2015 heart rhythm society expert consensus statement on the diagnosis and treatment of postural tachycardia syndrome, inappropriate sinus tachycardia, and vasovagal syncope

Physiological and clinical comparison of active stand and head-up tilt tests in Postural Orthostatic Tachycardia Syndrome (POTS)

Head-up tilt (HUT) and active stand tests (AST) are used in the diagnosis of Postural Orthostatic Tachycardia Syndrome (POTS), but their relative diagnostic accuracy is unclear. This necessitates a direct comparison under standardized conditions. We aimed to compare the hemodynamic responses and diagnostic accuracy of AST vs. HUT in POTS. To address this, patients with POTS (n = 60) completed a 10-min AST followed by HUT on the same day. Beat-to-beat hemodynamics were recorded during 10-min supine baselines and each test. Delta values were calculated for each test (upright 1-min averages minus baseline average). Δ[heart rate] increased significantly over time (1_Min: 28 bpm to 10_Min: 40 bpm; PTime < 0.001), and was greater for HUT (33 bpm vs. 37 bpm; PASTvHUT = 0.01), with significant Time x Condition interaction (38 bpm vs. 42 bpm at10min; PINT < 0.001). Δ[stroke volume] declined over time (1_Min: -18 ml to 10_Min: -32 ml); PTime < 0.001), with no significant test or interaction effects (PASTvHUT = 0.36; PINT = 0.21). Δ[SBP] decreased (1_Min: -0.3 mmHg to 10_Min: -5.7 mmHg); PTime < 0.001) over time, with no test or interaction effects. Fewer patients met POTS heart rate criteria during the AST (AST: 74 % vs. HUT: 98 %; p < 0.001). Lowering the threshold to 27 bpm for AST narrowed the gap but was still significantly higher for HUT (AST: 83 % vs HUT: 98 %; p = 0.02). Orthostatic tachycardia differs between AST and HUT in patients with POTS. The proportion of patients with POTS meeting the heart rate diagnostic criteria differs significantly between AST and HUT, a discrepancy that can be mitigated by lowering the heart rate threshold for the AST.

Hyperventilation during rest and exercise in orthostatic intolerance and Spiky-Leaky Syndrome

Background

Orthostatic intolerance, with or without postural orthostatic tachycardia syndrome (POTS), is collectively referred to as orthostatic intolerance dysautonomia syndromes (OIDS). This condition often presents with daytime hyperventilation, which is considered to be secondary to sympathetic hyperactivity. This hyperventilation appears to be a key characteristic in a newly described subset of patients with OIDS who also exhibit craniocervical instability, mast cell activation syndrome (MCAS), hypermobility spectrum disorder (HSD), and the phenomenon of alternating intracranial hypertension with hypotension due to cerebrospinal fluid (CSF) leaks, collectively termed Spiky-Leaky Syndrome (SLS).

Methods

We performed a retrospective review of clinical metabolic exercise data in young patients with SLS, comparing them to matched patients with OIDS and healthy controls (CTL). We assessed metabolic parameters at rest, at the anaerobic threshold (AT), and at maximal oxygen consumption (VO2max). The parameters included end-tidal CO2 (ETCO2), end-tidal O2 (ETO2), peak oxygen pulse, total work performed, and peak oxygen uptake efficiency slope (OUESp).

Results

Of 323 reviewed exercise stress tests, 44 were conducted on patients with SLS, 210 on those with OIDS, and 53 on healthy controls. VO2max, AT, peak oxygen pulse, total work performed, and OUESp were all significantly reduced in patients with OIDS and were further reduced in those with SLS. ETCO2 levels were notably lower at rest, at the time of the anaerobic threshold, and at the time of maximal oxygen uptake in the OIDS group, and even more so in the SLS group. These lower levels of ETCO2 persisted throughout exercise. In contrast, ETO2 demonstrated a similarly strong but opposite trend.

Conclusion

Compared to the control group, patients with OIDS-and especially those with SLS-exhibited reduced metabolic parameters, particularly a decrease in peak oxygen pulse and ETCO2 levels during both rest and exercise. These findings suggest a reduction in ventricular preload and chronic daytime hyperventilation. These exercise parameters may serve as markers for POTS physiology and sympathetic hyperactivity, both of which could play a role in the pathophysiology of SLS.

Association of supine and upright blood pressure differences with head-up tilt test outcomes in children with vasovagal syncope

Introduction

Vasovagal syncope (VVS) is the most common childhood neurally mediated syncope. This study aims to define the different hemodynamic patterns in pediatric cases of vasovagal syncope and the difference between supine and upright blood pressure (orthostatic blood pressure), and other factors affecting them.

Methods

Medical records of 88 children with normal laboratory and subclinical tests referred to Mofid Hospital for head-up tilt testing were retrospectively evaluated. Eighty-five children, 31 (36.5%) boys and 54 (63.5%) girls, aged 10.72 ± 3.52 years (median 10; range 4-17), with vasovagal syncope, were enrolled in the study. Age, sex, baseline heart rate, baseline blood pressure, orthostatic blood pressure, provoking factors, symptoms, and frequency were recorded. The test protocol included 10 min of supine rest followed by 30 min of upright positioning at a 70-degree angle. Subjects were divided into groups according to their differing hemodynamic patterns based on modified VASIS criteria.

Results

Our data showed a strong association between the difference in supine and upright blood pressure and positive HUTT results (p = 0.001). In the positive HUTT group, age had a higher probability of vasodepressor pattern in younger patients (p-value = 0.014). Also, a significant relationship is seen with the boys (p-value = 0.014, 0.038), which means that the male gender increases the probability of a positive tilt test.

Discussion

Our study indicates that orthostatic blood pressure can predict HUTT in VVS children. Also, our results showed there is a higher chance of having a positive response to HUTT for the younger boys. Further studies in this field are warranted.

Translational Anatomy of the Sinoatrial Node: Myoarchitecture and its Relevance for Catheter Ablation: Part II: Clinical Applications

ANATOMY

Clinical applications relevant to the sinoatrial node anatomy for interventional electrophysiology procedures are reviewed.

PATHOLOGY

Inappropriate sinus tachycardia, atrial tachycardia, and superior vena cava triggers for atrial fibrillation.

IMAGING CORRELATION

Three-dimensional electroanatomic mapping, intracardiac echocardiography.

TREATMENT

Ablation guided by activation mapping and intracardiac electrograms.

TAKE-HOME MESSAGE

Understanding the anatomy of the sinoatrial node and the perinodal region provides key anatomic concepts to safely and effectively guide ablation procedures.

Can standing replace upright tilt table testing in the diagnosis of postural tachycardia syndrome (POTS) in the young?

PURPOSE

We compared standing and upright tilt in patients with postural tachycardia syndrome (POTS) and healthy volunteers to determine whether standing accurately tests for POTS in youngsters < 19 years. POTS in adolescents is defined by orthostatic intolerance plus sustained excessive upright tachycardia, without hypotension during upright tilt. We examined whether active standing is a valid classifier for POTS in adolescents compared to tilt.

METHODS

Patients with POTS (N = 36, 12.2-18.8 years) and healthy volunteers (N = 39, 13.1-18.9 years) performed stand for a minimum of 5-min and were tilted to 70° for 10 min. Receiver operating characteristics analyses (ROC) were performed at 5-min stand, and at 5  and 10 min tilt for optimal threshold for heart rate (HR) increase (ΔHR), and test sensitivity and specificity.

RESULTS

Most subjects were unable to stand for 10 min. ΔHRs at 5 min stand were higher in POTS (31 ± 3) compared with control (21 ± 2) and elevated at 5- or 10-min tilt in POTS (51 ± 3 and 51 ± 2) versus control (26 ± 2 and 25 ± 2) compared with standing. ΔHR in POTS and controls for 10 min were not different from 5 min. For 5 min stand ROC threshold was 26 beats per min (bpm), sensitivity of 70.6%, and specificity of 68.2% compared with 39 bpm, 88.2%, and 95.1% for 5 min tilt, and 40 bpm, 94.1%, and 95.1% for 10-min tilt. A precision-recall graph confirmed the superior discriminating ability of 5 min and 10 min tilt compared to 5 min stand.

CONCLUSIONS

The stand test is relatively non-specific and imprecise compared to tilt and does not satisfactorily distinguish POTS from control in patients aged < 19 years old.

Understanding the experiences of people who have Postural Orthostatic Tachycardia Syndrome (POTS) and the health professionals who care for them: A grounded theory study

Understanding the experiences of people who have postural orthostatic tachycardia syndrome (POTS) and the health professionals who care for them: a grounded theory study.

BACKGROUND

Postural orthostatic tachycardia syndrome (POTS) is an under recognised, predominantly female condition. Awareness of this condition has increased due its association with Long-COVID. Understanding experiences informs areas for future study. Research into the experience of POTS is emerging, with no currently published studies including the experiences of health professionals.

AIM

This study aimed to understand experiences of POTS, its challenges, and aspects of care from the perspectives of people with the condition and health professionals who look after them.

DESIGN

A grounded theory approach was taken to develop a conceptual framework of the experience of POTS conceptualised through a critical realist lens.

SETTING

This United Kingdom based study included people with POTS from three national health care centres and a diverse range of health professionals.

PARTICIPANTS

Theoretical and purposive sampling recruited people with POTS, and snowball sampling recruited health professionals through a United Kingdom charity and arrhythmia nursing network. Health professionals were interviewed from a range of professions including nurses, secondary care consultants, primary care general practitioners, psychologists, physiotherapists, and an occupational therapist.

METHOD

Between September 2021 and September 2022 in-depth online semi-structured interviews were undertaken. Data were thematically analysed. Corbin and Strauss' Grounded Theory methods of constant comparison, memos, and a reflexive journal were used. Analysis moved from first open coding of health professional themes to more focused axial coding, data, and category linking. The study patient and public involvement group informed thematic development and theoretical sampling. The final themes were conceptualised through the critical realism's three layers of experience.

RESULTS

Forty-four participants were included, 19 people with POTS and 25 health professionals. Three core themes were found: 1) A challenging condition, 2) POTS healthcare provision - services by accident not design, and 3) The need to validate experiences. Health professionals experienced challenges in their clinical self-efficacy. POTS care was driven by individual human agency and interpersonal relationships. People with POTS took individual responsibility for their self-management but were impacted by gender inequalities, a medical model prioritising guidelines, and a poor evidence-base.

CONCLUSION

This is the first qualitative study to explore both people with POTS and health professional experiences of looking after people with this condition. Findings identified: 1) a need for empowering both people with POTS and health professionals through shared care and decision making, 2) the requirement for a system wide recognition of POTS to move the landscape away from one of individual responsibility, and 3) the need to develop the evidence-base.

REGISTRATION

Health Research Authority (IRAS: 281284). First recruitment: 13/09/2021.

TWEETABLE ABSTRACT

Understanding the experiences of people with POTS and the health professionals who see them. The findings of 44 in-depth interviews.

Blood volume deficit in postural orthostatic tachycardia syndrome assessed by semiautomated carbon monoxide rebreathing

PURPOSE

The semiautomated carbon monoxide (CO) rebreathing method has been introduced as a noninvasive and radiation-free blood volume estimation method. We tested whether the semiautomated CO rebreathing method can detect the blood volume deficit in postural orthostatic tachycardia syndrome (POTS). In addition, we explored the relationship between blood volume estimated from CO rebreathing and body impedance.

PATIENTS AND METHODS

We recruited 53 subjects (21 female patients with POTS, 19 healthy female participants, and 13 healthy male participants) to record blood volumes and hemodynamic data. Blood volumes were measured by CO rebreathing and segmental body impedance. Linear regression models to predict normal values of red blood cell volume (RBCV), plasma volume (PV), and total blood volume (BV) were developed. Percentage deviations from the predicted normal volumes were calculated.

RESULTS

Patients with POTS had lower RBCV (25.18 ± 3.95 versus 28.57 ± 3.68 mL/kg, p = 0.008, patients with POTS versus healthy female participants), BV (64.53 ± 10.02 versus 76.78 ± 10.00 mL/kg, p < 0.001), and BV deviation (-13.92 ± 10.38% versus -0.02 ± 10.18%, p < 0.001). Patients with POTS had higher supine heart rate (HR) (84 ± 14 versus 69 ± 11 bpm, p < 0.001) and upright HR (123 ± 23 versus 89 ± 22 bpm, p < 0.001). We found a correlation between BV deviation and upright HR in patients with POTS (r = -0.608, p = 0.003), but not in healthy participants. Volumes from the CO rebreathing and body impedance were well correlated (r = 0.629, p < 0.001).

CONCLUSIONS

The CO rebreathing method can detect BV deficit, as well as the RBCV deficit in patients with POTS. The negative correlation between BV deviation and upright HR indicates that hypovolemia is one of the pathophysiological causes of POTS. Correlations between body impedance and CO rebreathing volume suggest its usefulness for measurements of volume changes.

Corneal Confocal Microscopy in Postural Orthostatic Tachycardia Syndrome (POTS) as a Diagnostic Tool for Small Fiber Neuropathy

OBJECTIVE

Postural orthostatic tachycardia syndrome (POTS) is a debilitating condition characterized by autonomic dysregulation. Patients with this disorder may experience orthostatic intolerance, palpitations, fatigue, and a wide variety of other symptoms. The neuropathic symptoms of POTS may be caused by small fiber neuropathy (SFN), which is currently diagnosed using skin nerve biopsy. Corneal confocal microscopy (CCM) is an imaging modality that allows visualization of the corneal nerve layer. Our study aimed to determine whether CCM could detect differences in small nerve fiber parameters between POTS patients with and without signs or symptoms of SFN.

MATERIALS AND METHODS

CCM was performed on nine patients, along with a neurological examination. Participants were also asked about neuropathic symptoms by a researcher. Based on examination findings and/or reported symptoms, patients were categorized into SFN+ and SFN- groups for comparison. A chart review was conducted to gather demographic data, medications, autonomic testing results, and medical history, including common POTS comorbidities.

RESULTS

Comparison of nerve fiber parameters using CCM did not reveal a statistically significant difference between the groups. However, valuable insights were gained regarding the logistics of conducting this type of study in POTS patients, including adapting to challenges and improving coordination between the neurology and ophthalmology departments.

CONCLUSIONS

CCM may one day replace skin nerve biopsy as a diagnostic tool for SFN in POTS patients. Although this preliminary analysis did not demonstrate significant findings, likely due to the small sample size, we believe CCM may still have a role in POTS research and could eventually become a diagnostic tool used in autonomic clinics.

Clozapine-Related Tachycardia: An Analysis of Incidence

BACKGROUND AND OBJECTIVES

Sinus tachycardia commonly occurs at the start of clozapine treatment, often leading to discontinuation owing to perceived adverse cardiovascular effects. However, little evidence exists on its natural course after clozapine initiation. We aimed to determine the frequency and course of clozapine-induced tachycardia over the first month of treatment and to identify possible risk factors METHODS: In this cross-sectional study, we serially monitored heart rates (HRs) and other clinical variables of psychiatric inpatients commencing clozapine over the first 28 days. HRs were plotted over time and modelled by explanatory variables, including age group, sex, body mass index (BMI), smoking status and prescribed medications for HR.

RESULTS

In total, 123 consecutive inpatients undergoing clozapine titration were assessed daily, with 2901 HR measures collected. After starting clozapine, mean HR increased from 83.7 to 99.5 beats per minute (bpm). Almost all participants (93.5%) had at least one recorded HR > 100 bpm, and 68% had three consecutive days with HR > 100 bpm (being then defined as tachycardic). At least one HR > 120 bpm was recorded in 35.8%, and 8% had persistent HRs > 120 bpm. Tachycardia occurred early during clozapine titration, with a dose response effect at lower doses, which plateaued between 150 and 350 mg daily. Tachycardia spontaneously resolved for some but 44% remained tachycardic at day 28. Female sex was associated with early tachycardia at day 14 (p = 0.008) but not at day 28, while age, smoking status, and BMI were not significantly associated with tachycardia.

CONCLUSIONS

Sinus tachycardia occurred in over two thirds of participants during the first month of clozapine titration. Spontaneous resolution of tachycardia in some suggests watchful monitoring may be appropriate prior to treatment with rate-controlling agents such as β-blockers or ivabradine. Long term follow-up is required to determine the effects of sinus tachycardia on cardiovascular outcomes in patients treated with clozapine.

Incidence and influencing factors of vasovagal reaction in computed tomography (CT)-guided localisation of pulmonary ground-glass nodules prior to video-assisted thoracoscopic surgery

AIM

To investigate the incidence, clinical features, and influencing factors of vasovagal reaction (VVR) associated with computed tomography (CT)-guided localisation of pulmonary ground-glass nodules (GGNs) prior to video-assisted thoracoscopic surgery (VATS).

MATERIALS AND METHODS

A total of 1303 consecutive patients who underwent CT-guided localisation of GGNs were selected as research subjects. VVR related to CT-guided localisation was defined as the onset of otherwise unexplained transient hypotension and/or relative bradycardia during or after localisation, manifesting as symptoms such as pallor, sweating, nausea, and potentially syncope. Risk factors for VVR were identified through both univariate and multivariate analyses.

RESULTS

VVR was observed in 4.5% (58/1,303) of the patients. All VVRs occurred postlocalisation, with 91.4% (53/58) happening between the time patients rose from the CT table and their departure from the CT room. Prodromal symptoms were evident in all VVR cases, with two cases progressing to syncope, each with a brief loss of consciousness lasting less than one minute. Univariate analysis identified significant risk factors for VVR, including patient age, stress level, history of syncope, and the marking of multiple GGNs, as well as marking time. Multivariate logistic regression analysis revealed that patient stress (odds ratio [OR], 20.17; P < 0.001) and a history of syncope (OR, 8.06; P = 0.002) were independent risk factors for VVR.

CONCLUSION

VVR affects approximately 4.5% of patients undergoing CT-guided localisation of GGNs, often manifesting immediately after rising from the CT table. Patient stress and a history of syncope are significantly associated with an increased likelihood of VVR.

Endo-epicardial mapping of human sinus node in vivo: Novel electrophysiologic findings and anatomic correlations

BACKGROUND

The human sinoatrial node (SAN) pacemaker is a complex structure located at the right atrium (RA)-superior vena cava (SVC) junction.

OBJECTIVE

This study aimed to perform in vivo endocardial and epicardial electroanatomic mapping of human SAN in inappropriate sinus node tachycardia (IST) and to correlate electrical findings with anatomic observations from thoracoscopy during hybrid SAN-sparing IST ablation.

METHODS

All consecutive patients with diagnosis of symptomatic IST, refractory to or intolerant of drugs, and endocardial and epicardial mapping of SAN during hybrid ablation were included. Local activation time was defined by steepest -dV/dT on unipolar electrogram (EGM). Exit zone (EZ) was defined as the earliest activation site on endocardial and epicardial maps. Endo-epicardial delay was the time difference between the first endo-epicardial activations. Bipolar EGM morphology and SVC sleeve extension were analyzed.

RESULTS

A total of 61 patients were included. The SAN-EZ area was 1.4 ± 0.6 cm2; it was located in the superior anterior region of the RA in 46 (75.4%) patients and in the mid RA in 15 (24.6%) patients. The earliest activation occurred on epicardial SAN-EZ in all patients. The local activation time of the epicardial vs endocardial SAN-EZ was -30.8 ms vs -12.4 ms (P < .001). Endo-epicardial delay was 19.7 ms. Bipolar EGM reversed polarity at SAN-EZs was observed in 43 (70.5%) patients. SVC sleeve extension was 31.2 mm and inversely correlated with age.

CONCLUSION

The earliest SAN-EZ was found in the epicardium. Bipolar EGM reversed polarity is a novel electrophysiologic marker for SAN-EZs.

The Efficacy of Cardioneuroablation versus Midodrine in Patients with Vasovagal Syncope: Design and Rationale for the CAMPAIGN Trial

BACKGROUND

Current treatment strategies for vasovagal syncope (VVS) patients recommended by the guidelines are diverse, but effects of these therapies are still unsatisfactory with respective limitations on the indications. Cardioneuroablation (CNA), an innovative and promising therapy, has shown potently effective against syncopal recurrences in numerous observational studies. Recently, a single-center randomized clinical trial has reported CNA was superior to non-pharmacologic therapy for VVS patients. Therefore, this study is designed to compare the efficacy of CNA with pharmacologic treatment in a multicenter and randomized fashion.

METHODS AND RESULTS

The Cardioneuroablation versus Midodrine in Patients with Vasovagal Syncope (CAMPAIGN) study is an international multicenter, prospective, open-label, randomized controlled trial. The recurrent VVS patients with a positive response to tilt testing despite sufficient conventional treatment will be predominantly enrolled at different medical centers in China, Russia, and Turkey. All eligible participants will be randomized in a ratio of 1:1 to treatment with CNA versus midodrine, and followed up for 12 months after randomization. Approximately 184 subjects are projected to enroll from April 2023 to December 2024 with follow-up until 2025. The primary endpoint is the recurrence rate of syncope at 12 months of follow-up. The secondary endpoints are comprised of quality of life assessed with the Impact of Syncope on Quality of Life, tilt-induced syncope, blood pressure, cardiac deceleration capacity, and heart rate variability.

CONCLUSION

A prospective and multicenter clinical trial to compare outcomes of CNA with drug therapy is still lacking. The CAMPAIGN study will provide outcome-based evidence for VVS treatment strategy.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT05803148 (Date: March 9, 2023).

Pathophysiology and management of postural orthostatic tachycardia syndrome (POTS): A literature review

Postural Orthostatic Tachycardia Syndrome (POTS) is a form of cardiovascular autonomic disorders characterized by orthostatic intolerance and a symptomatic increase in heart rate upon standing, which can significantly impair patients' quality of life. Its pathophysiology is complex, multifactorial; thus, a variety of treatment approaches have been investigated. Recent studies have identified three primary POTS phenotypes-hyperadrenergic, neuropathic, and hypovolemic-each requiring tailored management strategies. First-line treatment for all patients focuses on lifestyle modifications, including increased fluid and salt intake, compression garment use, physical reconditioning, and postural training. Currently, there are no medications approved by the United States Food and Drug Administration (FDA)for POTS. Pharmacologic therapies are primarily used to manage specific symptoms, though the evidence supporting their efficacy is limited. In hyperadrenergic POTS, excessive norepinephrine production or impaired reuptake leads to sympathetic overactivity, making beta-blockers an effective option. Neuropathic POTS, resulting from impaired vasoconstriction during orthostatic stress, responds to agents that enhance vascular tone, such as pyridostigmine and midodrine. Hypovolemic POTS, often triggered by dehydration and physical deconditioning, respond primarily to volume expansion and exercise. This review article provides a comprehensive overview of the pathophysiology and management strategies for POTS, with a focus on phenotype-based approaches to guide tailored treatment and improve patient outcomes.

Evaluation and Management of Acute Transient Loss of Consciousness

Transient loss of consciousness (TLOC) is among the most common complaints encountered by clinicians across specialties. Possible etiologies of acute TLOC can be classified as neurologic, systemic, and functional. Neurologic causes occur due to a primary dysfunction of the neuronal circuitry that maintains awareness, as seen in epileptic seizures. Systemic conditions affect consciousness through global cerebral dysfunction or hypoperfusion with subsequent loss of postural tone through varied mechanisms such as hypoxia, hypoglycemia, and neurocardiogenic syncope. Functional neurologic disorders (also known as conversion disorders or psychogenic spells) refer to clinical conditions in which clinical presentation can mimic but does not completely fit with any specific neurologic or systemic disorder and conventional diagnostic testing reveals normal neurologic and systemic structures. The focus of this review will be on the diagnostic process and tools to differentiate between the multitudes of causes of TLOC.

Non-invasive Vagus Nerve Stimulation as an Adjunct Treatment for Inappropriate Sinus Tachycardia

Inappropriate sinus tachycardia (IST) is a type of cardiovascular autonomic dysfunction (CVAD) that mainly affects young women and has a prevalence of 1%-2%. IST is characterized by a sinus heart rate of >100 bpm at rest with a mean 24-h heart rate of >90 bpm associated with distressing symptoms such as palpitations, dizziness, and syncope. Here, we discuss a case of a 30-year-old woman who presented with complaints of tachycardia and associated symptoms, including dizziness, diaphoresis, and sudden loss of consciousness. The 24-h Holter monitoring was consistent with the diagnosis of IST. The patient had minimal improvement on β-blocker therapy. Due to persistent symptoms consistent with IST, she was started on non-invasive vagal nerve stimulation (n-VNS) therapy. Following 2 months of n-VNS applied twice daily over the carotid artery, the patient noted near-complete relief of her tachycardia and other debilitating symptoms. While n-VNS has recently been reported as a possible treatment for postural orthostatic tachycardia syndrome, another type of CVAD, to the best of our knowledge, this is the first report of low-level n-VNS as a treatment for IST. Our case study highlights the need for further clinical studies on the benefits of n-VNS in treating IST.

Inappropriate Sinus Tachycardia in Athletes: Could Nutraceuticals Play a Role?

Introduction: Inappropriate sinus tachycardia (IST) is a syndrome characterized by unexpectedly fast and prolonged sinus rates at rest or with minimal physical activity. Epidemiologic characteristics are uncertain, but most patients are young and female. When IST occurs in athletes, its management (controlling symptoms and reducing heart rate) can present additional challenges. We designed an observational pilot study to investigate whether a food supplement can be useful in the treatment of IST when standard therapy is refused. Methods: We enrolled 50 consecutive recreational athletes affected by frequent recurrences of IST. Twelve-lead ECG and Holter ECG parameters were recorded at enrollment (T0) and after a 6-month treatment (T1) with the food supplement. Symptoms and quality of life were also evaluated through specific questionnaires. The study population was compared to a historical control group of 25 patients receiving ivabradine as treatment for the same clinical condition. Results: The resting ECG heart rate was 88.7 ± 12.4 bpm (T0) and 73.6 ± 6.6 bpm (T1) (p < 0.00001); Holter average heart rate was 88.4 ± 3.3 bpm and 74.9 ± 4.8 bpm (p < 0.0001). Holter ECG maximum heart rate was 147.1 ± 16.7 bpm and 139.2 ± 16.8 bpm (p = 0.06); Holter minimum heart rate was 49.9 ± 6.5 bpm and 50.5 ± 6.9 bpm (p = 0.33). Finally, the number of sustained episodes decreased from 3.3 ± 1.7 to 0.8 ± 0.8 (p < 0.00001). The following variations in ASTA scores were observed: ASTA symptom scale (range: 0-27) decreased from 14.9 ± 2.1 to 5.8 ± 1.4 (p < 0.00001), while ASTA HR QoL (range: 0-39) decreased from 24.1 ± 2.1 to 10.8 ± 2.3 (p < 0.00001). Conclusions: The findings of our pilot study suggest that this food supplement could play a beneficial role in managing symptoms and improving quality of life in recreational athletes affected by IST who refuse standard medical therapy. These clinical effects appear to correlate with significant improvements in resting ECG parameters and some Holter ECG parameters.

Outcomes of Pediatric Patients with Excessive Postural Tachycardia After Attending an Intensive Interdisciplinary Pain Program: A Pilot Study

BACKGROUND/OBJECTIVES

Adolescents with autonomic disorders who attend Intensive Interdisciplinary Pain Treatment (IIPT) programs report improvements in functioning. However, it is unclear whether they experience corresponding improvements in physiological measures. As such, the aim of this pilot study was to examine changes in physiological measures in youth attending an IIPT program who demonstrated excessive postural tachycardia on an active stand test. The secondary goal was to examine associations between physiological measurements and self-reported measures of chronic orthostatic intolerance (cOI) and functioning.

METHODS

At admission and discharge, eighteen adolescents and young adults (AYAs) attending IIPT (M age = 17.39 years; SD = 2.15 years) completed an active stand test, measures of breathing rate and muscle tension, as well as self-reported measures of cOI symptoms and functioning.

RESULTS

AYAs showed significant reduction in active stand test heart rate increase (p < 0.001; d = 1.07) and maximum heart rate (p = 0.002, d = 0.76) from admission to discharge. Improvements were also observed in resting respiration rate (p = 0.001, d = 89) and resting trapezoid tension (p = 0.03, d = 0.49). Although patients showed significant improvements on self-report measures of functioning (p < 0.001, d = 1.78), changes on subjective report of cOI symptoms did not reach significance. Exploratory analyses that only included patients with a POTS diagnosis were consistent with the overall results.

CONCLUSIONS

Youth who demonstrated excessive postural tachycardia on active stand test at admission to an IIPT showed significant improvements from admission to discharge in their active stand maximum heart rate and heart rate increase, as well as respiration rate, muscle tension, and reports of their functioning. Future research is necessary to examine the mechanisms of change that contribute to symptom improvement.

Cerebral Blood Flow in Orthostatic Intolerance

Cerebral blood flow (CBF) is vital for delivering oxygen and nutrients to the brain. Many forms of orthostatic intolerance (OI) involve impaired regulation of CBF in the upright posture, which results in disabling symptoms that decrease quality of life. Because CBF is not easy to measure, rises in heart rate or drops in blood pressure are used as proxies for abnormal CBF. These result in diagnoses such as postural orthostatic tachycardia syndrome and orthostatic hypotension. However, in many other OI syndromes such as myalgic encephalomyelitis/chronic fatigue syndrome and long COVID, heart rate and blood pressure are frequently normal despite significant drops in CBF. This often leads to the incorrect conclusion that there is nothing hemodynamically abnormal in these patients and thus no explanation or treatment is needed. There is a need to measure CBF, as orthostatic hypoperfusion is the shared pathophysiology for all forms of OI. In this review, we examine the literature studying CBF dysfunction in various syndromes with OI and evaluate methods of measuring CBF including transcranial Doppler ultrasound, extracranial cerebral blood flow ultrasound, near infrared spectroscopy, and wearable devices.

Treatments for Long COVID autonomic dysfunction: a scoping review

PURPOSE

For Long COVID autonomic dysfunction, we have summarized published evidence on treatment effectiveness, clinical practice guidelines, and unpublished/ongoing studies.

METHODS

We first interviewed 11 stakeholders (clinicians, clinician/researchers, payors, patient advocates) to gain clinical insights and identify key areas of focus. We searched Embase, CINAHL, Medline, PsycINFO, and PubMed databases for relevant English-language articles published between 1 January 2020 and 30 April 2024. We also searched several other resources for additional relevant guidelines (e.g., UpToDate) and unpublished/ongoing studies (e.g., the International Clinical Trials Registry Platform). All information was summarized narratively.

RESULTS

We included 11 effectiveness studies that investigated numerous treatment regimens (fexofenadine + famotidine, maraviroc + pravastatin, selective serotonin reuptake inhibitors, nutraceutical formulations, multicomponent treatments, heart rate variability biofeedback, inspiratory muscle training, or stellate ganglion block). One randomized trial reported benefits of a nutraceutical (SIM01) on fatigue and gastrointestinal upset. The 11 guidelines and position statements addressed numerous aspects of treatment, but primarily exercise/rehabilitation, fluid/salt intake, and the use of compression garments. The 15 unpublished/ongoing studies are testing nine different interventions, most prominently ivabradine and intravenous immunoglobulin.

CONCLUSION

Existing studies on the treatment of Long COVID autonomic dysfunction are often small and uncontrolled, making it unclear whether the observed pre-post changes were due solely to the administered treatments. Guidelines display some overlap, and we identified no direct contradictions. Unpublished/ongoing studies may shed light on this critical area of patient management.

Isolated very low QRS voltage in at least one frontal lead is associated with vasovagal syncope in children

OBJECTIVE

To assess whether isolated very low QRS voltage of ≤0.3 mV in the frontal leads might be a marker for diagnosing paediatric vasovagal syncope and the risk of recurrence.

METHODS

We included 118 children with vasovagal syncope, comprising 70 males and 48 females in our retrospective analysis. All patients underwent head-up tilt test and supine 12-lead electrocardiography. Furthermore, the QRS voltage was measured from each one of the 12 leads on basal electrocardiography. Patients were followed up for 6-24 months (average, 16 months).

RESULTS

Eighty-six patients (73%) patients displayed isolated very low QRS voltage in frontal leads. Furthermore, the patients were classified into two groups based on the presence or absence of isolated very low QRS voltage. Enhanced syncopic spells over the past 6 months, and the positive rates of head-up tilt test were observed in patients having isolated very low QRS voltage in the frontal leads than those without isolated very low QRS voltage (p < 0.05). The single factor and time-to-event analyses also showed an increased syncope recurrence rate in patients with isolated very low QRS voltage in frontal leads when compared with those without isolated very low QRS voltage (p < 0.01).

CONCLUSIONS

Isolated very low QRS voltage in frontal leads is correlated with the positive response of the head-up tilt test in children who experience syncope and its recurrence post-treatment. Hence, isolated very low QRS voltage in frontal leads might become a novel diagnostic indicator and a risk factor for syncope recurrence in children with vasovagal syncope.

High Incidence of Autonomic Dysfunction and Postural Orthostatic Tachycardia Syndrome in Patients with Long COVID: Implications for Management and Health Care Planning

BACKGROUND

Autonomic dysfunction, including postural orthostatic tachycardia syndrome (POTS), has been reported in individuals with post-acute sequelae of COVID-19 (PASC). However, the degree of dysautonomia in PASC has not been compared to those with POTS and healthy controls.

METHODS

All participants were prospectively enrolled between August 5, 2021 and October 31, 2022. Autonomic testing included beat-to-beat hemodynamic monitoring to assess respiratory sinus arrhythmia, Valsalva ratio, and orthostatic changes during a 10-minute active standing test, as well as sudomotor assessment. The Composite Autonomic Symptom Score (COMPASS-31) was used to assess symptoms and the EuroQuol 5-Dimension survey (EQ-5D-5L) was used to assess health-related quality of life (HrQoL) measures.

RESULTS

A total of 99 participants (n = 33 PASC, n = 33 POTS, and n = 33 healthy controls; median age 32 years, 85.9% females) were included. Compared with healthy controls, the PASC and POTS cohorts demonstrated significantly reduced respiratory sinus arrhythmia (P < .001), greater heart rate increase during 10-minute active standing test (P < .001), greater burden of autonomic dysfunction evidenced by higher COMPASS-31 scores across all subdomains (all P < .001), and poor HrQoL across all EQ-5D-5L domains (all P < .001), lower median EuroQol-visual analogue scale (P < .001), and lower utility scores (P < .001). The majority (79%) of those with PASC met the internationally established criteria for POTS.

CONCLUSION

The prevalence of autonomic symptomology for POTS was high in those with PASC, leading to poor HrQoL and high health disutility. Autonomic testing should be routinely undertaken in those with PASC to aid diagnosis and direct appropriate management to improve health outcomes.

Novel brain SPECT imaging unravels abnormal cerebral perfusion in patients with postural orthostatic tachycardia syndrome and cognitive dysfunction

Cognitive dysfunction is frequently reported in individuals with postural orthostatic tachycardia syndrome (POTS), possibly resulting from reduced cerebral blood flow (CBF). We used brain SPECT, an accessible imaging modality that has not been systematically evaluated in this patient group. Retrospective review of participants from our registry was undertaken to identify those who had a brain SPECT performed for investigation of cognitive dysfunction. Abnormal CBF was taken as z-score > 2 standard deviations of healthy control reference values. Patient reported outcome measures (PROMs) such as autonomic, gastric and quality of life symptom scores were analyzed. From a total of 56 participants (mean 34.8 ± 10.7 years, 88% females), PROMs indicate: moderate to severe autonomic dysfunction in 75%; at least mild to moderate gastroparesis in 23%; low global health rating and utility scores. Abnormal CBF was seen in 61% but did not differ by POTS triggers. The regions with the lowest mean z-scores were the lateral prefrontal and sensorimotor cortices. Hierarchal regression analyses found number of brain regions with abnormal CBF, autonomic and gastric symptoms to account for 51% of variances in health utility. Cerebral hypoperfusion is prevalent in those with POTS and cognitive dysfunction even whilst supine, contributing to reduced quality of life.

Oral medications for the treatment of postural orthostatic tachycardia syndrome; a systematic review of studies before and during the COVID-19 pandemic

Background

Postural Orthostatic Tachycardia Syndrome (POTS) is a complex form of dysautonomia that presents with abnormal autonomic reflexes upon standing, leading to symptoms such as lightheadedness, tachycardia, fatigue, and cognitive impairment. The COVID-19 pandemic has brought renewed attention to POTS due to its overlap with post-acute sequelae of COVID-19 (PASC). Studies have found that a substantial percentage of COVID-19 survivors exhibit symptoms resembling POTS, elevating POTS diagnoses to previously unseen levels. We systematically reviewed the literature for existing high-quality evidence on potential interventions.

Methods

A systematic review of the literature was performed to identify studies of oral medications for the management of POTS. We searched for published manuscripts on the medical management of POTS through 6 April 2024 which met pre-specified inclusion criteria. We conducted quality appraisal and assessed risk of bias before extracting the data and performing synthesis to determine the current state of the evidence; particularly in the context of PASC.

Results

The study search and selection process identified 32 studies that met inclusion criteria, comprising randomized controlled trials, observational studies, and systematic reviews. Most included studies were judged to be of moderate to high quality, with largely low risk of bias. The most frequently studied medications were beta-blockers, ivabradine, and midodrine. Ivabradine and midodrine demonstrated the highest rate of symptomatic improvement, while beta-blockers showed the largest reduction in heart rate variability. Limited evidence was available for PASC-associated POTS, but findings suggest that treatments may have similar efficacy in both PASC and non-PASC cases.

Conclusion

Ivabradine, midodrine, and beta-blockers currently appear to be reasonable front-line choices in pharmacologic management of POTS (PASC associated and otherwise). Further RCTs that evaluate long term outcomes of medications are needed to further establish evidence based pharmacologic treatment approaches for POTS. Particular areas of inquiry include differential efficacy of recommended therapies based on POTS subtypes, and a need for treatments directly targeting the underlying autonomic nervous system dysfunction.

Systematic review registration

PROSPERO, identifier CRD42024505967, https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=505967.

Neuroinflammation at the Dorsolateral Inferior Medulla: A Possible Central Nervous System Localization for POTS and Long COVID

Both postural orthostatic tachycardia syndrome (POTS) and Long COVID are currently viewed as heterogeneous disorders with complex, multi-factorial and multi-systemic pathophysiology. POTS, one of the most common autonomic disorders, is a frequent sequela of SARS-CoV-2 infection. Both POTS and autonomic dysfunction, in general, are major pathophysiologic mechanisms of Long COVID. There is emerging evidence that neuroinflammation of the brainstem may be one of the mechanisms of POTS and Long COVID. This commentary argues that neuroinflammation at the dorsolateral inferior medulla is a possible central nervous system localization for POTS and Long COVID based on the limited scientific literature available to date and the neurologic manifestations of both disorders. Further studies involving advanced neuroimaging techniques and animal models with immunohistochemical brainstem tissue assessments are needed to understand how and why possible neuroinflammation at the dorsolateral inferior medulla may occur in patients with Long COVID, POTS and other disorders involving autonomic dysfunction.

A Community-Based Trial of Commercially Available Compression Tights in Patients With Postural Orthostatic Tachycardia Syndrome

BACKGROUND

Compression garments reduce heart rate and symptoms in patients with postural orthostatic tachycardia syndrome in an acute laboratory setting. Patients taking medications controlling heart rate have less benefit from compression than those not on medications. The effectiveness of commercially available garments in a community-based setting, with and without medication use, is not known.

OBJECTIVES

The authors sought to evaluate commercially available compression tights in a community-based setting both with, and without, medications modulating heart rate, using a clinical trial with 2 before-after protocols conducted in a randomized crossover fashion.

METHODS

Participants (N = 26) held medications during protocol #1 and took medications as normal during protocol #2. For each, participants completed 4, 10-minute active stand tests in the morning (AM) and afternoon (PM) with the garments on (ON) and off (OFF) (AM-OFF, AM-ON, PM-ON, and PM-OFF). Heart rate (Holter monitor) and symptoms (Vanderbilt Orthostatic Symptom Score [VOSS]) were measured for each standing test.

RESULTS

Protocol #1: Standing heart rate was reduced (105 [99-116] beats/min vs 119 [105-130] beats/min; P < 0.001) and symptoms improved (P < 0.001), during AM-ON vs AM-OFF. Standing heart rate (P = 0.04) and symptoms (P = 0.004) increased when compression was removed after several hours. Protocol #2: Standing heart rate was reduced (84 [77-90] beats/min vs 89 [84-100] beats/min; P < 0.001), and symptoms improved (P = 0.03), during AM-ON vs AM-OFF. Standing heart rate (P = 0.02) and symptoms (P < 0.001) increased when compression was removed after several hours.

CONCLUSIONS

Commercially available compression tights reduced heart rate and symptoms both acutely and after several hours of use. This additional benefit persisted whether concomitant medications were used. (Compression Garments in the Community With POTS [COM-COM-POTS]; NCT04881318).

Internal Tremor in Long COVID May Be a Symptom of Dysautonomia and Small Fiber Neuropathy

Background/Objectives: Internal tremor (IT) is often reported by patients with post-acute sequelae of SARS-CoV-2, also known as Long COVID, as a distressing and disabling symptom. Similarly, physicians are typically perplexed by the nature and etiology of IT and find it extremely challenging to manage. Methods: We describe a patient with Long COVID who experienced IT as part of post-COVID postural orthostatic tachycardia syndrome (POTS) and small fiber neuropathy (SFN) and review the limited literature available on this topic. Results: Our patient's IT improved significantly after intravenous saline infusions, but there was no effect on IT with oral hydration, increased oral sodium chloride intake, neuropathic pain medications, muscle relaxants, or medications used for the treatment of POTS. Conclusions: Based on this case, our clinical experience, and the limited literature available to date, we believe IT is a manifestation of POTS and SFN, which may be driven by hypovolemia, cerebral hypoperfusion, sympathetic overactivity, neuropathic pain, and mast cell hyperactivation. Subjective description, objective findings, and diagnostic and therapeutic considerations in patients with IT and Long COVID are discussed.

The Cardiac Output-Cerebral Blood Flow Relationship Is Abnormal in Most Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients with a Normal Heart Rate and Blood Pressure Response During a Tilt Test

INTRODUCTION

Orthostatic intolerance is highly prevalent in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and is caused by an abnormal reduction in cerebral blood flow (CBF). In healthy controls (HCs), the regulation of CBF is complex and cardiac output (CO) is an important determinant of CBF: a review showed that a 30% reduction in CO results in a 10% reduction in CBF. In previous and separate ME/CFS studies, we showed that CO and CBF decreased to a similar extent during tilt testing.

THE AIM OF THE STUDY

to test the relationship between CBF and CO, which seems to be abnormal in ME/CFS patients and is different from that in HCs.

METHODS

In this retrospective study we analyzed this relationship in a large group of patients. To compare the patient data with those of HCs, we focused on patients with a normal heart rate (HR) and blood pressure (BP) response to upright tilt. Also, the influence of clinical data was analyzed. A total of 534 ME/CFS patients and 49 HCs underwent tilt testing with measurements of HR, BP, CBF, CO, and end-tidal PCO2. To measure CBF, extracranial Doppler flow velocity and vessel diameters were obtained using a GE echo system. The same device was used to measure suprasternal aortic flow velocities. End-tidal PCO2 was recorded using a Nonin Lifesense device.

RESULTS

In 46 (9%) patients, CO and CBF changes were in the normal range for HCs, and in 488 (91%) an abnormal CO and CBF reduction was found. In patients with abnormal CO and CBF reductions, the slope of the regression line of CO versus CBF reduction was almost 1. The multiple regression analysis of the latter group showed that the CO reduction for the most part predicted the CBF reduction, with a limited role for the PETCO2 reduction.

CONCLUSIONS

Two different patient groups with a normal HR and BP response during the tilt were identified: those with a CO and CBF in the normal range for HCs and those with an abnormal CO and CBF reduction during the tilt (91% of patients). In the latter group of patients, an almost 1:1 relationship between the CO and CBF reduction suggests the absence of compensatory vasodilation in the cerebral vasculature. This might indicate endothelial dysfunction in most ME/CFS patients and may have clinical and therapeutic implications.

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

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

Exercise Interventions in the Management of Postural Orthostatic Tachycardia Syndrome: A Scoping Review

Objective

This review aims to identify the exercise rehabilitation approaches used for patients with POTS (Postural Orthostatic Tachycardia Syndrome).

Methods

An electronic literature search was conducted using the PubMed database, covering January 2005 to October 2023. Studies were included if they reported an exercise rehabilitation intervention for POTS patients and resulting clinical outcomes. Eligible study designs included randomized and non-randomized clinical trials and case reports.

Results

Initially, 34 publications were identified, but only 14 met the criteria for inclusion. After a thorough analysis, 7 studies were included in this scoping review. The majority of the studies stated aerobic exercise training significantly improves symptoms in most of the patients with orthostatic intolerance, reduces the frequency of syncope, enhances patient quality of life, and improves autonomic balance as assessed by heart rate variability analysis and cardiorespiratory endurance. Short-term exercise training was found to boost physical fitness and cardiorespiratory responses in patients with POTS. Therefore, exercise training can serve as an effective non-pharmacological therapy for managing POTS.

Conclusion

This scoping review identified different approaches used for exercise rehabilitation in POTS patients. However, more research is needed to identify the optimal exercise rehabilitation program for this patient population.

Adaptive Approaches to Exercise Rehabilitation for Postural Tachycardia Syndrome and Related Autonomic Disorders

Exercise is a well-documented, nonpharmacologic treatment for individuals with autonomic dysfunction and associated orthostatic intolerance, such as postural tachycardia syndrome and related disorders. Exercise has been shown to increase blood volume, reverse cardiovascular deconditioning, and improve quality of life. Current first-line standard of care treatment for autonomic dysfunction combines graded approaches to exercise with medications and lifestyle modifications. However, current exercise rehabilitation protocols for postural orthostatic tachycardia syndrome contain rigid timelines and progression paradigms that often threaten tolerability and adherence. In addition, they fail to account for clinical variables potentially critical to care and lack guidance for individualization, limiting accessibility to patients with co-morbidities that affect exercise appropriateness and safety. Therefore, we introduce an adaptive approach to exercise prescription for orthostatic intolerance that allows patient-specific modifications to meet functional goals for a wider spectrum of patients, thus improving adherence. The proposed approach integrates iterative physiological and symptomatic assessments to provide flexible, yet structured, exposure to aerobic exercise and strength training to improve functional capacity and tolerance of daily activities for patients with postural tachycardia syndrome and related autonomic disorders.

Yield of Tilt Table Test in Diagnosing Syncope in Patients With Suspected Neurally Mediated Syncope

Background

Syncope is a common medical condition. The reflex or neurally mediated syncope (NMS) is the most frequent type. The tilt table test (TTT) helps distinguish syncope from other common causes of complete loss of consciousness, such as epilepsy, define syncope subtypes and guide management. This study aimed to assess the TTT yield in patients with suspected NMS and to compare the nitroglycerin (NTG) and isoproterenol (Isuprel) provocative protocols.

Methods

This study was a retrospective analysis of the data of 426 consecutive patients who underwent TTT at the Heart Center at King Faisal Specialist Hospital and Research Center (KFSH&RC), Riyadh, Saudi Arabia, between January 1, 2006, and March 31, 2017.

Results

The age at referral for TTT ranged from 7 to 84 years (mean 38.4 ± 15.75 years), and 212 (49.8%) were males. The main clinical manifestations were recurrent syncope in 259 patients (60.8%), a single syncopal episode in 60 (14.1%), and pre-syncope or dizzy spells without loss of consciousness in 171(25.1%). The test was positive in 295 patients (69.2%), with type 1 (mixed response) seen in 151 patients (51.19%), type 2a (cardioinhibitory without pause) in 16 (5.4%), type 2b (cardioinhibitory with pause) in 10 patients (3.39%), and type 3 (vasodepressor) in 118 patients (40%). A false positive test was seen in 11 patients (2.6%) and a false negative in 27 patients (6.3%). The overall test sensitivity was 91%, specificity was 89%, positive predictive value (PPV) was 96%, and negative predictive value (NPV) was 79%.

Conclusions

The TTT is beneficial in diagnosing syncope in males and females and patients of young and old ages. A provocative test utilizing NTG provides a shorter, more straightforward test with the same diagnostic accuracy as the isoproterenol test. Lifestyle modification is effective and remains the primary intervention in managing patients with NMS.

Cerebral blood flow and end-tidal CO2 predict lightheadedness during head-up tilt in patients with orthostatic intolerance

Orthostatic intolerance (OI) is a common problem. Reliable markers of OI are missing, as orthostatic blood pressure and heart rate poorly correlate with orthostatic symptoms. The objective of this study was to assess the relationship between orthostatic lightheadedness and cerebral blood flow. In this retrospective study patients with OI were evaluated at the Autonomic Laboratory of the Department of Neurology, Brigham and Women's Faulkner Hospital, Boston. The 10-minute head-up tilt test was performed as a part of autonomic testing. Orthostatic lightheadedness was evaluated at every minute of the head-up tilt. Heart rate, blood pressure, capnography, and cerebral blood flow velocity (CBFv) in the middle cerebral artery using transcranial Doppler were measured. Repeated-measures design with a linear mixed-effects model was used to evaluate the relationship between orthostatic lightheadedness and hemodynamic variables. Correlation analyses were done by calculating Pearson's coefficient. Twenty-two patients with OI were compared to nineteen controls. Orthostatic CBFv and end-tidal CO2 decreased in OI patients compared to controls (p < 0.001) and predicted orthostatic lightheadedness. Orthostatic heart rate and blood pressure failed to predict orthostatic lightheadedness. The lightheadedness threshold, which marked the onset of lightheadedness, was equal to an average systolic CBFv decrease of 18.92% and end-tidal CO2 of 12.82%. The intensity of lightheadedness was proportional to the CBFv and end-tidal CO2 decline. Orthostatic lightheadedness correlated with systolic CBFv (r=-0.6, p < 0.001) and end-tidal CO2 (r=-0.33, p < 0.001) decline. In conclusion, orthostatic CBFv and end-tidal CO2 changes predict orthostatic lightheadedness and can be used as objective markers of OI.

Metabolic targets in the Postural Orthostatic Tachycardia Syndrome: A short thematic review

Postural Orthostatic Tachycardia Syndrome (POTS) is a chronic autonomic condition hallmarked by orthostatic intolerance and tachycardia in the upright position. POTS impacts approximately 1-3 million people in the U.S. alone, in which the majority of patients are premenopausal women. The etiology of POTS is multi-factorial with three primary clinical subtypes, including neuropathic, hyperadrenergic, and hypovolemic POTS. Recent evidence suggests potential metabolic associations with POTS pathophysiology, particularly involving insulin resistance and abnormal vasoactive gut hormones. This review aims to characterize POTS phenotypes and explore potential metabolic links, focusing on insulin resistance and vasoactive gut hormones. Understanding the metabolic aspects of POTS pathophysiology could provide novel insights into its mechanisms and guide therapeutic approaches.

Cardiac Arrhythmias and Autonomic Dysfunction Associated With COVID-19: A Scientific Statement From the American Heart Association

Cardiac arrhythmias are commonly noted in patients during infections with and recovery from COVID-19. Arrhythmic manifestations span the spectrum of innocuous and benign to life-threatening and deadly. Various pathophysiological mechanisms have been proposed. Debate continues on the impact of incident and exacerbated arrhythmias on the acute and chronic (recovery) phase of the illness. COVID-19 and COVID-19 vaccine-associated myocardial inflammation and autonomic disruption remain concerns. As the pandemic has transformed to an endemic, with discovery of new SARS-CoV-2 variants, updated vaccines, and potent antiviral drugs, vigilance for COVID-19-associated arrhythmic and dysautonomic manifestations remains. The objective of this American Heart Association scientific statement is to review the available evidence on the epidemiology, pathophysiology, clinical presentation, and management of cardiac arrhythmias and autonomic dysfunction in patients infected with and recovering from COVID-19 and to provide evidence-based guidance. The writing committee's consensus on implications for clinical practice, gaps in knowledge, and directions for future research are highlighted.

Prevalence of Autoantibodies in Patients with Hereditary Alpha-Tryptasemia

INTRODUCTION

Hereditary alpha-tryptasemia (HαT) is associated with postural orthostatic tachycardia syndrome (POTS), hypermobile Ehlers-Danlos syndrome (hEDS), and mast cell activation syndrome (MCAS). While POTS, hEDS, and MCAS have all demonstrated increased prevalence of autoimmunity, this has not been investigated in HαT populations. Our objective was to describe the prevalence of autoantibodies in individuals with HαT.

METHODS

We retrospectively studied a cohort of patients with positive genotyping for HαT at a tertiary-care allergy clinic. Demographic data including previous autoimmune history and autoantibody serologies were extracted on chart review. A literature search was conducted to determine the prevalence of specific autoimmune and autoantibody prevalences in the general population. We compared the proportions of autoantibody positivity and established autoimmune diseases in our cohort of HαT individuals against those in general populations.

RESULTS

We identified 101 patients with HαT. Median age was 43 years (range 15-75), and most were female (87/101; 86.1%). Prevalence of self-reported drug hypersensitivity was 52/101 (52.5%) patients. The proportion of individuals with HαT with positive tTG antibody (3/61, 4.9%) was significantly higher than that reported in the general population (133/16,667, 0.8%) (p < 0.001). The prevalence of systemic lupus erythematosus (SLE) (1/101, 1%) and celiac disease (5/101, 5%) in our cohort were found to be significantly higher than the prevalence in the general population (194/96,996, 0.2% [p = 0.035] and 26/2,845, 0.9% [p < 0.001], respectively).

CONCLUSION

Patients with HαT have increased prevalence of celiac disease, SLE, and positive anti-tTG serology, as well as self-reported drug hypersensitivity, relative to general populations.

Exercise in Postural Orthostatic Tachycardia Syndrome: Focus on Individualized Exercise Approach

Exercise is a vital component of health and is commonly utilized as a non-pharmacologic therapy for many disorders, including postural orthostatic tachycardia syndrome (POTS). However, exercise intolerance is a key feature of POTS and other autonomic disorders and, therefore, presents a major barrier for many patients. Despite exercise being uniformly recommended as a therapeutic intervention, a majority of patients with POTS, especially those with severe orthostatic intolerance and fatigue, are unable to complete or sustain rigorous exercise programs or successfully integrate them into their daily routine. In this narrative review, we discuss the current literature on exercise and POTS and our clinical experience with a home-based exercise approach developed at the Dysautonomia Clinic. We conclude that individualized exercise programs that are delivered remotely by a certified physical therapist may be convenient, easily accessible, and safe for patients with POTS, especially those with severe symptoms who may be home- or bedbound. Future randomized controlled studies are needed to quantify and characterize the benefits of home-based exercise programs delivered remotely compared to standard therapy.

One Size Does Not Fit All: An Exploration of Compression Garment Use in Patients With Postural Orthostatic Tachycardia Syndrome

Background

Postural orthostatic tachycardia syndrome (POTS) is a chronic form of orthostatic intolerance that primarily affects female patients. Despite the severity of POTS, there are no approved medications for use in patients with this disorder. Compression garments are a commonly prescribed nonpharmacological treatment, but little is known about the patient experience with compression. In this study we aimed to evaluate the patient experience with compression garments using a structured survey and semistructured telephone interviews.

Methods

A focused survey was designed as a component of a larger clinical trial on compression garment use in patients diagnosed with POTS. Building on the survey, semistructured telephone interviews were conducted with POTS patients. Recorded interviews were transcribed and coded in a thematic analysis using a descriptive-interpretive approach.

Results

A total of 27 participants completed the survey, and 20 participants completed the telephone interview. Patient experiences with compression were variable, with some participants experiencing significant benefits, and others reporting minimal to no benefits. Six themes that influenced garment use were identified: the potential benefit of the garment to improve symptoms, specific activities patients will be undertaking, environmental conditions, garment attributes, psychological and cognitive aspects, and financial considerations.

Conclusions

Participants engage in a daily cost-benefit analysis when making decisions to use a compression garment. Clinicians should be aware of the benefits of and factors that limit use of compression garments as a treatment for POTS.

Correlates and Predictors of Symptom Severity Over Time in People Under Investigation for Postural Orthostatic Tachycardia Syndrome

OBJECTIVE

Postural orthostatic tachycardia syndrome (POTS) is a poorly understood chronic disorder characterized by an unexplained excessive increase in heartbeat upon standing. The aim of this study was to investigate psychosocial and physiological correlates and predictors of symptom severity over time in patients presenting with POTS-like symptoms.

METHODS

Longitudinal cohort study of patients under investigation for POTS ( n = 149). Patients completed questionnaires at 1 month preclinic appointment and 6 months later. Diagnosis, blood pressure (BP), and heart rate (HR) measures were collected from medical records. Data were analyzed using hierarchical linear multiple regression.

RESULTS

Orthostatic and small fiber neuropathy (SFN) symptoms remained stable over time and were significantly correlated with distress, cardiac anxiety, threatening views of the illness, and cognitive-behavioral responses to symptoms, but not with emotional reactivity or social support. Baseline psychosocial factors collectively explained 48% ( F = 5.37, p < .001) of the variance in orthostatic symptoms, and 35% ( F = 3.49, p < .001) of the variance of SFN symptoms at baseline, but a nonsignificant amount of variance in symptoms at 6 months when controlling for baseline symptoms. Hemodynamic measures explained a significant 4% ( F = 3.37, p = .026) of variance of orthostatic symptoms at 6 months.

CONCLUSION

Symptom burden in patients with suspected POTS remained high over 6 months. Psychosocial factors explained a large amount of the variance in symptoms at baseline. As symptoms did not change/improve over time, baseline symptoms accounted for most of the variance in symptoms at 6 months. An integrated approach addressing psychosocial factors alongside medical treatments may promote adjustment to the condition and lessen symptom burden for this group.

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.

Current concepts in long COVID-19 brain fog and postural orthostatic tachycardia syndrome

Neurologic complications of long COVID-19 syndrome are one of the leading causes of global disability. In particular, post-COVID-19 cognitive dysfunction and dysautonomia in the form of postural orthostatic tachycardia syndrome (POTS) markedly affect patient quality of life and ability to return to work. The underlying pathophysiology of post-COVID-19 neurologic complications is unknown but is likely multifactorial with immune dysregulation and microvascular dysfunction playing central roles. Specific pathogenic factors with supportive evidence to date include cytokine-mediated inflammation, autoantibodies, immune exhaustion, disruption of the renin-angiotensin system, reduced serotonin levels, and microglial activation. The prevalence of post-COVID-19 cognitive dysfunction ranges from 10% to 88% and is affected by viral variant and hospitalization status among other factors, whereas that of long COVID-19 POTS is unknown due to referral bias and varying definitions. Treatment is largely supportive and often incorporates combined modalities. Marginal benefits with cognitive behavioral therapy, hyperbaric oxygen therapy, and supplements have been found for post-COVID-19 brain fog, whereas established POTS therapies aimed at improving venous return and reducing heart rate may reduce symptoms of long COVID-19 POTS. Although significant recovery has been noted for many cases of post-COVID-19 brain fog and POTS, prospective studies have revealed evidence of persistent symptoms and neurologic deficits a year after infection in some patients. Further studies that provide insight into the underlying pathophysiology of long COVID-19 are needed for development of target directed therapy.

Post-Acute COVID-19 Syndrome: Prevalence of Peripheral Microvascular Endothelial Dysfunction and Associations with NT-ProBNP Dynamics

BACKGROUND

Post-acute COVID-19 syndrome (PACS) has been linked to microvascular endothelial dysfunction as a potential underlying pathomechanism and can manifest even following a mild course of the initial infection. Prevalence of microvascular endothelial dysfunction and circulating natriuretic peptides in such PACS patients remains unknown.

METHODS

This prospective, cross-sectional cohort study enrolled 92 patients (82% females, median age 48 years) with PACS. Reactive hyperemia index (RHI) was evaluated with peripheral arterial tonometry, where <1.67 was defined as microvascular endothelial dysfunction, 1.67-2.0 as impaired function, and >2 normal endothelial function, on average 31 months after the acute infection. N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels were collected at 2 different time points within over a 1-year span.

RESULTS

In total, 41% of PACS subjects had microvascular endothelial dysfunction and 20% had impaired RHI. No major differences in clinical characteristics, routine chemistry laboratory testing, or symptom burden were observed across the groups. Only subjects with microvascular endothelial dysfunction and impaired endothelial function had a significant increase in NT-proBNP levels over time, and those with larger increase in NT-proBNP had significantly lower RHI. There was a significant correlation between relative or absolute increase in NT-proBNP and RHI, which remained significant in a multivariable adjusted linear regression.

CONCLUSIONS

Peripheral microvascular endothelial dysfunction was prevalent in a symptomatic PACS population long after recovery from a mild acute infection. Increases in NT-proBNP levels were associated with microvascular endothelial dysfunction, suggesting a link between, and providing a foundation for, future studies on post viral microvascular endothelial dysfunction in PACS.

Cardiovascular, autonomic symptoms and quality of life in children with hypermobile Ehlers-Danlos syndrome

Objectives

Hypermobile Ehlers-Danlos syndrome is a connective tissue disorder characterized by joint hypermobility and other systemic manifestations. Cardiovascular, autonomic symptoms and dysautonomia are frequently reported in adults with hypermobile Ehlers-Danlos syndrome and have been shown to have a negative impact on quality of life. However, there is scant literature on autonomic symptoms in pediatric patients with hypermobile Ehlers-Danlos syndrome. This study aims to characterize cardiovascular symptoms and diagnoses in pediatric patients with hypermobile Ehlers-Danlos syndrome and evaluate the impact of autonomic symptoms on quality of life.

Methods

As part of a longitudinal study, a consecutive sample of 70 patients with Ehlers-Danlos syndromes were recruited at routine clinical care visits. Medical history was reviewed, demographics were obtained, and patient-reported outcomes were completed by the patients.

Results

The average age of 70 patients was 15.8 years, and the majority were females (89%) and Caucasian (89%). The most common cardiovascular diagnoses were orthostatic intolerance (59%), dysautonomia (47%), and postural orthostatic tachycardia syndrome (21%). Most patients had an echocardiogram (77%), that was normal (82%). No patients had mitral valve prolapse, and only one patient had mild aortic root dilation (2%). Patient-reported outcomes revealed decreased quality of life associated with autonomic symptoms.

Conclusions

This study shows that most children with hypermobile Ehlers-Danlos syndrome have cardiovascular and autonomic symptoms, which have a negative impact on quality of life. Few patients with hypermobile Ehlers-Danlos syndrome have structural abnormalities on echocardiogram, which suggests that the cardiovascular symptoms experienced by patients are not due to structural cardiovascular disease and possibly reflective of autonomic pathology, though further studies will need to confirm this. This study confirms that cardiovascular and symptoms are prevalent and have a dramatic impact on quality of life in pediatric and young adult patients diagnosed with hypermobile Ehlers-Danlos syndrome.

Guidelines for the diagnosis and treatment of neurally mediated syncope in children and adolescents (revised 2024)

BACKGROUND

Significant progress has been made in the diagnosis and treatment of pediatric syncope since the publication of the "2018 Chinese Pediatric Cardiology Society (CPCS) guideline for diagnosis and treatment of syncope in children and adolescents" ("2018 Edition Guidelines"). Therefore, we have revised and updated it to assist pediatricians in effectively managing children with syncope.

DATA SOURCES

According to the "2018 Edition Guidelines", the expert groups collected clinical evidence, evaluated preliminary recommendations, and then organized open-ended discussions to form the recommendations. This guideline was developed by reviewing the literature and studies in databases including PubMed, Cochrane, EMBASE, China Biomedical Database, and Chinese Journal Full-text Database up to April 2024. Search terms included "syncope", "children", "adolescents", "diagnosis", and "treatment."

RESULTS

The guidelines were based on the latest global research progress and were evidence-based. The classification of syncope etiology, diagnostic procedures, postural tests, such as the active standing test, head-up tilt test, and active sitting test, clinical diagnosis, and individualized treatment for neurally mediated syncope in pediatric population were included.

CONCLUSIONS

The guidelines were updated based on the latest literature. The concepts of sitting tachycardia syndrome and sitting hypertension were introduced and the comorbidities of neurally mediated syncope were emphasized. Some biomarkers used for individualized treatment were underlined. Specific suggestions were put forward for non-pharmacological therapies as well as the follow-up process. The new guidelines will provide comprehensive guidance and reference for the diagnosis and treatment of neurally mediated syncope in children and adolescents.

Psychopathological Correlates and Psychosocial Functioning in Children and Adolescents with Syncope: A Systematic Review

Objective

Syncope is defined as a spontaneous and transient loss of consciousness and postural tone due to brief and reversible cerebral hypoperfusion. This review aimed to summarize the research findings regarding the psychological correlates associated with pediatric syncope. Moreover, the study aimed to deepen the understanding of the relationship between psychological disorders and the onset of syncopal episodes in childhood, focusing on clinical features and different clinical classifications.

Method

A systematic review was carried out from inception to January 2023, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, using the CINAHL Plus, APA PsycArticles, APA PsycInfo, MEDLINE, and Psychology and Behavioral Sciences Collection databases. The study search and selection were based on the Population Intervention Comparison Outcome Study Design (PICOS) strategy and the Quality Assessment was carried out using Critical Appraisal Skills Programme (CASP) scales. A combination of keywords related to a) syncope; b) psycho*; and c) child* (Subjects) was used. Studies concerning epilepsy-related syncope were excluded.

Results

Overall, 912 records were identified. After excluding non-English, non-original, and duplicate studies, 579 records were selected for the title screening, 88 for the abstract screening, 37 full-text articles were assessed for eligibility and a total of 14 were included. The Risk of Bias in the included studies was assessed and 78,6% of the studies satisfied robustness quality criteria. The findings highlighted that children and adolescents with syncope showed a higher rate of psychopathology as compared to the healthy and clinical controls. Furthermore, patients reported social withdrawal and poor quality of life.

Conclusions

The findings suggest that there is a robust relationship between psychopathology and syncope. Children and adolescents with syncope frequently report clinical symptoms related to emotional, relational, and psychosomatic dysregulation. Psychological assessment should be routinely included in the integrated care to identify potential targets for treatment and improve early differential diagnosis.

Role of new generation implantable loop recorders in managing undiagnosed pediatric cardiac symptoms

Pediatric cardiac symptoms such as palpitations, syncope, or seizure-like episodes pose diagnostic challenges for general pediatricians. These symptoms, though often benign, may reveal underlying arrhythmias or inherited cardiac conditions (ICCs), affecting the quality of life and limiting activity participation. The purpose of this study is to determine the effectiveness and safety of implantable loop recorders (ILRs) in diagnosing and managing arrhythmias in pediatric patients. A retrospective cohort study conducted over an 8-year period from January 2016 to December 2023 in a single pediatric cardiology center. A cohort of 155 pediatric patients (median age 11.4 years) who underwent ILR implantation were selected based on symptoms such as palpitations, chest pain, or syncope, and those with previously recorded arrhythmias or high-risk ICCs. The primary outcomes were the diagnostic yield of ILRs for arrhythmias and subsequent changes in patient management. Diagnostic yield was defined as the detection of relevant arrhythmias, such as pauses of 3 s or longer, high-degree AV block, sinus node dysfunction, supraventricular tachycardia, ventricular tachycardia, or inappropriate sinus tachycardia. The median follow-up period was 2.3 years (845 days). Diagnostic arrhythmias were recorded in 60% of patients with symptom-activated transmissions and 80% of device-activated transmissions. Sinus pauses (37.5%) and VT (30%) were the most common arrhythmias detected. In patients with syncope (n = 76), 30% had relevant arrhythmias. In the palpitations group (n = 20), 35% had relevant arrhythmias. Approximately 80% of patients with ILR-diagnosed arrhythmias underwent targeted management, including medication changes and additional procedures. No significant complications were observed; minor complications occurred in 2.5% of patients.Conclusions: New generation ILRs are effective and safe for diagnosing and managing pediatric arrhythmias, providing significant reassurance to patients and families. Further studies are needed to evaluate the impact of ILRs on quality of life and sports participation in high-risk young patients.

Management of Postural Orthostatic Tachycardia Syndrome in Pediatric Patients: A Clinical Review

Postural orthostatic tachycardia syndrome (POTS) is a chronic illness with unknown mortality and high morbidity, often diagnosed in the adolescent years. Published literature regarding POTS primarily focuses on the adult population, and guidance on treatment in pediatrics is sparse. The purpose of this clinical review is to evaluate the current literature on the management of POTS in pediatric patients. A search was conducted using the Cochrane database, Google Scholar, and PubMed. Studies were included if they evaluated the management of POTS, primarily in pediatric patients. Case reports and series were excluded. Eight published studies met the inclusion and exclusion criteria. To date, there are no US Food and Drug Administration-approved agents for the treatment of POTS. However, select pharmacological therapies have shown positive outcomes by addressing symptom origins, such as providing heart rate control, peripheral autonomic modulation, and targeting hypovolemia. Targeted pharmacological therapies studied in children and young adults include ivabradine, metoprolol, midodrine, pyridostigmine, intravenous crystalloid fluids, and fludrocortisone. Before adding pharmacotherapeutic interventions, non-pharmacologic interventions such as patient education, avoidance of symptom-triggering environments and medications, dietary fluid and sodium supplementation, exercise, and use of compression garments should be first attempted. Although the body of evidence for the management of POTS is expanding, additional research is needed to determine safe and efficacious dosing and establish clear guidelines for POTS in the pediatric population.