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

Orthostatic intolerance (OI), including postural orthostatic tachycardia syndrome (PoTS) and orthostatic hypotension (OH), are often reported in long covid, but published studies are small with inconsistent results. We sought to estimate the prevalence of objective OI in patients attending long covid clinics and healthy volunteers and associations with OI symptoms and comorbidities. Participants with a diagnosis of long covid were recruited from eight UK long covid clinics, and healthy volunteers from general population. All undertook standardized National Aeronautics and Space Administration Lean Test (NLT). Participants\' history of typical OI symptoms (e.g., dizziness, palpitations) before and during the NLT were recorded. Two hundred seventy-seven long covid patients and 50 frequency-matched healthy volunteers were tested. Healthy volunteers had no history of OI symptoms or symptoms during NLT or PoTS, 10% had asymptomatic OH. One hundred thirty (47%) long covid patients had previous history of OI symptoms and 144 (52%) developed symptoms during the NLT. Forty-one (15%) had an abnormal NLT, 20 (7%) met criteria for PoTS, and 21 (8%) had OH. Of patients with an abnormal NLT, 45% had no prior symptoms of OI. Relaxing the diagnostic thresholds for PoTS from two consecutive abnormal readings to one abnormal reading during the NLT, resulted in 11% of long covid participants (an additional 4%) meeting criteria for PoTS, but not in healthy volunteers. More than half of long covid patients experienced OI symptoms during NLT and more than one in 10 patients met the criteria for either PoTS or OH, half of whom did not report previous typical OI symptoms. We therefore recommend all patients attending long covid clinics are offered an NLT and appropriate management commenced.

High sodium intake is recommended for the treatment of postural tachycardia syndrome (POTS) to counteract the hypovolemia and elevated plasma norepinephrine that contribute to excessive orthostatic tachycardia, but evidence of its efficacy is not available.
This study tested whether a high sodium (HS) diet reduces orthostatic tachycardia (Δ heart rate) and upright heart rate compared with a low sodium (LS) diet in POTS patients, and secondarily its effect on plasma volume (PV) and plasma norepinephrine.
A total of 14 POTS patients and 13 healthy control subjects (HC), age 23 to 49 years, were enrolled in a crossover study with 6 days of LS (10 mEq sodium/day) or HS (300 mEq sodium/day) diet. Supine and standing heart rate, blood pressure, serum aldosterone, plasma renin activity, blood volume, and plasma norepinephrine and epinephrine were measured.
In POTS, the HS diet reduced upright heart rate and Δ heart rate compared with the LS diet. Total blood volume and PV increased, and standing norepinephrine decreased with the HS compared with the LS diet. However, upright heart rate, Δ heart rate, and upright norepinephrine remained higher in POTS than in HC on the HS diet (median 117 beats/min [interquartile range: 98 to 121 beats/min], 46 beats/min [interquartile range: 32 to 55 beats/min], and 753 pg/ml [interquartile range: 498 to 919 pg/ml] in POTS vs. 85 beats/min [interquartile range: 77 to 95 beats/min], 19 beats/min [interquartile range: 11 to 32 beats/min], and 387 pg/ml [interquartile range: 312 to 433 pg/ml] in HC, respectively), despite no difference in the measured PV.
In POTS patients, high dietary sodium intake compared with low dietary sodium intake increases plasma volume, lowers standing plasma norepinephrine, and decreases Δ heart rate. (Dietary Salt in Postural Tachycardia Syndrome; NCT01547117).

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UNASSIGNED: Activating autoantibodies (AAb) to adrenergic receptors (AR) have previously been reported in patients with postural tachycardia syndrome (POTS). These AAb may contribute to a final common pathway for overlapping disease processes, reflecting a possible autoimmune contribution to POTS pathophysiology. In prior studies, measurement of AAb activity was inferred from costly, low-throughput, and laborious physiological assays. In the present study, we developed and validated an alternative cell-based bioassay for measuring AAb activity in serum by means of pre-treatment with monoamine oxidase (MAO).
UNASSIGNED: A total of 37 POTS patients and 61 sex-matched healthy control participants were included. Serum was pre-treated with MAO to remove endogenous catecholamines that could falsely inflate AR activation by AAb. A receptor-transfected cell-based bioassay was used to detect presence of α1AR-AAb and β1AR-AAb in serum.
UNASSIGNED: MAO effectively degraded catecholamines as demonstrated by suppression of norepinephrine-induced α1AR activation in POTS (6.4 ​± ​0.7 vs. 5.5 ​± ​0.9; P ​= ​0.044) and in controls (4.1 ​± ​0.5 vs. 3.9 ​± ​0.6; P ​= ​0.001). Mean activity values were greater in the POTS vs. Controls for α1AR-AAb (6.2 ​± ​1.2 vs. 5.3 ​± ​1.0; P ​< ​0.001) and β1AR-AAb (5.7 ​± ​1.8 vs. 4.1 ​± ​0.9; P ​< ​0.001). Compared to controls, more POTS patients were positive for α1AR-AAb activity (22% vs 4%; P ​= ​0.007) and β1AR-AAb activity (52% vs. 2%; P ​< ​0.001).
UNASSIGNED: The co-presence of norepinephrine in serum samples can artifactually elevate α1AR and β1AR activity, which can be avoided by serum pre-treatment with MAO. Using this novel bioassay, we show that POTS patients have increased α1AR-AAb and β1AR-AAb activity compared to healthy controls in the largest POTS cohort reported to-date.

Orthostatic hypotension is a phenomenon triggered by a change in the position or posture of an animal, from a horizontal to a vertical head-up orientation, characterised by a blood pooling in the lower body and a reduction in central and cranial arterial blood pressure (P A). This hypotension elicits systemic vasoconstriction and tachycardia, which generally reduce blood pooling and increase P A Little is known about the mediation and importance of such cardiovascular adjustments that counteract the haemodynamic effects of orthostasis in ectothermic vertebrates, and some discrepancies exist in the information available on this subject. Thus, we sought to expand our knowledge on this issue by investigating it in a more elaborate way, through an in vivo pharmacological approach considering temporal circulatory changes during head-up body inclinations in unanaesthetised Boa constrictor To do so, we analysed temporal changes in P A, heart rate (f H) and cardiac autonomic tone associated with 30 and 60 deg inclinations, before and after muscarinic blockade with atropine, double blockade with atropine and propranolol, and α1-adrenergic receptor blockade with prazosin. Additionally, the animals\' f H variability was analysed. The results revealed that, in B. constrictor: (1) the orthostatic tachycardia is initially mediated by a decrease in cholinergic tone followed by an increase in adrenergic tone, a pattern that may be evolutionarily conserved in vertebrates; (2) the orthostatic tachycardia is important for avoiding an intense decrease in P A at the beginning of body inclinations; and (3) α1-adrenergic orthostatic vasomotor responses are important for the maintenance of P A at satisfactory values during long-term inclinations.

We investigated how the diagnosis of postural orthostatic tachycardia syndrome (POTS) would be changed due to diurnal variability in orthostatic tachycardia. The orthostatic vital sign test was administered to each patient twice, in the afternoon of the day of admission and the next morning (n = 113). Forty-six patients were diagnosed with POTS, and the remaining 67 patients were assigned to non-POTS group. Heart rate increments after standing were larger in the morning than in the afternoon in every group (all P < .001). Among the POTS patients, 82.6% fulfilled the diagnostic criteria for POTS in the morning and 52.2% in the afternoon. Most POTS group (65.2%) displayed normal result on single orthostatic vital sign test. Orthostatic intolerance symptoms were provoked in only 45.7% of the POTS patients, more frequently in the morning. In conclusion, diurnal variability in hemodynamic parameters and provoked symptoms significantly challenged the diagnosis of POTS.

OBJECTIVE: Healthy subjects with asymptomatic postural tachycardia at baseline were evaluated over a one year period to determine whether they developed non-postural versus orthostatic symptoms that could predispose them to develop Postural Tachycardia Syndrome (POTS).
METHODS: Participants (n=30) were recruited for a 1-year follow-up (FUP) study if at baseline they demonstrated a heart rate increment of ≥30bpm on head-up tilt (HUT). At FUP, HUT was repeated and four self-report questionnaires were used to assess symptoms.
RESULTS: Heart rate (HR) increment was reduced in 19 subjects (-11.8±7.4bpm) and increased in 11 subjects (8.3±6.1bpm) at FUP versus baseline. Heart rate increment at FUP demonstrated no correlation to general fatigue (r=0.006), body vigilance (r=0.195), or the component scores for physical (r=-0.087) and mental (r=-0.137) health of the SF-36. Similarly, there was no correlation between HR increment at FUP and orthostatic scores (r=0.04). However, orthostatic scores did show a significant positive correlation with general fatigue and body vigilance scores (r=0.374, r=0.392, respectively; p<0.05).
CONCLUSIONS: Despite meeting the heart rate criteria for POTS, these findings further support that the majority of young individuals express benign orthostatic tachycardia. In addition, after one year this patient population showed no predisposition to develop non-postural or postural symptoms that could lead to the full syndrome of POTS. These data further argue for the re-evaluation of the heart rate criteria for diagnosing POTS in young populations.

The school nurse is often the first person with whom a student may discuss untoward health symptoms and concerns. Being cognizant of the clinical features of postural orthostatic tachycardia syndrome (POTS) will help the nurse alleviate some of the student\'s anxiety. Due to misunderstandings and misconceptions about POTS, family and peers may disbelieve a student who is experiencing symptoms. Displaying compassion and support will help the student understand that someone does believe his or her symptoms. As the student\'s advocate, the school nurse will champion a plan for the student\'s health and safety in the academic environment.

OBJECTIVE: Patients with postural tachycardia syndrome (POTS) commonly complain of fatigue, unrefreshing sleep, daytime sleepiness and diminished quality of life. The study objective was to assess sleep quality in POTS patients using wrist actigraphy.
METHODS: Prospective study with control group.
METHODS: Patients with POTS (n = 36) and healthy subjects (n = 36) completed a detailed sleep log and actigraphy for 7 days.
RESULTS: Compared with healthy subjects, POTS patients have more self-reported problems including days with restless sleep (53 ± 30% vs. 21 ± 20%; P<0.001) and tiredness (75 ± 23% vs. 39 ± 27%; P<0.001). Using actigraphy, POTS patients have lower sleep efficiency (73 ± 13% vs. 79 ± 6%; P = 0.01). Actigraphy determined sleep onset latency (SOL) did not vary significantly in the two groups, but subjective SOL was higher in POTS patient (56 ± 66 min vs. 1 3 ± 9 min; P = 0.001). In POTS patients, there was a significant correlation between subjective complaints of tiredness and actigraphic sleep efficiency (Rs = -0.36; R(2) = 0.15; P = 0.01), significant correlations between actigraphic SOL and upright norepinephrine levels (P = 0.040), and between wake after sleep onset and standing heart rate (P = 0.02).
CONCLUSIONS: POTS patients have more sleep-related symptoms and poor sleep efficiency. The pattern of subjective vs. objective SOL mismatch is suggestive of sleep-state misperception. High norepinephrine correlated with actigraphic SOL, and this activation of the stress system may contribute significantly to a hyperarousal state with consequent insomnia, poor mental and physical health in POTS patients.