We previously showed that one-third of adolescents with postural orthostatic tachycardia syndrome (POTS) have hyperkinetic circulation. In a subsequent cohort, we compare participants with POTS grouped according to cardiac output (Q˙) versus oxygen uptake (V˙O2) function, whose circulatory response to exercise lay at the lower end of this distribution. We hypothesized that such grouping determines the circulatory response to incremental-protocol, upright, cycle ergometry by whatever blend of flow and resistance adjustments best maintains normal blood pressure. We reviewed data on 209 POTS participants aged 10-19 years (73% female) grouped as follows: Q˙-V˙O2 < 3.20 L·min per L·min were designated low Q˙ or hypokinetic variant (N = 31); normal-Q˙ had slopes between 3.21 and 7.97; hyperkinetic participants had Q˙-V˙O2 slope >8 L·min per L·min (N = 32). Heart rate response to exercise was virtually identical in each group. Mean stroke volume (SV) rose normally in the hyperkinetic group (51 ± 38%); less in the normal Q˙ group (22 ± 27%); but was flat in the low Q˙ group (-7 ± 16%). Mean arterial pressure was similar at rest while systemic vascular conductance was flat from rest to exercise in the hypokinetic group, and by comparison rose more steeply in the normal Q˙ (P < 0.001) and in the hyperkinetic (P = 0.02) groups. In conclusion, we identified a variant of POTS with a hypokinetic circulation maintained by a vasoconstricted state. We speculate that they cannot muster preload to augment exercise SV due to profound thoracic hypovolemia, and must resort to vasoconstriction in order to maintain perfusion pressure within working muscle.

To investigate the familial genetic characteristics of syncope in children. A detailed medical history was taken from four twin pairs of children complaining of dizziness, headache, chest tightness, chest pain, prodromal symptoms of syncope or syncope, meanwhile, these patients were given routine physical examination, 12-lead ECG, echocardiography, Holter ECG, EEG, MRI of the head and other tests to exclude cardio-cerebrovascular and pulmonary diseases, with those with unknown origin for syncope undergoing head-up tilt test (HUTT) and inquiry of detailed family history. The four pairs of twins with syncope beginning at 7-12years and induced mostly by standing position (4/5), and positive family history was noted in two pairs. Vasovagal syncope (VVS)-vasoinhibitory response pattern was predominant in HUTT (4/5). The results and the response pattern in HUTT might diversify between two members within same twin pair: one appeared as vasoinhibitory response pattern and one postural orthostatic tachycardia syndrome (POTS) pattern in the first pair, one vasoinhibitory response pattern and one negative response pattern in the second pair, vasoinhibitory response pattern in the third pair and negative response pattern in the fourth pair. The hereditary factors may play a more important role in younger children with syncope. Environment and psychological factors may induced syncope attack. The results and the response pattern in HUTT are diversified and which might different between two members within twin pair.

Patients with postural tachycardia syndrome often appear depressive and report diminished quality of life (QOL). In the current study, we first evaluated if the maximal heart rate (HR) increment after standing is associated with the clinical symptoms in patients with excessive orthostatic tachycardia (OT). Next, we investigated the correlations among the symptoms of orthostatic intolerance (OI), depression, and health-related QOL in these patients. Finally we assessed if patients with minimal OI symptoms suffer from depression or diminished QOL. We performed a comprehensive questionnaire-based assessment of symptoms in 107 patients with excessive OT with a ≥ 30 beats/min heart rate increment (or ≥ 40 beats/min in individuals aged between 12 and 19) within 10 min after standing up. An existing orthostatic intolerance questionnaire (OIQ), the Beck depression inventory-II (BDI-II), and the 36 Item Short-Form Health Survey were completed prior to any treatment. Correlation analyses among the items of the questionnaires and other parameters were performed. Additionally, patients with minimal OI symptoms were analysed separately. The maximal orthostatic HR increment was not associated with the clinical symptoms. The OI symptoms were significantly correlated with depression and diminished QOL. The BDI-II score demonstrated a positive linear relationship with total OIQ score (r = 0.516), and both physical and mental component summary scales of SF-36 showed a negative linear relationship with total OIQ score (r = -0.542 and r = -0.440, respectively; all p <0.001). Some OI symptoms were more strongly associated with depression, and others were more strongly related to QOL. Chest discomfort and concentration difficulties were the most influential OI symptoms for depression, while nausea and concentration difficulties were the most influential symptoms for physical and mental QOL, respectively. Dizziness and headache were the two most common complaints in patients with mild to moderate OI symptoms. In addition, subjects with minimal OI symptoms also had considerable deterioration in QOL. The OI symptoms, but not the maximal HR increment, are significantly correlated with depression and diminished QOL in patients with excessive OT. Therefore, pervasive history taking is important when encountering patients with excessive OT.

We aimed to explore whether the body mass index (BMI) was associated with the therapeutic response to oral rehydration solution (ORS) in children with postural tachycardia syndrome (POTS). Fifty-four children diagnosed as having POTS were included in this study. Fifty-six healthy children served as the controls. Children with POTS were treated with ORS, and their treatment response was evaluated. The baseline BMI was obtained by measuring the height and weight. The Pearson correlation was made between the baseline BMI and change in heart rate from supine to upright (ΔHR) and between baseline BMI and symptom score change (post-treatment vs. pre-treatment) in the POTS group. The value of BMI in predicting the therapeutic response to ORS was assessed by analyses of the receiver operating characteristic (ROC) curve. The BMI in the POTS group was significantly lower than that in the control group (18.22 ± 3.23 vs. 20.62 ± 3.05 kg/m(2), p < 0.01). There were no statistical differences between responders and non-responders in symptom scores before treatment (p > 0.05), but symptom score was lower in responders than that in non-responders (1.52 ± 0.95 vs. 2.32 ± 1.22, p < 0.01) after treatment. The BMI in responders to ORS was significantly lower than that of non-responders (16.32 ± 2.28 vs. 20.43 ± 2.74 kg/m(2), p < 0.01). The BMI was correlated negatively with ΔHR in the POTS group (n = 54, r = -0.766, p < 0.01) and with the decrease in symptom scores after treatment in POTS patients (n = 54, r = -0.28, p < 0.05). ROC curve revealed the area under the curve to be 92.3 % (95 % confidence interval 0.829-0.996). A cutoff value of the BMI of 18.02 kg/m(2) had high sensitivity (92 %) and high specificity (82.8 %) for predicting the effect of ORS treatment for POTS. BMI is associated with the therapeutic response to ORS in children with POTS.

To determine if children with benign joint hypermobility (BJH) syndrome and chronic functional pain disorders have more autonomic dysfunction. Retrospective chart review study of pediatric patients seen in the pediatric neurogastroenterology and autonomic clinic who underwent autonomic testing and had either a Beighton score of ≥6 and met Brighton criteria for BJH (with BJH) or a score of ≤2 (no BJH). Twenty-one female subjects (10 without BJH) met inclusion criteria; 64% of BJH had diagnosis confirmed by genetics consultation. We evaluated for postural tachycardia syndrome, syncope, orthostatic intolerance, and orthostatic hypotension. None of these diagnoses, as well as baseline heart rate, peak heart rate in first 10 minutes of head up tilt (P = .35 and P = .61, respectively), and sudomotor index (suggestive of autonomic neuropathy) (P = .58), showed differences between the groups. Age of onset of symptoms was also similar (P = .61) (BJH vs without BJH: median [range]:15.6 years [12.9-17.5] vs 15.4 years [11.1-18.2]). There was no difference between groups in complaints of migraine, chronic nausea, chronic fatigue, lightheadedness, dizziness, fainting >3 times/lifetime, delayed onset of sleep, irritable bowel syndrome, dyspepsia, abdominal migraine, functional abdominal pain, constipation, or fibromyalgia. Children with chronic functional pain disorders and BJH have autonomic testing findings and comorbid features compared with a similar cohort of subjects without BJH, suggesting that BJH is not the driver of the autonomic and comorbid disorders.

Patients with autonomic dysfunction may present with a variety of seemingly unrelated symptoms, both generalised and involving specific systems, including fatigue, difficulty concentrating, orthostatic intolerance, palpitations, constipation or diarrhoea, early satiety, urinary retention or incontinence and erectile dysfunction. Failure to connect the diverse symptoms with a single underlying mechanism may lead to incorrect diagnoses, inappropriate interventions and frustration on the part of both doctors and patients. We describe recent developments in the understanding of the pathophysiology of autonomic dysfunction, including the link between the autonomic and immune systems resulting in the 'inflammatory reflex'. We then provide a rationale to guide the management of patients exhibiting features of autonomic dysfunction, including postural tachycardia syndrome.

Postural tachycardia syndrome (POTS) is one of the major causes of orthostatic intolerance in children. We systematically reviewed the pathogenesis and the progress of individualized treatment for POTS in children. The data analyzed in this review are mainly from articles included in PubMed and EMBASE. The original articles and critical reviews about POTS were selected for this review. Studies have shown that POTS might be related to several factors including hypovolemia, high catecholamine status, abnormal local vascular tension, and decreased skeletal muscle pump activity. In addition to exercise training, the first-line treatments mainly include oral rehydration salts, beta-adrenoreceptor blockers, and alpha-adrenoreceptor agonists. However, reports about the effectiveness of various treatments are diverse. By analyzing the patient's physiological indexes and biomarkers before the treatment, the efficacy of medication could be well predicted. The pathogenesis of POTS is multifactorial, including hypovolemia, abnormal catecholamine state, and vascular dysfunction. Biomarker-directed individualized treatment is an important strategy for the management of POTS children.

Central nervous system dysfunction with myalgic encephalomyelitis (ME) has been suggested as the main cause of chronic fatigue syndrome. Fluctuation of the symptom severity and hierarchy is a characteristic feature in ME patients. The characteristics of the sympathetic activation may differ between the "good days" and "bad days" in them. Twenty-four ME patients with orthostatic intolerance underwent a conventional 10-min active standing test and echocardiography both on a "good day" and a "bad day", defined according to the severity of their symptoms. The mean heart rate at rest was significantly higher on the "bad days" than on the "good days". During the standing test on a "bad day", 5 patients (21 %) failed to maintain an upright posture for 10 min, whereas on a "good day" all the 24 patients maintained it. Postural orthostatic tachycardia (POT) (increase in heart rate ≥30 beats/min) or severe POT (heart rate ≥120 beats/min) was observed on the "bad days" in 10 patients (43 %) who did not suffer from the severe tachycardia on the "good days", suggesting the exaggerated sympathetic nervous activation. In contrast, POT did not occur or severe POT was attenuated on the "bad days" in 5 patients (21 %) who developed POT or severe POT on the "good days", suggesting the impaired sympathetic activation. Echocardiography revealed significantly lower mean values of both the left ventricular end-diastolic diameter and stroke volume index on the "bad days" compared with the "good days". In conclusion, in ME patients with orthostatic intolerance, the exaggerated activation of the sympathetic nervous system while standing appears to switch to the impaired sympathetic activation after the system is loaded with the additional accentuated stimuli associated with the preload reduction.

Gastrointestinal (GI) symptoms of nausea, vomiting, and abdominal pain are common in patients with orthostatic intolerance (OI), including neurally mediated hypotension (NMH) and postural orthostatic tachycardia syndrome (POTS). Autonomic dysregulation is considered the underlying pathophysiology behind the cardiovascular symptoms of POTS. Because the autonomic nervous system also regulates GI motility, we hypothesized that patients with POTS and GI symptoms will have evidence of autonomic dysmotility of the upper GI tract. Thirty-five subjects with OI and GI symptoms were studied. All the subjects had a 24-hour antroduodenal manometry (ADM) study, in conjunction with pharmacologic challenge and autonomic and tilt table testing (TTT). The mean subject age was 16.2 ± 2.8 years (range 10-23.8 years), and male to female ratio was 10:25. TTT was abnormal in all the 35 subjects, whereas Valsalva testing was abnormal (+40 mmHG) in 21 of 34 (62%) subjects, and corrected QT interval was ≥0.44 seconds in 19 of 35 (54%) subjects. During TTT, GI symptoms were reproduced in 31 of 35 (89%) studies. ADM was found to be abnormal at baseline, before the TTT in 5 of 35 (14%) subjects, whereas it became abnormal in 23 of 34 (68%) subjects during TTT. In addition, the expected response to the pharmacologic challenge was limited. Overall, ADM was abnormal in 26 of 35 (74%) patients either at baseline or during TTT in these subjects with OI. ADM is frequently abnormal in children with OI and GI symptoms. Upper GI motility studies should be a part of the comprehensive evaluation in this population.

To explore whether electrocardiography (ECG) variables could be used to predict responses to physical treatment in children with postural tachycardia syndrome (POTS). Forty children with POTS and 32 healthy controls were enrolled in this study. General information and hemodynamic and supine ECG variables, including QT interval dispersion (QTd), were collected. The children with POTS received physical treatment and 3 months of follow-up. A receiver-operating characteristic curve was used to evaluate the value of ECG variables for predicting the effectiveness of physical treatment. Compared with the healthy children, the children with POTS had longer baseline QTd and heart rate (HR)-corrected QTd (QTcd), but shorter minimum QT intervals (QTmin) and minimum HR-corrected QT intervals (P < .05). In children with POTS, responders to physical treatment had a longer baseline time between QRS complexes (RR) interval of minimum QT interval and a longer QTcd compared with nonresponders. A longer QTcd was a significant risk factor for the presence of POTS (OR, 1.022; P = .02) and for undesirable responses to physical treatment in children with POTS (OR, 1.044; P = .03). Baseline QTcd was positively correlated with the HR elevation from supine to upright seen in children with POTS (r = 0.348; P = .003). Receiver operating characteristic curve analysis demonstrated an area under the curve of 0.73, and using 43.0 msec as a cutoff of QTcd yielded a sensitivity of 90% and a specificity of 60%. QTcd might be useful for predicting the effectiveness of physical treatment for POTS in children.

Mechanisms have been postulated to explain postural orthostatic tachycardia syndrome (POTS), however, the etiology of this often debilitating disorder remains unknown. We conducted a retrospective case-control study of 181 POTS patients who exhibited/reported bleeding symptoms for a specific platelet (PL) dysfunction disorder, delta granule storage pool deficiency (δ-SPD).Patients were included only if results of blood tests for δ-SPD were available. Electron microscopy was utilized to diagnose δ-SPD. An ELISA assay was used to determine serotonin (5HT) concentration in PLs and medical record review was employed to collect patients' clinical symptoms.The most common bleeding symptom was easy bruising (71%) but frequent nose bleeds, heavy menstrual bleeding, and a family history of bleeding were also commonly reported. Of the patients studied, 81% were diagnosed with δ-SPD. Our investigation of 5HT concentration extracted from PLs revealed significantly lower levels of 5HT in POTS patients when compared to that of control subjects. Our data suggest that patients with POTS have significant comorbidities including bleeding symptoms and/or family bleeding histories, and have diminished PL 5HT levels supporting the hypothesis that POTS is a low 5HT level disorder. While we describe a significant relationship with POTS and δ-SPD, this finding does not constitute an etiology for POTS.Our results establish an additional comorbidity frequently seen in POTS that could explain a number of disparate symptoms often affecting the severity of POTS.

Orthostatic hypotension (OH) and postural orthostatic tachycardia syndrome (POTS) are well-known causes of orthostatic intolerance (OI). In addition, there are OI patients who are characterized by the symptoms of OI and lack of abnormal findings in head-up tilt (HUT) test. The aim of this study was to determine the cerebral hemodynamic changes in HUT test of OI patients with normal HUT (OINH). Two hundred and sixty-one OI patients and 50 healthy controls were enrolled in this study. All subjects underwent transcranial Doppler test while performing the HUT test. Forty-five patients had OH, 33 patients had POTS, and 183 patients had OINH. Blood pressures, heart rate, cerebral blood flow velocities (CBFVs), end-tidal carbon dioxide (ET-PCO2 ), cerebral critical closing pressure (CCP), cerebral perfusion pressure (CPP), and cerebral vascular resistance (CVR) were measured during HUT test. We compared the hemodynamic parameters of OINH with those of OH, POTS, and healthy controls. Reduced CBFVs, CPP, and ET-PCO2 and elevated CCP were observed in the HUT test of all four groups. CVR was reduced in three OI patients. The drops in systolic CBFV, CPP, and CVR of OINH patients were greater than those of healthy controls. The changes in parameters in the HUT test of OINH group were not different from those of OH and POTS groups except prominent decrements of CPP and CVR in OH group. Our findings suggest that OINH is true OI sharing the common pathomechanism of OH and POTS.

We determined whether abnormal autonomic nervous system innervation of the bladder underlies IC (interstitial cystitis)/BPS (bladder pain syndrome) differently than other chronic pelvic pain. In this institutional review board approved protocol 39 healthy controls and 134 subjects were enrolled, including 36 with IC/BPS, 14 with myofascial pelvic pain and 42 with IC/BPS plus myofascial pelvic pain. Three subjects were excluded from study. Autonomic nervous system evaluations included deep breathing, the Valsalva maneuver, and the tilt table and sudomotor tests. The latter evaluates autonomic neuropathy. A modified validated composite autonomic laboratory score was applied. Median age in the IC/BPS group was 47.5 years (range 21 to 78), greater than in healthy controls (34 years, range 20 to 75, p = 0.006), the myofascial pelvic pain group (33 years, range 22 to 56, p = 0.004) and the IC/BPS plus myofascial pelvic pain group (38 years, range 18 to 64, p = 0.03). Body mass index did not significantly differ but the myofascial pelvic pain and IC/BPS plus myofascial pelvic pain groups had a higher body mass index than healthy controls (p = 0.05 and 0.03, respectively). Cardiovascular and adrenergic indexes did not differ. The tilt table test showed more orthostatic intolerance in all chronic pelvic pain groups. Tilt table test diagnoses (orthostatic hypotension, postural tachycardia syndrome and reflex syncope) were rare. Baseline heart rate was higher in all chronic pelvic pain groups (p = 0.004). Compared to healthy controls all myofascial pelvic pain groups showed significantly more clear-cut autonomic neuropathy, defined as a sweat score of 3 or greater (vs IC/BPS plus myofascial pelvic pain p = 0.007 and vs myofascial pelvic pain p = 0.03). Some chronic pelvic pain types show autonomic neuropathy and some show vagal withdrawal. In all types orthostatic intolerance likely reflects central sensitization and perhaps catastrophizing. Some of these findings suggest novel therapeutic targets.

Gastroparesis (GP) is a disabling chronic gastroenterologic disorder with high morbidity that severely impacts patients' quality of life. GP can present acutely after a viral-like gastrointestinal illness resulting in speculation that in some patients, neurologic damage caused by the infection might underlie the pathogenesis of idiopathic gastroparesis (IGP). The aim of this study is to document case reports of Enterovirus (EV) infection as a possible cause of IGP. Eleven patients referred with a diagnosis of GP underwent workup to exclude known causes of GP. Those with a history of flu-like symptoms or gastroenteritis prior to onset of GP symptoms had gastric biopsies taken during upper endoscopy to assess for the presence of gastric mucosal EV infection. Data on presenting symptoms, extra-intestinal symptoms and conditions, prior nutritional support requirements, upper endoscopy findings, and response to therapy were cataloged. Eleven patients were diagnosed as IGP. Nine had active EV infection on gastric biopsies and were included (7/9 female, mean age 43 years). Eight out of nine received EV treatment with antivirals and/or immune therapies, with a wide degree of variability in treatment regimens. Four out of eight who received EV treatment had symptomatic improvement. One patient had stable symptoms. Three patients are currently undergoing therapy. Gastric EV infection was frequently detected (82 %) in patients undergoing investigation for IGP. Antiviral and/or immune therapies against EV seem to be favorable, as most of our patients had resolution of their GP symptoms after treatment. This is the first study to identify EV as a possible infectious etiology of IGP.

Postural tachycardia syndrome (POTS), inappropriate sinus tachycardia (IST) and vasovagal syncope (VVS) are relatively common clinical syndromes that are seen by physicians in several disciplines. They are often not well recognised and are poorly understood by physicians, are associated with significant morbidity and cause significant frustration for both patients and their physicians. The 2015 Heart Rhythm Society Expert Consensus Statement on the Diagnosis and Treatment of Postural Tachycardia Syndrome, Inappropriate Sinus Tachycardia and Vasovagal Syncope provides physicians with an introduction to these disorders and initial recommendations on their investigation and treatment. Here we summarise the consensus statement to help physicians in the management of patients with these frequently distressing problems.

Loss of consciousness (LOC) in long QT syndrome (LQTS) patients can be caused by torsade de pointes (TdP) or vasovagal syncope (VVS). On genetic testing and head-up tilt testing (HUTT), we diagnosed three young patients with both genotyped LQTS and autonomic dysregulation. According to grade of prolongation of QT interval and LOC status, syncope episodes in two patients were classified as due to VVS, while those of the other patient were due to TdP. We also diagnosed one patient with postural orthostatic tachycardia syndrome. Syncope in LQTS patients should not automatically be labeled TdP. If there is a possibility of VVS, HUTT should be performed, but careful observation is required because TdP cannot be completely ruled out.

The prevalence and costs of the obesity epidemic and obesity-related conditions, including diabetes mellitus, is consistently increasing worldwide. Bariatric medicine is attempting to address this with weight loss and exercise programmes, and with increasing frequency, various forms of bariatric surgery. There has been considerable success reported after bariatric surgery but not without. We describe 14 patients with orthostatic intolerance (OI) post bariatric surgery. We report on OI (postural dizziness, palpitations and fainting), the results of cardiovascular autonomic testing and the associated and/or causative findings as well as reviewing the literature to consider the possible mechanisms. Comprehensive autonomic testing revealed that 35.7% (Buchwald et al., 2004) of these patients fulfilled the criteria for the Postural Tachycardia Syndrome (PoTS), 57.1% (Cremieux et al., 2008) had low levels of basal BP and 42.9% (Cammisotto & Bendayan, 2007) patients were presyncopal and 14.3% (Billakanty et al., 2008) experienced syncope. We propose that the incidence of OI post-bariatric surgery is higher than considered, that certain cohorts may be more susceptible to complications, and that further research is needed to identify the prevalence and, ideally anticipate occurrence. With the increasing prevalence of obesity and required clinical interventions, further understanding of the pathophysiological processes causing autonomic dysfunction after bariatric interventions will aid management, which may differ in those with an underlying disposition to autonomic involvement, such as diabetics, in whom such procedures are increasingly used.

Postural tachycardia syndrome (POTS) is an autonomic disturbance characterized by an excessive increase in heart rate when an individual moves from a sitting to an upright position. POTS patients often complain of fatigue, daytime sleepiness and insomnia, but there is limited evidence to elucidate the mechanism or the prevalence of sleep-related symptoms in POTS, as well as the effect on patient quality of life. Here, we investigated the prevalence of sleep disturbances in POTS patients, as well as the use of medication and effects on daily life. A survey was administered to 30 patients with POTS. The survey contained 22 questions on various characteristics of sleep disturbances in POTS. Answers were recorded on a five-point Likert rating scale. The majority of the patients reported fatigue (96.7%) and low energy (93.3%) during the day. Most (83.3%) patients reported that they do not feel well rested when waking up in the morning. More than half of the patients reported trouble falling asleep at night (63.3%) and maintaining sleep through the night (62.1%). Despite the frequent complaint of sleep disturbance, a very low percentage of POTS patient actually report seeking treatment. In this study, we explored the prevalence of sleep disturbance in patients with POTS. Almost all POTS patients reported trouble with sleep and fatigue; however, there is major discrepancy between the high percentage of symptoms and small percentage of patients seeking medical assistance for better sleep quality.

Inappropriate sinus tachycardia (IST) is a clinical syndrome lacking formal diagnostic criteria. It is generally defined as an elevated resting heart rate (HR; >90-100 bpm) with an exaggerated response to physical or emotional stress and a clearly sinus mechanism. Clinical manifestations are broad from a complete lack of symptoms to incapacitating incessant tachycardia. Now understood to be relatively prevalent, it is observed to have a generally benign prognosis, though symptoms may persist for years. Whether IST is a single discrete entity or a heterogeneous condition with overlap to other syndromes such as postural orthostatic tachycardia syndrome remains a matter of debate.

Inappropriate sinus tachycardia (IST) is a syndrome characterized by a sinus tachycardia not related to a medical condition, to a physiological response, or to medication or drugs and associated with symptoms, often invalidating and altering the quality of life of affected patients. It occurs predominantly in adolescents and young adults, and in the female sex. The diagnosis requires a complete work-up in order to exclude other causes of sinus tachycardia and one or several additional tests: 24-h ECG ambulatory recordings, echocardiogram, exercise testing, and autonomous nervous system assessment. It should be differentiated from the postural orthostatic tachycardia syndrome, with which it shares a number of symptoms, and other supraventricular tachycardias originating in the high right atrium. An electrophysiological study should be considered in selected cases in order to differentiate IST from other supraventricular tachycardias. The mechanism is still unclear, and possible etiologies may include intrinsic abnormality of the sinus node, autonomic dysfunction, hypersensitivity of the sinus node to catecholamines, blunted vagal system, or a combination of the above. The authors emphasize the wide spectrum of clinical presentations and the need to better define the IST and the criteria required to ascertain its diagnosis.

The prevalence of postural orthostatic tachycardia syndrome (POTS) in adolescents and young adults has been increasing during the past decade. Despite this increase, documentation regarding treatment of these patients is just beginning to emerge. In addition, despite a call for a multidisciplinary or interdisciplinary approach, no studies have examined the efficacy of such an approach to treatment. This paper describes a case study of a 19-year-old male with debilitating POTS seen at a tertiary clinic for evaluation and subsequent intensive interdisciplinary treatment. The treatment approach is described and outcomes are presented.

Ivabradine is a newly approved medication which reduces the heart rate by antagonizing the If channel. We report a case of intentional overdose on ivabradine. A 26-year-old female presented after taking 250 mg ivabradine. On arrival, her vital signs and neurologic exam were unremarkable. Within 30 min, her heart rate decreased to 31 bpm, but she remained normotensive with no change in mentation. Her bradycardia resolved after treatment with atropine. She experienced two further bradycardic episodes responsive to atropine; the second episode was associated with hypotension, responsive to a fluid bolus. For the remainder of her hospitalization, she remained hemodynamically stable without further interventions. She was dispositioned to the psychiatry service approximately 36 h post-ingestion with a heart rate of 67 bpm. Laboratory analysis confirmed a serum ivabradine concentration of 525 ng/mL, greater than 50 times the mean level in therapeutic trials. Proposed treatments for ivabradine include activated charcoal, atropine, isoproterenol, and intravenous pacing. Further study is needed to identify ideal treatment modalities.

Stimulant medication may mimic the tachycardia of postural orthostatic tachycardia syndrome. Two case histories illustrate how missing the clinical distinction between a primary dysautonomia and a medication effect may have avoidable adverse consequences.

To determine the clinical course of adolescent-onset postural orthostatic tachycardia syndrome (POTS) and to assess health-related quality of life, 2-10 years after diagnosis. Pediatric patients, 13-18 years of age, diagnosed with POTS at Mayo Clinic, Rochester, from 2003 to 2010 were mailed a questionnaire if they were at least 18 years of age at the time of the mailing. The primary outcome measures were norm-based, age- and sex-adjusted, 36-Item Short Form Health Survey physical composite score and mental composite score. The survey was mailed to 502 patients with a response rate of 34% (n = 172). The mean duration from diagnosis to survey completion was 5.4 (SD, 1.9) years; the mean age of the respondents at the time of the survey was 21.8 (2.2) years. The responders were predominantly females (84% vs 68% of nonresponders; P < .001). Only 33 (19%) respondents reported complete resolution of symptoms, and an additional 51% reported persistent but improved symptoms, and 28 (16%) had only intermittent symptoms. The majority (71%) consider their health at least "good." The mean physical composite score was significantly lower than the population norm (mean [SD], 36.6 [15.8] vs 50; P < .001), however, the corresponding mean mental composite score was normal (50.1 [11.2]). Overall, 86% of adolescents with POTS report resolved, improved, or just intermittent symptoms, when assessed via questionnaire at an average of 5 years after initial treatment. Patients with persistent symptoms have more physical than mental health concerns.

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 objective sleep quality in POTS patients using overnight polysomnography. We studied 16 patients with POTS and 15 healthy control subjects performing daytime autonomic functions tests and overnight polysomnography at the Vanderbilt Clinical Research Center. There were no significant differences in the objective sleep parameters including sleep efficiency, sleep onset latency, wake time after sleep onset, REM latency, percentage of time spent in N1, N2, N3, and REM sleep, arousal index, apnea-hypopnea index, or periodic leg movement index in POTS patients as compared with healthy control subjects. There were significant negative correlations between sleep efficiency and the change in HR from supine to stand (rs = -0.527; p = 0.036). POTS patients do not have significant differences in objective sleep parameters as compared to control subjects based on overnight polysomnograms. Activation of the sympathetic nervous system may contribute significantly to the hyper arousal state and worsening of subjective estimates of sleep quality as previously reported in POTS patients.