, autonomic testing results, and COMPASS-31 autonomic questionnaire and PROMIS fatigue survey results.

Results

Palpitations (68.75%) and fatigue (62.5%) were the most common of the impactful symptoms reported by patients in their initial Cleveland Clinic neurology visit. The most frequent comorbidities in our sample were chronic migraines (37.5%), irritable bowel syndrome (IBS) (18.75%), and Raynaud's (18.75%). Neurological exam findings and autonomic testing results other than tilt table yielded variable findings without clear trends. Survey results showed substantial autonomic symptom burden (COMPASS-31 autonomic questionnaire average score 44.45) and high levels of fatigue (PROMIS fatigue survey average score 64.64) in post-COVID POTS patients.

Conclusion

Our sample of post-COVID POTS patients are similar to the diagnosed POTS general population including in comorbidities and autonomic testing. Fatigue was identified by patients as a common and debilitating symptom. We hope that our study will be an early step toward further investigation of post-COVID POTS with focus on the trends identified in this chart review.

Cardiovascular dysautonomia in postacute sequelae of SARS-CoV-2 infection

Coronavirus disease 2019 (COVID-19) has led to a worldwide pandemic that continues to transform but will not go away. Cardiovascular dysautonomia in postacute sequelae of severe acute respiratory syndrome coronavirus 2 infection has led to persistent symptoms in a large number of patients. Here, we define the condition and its associated symptoms as well as potential mechanisms responsible. We provide a careful and complete overview of the topic addressing novel studies and a generalized approach to the management of individuals with this complex and potentially debilitating problem. We also discuss future research directions and the important knowledge gaps to be addressed in ongoing and planned studies.

Comorbid anxiety is associated with more changes in the Management of Postural Orthostatic Tachycardia Syndrome

OBJECTIVE

Postural Orthostatic Tachycardia Syndrome (POTS) is not an anxiety disorder, but it shares similar symptomatology. The impact of this comorbidity on management is unknown. This information may lead to better strategies to improve the care of this subgroup.

METHOD

The electronic medical records of 322 patients seen at our institution between 2018 and 2022 with confirmed POTS diagnoses were analyzed. Demographics, anxiety comorbidities, questionnaire responses, and treatment course changes were collected. Negative binomial regression models examined if the presence of an anxiety disorder was associated with the number of POTS treatment course changes offset by observation time.

RESULTS

When adjusted for sex, age, baseline GAD-7 score, and baseline PROMIS global mental health score, those with a diagnosis of an anxiety disorder had2.6 times the incident rate of treatment changes for POTS management (IRR = 2.66 (95% CI: 1.43-4.95)).

CONCLUSION

Individuals carrying the diagnosis of an anxiety disorder had an increase in the incident rate of treatment changes for POTS therapy. This finding may be due to the underlying pathophysiology and treatment of anxiety disorders, the effect of bias, and difficulty with symptom differentiation. More work needs to be done to determine how to best care for POTS patients with comorbid anxiety.

Novel pharmacotherapeutic options for the treatment of postural orthostatic tachycardia syndrome

INTRODUCTION

Postural tachycardia syndrome (POTS) is a disorder characterized by a constellation of symptoms including lightheadedness, fatigue, and palpitations when upright, associated with an increase in the heart rate (HR) of > 30 beats per minute when changing from a lying down to standing position or head-up tilt position and not associated with orthostatic hypotension. The causes as well as the management of POTS are not quite fully understood.

AREAS COVERED

We performed a literature review on the diagnosis and management of POTS, and this article includes an overview of novel pharmacotherapeutic options for the treatment of (POTS), although an effective treatment has not been established.

EXPERT OPINION

POTS is a clinical syndrome characterized by a constellation of symptoms that are nonspecific. No single etiology or unified hypothesis could be identified. In fact, multiple pathophysiological mechanisms have been proposed, and none of the suggested medications have been approved by the FDA for this indication. Further understanding of the autonomic nervous system and its adjustment to standing position is needed to provide better management strategies.

The Impact of Long COVID-19 on the Cardiovascular System

Long coronavirus disease (COVID) is the development or persistence of symptoms after an acute SARS-CoV-2 (COVID-19) infection. Fewer patients are developing acute COVID-19 infections, but patients with long COVID continue to have alarming long-term sequelae. Many cardiac magnetic resonance imaging studies show significant changes in cardiac structure after a COVID-19 infection, suggestive of an increased burden of many cardiovascular diseases, notably myocarditis. The pathophysiology of COVID-19 requires viral binding to angiotensin-converting enzyme 2 protein receptors throughout the body, which are upregulated by inflammation. Consequently, the numerous preexisting conditions that worsen or prolong inflammation enhance this binding and have differing effects on patients based on their unique immune systems. These pathophysiological changes drive long COVID cardiac sequelae such as inappropriate sinus tachycardia, postural orthostatic tachycardia, and other types of orthostatic intolerance. Increased screening for long COVID and low-risk interventions such as exercise regimens could alleviate the suffering endured by patients with long COVID. Many studies such as the Researching COVID to Enhance Recovery Initiative (RECOVER) trials at the National Institutes of Health are exploring potential treatments for long COVID patients.

Recognizing postural orthostatic tachycardia syndrome in primary care

ABSTRACT

Postural orthostatic tachycardia syndrome (POTS) is a complex autonomic disorder characterized by abnormal tachycardia on standing. This disorder predominantly affects young women, with a peak incidence between ages 20 and 30 years. POTS often is associated with a variety of symptoms, including dizziness, palpitations, fatigue, generalized weakness, anxiety, and exercise intolerance, which can significantly impair patient quality of life. Primary care providers (PCPs) often are the first healthcare professionals to whom patients present. This article provides an overview of POTS, including diagnostic criteria and the importance of a thorough clinical evaluation to rule out other causes of symptoms. PCPs play a critical role in the comprehensive approach to care, involving patient education, lifestyle modifications, and treatment to improve outcomes and enhance patient quality of life.

Autonomic nervous system dysfunction in pediatric sport-related concussion: a systematic review

Objective

To identify, appraise and synthesize the evidence of autonomic nervous system (ANS) dysfunction following sport-related concussion in pediatric populations.

Methods

A literature search was conducted using MEDLINE (Ovid), SportDiscus (EBSCO), CINAHL (EBSCO), EMBASE (Ovid) and PsycINFO (Ovid). Studies were selected and appraised using the Joanna Briggs Institute (JBI) critical appraisal tools. Data was extracted from the included studies and qualitatively synthesized.

Results

Eleven studies were included in the synthesis. There was variability in the methods used to measure ANS function between studies, and sample populations and time to assessment following concussion varied considerably. There was also variability in the direction of change of ANS function between some studies.

Conclusion

This systematic review identifies that concussion is associated with dysregulation of ANS function in pediatric athletes. We identified some weaknesses in the extant literature which may be due to existing logistical and financial barriers to implementing valid ANS measurements in clinical and sports settings.

Tilt testing

Tilt testing can help to diagnose unexplained syncope, by precipitating an episode during cardiac monitoring. The Italian protocol, now most widely used, involves giving sublingual nitroglycerine after 15 min, while monitoring beat-to-beat blood pressure (BP) and recording on video. Tilt testing is time-consuming but it is clinically useful and can guide therapy. Complications are rare. Syncope types include vasovagal syncope where BP falls after >3 min of tilt-up and later the heart rate falls; classic orthostatic hypotension where there is an immediate, progressive BP fall with minimal heart rate change; delayed orthostatic hypotension with a late BP fall after a stable phase but little or no heart rate rise; psychogenic pseudosyncope with apparent loss of consciousness, but no BP fall and a moderate heart rate rise; and postural orthostatic tachycardia syndrome where there is a significant heart rate rise but no BP fall.

A framework to simplify paediatric syncope diagnosis

This paper aims to improve the diagnosis of syncope and transient loss of consciousness (TLOC) in children. Diagnostic problems stem, first, from some causes spanning various disciplines, e.g. cardiology, neurology and psychiatry, while the most common cause, vasovagal syncope, is not embraced by any specialty. Second, clinical variability is huge with overlapping signs and symptoms. Third, the approach to TLOC/syncope of the European Society of Cardiology (ESC) is underused in childcare. We explain the ESC guidelines using an additional paediatric literature review. Classification of TLOC and syncope is hierarchic and based on history taking. Loss of consciousness (LOC) is defined using three features: abnormal motor control including falling, reduced responsiveness and amnesia. Adding a < 5 min duration and spontaneous recovery defines TLOC. TLOC simplifies diagnosis by excluding long LOC (e.g. some trauma, intoxications and hypoglycaemia) and focussing on syncope, tonic-clonic seizures and functional TLOC. Syncope, i.e. TLOC due to cerebral hypoperfusion, is divided into reflex syncope (mostly vasovagal), orthostatic hypotension (mostly initial orthostatic hypotension in adolescents) and cardiac syncope (arrhythmias and structural cardiac disorders). The initial investigation comprises history taking, physical examination and ECG; the value of orthostatic blood pressure measurement is unproven in children but probably low. When this fails to yield a diagnosis, cardiac risk factors are assessed; important clues are supine syncope, syncope during exercise, early death in relatives and ECG abnormalities.  Conclusions: In adults, the application of the ESC guidelines reduced the number of absent diagnoses and costs; we hope this also holds for children. What is Known: • Syncope and its mimics are very common in childhood, as they are at other ages. • Syncope and its mimics provide considerable diagnostic challenges. What is New: • Application of the hierarchic framework of transient loss of consciousness (TLOC) simplifies diagnosis. • The framework stresses history-taking to diagnose common conditions while keeping an eye on cardiac danger signs.

Importance of resting heart rate

Resting heart rate is a determinant of cardiac output and physiological homeostasis. Although a simple, but critical, parameter, this vital sign predicts adverse outcomes, including mortality, and development of diseases in otherwise normal and healthy individuals. Temporal changes in heart rate can have valuable predictive capabilities. Heart rate can reflect disease severity in patients with various medical conditions. While heart rate represents a compilation of physiological inputs, including sympathetic and parasympathetic tone, aside from the underlying intrinsic sinus rate, how resting heart rate affects outcomes is uncertain. Mechanisms relating resting heart rate to outcomes may be disease-dependent but why resting heart rate in otherwise healthy, normal individuals affects outcomes remains obscure. For specific conditions, physiologically appropriate heart rate reductions may improve outcomes. However, to date, in the normal population, evidence that interventions aimed at reducing heart rate improves outcomes remains undefined. Emerging data suggest that reduction in heart rate via vagal activation and/or sympathetic inhibition is propitious.

Postural orthostatic tachycardia syndrome and other related dysautonomic disorders after SARS-CoV-2 infection and after COVID-19 messenger RNA vaccination

The COVID-19 pandemic has caused a challenge for our society due to the post-acute sequelae of the disease. Persistent symptoms and long-term multiorgan complications, known as post-acute COVID-19 syndrome, can occur beyond 4 weeks from the onset of the COVID-19 infection. Postural orthostatic tachycardia syndrome (POTS) is considered a variety of dysautonomia, which is characterized by chronic symptoms that occur with standing and a sustained increase in heart rate, without orthostatic hypotension. POTS can lead to debilitating symptoms, significant disability, and impaired quality of life. In this narrative review, the etiopathogenic basis, epidemiology, clinical manifestations, diagnosis, treatment, prognosis, and socioeconomic impact of POTS, as well as other related dysautonomic disorders, after COVID-19 infection and SARS-CoV-2 postvaccination, were discussed. After a search conducted in March 2023, a total of 89 relevant articles were selected from the PubMed, Google Scholar, and Web of Science databases. The review highlights the importance of recognizing and managing POTS after COVID-19 infection and vaccination, and the approach to autonomic disorders should be known by all specialists in different medical areas. The diagnosis of POTS requires a comprehensive clinical assessment, including a detailed medical history, physical examination, orthostatic vital signs, and autonomic function tests. The treatment of POTS after COVID-19 infection or vaccination is mainly focused on lifestyle modifications, such as increased fluid and salt intake, exercise, and graduated compression stockings. Pharmacotherapy, such as beta-blockers, fludrocortisone, midodrine, and ivabradine, may also be used in selected cases. Further research is needed to understand the underlying mechanisms, risk factors, and optimal treatment strategies for this complication.

Sinus Node Dysfunction

Sinus node dysfunction (SND) is a multifaceted disorder most prevalent in older individuals, but may also occur at an earlier age. In most cases, the SND diagnosis is ultimately established by documenting its ECG manifestations. EPS has limited utility. The treatment strategy is largely dictated by symptoms and ECG manifestations. Not infrequently, both bradycardia and tachycardia coexist in the same patients, along with other diseases common in the elderly (e.g., hypertension, coronary artery disease), thereby complicating treatment strategy. Prevention of the adverse consequences of both bradyarrhythmia and tachyarrhythmia is important to reduce susceptibility to syncope, falls, and thromboembolic complications.

Augmented ocular vestibular-evoked myogenic potentials in postural orthostatic tachycardia syndrome

PURPOSE

To delineate the association between otolith function and changes in mean orthostatic blood pressure (BP) and heart rate (HR) in patients with postural orthostatic tachycardia syndrome (POTS).

METHODS

Forty-nine patients with POTS were prospectively recruited. We analyzed the results of ocular vestibular-evoked myogenic potentials (oVEMPs) and cervical vestibular-evoked myogenic potentials (cVEMPs), as well as head-up tilt table tests using a Finometer. The oVEMP and cVEMP responses were obtained using tapping stimuli and 110 dB tone-burst sounds, respectively. We measured maximal changes in 5-s averaged systolic BP (SBP), diastolic BP (DBP), and heart rate (HR) within 15 s and during 10 min after tilting. We compared the results with those of 20 age- and sex-matched healthy participants.

RESULTS

The n1-p1 amplitude of oVEMPs was larger in patients with POTS than in healthy participants (p = 0.001), whereas the n1 latency (p = 0.280) and interaural difference (p = 0.199) did not differ between the two. The n1-p1 amplitude was a positive predictor for POTS (odds ratio 1.07, 95% confidence interval 1.01-1.13, p = 0.025). Body weight (p = 0.007) and n1-p1 amplitude of oVEMP (p = 0.019) were positive predictors for ΔSBP15s in POTS, whereas aging was a negative predictor (p = 0.005). These findings were not observed in healthy participants.

CONCLUSIONS

Augmented utricular inputs may be associated with a relative predominance of sympathetic over vagal control of BP and HR, especially for an early response during orthostasis in patients with POTS. Overt sympathoexcitation due to exaggerated utricular input and lack of readaptation may be associated with the pathomechanism of POTS.

Postural Orthostatic Tachycardia Syndrome After COVID-19: A Systematic Review of Therapeutic Interventions

ABSTRACT

Postural orthostatic tachycardia syndrome (POTS) is a clinical syndrome of inappropriate increase in heart rate on standing that has been recently also associated with Coronavirus Disease 2019 (COVID-19) as part of the postacute sequelae of COVID-19 (PASC) or long-COVID. We herein aimed to systematically review reported cases of POTS after COVID-19 and determine the characteristics of the subjects, the diagnostic approach used, and the treatment strategies. We searched the literature according to the following criteria: (1) diagnosis of POTS according to standard definition; (2) timely association with a probable or definite diagnosis of COVID-19; and (3) a description of the individual subject(s). We identified 21 reports meeting criteria between March 2020 and September 2022, including 68 subjects (51 females and 17 males, 3:1 ratio) with a mean age of 34 ± 12 years, with reports deriving from the United States, Norway, Sweden, Israel, Ireland, United Kingdom, Singapore, and Japan. Most cases had mild COVID-19 symptoms. The most common POTS symptoms were palpitations, chest pain, lightheadedness, and debilitating fatigue. The diagnosis was established by means of head-up tilt table or active stand test. Nonpharmacologic treatments (fluids, sodium intake, and compression stockings) were virtually always used, but largely ineffective. Subjects received different treatments, the most common being beta-adrenergic blockers (ie, propranolol), mineral corticosteroids (ie, fludrocortisone), midodrine, and ivabradine. Symptoms tended to improve over time, but most patients remained symptomatic for several months. In conclusion, POTS after COVID-19 is a clinical condition affecting young individuals, and disproportionately young women, occurring as part of PASC-long-COVID, often debilitating, which can be easily diagnosed with a thorough clinical assessment and measuring changes in orthostatic heart rate and blood pressure. POTS after COVID-19 seems to be poorly responsive to nonpharmacological treatments but with symptoms improving with pharmacological interventions. Given the limited data available, additional research is urgently needed with respect to its epidemiology, pathophysiology, and treatments.

Predicting Therapeutic Efficacy of Pharmacological Treatments in Children with Postural Orthostatic Tachycardia Syndrome: A Mini-Review

Postural orthostatic tachycardia syndrome (POTS) is common in children, with an excessive increment in heart rate when moving from the supine to upright position. It has significant negative impacts on the daily life of pediatric patients. The pathogenesis of POTS includes peripheral vascular dysfunction, central hypovolemia, abnormal autonomic function, a high-adrenergic state, impaired skeletal-muscle pump function, the abnormal release of vasoactive factors, and autoimmune abnormalities. Therefore, the empirical use of pharmacological treatments has limited therapeutic efficacy due to the diversity of its mechanisms. A crucial aspect of managing POTS is the selection of appropriate treatment targeting the specific pathogenesis. This review summarizes the commonly used pharmacological interventions, with a focus on their predictive indicators for treatment response. Factors such as heart rate variability, plasma biomarkers, and cardiac-function parameters are discussed as potential predictors of therapeutic efficacy, enabling the implementation of individualized treatment to improve therapeutic effectiveness. This review consolidates the current knowledge on POTS, encompassing its clinical characteristics, epidemiological patterns, underlying pathogenic mechanisms, and predictive indicators for treatment response. Further research is warranted to enhance the understanding of POTS and facilitate the development of more effective therapeutic approaches for this challenging syndrome.

Parasympathetic autonomic dysfunction is more often evidenced than sympathetic autonomic dysfunction in fluctuating and polymorphic symptoms of "long-COVID" patients

Several disabling symptoms potentially related to dysautonomia have been reported in "long-COVID" patients. Unfortunately, these symptoms are often nonspecific, and autonomic nervous system explorations are rarely performed in these patients. This study aimed to evaluate prospectively a cohort of long-COVID patients presenting severe disabling and non-relapsing symptoms of potential dysautonomia and to identify sensitive tests. Autonomic function was assessed by clinical examination, the Schirmer test; sudomotor evaluation, orthostatic blood pressure (BP) variation, 24-h ambulatory BP monitoring for sympathetic evaluation, and heart rate variation during orthostatism, deep breathing and Valsalva maneuvers for parasympathetic evaluation. Test results were considered abnormal if they reached the lower thresholds defined in publications and in our department. We also compared mean values for autonomic function tests between patients and age-matched controls. Sixteen patients (median age 37 years [31-43 years], 15 women) were included in this study and referred 14.5 months (median) [12.0-16.5 months] after initial infection. Nine had at least one positive SARS-CoV-2 RT-PCR or serology result. Symptoms after SARS-CoV-2 infection were severe, fluctuating and disabling with effort intolerance. Six patients (37.5%) had one or several abnormal test results, affecting the parasympathetic cardiac function in five of them (31%). Mean Valsalva score was significantly lower in patients than in controls. In this cohort of severely disabled long-COVID patients, 37.5% of them had at least one abnormal test result showing a possible contribution of dysautonomia to these nonspecific symptoms. Interestingly, mean values of the Valsalva test were significantly lower in patients than in control subjects, suggesting that normal values thresholds might not be appropriate in this population.

Choices and Challenges With Drug Therapy in Postural Orthostatic Tachycardia Syndrome: A Systematic Review

The literature on pharmacologic treatments for postural orthostatic tachycardia syndrome (POTS) is inconsistent and unstandardized. Therefore, we aimed to evaluate choices in pharmacologic treatment options for POTS and the challenges encountered in the studies. We searched numerous databases like PubMed, Scopus, Embase, Web of Science, and Google Scholar for literature published before April 8, 2023. The search was done to retrieve potential peer-reviewed articles that explored drug therapy in POTS. Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines were used to conduct the systematic review. Of the 421 potential articles assessed, 17 met the inclusion criteria. Results demonstrated that pharmacologic treatment options for POTS were effective in reducing symptoms of POTS, but most of the studies were underpowered. Several were terminated due to various reasons. Midodrine ivabradine, bisoprolol, fludrocortisone, droxidopa, desmopressin, propranolol, modafinil, methylphenidate, and melatonin have been studied with positive impact but sample sizes that were low in the range of 10-50 subjects. Therefore, we concluded the treatment options effectively improve symptoms of POTS and increase orthostatic tolerance, but more evidence is needed as most studies had a low sample size and thus are underpowered.

Autoimmunity in Long Covid and POTS

Orthostatic intolerance and other autonomic dysfunction syndromes are emerging as distinct symptom clusters in Long Covid. Often accompanying these are common, multi-system constitutional features such as fatigue, malaise and skin rashes which can signify generalized immune dysregulation. At the same time, multiple autoantibodies are identified in both Covid-related autonomic disorders and non-Covid autonomic disorders, implying a possible underlying autoimmune pathology. The lack of specificity of these findings precludes direct interpretations of cause and association, but their prevalence with its supporting evidence is compelling.

Postural Orthostatic Tachycardia Syndrome in COVID-19: A Contemporary Review of Mechanisms, Clinical Course and Management

The long-term implications of COVID-19 have garnered increasing interest in recent months, with Long-COVID impacting over 65 million individuals worldwide. Postural orthostatic tachycardia syndrome (POTS) has emerged as an important component of the Long-COVID umbrella, estimated to affect between 2 and 14% of survivors. POTS remains very challenging to diagnose and manage - this review aims to provide a brief overview of POTS as a whole and goes on to summarize the available literature pertaining to POTS in the setting of COVID-19. We provide a review of available clinical reports, outline proposed pathophysiological mechanisms and end with a brief note on management considerations.

Malmö POTS symptom score: Assessing symptom burden in postural orthostatic tachycardia syndrome

BACKGROUND

Postural orthostatic tachycardia syndrome (POTS) is a common cardiovascular autonomic disorder characterized by excessive heart rate (HR) increase on standing and symptoms of orthostatic intolerance, posing significant limitations on functional capacity. No objective tool exists to classify symptom burden in POTS.

METHODS

We conducted a case-control study in 62 POTS patients and 50 healthy controls to compare symptom burden between groups using the newly developed, self-rating, 12-item, Malmö POTS Score (MAPS; 0-10 per item, total range 0-120) based on patients own perception of symptoms through visual analogue scale assessment. We have also explored correlations between symptom severity assessed by MAPS, basic clinical parameters and postural haemodynamic changes.

RESULTS

POTS patients showed significantly higher total MAPS score (78 ± 20 vs. 14 ± 12, p < 0.001), higher baseline systolic blood pressure (BP), diastolic BP and HR (p < 0.001) compared with healthy controls. The most prominent symptoms in POTS were palpitations, fatigue and concentration difficulties. Haemodynamic parameters on standing were significantly correlated with palpitations in POTS after adjustment for age and sex (lower systolic and diastolic BP, and higher HR) (p < 0.001 for all). Orthostatic HR was significantly associated with concentration difficulties and total MAPS score. The optimal cut-point value of MAPS to differentiate POTS and healthy controls was ≥42 (sensitivity, 97%; specificity, 98%).

CONCLUSIONS

Symptom severity, as assessed by MAPS score, is fivefold higher in POTS compared with healthy individuals. The new MAPS score can be useful as a semiquantitative system to assess symptom burden, monitor disease progression and evaluate pre-test likelihood of disease.

Sympathetic toggled sinus rate acceleration as a mechanism of sustained sinus tachycardia in chronic orthostatic intolerance syndrome

BACKGROUND

The role of sympathetic nerve activity to maintain sinus rate acceleration remains unclear.

OBJECTIVE

The purpose of this study was to test the hypothesis that sustained (>30 seconds) sinus rate acceleration can be associated with either a sympathetic driven or a sympathetic toggled mechanism.

METHODS

We used a patch monitor to record skin sympathetic nerve activity (SKNA) and electrocardiogram over 24 hours. Study 1 included chronic orthostatic intolerance (OI) (n = 18), atrial fibrillation (n = 7), and asymptomatic normal control (n = 19) groups. Study 2 included 17 participants with chronic OI not treated with ivabradine, pyridostigmine, or β-blockers.

RESULTS

While a majority of sinus rate acceleration was driven by persistent SKNA in study 1, some episodes were toggled on and off by SKNA bursts without persistent SKNA elevation. The sympathetic toggled sinus rate acceleration episodes were found in 7 of 18 participants with chronic OI (39%), 2 of 7 participants with atrial fibrillation (29%), and 6 of 19 normal control participants (32%) (P = .847) and were faster and longer in the chronic OI group than in other groups. In study 2, there were a total of 11 episodes of sinus rate acceleration that persisted for >200 seconds. Among these episodes, 6 (35%) were toggled on and off by SKNA bursts.

CONCLUSION

Sustained sinus rate acceleration (may be toggled on or off) is associated with SKNA bursts in participants with chronic OI, participants with atrial fibrillation, and normal controls. Patients with OI had more frequent and longer episodes than did other groups.

Orthostatic intolerance in post-concussion patients

Orthostatic intolerance (OI) following pediatric concussion is not well understood. Assessing the prevalence of concussion-related OI and how it compares to non-concussion-related OI will improve care for patients suffering with these symptoms. OBJECTIVE: We set out to describe concussion-related OI in adolescence, with particular emphasis on time to recovery and differences from non-concussion-related OI (including male vs. female prevalence). Retrospective chart reviews were completed on post-concussion patients endorsing symptoms of OI. The patients' sex, sport history, previous concussions, time since injury, and recovery time were analyzed and compared between males and females as well as against general OI statistics. Thirty-nine pediatric patients, representing 8.7% of all new patients referred to a specialized concussion clinic over a 13-month interval, were included in the chart review. Mean age of onset was 15.0 ± 2.5 years and 18 (46%) were males. The median times from evaluation to symptom resolution were 120 days. Of 18 patients who completed head-up tilt table testing, 17 (94%) had orthostatic tachycardic response (>40 bpm heart rate increment). Post-concussive OI differs from other orthostatic intolerance etiologies, lacking a strong female predominance and exhibiting a shorter time course to recovery compared to other etiologies of OI (but longer recovery time compared to concussion patients in general). Clinical orthostatic vital signs may not be sensitive for diagnosing orthostatic intolerance in athletes, likely due to higher vagal tone and more efficient skeletal muscle pump.

Sinus Tachycardia: a Multidisciplinary Expert Focused Review

Sinus tachycardia (ST) is ubiquitous, but its presence outside of normal physiological triggers in otherwise healthy individuals remains a commonly encountered phenomenon in medical practice. In many cases, ST can be readily explained by a current medical condition that precipitates an increase in the sinus rate, but ST at rest without physiological triggers may also represent a spectrum of normal. In other cases, ST may not have an easily explainable cause but may represent serious underlying pathology and can be associated with intolerable symptoms. The classification of ST, consideration of possible etiologies, as well as the decisions of when and how to intervene can be difficult. ST can be classified as secondary to a specific, usually treatable, medical condition (eg, pulmonary embolism, anemia, infection, or hyperthyroidism) or be related to several incompletely defined conditions (eg, inappropriate ST, postural tachycardia syndrome, mast cell disorder, or post-COVID syndrome). While cardiologists and cardiac electrophysiologists often evaluate patients with symptoms associated with persistent or paroxysmal ST, an optimal approach remains uncertain. Due to the many possible conditions associated with ST, and an overlap in medical specialists who see these patients, the inclusion of experts in different fields is essential for a more comprehensive understanding. This article is unique in that it was composed by international experts in Neurology, Psychology, Autonomic Medicine, Allergy and Immunology, Exercise Physiology, Pulmonology and Critical Care Medicine, Endocrinology, Cardiology, and Cardiac Electrophysiology in the hope that it will facilitate a more complete understanding and thereby result in the better care of patients with ST.

Dysautonomia in COVID-19 Patients: A Narrative Review on Clinical Course, Diagnostic and Therapeutic Strategies

Introduction

On March 11, 2020, the World Health Organization sounded the COVID-19 pandemic alarm. While efforts in the first few months focused on reducing the mortality of infected patients, there is increasing data on the effects of long-term infection (Post-COVID-19 condition). Among the different symptoms described after acute infection, those derived from autonomic dysfunction are especially frequent and limiting.

Objective

To conduct a narrative review synthesizing current evidence of the signs and symptoms of dysautonomia in patients diagnosed with COVID-19, together with a compilation of available treatment guidelines.

Results

Autonomic dysfunction associated with SARS-CoV-2 infection occurs at different temporal stages. Some of the proposed pathophysiological mechanisms include direct tissue damage, immune dysregulation, hormonal disturbances, elevated cytokine levels, and persistent low-grade infection. Acute autonomic dysfunction has a direct impact on the mortality risk, given its repercussions on the respiratory, cardiovascular, and neurological systems. Iatrogenic autonomic dysfunction is a side effect caused by the drugs used and/or admission to the intensive care unit. Finally, late dysautonomia occurs in 2.5% of patients with Post-COVID-19 condition. While orthostatic hypotension and neurally-mediated syncope should be considered, postural orthostatic tachycardia syndrome (POTS) appears to be the most common autonomic phenotype among these patients. A review of diagnostic and treatment guidelines focused on each type of dysautonomic condition was done.

Conclusion

Symptoms deriving from autonomic dysfunction involvement are common in those affected by COVID-19. These symptoms have a great impact on the quality of life both in the short and medium to long term. A better understanding of the pathophysiological mechanisms of Post-COVID manifestations that affect the autonomic nervous system, and targeted therapeutic management could help reduce the sequelae of COVID-19, especially if we act in the earliest phases of the disease.

Post-Concussive Orthostatic Tachycardia is Distinct from Postural Orthostatic Tachycardia Syndrome (POTS) in Children and Adolescents

Background: Orthostatic tachycardia (OT) affects some patients after concussion/mild traumatic brain injury (mTBI). In this study, we sought to identify the factors associated with increased risk for OT in patients with mTBI. Methods: We conducted a retrospective review of 268 patients (8-25 years) with mTBI/concussion to determine the prevalence of OT, defined as orthostatic heart rate change ≥40 bpm for those ≤19 years of age and ≥30 bpm on active standing test for those >19 years of age. Results: Among the study population, 7% (n = 19) exhibited post-concussive OT. The only significant difference between OT and non-OT groups was that history of prior concussion was more prevalent in the OT group. Conclusion: A substantial subset (7%) of concussion clinic patients exhibit OT. While POTS literature describes female and adolescent predominance, post-concussive OT had similar prevalence across age and gender groups in this study, suggesting that it may be distinct from POTS.

Rehabilitation needs following COVID-19: Five-month post-discharge clinical follow-up of individuals with concerning self-reported symptoms

BACKGROUND

This report describes and objectivizes reported problems among a cohort of previously hospitalized COVID-19 patients by clinical examination and determination of the required level of rehabilitation sevices.

METHODS

This report forms part of the Linköping COVID-19 Study (LinCoS) that included 745 individuals from one of 21 Swedish healthcare regions, Region Östergötland (RÖ), admitted to hospital for COVID-19 during March 1st-May 31st, 2020. In this descriptive ambidirectional cohort study, all 185 individuals who had reported concerning persisting symptoms were invited to a multi-professional clinical assessment of somatic, functional, affective, neuropsychological status and rehabilitation needs. Rehabilitation needs were assessed using three sub-scales of the Rehabilitation Complexity Scale-Extended.

FINDINGS

Among the 158 (85·4%) cases consenting and included in the analysis, we found a broad array of symptoms and signs attributable to COVID-19 involving respiratory, visual, auditory, motor, sensory and cognitive functions that could be confirmed clinically at five months post-discharge. This translated into 16% [95% CI 13-20] of survivors (70/433) of the total regional cohort of hospitalised patients requiring further rehabilitative interventions at follow-up. Weakness in extremities was reported in 28·5% [21·6, 36·2] (45/158). On examination, clinically overt muscle weakness could be corroborated in 15 individuals (10·5%) [6·1, 16·4]. 48% [40, 56] (76/158) reported cognitive symptoms, while the physician noted overt cognitive impairments in only 3% [1·1, 7·5]. In neuropsychological testing, 37% [28-46] (45/122) performed 1.5 SD below the norm, indicating neurocognitive deficits. Fifty-five individuals (34·8%) [27·4, 42·8] reported new or aggravated pain. In three fourths of them, it exerted a 'moderate' or worse detrimental effect on their ability to work.

INTERPRETATION

Our study underscores the importance of providing extensive examination of cases with persisting problems after COVID-19, especially since symptoms such as fatigue and breathlessness are highly nonspecific, but may represent significant underlying functional impairments. Robust neurocognitive testing should be performed, as cognitive problems may easily be overlooked during routine medical consultation. In the Swedish context, most rehabilitative interventions could be provided in a primary care setting. A substantial minority of patients should be triaged to specialized rehabilitation services.

Predictive Value of Heart Rate and Blood Pressure on the Prognosis of Postural Tachycardia Syndrome in Children

BACKGROUND

To investigate the predictive value of heart rate (HR) and blood pressure (BP) on the prognosis of postural tachycardia syndrome (POTS) in children.

MATERIALS AND METHODS

53 cases of children aged 5 to 15 years who visited in the Pediatric Syncope Specialist Clinic of The Second Xiangya Hospital of Central South University for unexplained syncope or syncope precursor were diagnosed with POTS by head-up tilt test (HUTT) as the POTS group. 38 healthy children aged 5 to 16 years who underwent physical examination at the Child Health Care Clinic of the hospital in the same period were matched as controls (control group). The children with POTS were followed up after 3 months of treatment and were divided into good prognosis group (40 cases) and poor prognosis group (13 cases) according to the results of HUTT re-examination and whether the symptoms improved or not. HR and BP indicators were collected from each group at baseline and during HUTT.

RESULTS

There were 91 research subjects, of which 45 are males, with a mean age of 11.52 ± 2.13 years. (1) HR at 5 and 10 min (HR 5 and HR 10, respectively), HR difference at 5 and 10 min (HRD 5 and HRD 10, respectively), and HR and BP product at 5 and 10 min (RPP 5 and RPP 10, respectively) were greater in the POTS group than in the control group (P < 0.01). (2) HR 5, HR 10, HRD 5, HRD 10, and RPP 10 in children with POTS were smaller in the good prognosis group than the poor prognosis group (P < 0.01). (3) The area under curve was 0.925 on the four combined indicators (HR 5, HR 10, HRD 5, and HRD 10), predicting a good prognosis of POTS, sensitivity of 99.99%, and specificity of 75.00%.

CONCLUSIONS

HR 5, HR 10, HRD 5, HRD 10, and RPP 10 and the four combined indicators (HR 5, HR 10, HRD 5, and HRD 10) had predictive value for the POTS prognosis in children. The predictive value of the four combined indicators for the POTS prognosis was better than that of the single HR 5, HRD 5, and RPP 10.

Sinus Node Dysfunction

Sinus node dysfunction (SND) is a multifaceted disorder most prevalent in older individuals, but may also occur at an earlier age. In most cases, the SND diagnosis is ultimately established by documenting its ECG manifestations. EPS has limited utility. The treatment strategy is largely dictated by symptoms and ECG manifestations. Not infrequently, both bradycardia and tachycardia coexist in the same patients, along with other diseases common in the elderly (e.g., hypertension, coronary artery disease), thereby complicating treatment strategy. Prevention of the adverse consequences of both bradyarrhythmia and tachyarrhythmia is important to reduce susceptibility to syncope, falls, and thromboembolic complications.

Nonvestibular Dizziness

Dizziness is a common chief complaint with an extensive differential diagnosis that ranges from peripheral, central, to nonvestibular conditions. An understanding of nonvestibular conditions will aid accurate diagnosis and initiation of appropriate management. Thus, the objective of this article is to present an overview of nonvestibular etiologies that may plague a dizzy patient and the recommended treatment options.

Occupational Therapy Interventions for Clients with Ehlers-Danlos Syndrome (EDS) in the Presence of Postural Orthostatic Tachycardia Syndrome (POTS)

Postural orthostatic tachycardia syndrome (POTS) is often seen in clients with Ehlers-Danlos syndrome (EDS), primarily hypermobile EDS. Research has shown clients with EDS and POTS may experience limitations affecting not only their physical function, but also their social, emotional, and mental well-being. Using a client-centered approach, occupational therapy practitioners assess health, well-being, symptomatology (fatigue, muscle pain, dizziness, etc.), participation and engagement in occupation, and provide interventions to improve quality of life. This paper will address occupational therapy interventions to treat common symptomatology for clients with EDS in the presence of POTS, including environmental modifications, use of adaptive equipment and orthoses, exercise and fall prevention, energy conservation and pacing, sleep hygiene, and routine and habit development to promote optimal engagement in meaningful occupations.

Mast Cell Activation Disorder and Postural Orthostatic Tachycardia Syndrome: A Clinical Association

Background

Recently there has been increased interest in a possible association between mast cell activation (MCA) disorder and postural orthostatic tachycardia syndrome (POTS). This study examined the frequency with which symptoms and laboratory findings suggesting MCA disorder occurred in patients diagnosed with POTS.

Methods and Results

Data were obtained from patients in whom symptoms and orthostatic testing were consistent with a POTS diagnosis. Individuals with <4 months symptom duration, evident ongoing inflammatory disease, suspected volume depletion, or declined consent were excluded. All patients had typical POTS symptoms; some, however, had additional nonorthostatic complaints not usually associated with POTS. The latter patients underwent additional testing for known MCA biochemical mediators including prostaglandins, histamine, methylhistamine, and plasma tryptase. The study comprised 69 patients who met POTS diagnostic criteria. In 44 patients (44/69, 64%) additional nonorthostatic symptoms included migraine, allergic complaints, skin rash, or gastrointestinal symptoms. Of these 44 patients, 29 (66%) exhibited at least 1 laboratory abnormality suggesting MCA disorder, and 11/29 patients had 2 or more such abnormalities. Elevated prostaglandins (n=16) or plasma histamine markers (n=23) were the most frequent findings. Thus, 42% (29/69) of patients initially diagnosed with POTS exhibited both additional symptoms and at least 1 elevated biochemical marker suggesting MCA disorder.

Conclusions

Laboratory findings suggesting MCA disorder were relatively common in patients diagnosed with POTS and who present with additional nonorthostatic gastrointestinal, cutaneous, and allergic symptoms. While solitary abnormal laboratory findings are not definitive, they favor MCA disorder being considered in such cases.

Ablation therapy of postural orthostatic tachycardia syndrome, inappropriate sinus tachycardia and primary electrical diseases: new insights in invasive treatment options in severely symptomatic patients

Achieving the goal management of some arrhythmic syndromes can be challenging; medical treatment for inappropriate sinus tachycardia (IST) and postural orthostatic tachycardia syndrome (POTS) may be ineffective, necessitating multidisciplinary team treatment. Implantable defibrillator devices (ICDs), along with anti-arrhythmic drugs (AADs), remain the first-line treatment for primary electrical diseases that pose a risk of sudden cardiac death (SCD). Ablation of the arrhythmogenic substrate is not always suggested in patients with these pathologies, but it may be a valuable support for reducing arrhythmic burden, improving quality of life, and treating pathologies that are resistant to pharmacological treatment; however, this option is not often considered due to the potential risks associated with an invasive approach. Minimally invasive hybrid ablation in these syndromes, such as a hybrid thoracoscopic approach and the use of non-invasive mapping systems, reduces post-surgery complications and ensures the best possible outcome for the patient.

Postural orthostatic tachycardia syndrome (POTS): Priorities for POTS care and research from a 2019 National Institutes of Health Expert Consensus Meeting - Part 2

The National Institutes of Health hosted a workshop in 2019 to build consensus around the current state of understanding of the pathophysiology of postural orthostatic tachycardia syndrome (POTS) and to identify knowledge gaps that must be addressed to enhance clinical care of POTS patients through research. This second (of two) articles summarizes current knowledge gaps, and outlines the clinical and research priorities for POTS.

POTS is a complex, multi-system, chronic disorder of the autonomic nervous system characterized by orthostatic intolerance and orthostatic tachycardia without hypotension. Patients often experience a host of other related disabling symptoms. The functional and economic impacts of this disorder are significant. The pathophysiology remains incompletely understood.

Beyond the significant gaps in understanding the disorder itself, there is a paucity of evidence to guide treatment which can contribute to suboptimal care for this patient population. The vast majority of physicians have minimal to no familiarity or training in the assessment and management of POTS.

Funding for POTS research remains very low relative to the size of the patient population and impact of the syndrome. In addition to efforts to improve awareness and physician education, an investment in research infrastructure including the development of standardized disease-specific evaluation tools and outcome measures is needed to facilitate effective collaborative research. A national POTS research consortium could facilitate well-controlled multidisciplinary clinical research studies and therapeutic trials. These priorities will require a substantial increase in the number of research investigators and the amount of research funding in this area.

Post-COVID Syndrome and Tachycardia: Theoretical Base and Treatment Experience

The coronavirus pandemic showed not only an increase in levels of excess morbidity and mortality in the acute phase, but also persisting symptoms 4 weeks after the onset of the disease. A review of international studies on the prevalence and diversity of the manifestations of postcoid syndrome is presented. The data on such a manifestation of post-COVID syndrome as postural orthostatic tachycardia syndrome (POTS) are accumulating. Pathogenetic mechanisms, modern diagnostic criteria and research data on the prevalence of this syndrome are presented in the article. The Canadian Cardiovascular Society has proposed medications as a treatment for POTS, including the sinus node If channel inhibitor ivabradine. Data from several studies showing the effectiveness of this drug for POTS, including after suffering COVID-19, are presented in the article. Clinical data on the prevalence of tachycardia among patients admitted to the Sechenov University hospital are presented. About 18% of patients with hypertension and 21% of patients with normal blood pressure had a high heart rate. A clinical example of the use of ivabradine in a patient after a coronavirus infection is presented. Drug interactions and individual tolerance of ivabradine in patients after coronavirus infection are being discussed. The authors put forward the hypothesis about the further prospect of using ivabradine in the treatment of clinical manifestations of postcoid syndrome on the basis of literature data and their own experience.

Mast cell activation syndrome: Myths and realities

Background: Mast cells (MCs) have been implicated in a spectrum of allergic, immunologic, and infectious inflammatory conditions that involve different organ systems. MC activation can occur through several different surface receptors other than the well known IgE mediated pathway. Methods: We use two representative case reports from our practice to summarize what is currently known about MCAS disorders (reality) so that the clinician can more easily differentiate these conditions from other complex unexplained conditions that are being associated with MC activation (myth). Results: Many complex MC-related conditions, such as clonal MC diseases, have been well characterized but other MC-related disorders, such as MC activation syndrome (MCAS) and idiopathic anaphylaxis, still remain poorly defined. The current consensus recommendations for a diagnosis of MCAS require clinical symptoms of anaphylaxis that correlate with elevation of a MC activation biomarker(s), which improves with H1-antihistamines. Conclusion: Clinical symptoms of MCAS can overlap with other conditions, including neurogenic disorders, e.g., dysautonomia, which necessitate the importance for the clinician to render an accurate diagnosis so that appropriate treatment is provided.

Long-Haul Post-COVID-19 Symptoms Presenting as a Variant of Postural Orthostatic Tachycardia Syndrome: The Swedish Experience

Major clinical centers in Sweden have witnessed an inflow of patients with chronic symptoms following initial outpatient care for coronavirus disease-2019 (COVID-19) infection, suggestive of postural orthostatic tachycardia syndrome. This report presents the first case series of 3 Swedish patients diagnosed with postural orthostatic tachycardia syndrome more than 3 months after the primary COVID-2019 infections. (Level of Difficulty: Intermediate.).

Comparisons of the Nonlinear Relationship of Cerebral Blood Flow Response and Cerebral Vasomotor Reactivity to Carbon Dioxide under Hyperventilation between Postural Orthostatic Tachycardia Syndrome Patients and Healthy Subjects

Postural orthostatic tachycardia syndrome (POTS) typically occurs in youths, and early accurate POTS diagnosis is challenging. A recent hypothesis suggests that upright cognitive impairment in POTS occurs because reduced cerebral blood flow velocity (CBFV) and cerebrovascular response to carbon dioxide (CO₂) are nonlinear during transient changes in end-tidal CO₂ (P_ETCO2). This novel study aimed to reveal the interaction between cerebral autoregulation and ventilatory control in POTS patients by using tilt table and hyperventilation to alter the CO₂ tension between 10 and 30 mmHg. The cerebral blood flow velocity (CBFV), partial pressure of end-tidal carbon dioxide (P_ETCO2), and other cardiopulmonary signals were recorded for POTS patients and two healthy groups including those aged >45 years (Healthy-Elder) and aged <45 years (Healthy-Youth) throughout the experiment. Two nonlinear regression functions, Models I and II, were applied to evaluate their CBFV-P_ETCO2 relationship and cerebral vasomotor reactivity (CVMR). Among the estimated parameters, the curve-fitting Model I for CBFV and CVMR responses to CO₂ for POTS patients demonstrated an observable dissimilarity in CBFV_max (p = 0.011), mid-P_ETCO2 (p = 0.013), and P_ETCO2 range (p = 0.023) compared with those of Healthy-Youth and in CBFV_max (p = 0.015) and CVMR_max compared with those of Healthy-Elder. With curve-fitting Model II for POTS patients, the fit parameters of curvilinear (p = 0.036) and P_ETCO2 level (p = 0.033) displayed significant difference in comparison with Healthy-Youth parameters; range of change (p = 0.042), P_ETCO2 level, and CBFV_max also displayed a significant difference in comparison with Healthy-Elder parameters. The results of this study contribute toward developing an early accurate diagnosis of impaired CBFV responses to CO₂ for POTS patients.

Defining Cardiac Dysautonomia - Different Types, Overlap Syndromes; Case-based Presentations

The cardiovascular branch of autonomic nervous system (ANS) is responsible for the regulation of heart rate, blood pressure, and maintaining homeostasis during physiological stress such as exercise and standing upright. ANS constantly controls the rate and force of heart contractions and the vascular tone with the aim to maintain the sufficient tissue perfusion with oxygenated blood and secure venous return to the heart. Dysautonomias, result of ANS malfunction, are often found in patients with cardiovascular symptoms. Apart from the most prevalent one, arterial hypertension, the cardiovascular dysautonomic continuum encompasses other important although less known conditions: postural orthostatic tachycardia syndrome, inappropriate sinus tachycardia, orthostatic hypotension and reflex syncope. Moreover, heart diseases may evoke autonomic imbalance by themselves; cardiac pump failure is usually associated with sympathetic hyperactivity, neuroendocrine vasopressor activation, higher heart rate, reduced heart rate variability and baroreflex hyposensitivity, all of which are predictors of adverse outcomes. Cardiologists and electrophysiologist frequently see patients for the evaluation and management of unexplained syncope, orthostatic intolerance, heart rhythm abnormalities and symptoms of palpitations. Recognizing the presence of cardiac dysautonomia is an important skill which is necessary for the appropriate evaluation and treatment of these patients. Clinical presentations may overlap, and the importance of a thorough history cannot be over-emphasized. In this review we will present a cases of a patients with cardiac dysautonomia which is illustrative of a typical patient experience, followed by a review of the autonomic nervous system and discussion of prevalence, clinical presentation, and pathophysiology of common cardiac dysautonomias.