Postural tachycardia syndrome (POTS), a chronic form of orthostatic intolerance, has signs and symptoms of lightheadedness, loss of vision, headache, fatigue, and neurocognitive deficits consistent with reductions in cerebrovascular perfusion. We hypothesized that young, normocapnic POTS patients exhibit abnormal cerebral autoregulation (CA) that results in decreased static and dynamic cerebral blood flow (CBF) autoregulation. All subjects had continuous recordings of mean arterial pressure (MAP) and CBF velocity (CBFV) using transcranial Doppler sonography in both the supine supine position and during a 70 degrees head-up tilt. During tilt, POTS patients (n = 9) demonstrated a higher heart rate than controls (n = 7) (109 +/- 6 vs. 80 +/- 2 beats/min, P < 0.05), whereas controls demonstrated a higher MAP than POTS (87 +/- 2 vs. 77 +/- 3 mmHg, P < 0.05). Also during tilt, mean CBFV decreased 19.5 +/- 2.6% in POTS patients versus 10.3 +/- 2.0% in controls (P < 0.05). We then used a transfer function analysis of MAP and CFBV in the frequency domain to quantify these changes. The low-frequency (LF; 0.04-0.15 Hz) component of CBFV variability increased during tilt in POTS patients (supine: 3 +/- 0.9 vs. tilt: 9 +/- 2, P < 0.02). In POTS patients, there was an increase in LF and high-frequency coherence between MAP and CBFV, an increase in LF gain, and a lack of significant change in phase. Static CA may be less effective in POTS patients compared with controls, since immediately after tilt CBFV decreased more in POTS patients and was highly oscillatory and autoregulation did not restore CBFV to baseline values until the subjects became supine. Dynamic CA may be less effective in POTS patients because MAP and CBFV during tilt became almost perfectly synchronous. We conclude that dynamic and static autoregulation of CBF are less effective in POTS patients compared with control subjects during orthostatic challenge.

Postural tachycardia syndrome (POTS) induces disabling chronic orthostatic intolerance with an excessive increase in heart rate on standing. beta-Blockade is an appealing treatment approach, but conflicting preliminary reports are conflicting. We tested the hypothesis that propranolol will attenuate the tachycardia and improve symptom burden in patients with POTS. In protocol 1, a low dose (20 mg) was compared with placebo, and the dose response was assessed in protocol 2. In protocol 1, patients with POTS (n=54) underwent acute drug trials of propranolol 20 mg orally and placebo, on separate mornings, in a randomized crossover design. Blood pressure, heart rate, and symptoms were assessed while the patients were seated and after standing for up to 10 minutes before and hourly after the study drug. Supine (P<0.001) and standing (P<0.001) heart rates were significantly lower after propranolol compared with placebo. The symptom burden improvement from baseline to 2 hours was greater with propranolol than placebo (median, -4.5 versus 0 arbitrary units; P=0.044). In protocol 2, 18 patients with POTS underwent similar trials of high-dose (80 mg) versus low-dose (20 mg) propranolol. Although the high dose elicited a greater decrease than the low dose in standing heart rate (P<0.001) and orthostatic tachycardia (P<0.001), the improvement in symptoms at 2 hours was greater with low-dose propranolol (-6 versus -2 arbitrary units; P=0.041). Low-dose oral propranolol significantly attenuated tachycardia and improved symptoms in POTS. Higher-dose propranolol did not further improve, and may worsen, symptoms.

The treacherous and deceptive nature of pheochromocytoma makes it crucial to detect and treat it promptly; otherwise it will almost certainly be fatal from cardiovascular complications or metastases. Hypertension occurring in patients with pheochromocytomas is sustained in about 50% and paroxysmal in the remainder; however, many patients remain normotensive. Hypertension attacks may be precipitated by physical activity, postural changes, anxiety, certain foods or wine, some drugs, operative procedures, etc. Cardinal manifestations are paroxysmal hypertension, headache, palpitations +/- tachycardia, inappropriate sweating; anxiety, tremulousness, pallor (rarely flushing), chest and abdominal pains; nausea and vomiting often occur. Hypercatecholaminemia manifestations are more common and pronounced when paroxysmal hypertension occurs, but persons with familial pheochromocytoma may be asymptomatic. Protean manifestations of pheochromocytoma may simulate many conditions, some of which may have elevated plasma and urine catecholamines and their metabolites. Baro-reflex failure, postural tachycardia syndrome, sleep apnea, carcinoid, renal failure, and pseudopheochromocytoma may be diagnostic challenges. The history, physical examination, biochemical testing (after eliminating interfering drugs, when possible) for plasma and urinary metanephrines can usually establish or exclude presence of pheochromocytomas. Occasionally a clonidine suppression test is needed to differentiate neurogenic from pheochromocytic hypertension. Manifestations suggesting hypercatecholaminemia without hypertension are highly atypical of pheochromocytoma. Pheochromocytoma may present as panic attacks, pre-eclampsia, cardiomyopathy, infection with fever and leucocytosis, diabetes, migraine, shock, Cushing's syndrome, multiple organ failure with lactic acidosis, neurological manifestations, transitory electrocardiogram abnormalities, constipation, intestinal obstruction, visual impairment, convulsions, etc. The key to diagnosis is always to think of pheochromocytoma in the differential diagnosis of hypertension.

Autonomic dysregulation (also called diencephalic epilepsy) has been reported following traumatic brain injuries (TBI). However, until now, postural tachycardia syndrome (POTS) has not been reported as a long-term complication in patients who have suffered a TBI. We report on a series of patients who developed POTS after suffering TBI. Eight patients who were referred to our center had suffered TBI and developed features of orthostatic intolerance following head trauma. The patients' neurological, neurosurgical and autonomic data (charts and/or physician letters) were then carefully reviewed for demographic characteristics, comorbid conditions, symptoms of orthostatic intolerance, medications and response to medication. These patients were diagnosed as having POTS, primarily based on their clinical features and findings from the head-up tilt test (HUTT). The data presented is observational and descriptive (percentages or means). Eight patients (seven of them women) aged 21-41 years had suffered from TBI and had developed features of POTS. All had been normal with no symptoms prior to their TBI. All patients experienced orthostatic dizziness, fatigue, palpitations and near syncope. Six patients suffered from frank syncope. Six patients developed significant cognitive dysfunction, and three developed a chronic pain syndrome following trauma. All of the patients reported severe limitations to their daily activities and had been unable to keep their jobs, and two were housebound. Six patients demonstrated a good response to therapy with various combinations of medication. The symptoms of orthostatic intolerance and syncope improved with the initiation of medical therapy, as well as their reported quality of life. Two patients failed to show any improvement with various combinations of medications and tilt training, and continued to experience orthostatic difficulties. Postural tachycardia syndrome may, in some cases, be a late complication of traumatic brain injury.

Topiramate is an anticonvulsant medication commonly used for a variety of neurological disorders including migraine prophylaxis. Broadened use of topiramate has brought an increased awareness of toxicity from this medication, particularly central nervous system side effects and metabolic acidosis. We describe a case of topiramate toxicity occurring in a 22-year-old female following the ingestion of two 200 mg tablets, which she was prescribed for the treatment of migraines. During her outpatient cardiology evaluation for suspected postural orthostatic tachycardia syndrome (POTS), the patient experienced flushing and anxiety. Upon transfer to our hospital she was tachycardic, hypertensive, and confused. Her autonomic symptoms were consistent with her prior episodes of autonomic instability, while the confusion was new. Admission laboratory values revealed a metabolic acidosis with a mildly elevated anion gap. A blood topiramate level returned a value of 8.4 mg/L 15 h after the ingestion. Her symptoms cleared within 24 h following admission. Clinicians should consider topiramate toxicity in their differential diagnosis for patients with neurological diseases presenting with acute-onset confusion and metabolic acidosis.

Postural orthostatic tachycardia syndrome (POTS) is characterized by inappropriate increase in heart rate on assuming upright position from a supine position without a necessary drop in blood pressure. Etiology of this condition is complex and multifactorial. Autonomic dysfunction,[1] hypovolemia,[2] hyper responsiveness of beta adrenergic receptors[3] with associated elevations of plasma norepinephrine levels have been implicated as underlying pathophysiologic mechanisms. Beta blockers have previously been used to treat this condition. Ivabradine which selectively inhibits If ion current in the sino atrial node, has been reported to be useful in patients with POTS.[4,5] We present one further such case of POTS successfully treated by Ivabradine.

Postural orthostatic tachycardia syndrome (POTS) is a disorder characterized by postural tachycardia in combination with orthostatic symptoms without associated hypotension. Symptoms include light-headedness, palpitations, fatigue, confusion, and anxiety, which are brought on by assuming the upright position and usually relieved by sitting or lying down. Given the associated autonomic dysfunction that occurs with POTS, various perioperative concerns must be considered when providing anesthetic care for such patients. We present an adolescent with POTS who required anesthetic care during posterior spinal fusion for the treatment of scoliosis. The potential perioperative implications of this syndrome are discussed.

Cardiac output is controlled by the autonomic nervous system by changing the heart rate and/or the contractions of the heart muscle in response to the hemodynamic needs of the whole body. Malfunction of these mechanisms causes the postural orthostatic tachycardia syndrome and/or the chronic fatigue syndrome. Evaluation of functionality and efficiency of the control mechanisms could give valuable diagnostic information in the early stages of dysfunction of the heart control systems and help to monitor the healing process in rehabilitation period after interventions. In this study we demonstrate how P-wave changes evoked by an orthostatic test could be quantitatively evaluated by using the method based on the principal component analysis. ECG signals were recorded during an orthostatic test performed according to the typical protocol in three groups of volunteer subjects representing healthy young and older persons, part of which had transient periods of supraventricular arrhythmias. Quantitative evaluation of P-wave morphology changes was performed by means of principal component analysis-based method. Principal component-based estimates showed certain variety of P-wave shape during orthostatic test, what revealed a possibility to evaluate the properties of parasympathetic heart control. Quantitative evaluation of ECG P-wave changes evoked by an orthostatic test by using a newly developed method provides a quantitative estimate for functionality and efficiency of the heart rate control mechanisms. The method could be used in eHealth systems.

NXN-188 is a dual-action oral therapeutic being developed for the treatment of acute migraine. The mechanism of action of NXN-188 involves inhibition of both the neuronal nitric oxide synthase enzyme isoform and affinity for serotonin (5-hydroxytryptamine1B/D) receptors. The aims of the initial Phase I clinical studies were to compare the pharmacokinetic (PK) properties of NXN-188 administered as a single dose or multiple twice-daily doses to healthy adult volunteers and to determine the tolerability of NXN-188 in these individuals. Healthy adult male and female subjects were enrolled in 5 Phase I, randomized, double-blind studies, all of which (except for a fed/fasted trial) were placebo controlled. In the 4 single-dose studies, which differed with respect to feeding status and the formulation used (capsules or solution), subjects received NXN-188 at doses of 2 to 800 mg (0.027-11.2 mg/kg). In the repeat-dose study, subjects received 50-mg (0.71 mg/kg) doses twice daily for 4 days. Serum samples were analyzed for NXN-188 using validated HPLC-MS/MS methods. Standard clinical laboratory analyses (chemistry, hematology, and urinalysis) and measurements of serum creatine kinase and myoglobin levels were conducted at screening, admission, discharge, and follow-up. Baseline and postexposure values were compared to assess tolerability. Electrocardiography and physical examination were conducted at screening and at discharge and follow-up if any negative change occurred from the previous findings. Vital signs (heart rate, blood pressure, respiration), including assessment for orthostatic changes, were measured at screening, check-in, and follow-up visits (1 hour before dosing, every 30 minutes for the first 4 hours, then every hour for the next 4 hours, then every 4 hours for the remainder of the 24-hour study). Adverse events were recorded, reviewed, and monitored throughout the study. Two hundred three subjects (102 women, 101 men) 18 to 50 years of age were enrolled in the 5 studies; 168 subjects received NXN-188 and 35 received placebo. Most (91%) of the subjects were white; weight ranged from 69.3 to 71.8 kg (body mass index, 24.5-25.8 kg/m(2)). The initial absorption phase of orally administered NXN-188 peaked at approximately 1 hour, followed by a second absorption phase with a T(max) of approximately 4 to 5 hours. Exposure (C(max) and AUC) increased in a slightly greater than dose-proportional manner across a dose range of 2 to 800 mg (0.027-11.2 mg/kg). Elimination was multiexponential, with an initial rapid plasma drug elimination (plasma concentrations decreased approximately 70%-90% from Cmax within 24 hours after dosing), followed by a prolonged clearance phase of very low NXN-188 concentrations ( approximately 1%-5% of Cmax) that persisted for several weeks. Clearance ranged from 70 to 130 L/h, and the NXN-188 halflife ranged from 11 to 178 hours. Neither food nor gender had any measurable effect on the PK properties of NXN-188. Overall, dizziness was reported more often in the NXN-188 groups than in the placebo groups (6.3% vs 2.9%, respectively). Frequently reported adverse events that occurred more often in the placebo groups than in the NXN-188 groups were somnolence (11.4% vs 6.3%, respectively), and headache (8.6% vs 6.9%). Incidences of orthostatic hypotension (6.3% vs 5.7%) and postural (orthostatic) tachycardia syndrome (6.3% vs 5.7%) were comparable in the NXN-188 and placebo groups, respectively. No serious adverse events were reported at any dose of NXN-188 up to the current maximum dose (800 mg or 11.2 mg/kg). NXN-188 exhibited linear pharmaco-kinetics over the dose range studied and appeared to be well tolerated in these healthy volunteers.

Postural orthostatic tachycardia syndrome was defined in adult patients as an increase >30 beats per minute in heart rate of a symptomatic patient when moving from supine to upright position. Clinical signs may include postural tachycardia, headache, abdominal discomfort, dizziness/presyncope, nausea, and fatigue. The most common adolescent presentation involves teenagers within 1-3 years of their growth spurt who, after a period of inactivity from illness or injury, cannot return to normal activity levels because of symptoms induced by upright posture. Postural orthostatic tachycardia syndrome is complex and likely has numerous, concurrent pathophysiologic etiologies, presenting along a wide spectrum of potential symptoms. Nonpharmacologic treatment includes (1) increasing aerobic exercise, (2) lower-extremity strengthening, (3) increasing fluid/salt intake, (4) psychophysiologic training for management of pain/anxiety, and (5) family education. Pharmacologic treatment is recommended on a case-by-case basis, and can include beta-blocking agents to blunt orthostatic increases in heart rate, alpha-adrenergic agents to increase peripheral vascular resistance, mineralocorticoid agents to increase blood volume, and serotonin reuptake inhibitors. An interdisciplinary research approach may determine mechanistic root causes of symptoms, and is investigating novel management plans for affected patients.

There are conflicting opinions on whether postural tachycardia syndrome predisposes to syncope. We investigated this relationship by comparing the frequency of syncope in postural tachycardia syndrome and orthostatic hypotension. We queried our autonomic laboratory database of 3700 patients. Orthostatic hypotension and postural tachycardia syndrome were defined in standard fashion, except that postural tachycardia syndrome required the presence of orthostatic symptoms and a further increase in heart rate beyond 10 minutes. Syncope was defined as an abrupt decrease in blood pressure and often, heart rate, requiring termination of the tilt study. Statistical analysis utilized Fisher's exact test and Student's t test, as appropriate. Of 810 patients referred for postural tachycardia syndrome, 185 met criteria while another 328 patients had orthostatic hypotension. Of the postural tachycardia syndrome patients, 38% had syncope on head-up tilt, compared with only 22% of those with orthostatic hypotension (P<.0001). In the postural tachycardia group, syncope on head-up tilt was associated with a clinical history of syncope in 90%, whereas absence of syncope on head-up tilt was associated with a clinical history of syncope in 30% (P<.0001). In contrast, syncope on head-up tilt did not bear any relationship to clinical history of syncope in the orthostatic hypotension group (41% vs 36%; P=.49). Our results demonstrate that syncope (both tilt table and clinical) occurs far more commonly in patients who have postural tachycardia syndrome than in patients with orthostatic hypotension. These findings suggest that one should be clinically aware of the high risk of syncope in patients with postural tachycardia syndrome, and the low-pressure baroreceptor system that is implicated in postural tachycardia syndrome might confer more sensitivity to syncope than the high pressure system implicated in orthostatic hypotension.

Postural orthostatic tachycardia syndrome (POTS) is a disorder of orthostatic intolerance characterised by excessive tachycardia of unknown aetiology. Whether this condition involves abnormal cardiac sympathetic innervation or function remains elusive. Meta-iodobenzylguanidine (MIBG) resembles guanethidine and is a pharmacologically inactive analogue of norepinephrine, which is similarly metabolised in noradrenergic neurons. MIBG myocardial scintigraphy is used clinically to estimate local myocardial sympathetic nerve damage in some forms of heart disease and autonomic neuropathy. The objective of this study was to evaluate cardiac sympathetic innervation in patients with POTS. 20 patients with POTS were studied using (123)I-MIBG-single photon emission computed tomography, standardised autonomic testing, assessment of catecholamine plasma levels and sympathetic skin response. In four POTS patients (20.0%), myocardial MIBG uptake was markedly decreased. The mean heart to mediastinum ratio was reduced to 1.22+/-0.08 compared with the normal range of >1.7. No correlation was found between myocardial MIBG uptake and degree of postural tachycardia, baroreflex sensitivity, catecholamine plasma levels or other autonomic parameters. Sympathetic skin responses were normal in all patients. These findings suggest that POTS may be, in part, a manifestation of autonomic cardiac neuropathy. MIBG myocardial scintigraphy may be helpful to distinguish patients with neuropathic POTS from patients with orthostatic intolerance of other origin.

Autonomic dysfunction is common in patients suffering from multiple sclerosis (MS) and orthostatic dizziness occurs in almost 50% of these patients. However, there have been no reports on postural orthostatic tachycardia syndrome (POTS) in patients suffering from MS. The patients were included for analysis in this study if they had POTS with either a prior history of MS or having developed MS while being followed for POTS. Postural orthostatic tachycardia (POTS) is defined as symptoms of orthostatic intolerance(>6 months) accompanied by a heart rate increase of at least 30 beats/min (or a rate that exceeds 120 beats/min) that occurs in the first 10 minutes of upright posture or head up tilt test (HUTT) occurring in the absence of other chronic debilitating disorders. We identified nine patients with POTS who were suffering from MS as well. Each of these patients had been referred from various other centers for second opinions. The mean age at the time of diagnosis of POTS was 49+/-9 years and eight of the 9 patients were women. Five patients (55%) had hyperlipidemia, 3 (33%) migraine and 2 (22%) patients had coronary artery disease and diabetes each. Fatigue and palpitations (on assuming upright posture) were the most common finding in our patients (9/9). All patients also had orthostatic dizziness. Syncope was seen in 5/9(55%) of patients. Four patients (44%), who did not have clear syncope, were having episodes of near syncope. The presence of POTS in our study population resulted in substantial limitation of daily activities. Following recognition and treatment of POTS, 6/9(66%), patients were able to resume daily activities of living. Their symptoms (especially fatigue and orthostatic intolerance) improved. The frequency and severity of syncope also improved. Three (33%) patients failed to show a good response to treatment. Patients suffering from MS may manifest autonomic dysfunction by developing POTS. Early recognition and proper management may help improve the symptoms of POTS.

Postural tachycardia syndrome (POTS) is a heterogeneous disorder characterized by excessive orthostatic tachycardia in the absence of orthostatic hypotension and by sympathetic nervous system activation. Postganglionic sudomotor deficits have been used to define a neurogenic postural tachycardia POTS subtype. Norepinephrine levels above 600 pg/ml have also been used to delineate patients with a hyperadrenergic state. This study aims to determine the relationship of sudomotor abnormalities to other aspects of dysautonomia in POTS. Autonomic function was quantified in thirty women through tests of cardiovagal, adrenergic, and sudomotor function including quantitative sudomotor axon reflex testing (QSART) and spectral indices. Differences between patients with and without sudomotor dysfunction as defined by QSART and between patients with and without hyperadrenergic POTS were assessed with Mann-Whitney U test and Mantel-Haenszel Chi-Square test using a p value of 0.01 for significance. Spearman correlation coefficients were used to test raw sweat volume correlations with other variables. Of 30 women (ages 20-58), 17 patients (56%) had an abnormal QSART which was typically patchy and involved the lower extremity, while 13 patients had normal QSART results. Other autonomic tests, catecholamines or spectral indices did not correlate with QSART results. No differences in autonomic tests or spectral indices were observed between hyperadrenergic and non-hyperadrenergic POTS. Our findings confirm that a large subset of POTS patients have sudomotor abnormalities which are typically patchy in distribution but do not correlate with other tests of autonomic function. Further studies are needed to determine the best method of endophenotyping patients with POTS.

Autonomic dysfunction is common in patients with the joint hypermobility syndrome (JHS). However, there is a paucity of reported data on clinical features of Postural orthostatic tachycardia syndrome (POTS) in patients suffering from JHS. This retrospective study was approved by our local Institutional Review Board (IRB). Over a period of 10 years, 26 patients of POTS were identified for inclusion in this study. All these patients had features of Joint Hypermobility Syndrome (by Brighton criterion). A comparison group of 39 patients with other forms of POTS were also followed in the autonomic clinic during the same time. We present a descriptive report on the comparative clinical profile of the clinical features of Postural Orthostatic Tachycardia patients with and without Joint Hypermobility syndrome. The data is presented as a mean+/-SD and percentages wherever applicable. Out of 65 patients, 26 patients (all females, 20 Caucasians) had POTS and JHS. The mean age at presentation of POTS was 24+/-13 (range 10-53 years) vs 41+/-12 (range 19-65 years), P=0.0001, Migraine was a common co morbidity 73 vs 29% p=0,001. In two patients POTS was precipitated by pregnancy, and in three by surgery, urinary tract infection and a viral syndrome respectively. The common clinical features were fatigue (58%), orthostatic palpitations (54%), presyncope (58%), and syncope (62%). Patients with POTS and JHS appear to become symptomatic at an earlier age compared to POTS patients without JHS. In addition patients with JHS had a greater incidence of migraine and syncope than their non JHS counterparts.

We present a 30-year-old male with complex and predominantly cardiovascular autonomic dysfunction. He had frequent syncopal attacks and paroxysmal atrial fibrillation (PAF). Physical, electrocardiographic, and echocardiographic findings were unremarkable. Syncopal attacks were precipitated by emotional stress, upright position, and micturition. Electrocardiograms obtained immediately after syncopal events revealed PAF with a low ventricular rate, which spontaneously returned to sinus rhythm without any medication. Syncopal events were suggestive of postural orthostatic tachycardia syndrome (POTS), were induced during upright position, and were associated with a sudden increase in heart rate to approximately 140 beats per minute and a sudden drop in blood pressure. Syncope was also induced during carotid sinus massage (CSM) in the upright position. It was thought that cardiac autonomic dysfunction, with POTS as the main component, was responsible for this clinical condition. Syncopal episodes increased in frequency during treatment with metoprolol. Treatment with ivabradine (5 mg twice a day) resulted in disappearance of syncopal episodes both during upright position and CSM. During six months of follow-up, the patient remained asymptomatic without syncope or atrial fibrillation.

Orthostatic intolerance (OI) refers to a group of clinical conditions, including postural orthostatic tachycardia syndrome (POTS) and neurally mediated hypotension (NMH), in which symptoms worsen with upright posture and are ameliorated by recumbence. The main symptoms of chronic orthostatic intolerance syndromes include light-headedness, syncope or near syncope, blurring of vision, headaches, problems with short-term memory and concentration, fatigue, intolerance of low impact exercise, palpitations, chest pain, diaphoresis, tremulousness, dyspnea or air hunger, nausea, and vomiting. This review discusses what is known about the pathophysiology of this disorder, potential treatments, and understanding its role in the patient with chronic headache pain.

The purpose of this study was to test the hypothesis that a small heart coupled with reduced blood volume contributes to the postural orthostatic tachycardia syndrome (POTS) and that exercise training improves this syndrome. Patients with POTS have marked increases in heart rate during orthostasis. However, the underlying mechanisms are unknown and the effective therapy is uncertain. Twenty-seven POTS patients underwent autonomic function tests, cardiac magnetic resonance imaging, and blood volume measurements. Twenty-five of them participated in a 3-month specially designed exercise training program with 19 completing the program; these patients were re-evaluated after training. Results were compared with those of 16 healthy controls. Upright heart rate and total peripheral resistance were greater, whereas stroke volume and cardiac output were smaller in patients than in controls. Baroreflex function was similar between groups. Left ventricular mass (median [25th, 75th percentiles], 1.26 g/kg [1.12, 1.37 g/kg] vs. 1.45 g/kg [1.34, 1.57 g/kg]; p < 0.01) and blood volume (60 ml/kg [54, 64 ml/kg] vs. 71 ml/kg [65, 78 ml/kg]; p < 0.01) were smaller in patients than in controls. Exercise training increased left ventricular mass and blood volume by approximately 12% and approximately 7% and decreased upright heart rate by 9 beats/min [1, 17 beats/min]. Ten of 19 patients no longer met POTS criteria after training, whereas patient quality of life assessed by the 36-item Short-Form Health Survey was improved in all patients after training. Autonomic function was intact in POTS patients. The marked tachycardia during orthostasis was attributable to a small heart coupled with reduced blood volume. Exercise training improved or even cured this syndrome in most patients. It seems reasonable to offer POTS a new name based on its underlying pathophysiology, the "Grinch syndrome," because in this famous children's book by Dr. Seuss, the main character had a heart that was "two sizes too small."

Here we describe a 26-year-old woman who developed peripartum cardiomyopathy characterized by fatigue, poor exercise tolerance, and palpitations. Initial echocardiography showed global left ventricular dysfunction with an ejection fraction of 40%. Subsequently, the patient developed a resting tachycardia associated with symptomatic postural tachycardia. A diagnosis of Inappropriate Sinus Tachycardia was made based on Holter monitoring studies with an average heart rate of 121 beat per minute (bpm). Standard autonomic evaluation confirmed the diagnosis of Postural Tachycardia Syndrome. The cardiomyopathy subsequently resolved (ejection fraction 60%, normal left ventricular function). However, both the postural tachycardia and sinus tachycardia persisted.

To compare the clinical presentation, autonomic dysfunction, and pregnancy outcomes in parous and nulliparous women with postural tachycardia syndrome (POTS) and in women with POTS before and after pregnancy. This study consists of women who had at least 1 pregnancy during which time they met criteria for POTS between May 1993 and July 2009. All patients underwent standard autonomic testing. POTS was defined as a heart rate (HR) increase of greater than 30 beats/min on head-up tilt (HUT) with symptoms of orthostatic intolerance. Patients' charts were reviewed retrospectively to determine pregnancy outcomes. Clinical characteristics related to POTS did not differ between parous and nulliparous women except for disease duration (parous, 3.7+/-2.6; nulliparous, 2.1+/-2.2; P<.001). Autonomic dysfunction did not differ between groups (change in HR on HUT: parous, 42.6+/-12.0 beats/min; nulliparous, 41.3+/-10.6 beats/min; P=.39). Of 116 total pregnancies, adverse pregnancy outcomes were reported in 9% and maternal complications in 1%. No complication was related to POTS. There was a trend toward modest improvement in autonomic dysfunction before and after pregnancy (change in HR on HUT: before pregnancy, 38.1+/-22.7 beats/min; after pregnancy, 21.9+/-14.9 beats/min; P=.07). The long-term impact of pregnancy on POTS does not appear to be clinically important. However, there does appear to be a trend toward improvement in the short-term postpartum period. Adverse pregnancy events were similar to those seen in the general public and do not present a barrier to women with POTS who want to have children.

Approximately 500,000 American premenopausal women have the postural orthostatic tachycardia syndrome (POTS). We tested the hypothesis that in POTS women during orthostasis, activation of the renin-angiotensin-aldosterone system is greater, leading to better compensated hemodynamics in the midluteal phase (MLP) than in the early follicular phase of the menstrual cycle. Ten POTS women and 11 healthy women (controls) consumed a constant diet 3 days before testing. Hemodynamics and renal-adrenal hormones were measured while supine and during 2-hour standing. We found that blood pressure was similar, heart rate and total peripheral resistance were greater, and cardiac output and stroke volume were lower in POTS subjects than in controls during 2-hour standing. In controls, hemodynamic parameters were indistinguishable between menstrual phases. In POTS subjects, cardiac output and stroke volume were lower and total peripheral resistance was greater in the early follicular phase than MLP after 30 minutes of standing; however, blood pressure and heart rate were similar between phases. Plasma renin activity (9+/-6 [SD] versus 13+/-9 ng/mL per hour; P=0.04) and aldosterone (43+/-22 versus 55+/-25 ng/dL; P=0.02) were lower in the early follicular phase than MLP in POTS subjects after 2 hours of standing. Catecholamine responses were similar between phases. The percentage rate of subjects having presyncope was greater in the early follicular phase than MLP for both groups (chi(2) P<0.01). These results suggest that the menstrual cycle modulates the renin-angiotensin-aldosterone system and affects hemodynamics during orthostasis in POTS. The high estrogen and progesterone in the MLP are associated with greater increases in renal-adrenal hormones and presumably more volume retention, which improve late-standing tolerance in these patients.

We report on two previously healthy patients who developed severe form of postural orthostatic tachycardia syndrome (POTS) following an electric injury. Both the patients developed symptoms of orthostatic intolerance in the form of dizziness, fatigue, lightheadedness, and palpitations, weeks to months after electrical injury. Orthostatic intolerance produced considerable functional impairment in these patients. Early recognition of POTS when it occurs after an electrical injury allows for prompt evaluation and management to occur.

The study was designed to explore flow-mediated vasodilation (FMD) and endothelium function in children with postural orthostatic tachycardia syndrome (POTS). The patient group consisted of 46 children 12 +/- 3 years of age who were diagnosed with POTS from June 2008 to January 2009 by head-up test or head-up tilt test at Peking University First Hospital. Twenty healthy children 12 +/- 4 years of age were selected for the control group. Plasma concentrations of nitric oxide (NO) and activity of NO synthase (NOS) were determined in the patient and control groups. FMD of each participant's brachial artery was measured using color Doppler vascular ultrasound and a comparison of FMDs and plasma NO and NOS activities between the 2 groups was done using independent t test. No significant differences were found between the POTS and control groups in age, sex ratio, height, body weight, baseline blood pressure, heart rate, and baseline brachial artery diameter. Patients in the POTS group had larger FMD (10.8 +/- 4.4%) than children in the control group (5.7 +/- 2.2%), and this difference was significant (p <0.01). Plasma NO and NOS levels were significantly higher in the POTS group than in the control group (NO 74 +/- 19 micromol/L in POTS group vs 62 +/- 6 micromol/L in control group, p <0.01; NOS 21 +/- 3 U/mL in POTS group vs 15 +/- 1 U/mL in control group, p <0.01). In addition, there was a significant correlation between FMD and the NOS activity. In conclusion, augmented FMD and abnormal function of vascular endothelium may play an important role in POTS in children.

We determine the comorbid conditions associated with syncope in women. In addition, we hypothesize a higher proportion of autonomic comorbid conditions during the female reproductive age. We identified a cohort of patients admitted to US hospitals with the principal diagnosis of syncope. We compare patient demographics stratified by gender as well as syncope associated comorbidities. We compared these comorbidities in female of reproductive age (15-45) to men as control. From a total sample of 305,932, females constituted 56.7% (n = 173,434). Females were slightly older (mean age 70.9 +/- 17.9 vs. 66.7 +/- 17.3; P < 0.0001); with similar racial distribution (white 57.8 vs. 57.5%), and similar length of hospital stay (mean 2.66 +/- 2.63 vs. 2.68 +/- 2.72 days; P > 0.05). Females had higher proportion of migraine (1.65 vs. 1.29%; odds ratio 'OR' 1.29; 95% confidence interval 'CI' 1.21, 1.36); chronic fatigue syndrome (1.73 vs. 1.3%; OR 1.32; 95% CI 1.25, 1.4); gastroparesis (0.2 vs. 0.12%; OR 1.64; 95% CI 1.35, 1.98); interstitial cystitis (0.07 vs. 0.01%; OR 7.44; 95% CI 4.10, 13.5); and postural tachycardia syndrome (0.49 vs. 0.44%; OR 1.1; 95% CI 1.001, 1.23). Orthostatic hypotension was not different between the groups (P = 0.24). When the sample was stratified by age category, the odds ratio for gastroparesis, orthostatic hypotension, and postural tachycardia syndrome was increased (P < 0.05). A higher proportion of autonomic dysfunction was present in women compared to men. In addition, these comorbid autonomic conditions were especially prominent during the female reproductive age.

To review clinical experience at our institution on postural tachycardia syndrome (POTS) complicating pregnancy. In a retrospective review, we identified nine pregnancies in seven patients with POTS syndrome at our institution. Patients who did not require treatment for POTS before conception were less likely to have an exacerbation of symptoms or need reintroduction of treatment. Exacerbations of POTS during pregnancy are variable. Of our patients with exacerbations of symptoms, increases in the existing pharmacologic treatments, such as increasing beta-blocker dosage, was effective in palliation of symptoms. There were seven vaginal deliveries. Two patients delivered without neuraxial anesthesia; the other five deliveries were done using epidural anesthesia without associated complications. POTS does not seem to contribute to pregnancy-related complications. Importantly, there were no adverse intrapartum events attributable to POTS. Pregnant women with POTS may undergo safe regional anesthesia and vaginal delivery. This contradicts earlier reports in the literature recommending cesarean delivery.