Upright Tilt Table Testing Research Articles

Autonomic dysfunction detected by skin sympathetic response in Lambert-Eaton myasthenic syndrome: a case report

BackgroundLambert-Eaton myasthenic syndrome (LEMS) is a type of paraneoplastic syndrome that may initially manifest itself with proximal weakness and gait abnormalities. Approximately up to 50% of LEMS patients have a primary autonomic dysfunction.Case presentationWe present here a case of a 75-year-old male with symmetric proximal muscle weakness, dry mouth and constipation. The cutaneous response to scratch and upright tilt-table testing were positive. A repetitive nerve stimulation test showed that there was a decremental response of compound muscle action potential (CMAP) amplitude at 3 Hz while an incremental response at 20 Hz. The presence of antibodies against voltage-gated calcium channels (VGCC) confirmed the diagnosis. Because of the prominent symptom of autonomic disorder, the patient further underwent the test of skin sympathetic response (SSR). Lower amplitude and longer response duration were found in palms, while it evoked no response in soles.ConclusionsIn this case, we present the detailed results of SSR test on a patient suffering LEMS with autonomic disorder. Since autonomic dysfunction has a significant impact on clinical management and SSR test is an effective detection method, we recommend that SSR test be performed on patients with LEMS regularly.

Asystole during Tilt Testing-Induced Syncope: A Long-Term Follow-Up

The vasovagal (VV) syncope, a variant of neurally mediated reflex syncopal syndromes is a common clinical entity and is one of a heterogeneous group of disorders of orthostatic intolerance that can be identified during an upright tilt table (TT) test.

Delayed orthostatic hypotension.

Delayed orthostatic hypotension is a fall in blood pressure beyond 3min of standing or upright tilt table testing. The prevalence, clinical features and pathophysiology are reviewed. To date, there is little data to support a standardized or recommended treatment. However, the 10-year mortality rates of individuals with delayed orthostatic hypotension are approximately 50%. Despite the fact that delayed orthostatic hypotension carries the same symptoms, risks and high mortality rate as classical orthostatic hypotension, but is under-recognized. The frequency with which delayed orthostatic hypotension develops into classical orthostatic hypotension, the high associated mortality rates and risk of development of the neurodegenerative disorders classified as alpha-synucleinopathies underscores the need for further study of this condition.

Mechanisms of tilt-induced vasovagal syncope in healthy volunteers and postural tachycardia syndrome patients without past history of syncope.

Upright tilt table testing has been used to test for vasovagal syncope (VVS) but can result in “false positives” in which tilt‐induced fainting (tilt+) occurs in the absence of real‐world fainting. Tilt+ occurs in healthy volunteers and in patients with postural tachycardia syndrome (POTS) and show enhanced susceptibility to orthostatic hypotension. We hypothesized that the mechanisms for hypotensive susceptibility differs between tilt+ healthy volunteers (Control‐Faint (N = 12)), tilt+ POTS patients (POTS‐Faint (N = 12)) and a non‐fainter control group of (Control‐noFaint) (N = 10). Subjects were studied supine and during 70° upright tilt while blood pressure (BP), cardiac output (CO), and systemic vascular resistance (SVR), were measured continuously. Impedance plethysmography estimated regional blood volumes, flows, and vascular resistance. Heart rate was increased while central blood volume was decreased in both Faint groups. CO increased in Control‐Faint because of reduced splanchnic vascular resistance; splanchnic pooling was similar to Control‐noFaint. Splanchnic blood flow in POTS‐Faint decreased and resistance increased similar to Control‐noFaint but splanchnic blood volume was markedly increased. Decreased SVR and splanchnic arterial vasoconstriction is the mechanism for faint in Control‐Faint. Decreased CO caused by enhanced splanchnic pooling is the mechanism for faint in POTS‐Faint. We propose that intrahepatic resistance is increased in POTS‐Faint resulting in pooling and that both intrahepatic resistance and splanchnic arterial vasoconstriction are reduced in Control‐Faint resulting in increased splanchnic blood flow and reduced splanchnic resistance.

Gastric Myoelectrical Activity and Autonomic Nervous System Abnormalities in Patients with Chronic Unexplained Nausea and Vomiting and in Patients with Gastroparesis

Background: Patients with chronic unexplained nausea and vomiting (CUNV) and Gastroparesis (GP) have similar symptoms, suggesting they share pathophysiological abnormalities along a continuum of disease.Objectives: To determine the incidence of gastric myoelectrical, accommodation dysfunction and autonomic abnormalities in patients with CUNV and GP.Methods: Outpatients with CUNV and GP who underwent standard 4-hr solid phase gastric emptying, upright tilt table test and electrogastrogram (EGG) recordings with water load satiety test (WLST) were identified from chart review. Subjects with normal emptying were in the CUNV group; those with delayed emptying were in the GP group. EGGs were recorded before and 30 minutes after the WLST and symptoms were recorded on a 100mm visual analog scale.Results: 44 patients (35 women and 9 men, ages 17-76 years) were identified: 24 had normal gastric emptying and CUNV and 20 had GP. Gastric dysrhythmias were found in 70% of CUNV and 69% of GP patients. Twenty percent of CUNV patients and 44% of GP patients ingested abnormally low volumes (< 300mL) during the WLST. Nausea increased similarly after the WLST in the subjects with CUNV and GP (Ps > 0.05). Postural orthostatic tachycardia syndrome (POTS) was diagnosed in 17% of CUNV patients and 20% of GP patients.Conclusions: Gastric myoelectrical and accommodation abnormalities and autonomic nervous system (ANS) dysfunctions frequently occur in subjects with CUNV and GP. These pathophysiological abnormalities support the idea that CUNV and GP occur along the same continuum of gastric neuromuscular dysfunction and may be targets for therapeutic approaches.

A new guideline for diagnosis and treatment of syncope in children and adolescents that stimulates further thought and discussion

A new guideline for diagnosis and treatment of syncope in children and adolescents was published by Chinese Pediatric Cardiology Society (CPCS). This guideline admirably outlines a differential diagnosis of syncope in the Chinese population, placing appropriate emphasis on vasovagal syncope (VVS, simple faint), the most common cause. The authors appropriately discuss other more ominous causes of syncope such as cardiogenic syncope and neurogenic orthostatic hypotension. In particular, cardiogenic syncope can have lethal consequences if not promptly treated. The paper provides a useful algorithm for diagnostic evaluation of syncope patients placing primary emphasis on history, physical exam, and ECG, and further discussing testing procedures such as standing tests used in screening patients, and upright tilt table testing which remains the reference standard for orthostatic testing in younger patients. Indeed, most vasovagal and other forms of reflex or situational syncopes can be best diagnosed on clinical history. The authors further consider other forms of orthostatic intolerance such as orthostatic hypertension, postural tachycardia syndrome (POTS), and “initial orthostatic hypotension” experienced as transient lightheadedness upon rapid standing. The authors regard POTS as a cause of vasovagal syncope. This supposition is controversial and deserves further comment.

PP-157 A New Diagnostic Maneuver for Cardioinhibitory Syncope

Vasovagal syncope is the most common cause of syncope. Upright tilt table test is commonly performed for the evaluation of syncope, although the test has limited specificity, sensitivity, and reproducibility. The most frequent mechanism for vasovagal syncope is a cardioinhibitory response. Alterations in autonomic activation are responsible for cardioinhibitory syncope. Objective of our preliminary study is to investigate the potential diagnostic role of a maneuver previously described by Un et al. in patients with syncope. We hypothesize that maneuver significantly lowers heart rate in cardioinhibitory syncope patients with altering autonomic activation. Mentioned maneuver is consisted of quickly lying the subject backward from a seated to supine position (Figure1a). We enrolled 20 patients (10 syncope patients,10 healthy control) to this preliminary study. Study groups were constructed with sex and age matched participants. Median age was 25 years old in both groups.

Cardiac autonomic functions in children with familial Mediterranean fever.

Familial Mediterranean fever (FMF) is the most common inherited autoinflammatory disease in the world. The long-term effects of subclinical inflammation in FMF are not well recognized. Some studies have suggested that FMF is associated with cardiac autonomic dysfunction in adult FMF patients. The objective of this study was to investigate the cardiac autonomic functions in pediatric FMF patients by using several autonomic tests. Thirty-five patients with FMF and 35 healthy controls were enrolled in this cross-sectional study. Demographic data, disease-specific data, and orthostatic symptoms were recorded. In all participants, 12-lead electrocardiography (ECG), 24h ambulatory electrocardiographic monitoring, transthoracic echocardiography, treadmill exercise test, and head upright tilt-table (HUTT) test were performed. The heart rate recovery (HRR) indices of the two groups were similar. Also, chronotropic response was similar in both groups. The time-domain parameters of heart rate variability (HRV) were similar in both groups, except mean RR (p = 0.024). Frequencies of ventricular and supraventricular ectopic stimuli were similar in both groups. There were no statistically significant differences between the groups in average QT and average corrected QT interval length, average QT interval dispersion, and average QT corrected dispersion. There was no significant difference between the two groups regarding the ratio of clinical dysautonomic reactions on HUTT. However, we observed a significantly higher rate of dysautonomic reactions on HUTT in patients with exertional leg pain than that in patients without (p = 0.013). When the fractal dimension of time curves were compared, FMF patients exhibited significantly lower diastolic blood pressure parameters than controls in response to HUTT. Cardiovascular autonomic dysfunction in children with FMF is not prominent. Particularly, patients with exertional leg pain are more prone to have dysautonomic features. Further studies are needed to elucidate the exact mechanisms leading to impaired cardiac autonomic functions in FMF.

Tilt Table Test & Misdiagnosis of Epilepsy (P02.169)

Objective: To discuss four cases, where diagnosis of epilepsy was missed secondary to an “abnormal tilt table test.” Background Although patho-physiologically distinct, syncope and seizures share clinical characteristics which may make diagnosis difficult. Syncope may be associated with seizure-like motor manifestations, and seizures may be complicated by cardiac arrhythmia and loss of consciousness. Over the last decade, upright tilt table testing has emerged as an important diagnostic method for the identification of individuals whose syncope is likely to be neurocardiogenic in origin. Design/Methods: We studied all the patients referred to our epilepsy center for evaluation of loss of consciousness between ages 18 to 65 years. This included all outpatient referrals and direct admits to the video-EEG monitoring (VEEM) unit over one year. The diagnosis of epilepsy was made based on the presence of strong interictal EEG abnormalities, or ictal EEG abnormality correlating with the events to suggest the diagnosis of epilepsy. Results: We diagnosed four patients with epilepsy, who were previously diagnosed with syncope based on “abnormal tilt-table test.” Two patients were diagnosed based on outpatient EEG, during which one patient had clinical and electrographic seizure and the other one had strong evidence of interictal generalized spikes. The remaining two patients had prolonged VEEM, and multiple events were captured, which confirmed the diagnosis of epilepsy. At present time, three out of four patients are seizures-free with appropriate antiepileptic drugs (AEDs), and one has improved dramatically with addition of AEDs. Conclusions: Although the vast majority of patients that neurologist encounters in day to day life with possible syncope truly suffer from syncope, a small fraction of them may have epilepsy. The correct diagnosis can often be made if emphasis is put on adequate history taking instead of overemphasis on unnecessary ancillary testing. Disclosure: Dr. Jain has nothing to disclose. Dr. Bozorg has nothing to disclose.

Delayed orthostatic hypotension

To investigate the prevalence, symptoms, and neurophysiologic features of delayed orthostatic hypotension (OH). Blood pressures (BP) were measured at 1-minute intervals on 230 patients during 60 degrees head-up tilt for 45 minutes and standing for 5 minutes. OH was defined as a sustained fall in BP (>or=20 mm Hg systolic or >or=10 mm Hg diastolic) and delayed OH as a sustained BP fall occurring beyond 3 minutes of standing or upright tilt table testing. Beat-to-beat BP, tests of cardiovagal function, and sympathetic-adrenergic function were performed. Of patients with OH, only 46% had OH within 3 minutes of head up tilt; 15% had OH between 3 and 10 minutes; and 39% had OH only after 10 minutes of tilt table testing. The magnitude and the temporal distribution of the BP fall did not differ between those with and without symptoms of orthostatic intolerance. Patients with OH beyond 10 minutes tended to be younger (p < 0.05), have smaller BP falls during phase II of the Valsalva maneuver (p < 0.01), and have greater phase IV overshoot (p < 0.01). Delayed orthostatic hypotension occurred in 54% of our tested population and was associated with milder abnormalities of sympathetic adrenergic function, suggesting this disorder may be a mild or early form of sympathetic adrenergic failure.

Neurocardiogenic Syncope: Mechanisms, Evaluation and Treatment

Syncope is the abrupt and transient loss of consciousness due to a temporary reduction in cerebral blood flow, associated with an absence of postural tone, followed by a rapid and usually complete recovery. It may result from several possible etiologies, ranging from the benign to the potentially fatal. Neurocardiogenic (vasovagal) syncope is the most common of a group of neurally mediated syncopes, characterized by a sudden failure of autonomic regulatory mechanisms to maintain adequate blood pressure and, occasionally, heart rate, to sustain cerebral perfusion and consciousness. The diagnosis may be suggested by a characteristic history and by exclusion of other causes of syncope; however, in some cases, upright tilt table testing may be required to provoke typical hemodynamic responses. Cardiologists and cardiac electrophysiologists are frequently expected to manage patients with suspected neurocardiogenic syncope. The following review aims to provide a basic framework for understanding its pathophysiology, clinical presentations, diagnosis and treatment.

Clinical recognition of neurally mediated syncope

Most cases of syncope are due to hypotension, with a vasovagal response the commonest single mechanism. Neurally mediated syncope (NMS) is a vasovagal response evoked by common physical or psychological stress factors in susceptible individuals. Although upright tilt table testing (TTT) has been developed to diagnose this condition, the clinical recognition of this common syndrome in the general community remains poor. To evaluate the clinical presentation of patients with NMS and pre-syncope, proven by TTT, and compare them to patients with syncope that have a low probability of having NMS (e.g. older patients with cardiac disease and negative TTT). Prospective evaluation by questionnaire at the time of TTT, including documentation of presenting symptoms and signs, and provoking factors in consecutive patients. Comparisons between patient groups analyzed using chi-squared tests and logistic regression. Neurally mediated syncope patients were more likely to present with both syncope and pre-syncope, often with prolonged histories of pre-syncope. Certain provoking stress factors were more common in NMS, with multiple factors often present. Most NMS patients had a hypotensive prodrome before syncope, whereas control patients had a higher incidence of syncope without warning. Neurally mediated syncope patients present with situational syncope that is not only stereotypical for the individual, but shares common features with other similar patients. While none of the clinical observations is unique to NMS, a carefully detailed history can elicit a convincing diagnostic pattern that can often obviate the need for extensive and expensive investigation, and in younger patients a TTT may not be required to make the diagnosis.

Atrioventricular block during upright tilt table test.

Patients with a cardioinhibitory response (asystole or atrioventricular block [AVB]) during upright tilt table test (UTT) constitute a therapeutic challenge. Our present knowledge is partial and in those who experience AVB is absent. Furthermore, we ignore if there is any difference between both groups, particularly pacemaker indication. We aimed to study patients with a cardioinhibitory response during UTT and incidence of AVB during UTT, compared to asystole; plus the outcome during prolonged follow-up. Of 867 patients who underwent UTT, 172 were positive for a neurally mediated response, all with normal neurocardiovascular evaluation. Of the 172 patients, 6 (3.4%) developed AV block (group A), and 26 (15.1%) experienced asystole (group B). Group A included 6 women (100%), mean age 21 +/- 12 years. All patients in group A had sinus rate deceleration during AVB. Group B included 10 women (38%), mean age 28 +/- 17 years, and a mean pause of 15 +/- 9 seconds. We contacted 30 of 32 patients, mean follow-up of 45 +/- 38 months. Seven patients in group B had syncopal recurrences; five had 2 or more episodes. One patient from group B received a DDD pacemaker. In group A, one had one recurrence. No deaths were observed. AVB during UTT is rare, occurs in young women, and is always associated with sinus rate deceleration. Medium- to long-term prognosis is good, and equivalent to patients with asystole. There is no evidence that patients with AVB during UTT require a pacemaker implant.

Transcranial Doppler monitoring during head upright tilt table testing in patients with suspected neurocardiogenic syncope.

The aim of the present study was to evaluate the mechanism of cerebrovascular autoregulation in patients with neurocardiogenic syncope using bilateral transcranial Doppler (TCD) monitoring during head upright tilt table testing (HUT). Two hundred and six patients were prospectively studied. One hundred and fifty-nine subjects (77%) had a prior history of syncope and 47 (23%) had presyncope. Ninety-nine patients (48%) had syncope or presyncope during HUT with a 76% fall in diastolic middle cerebral artery blood flow velocity (D-MCA-BFV). Systolic MCA-BFV (S-MCA-BFV) fell by 33%. Deepening of the dicrotic notch in the Doppler waveform always preceded the fall in D-MCA-BFV. Patients without syncope or presyncope (n=96) had smaller changes in cerebral blood flow velocities during HUT and only twenty-two subjects had transient deepening of the dicrotic notch. Eleven subjects had presyncope during HUT due to an exaggerated response to nitrates with progressive arterial hypotension without bradycardia and changes during TCD monitoring that were intermediate between positive and negative HUT. In conclusion, patients with neurocardiogenic syncope have changes in cerebral blood flow during the event. TCD monitoring during HUT helps to assess these alterations.

Pain in the neck

A 76-year-old man presented with a 4-week history of recurrent syncope in July, 2000. Syncope was heralded by a sensation of lightheadedness and occasionally by a mild burning sensation in the left side of his throat. Loss of consciousness was associated with urinary incontinence and generalised rigidity. There was no relationship to posture. Recovery was followed by nausea and vomiting. His past history included diabetes mellitus, peripheral vascular disease, cerebrovascular disease with left carotid endarterectomy 4 months earlier, hypertension, chronic obstructive airways disease, and excision of multiple cutaneous squamous-cell carcinomas. He was a former smoker. No significant findings were noted on examination apart from a left Horner’s syndrome attributed to the previous endarterectomy. A 12-lead electrocardiogram was normal. A computed tomograph (CT) of his head showed a small right-sided subdural haematoma without evidence of raised intracranial pressure. He was admitted to hospital. He continued to have syncopal episodes every day, associated with the absence of a palpable pulse or recordable blood pressure. Upright tilt-table testing and carotid sinus massage failed to provoke syncope. 24-h ambulatory electroencephalography was normal but 24-h Holter monitoring showed transient episodes of asymptomatic complete atrioventricular dissociation. Trials of fludrocortisone, phenytoin, salt tablets, fluoxetine, and cessation of antihypertensive therapy had no effect. An atrioventricular pacemaker was implanted and he was discharged from hospital. He returned the following day with another syncope. Pacemaker function was normal and during syncopal episodes, telemetry showed atrioventricular sequential pacing at the programmed lower rate. Cardiac catheterisation showed normal left ventricular function and a chronically occluded right coronary artery. A contrast-enhanced CT of his neck was done on the suspicion that syncope was related to a neck tumour. The CT showed a large soft-tissue mass arising from the fossa of Rosenmuller extending into the left parapharyngeal space. The tumour infiltrated the skull base and the carotid sheath with erosion of the foramen lacerum and jugular foramen, and compression of the internal jugular vein (figure). Further examination showed a midline soft palate which moved on the right side only, and slight wasting of the left sternocleidomastoid muscle. Nasoendoscopy showed left vocal cord paralysis and a large lesion in the left nasopharyngeal area. A diagnosis of malignancy with jugular foramen syndrome was made. A biopsy specimen

Does a role exist for tilting-guided therapy in the management of neurocardiogenic syncope?

Upright tilt-table testing (UTT) is an useful method for identifying patients with neurocardiogenic syncope, but its role in the evaluation of therapeutic efficacy is controversial. The aim of this study was to determine the correlation between negative UTT after therapy introduction (acute efficacy) and symptom recurrence during follow-up (chronic efficacy). We studied 56 severely symptomatic patients (age 27 +/- 19 years) with recurrent (7 +/-12 episodes) neurocardiogenic syncope (positive UTT). Once empirical pharmacological therapy was initiated, all patients underwent another UTT (therapeutic evaluation test - TET). Therapy was not modified after TET results. The probability of symptom recurrence was analyzed with the Kaplan-Meier method and compared by log-rank test in patients with negative and positive TET. Negative UTT after therapy was related to a significantly lower probability of recurrence during follow-up (4.9 versus 52.4% in 12 months, P<0.0001). A good correlation exists between acute and long-term efficacy of pharmacological therapy for neurocardiogenic syncope, so that serial UTT may be considered a good method for identifying an effective therapeutic strategy.

Ambulatory norepinephrine treatment of severe autonomic orthostatic hypotension

OBJECTIVESThis study was designed to establish a patient-controlled, ambulatory norepinephrine treatment of refractory orthostatic hypotension due to primary autonomic failure.BACKGROUNDAutonomic dysfunction leads to disabling postural hypotension. Particularly in primary autonomic dysfunction, repeated syncope and immobilization can be the result. Medical treatment of orthostatic hypotension often fails in advanced cases.METHODSAmbulatory, patient-controlled norepinephrine therapy was initiated in six patients with orthostatic hypotension due to primary autonomic failure that had been refractory to conventional treatment. Before this therapy, three patients were bedridden; one was immobilized in a wheelchair. All had recurrent syncope and tolerated upright tilt-table testing for less than 15 min despite extensive medical treatment. For ambulatory treatment, a port-a-cath system was implanted and, using a CADD ambulatory infusion pump, norepinephrine was infused in individually adjusted dosages.RESULTSNorepinephrine infusion therapy enabled all patients to sit, stay and walk around for more than 45 min. One patient died after a five-year treatment period, another after nine months because of nonhemorrhagic brain stem infarctions, both in the absence of norepinephrine treatment. The remaining four patients are still mobile after a period of 19, 10, 9 and 7 months, respectively. None of them has suffered complications due to arterial hypo- or hypertension, and there has been no infection of the infusion system.CONCLUSIONSIn these selected patients with refractory orthostatic hypotension due to primary autonomic dysfunction, ambulatory norepinephrine infusion therapy has proved to be a promising new therapeutic option. Further long-term studies including more patients are necessary to assess additional indications, reliability and safety of this new method.

The capnography head-up tilt test for evaluation of chronic fatigue syndrome

Objectives: To compare the hemodynamic and ventilatory responses to autonomic challenge evoked by upright tilt table testing in patients with chronic fatigue syndrome (CFS) to healthy individuals. Methods: Thirty-two consecutive patients with CFS and 32 healthy volunteers were evaluated with the aid of the recently introduced capnography head-up tilt test (CHUTT). The main outcome measures were values of blood pressure (BP), heart rate (HR), respiratory rate (RR), and end-tidal pressure of CO2 (ETPCO2) recorded during recumbence and tilt. In addition, the end points of vasodepressor and cardioinhibitory reactions, hyperventilation (defined by ETPCO2 <25 mm Hg) and the postural tachycardia syndrome, were recorded. Results: The BP, HR, RR, and ETPCO2 recorded during recumbence were similar in both groups. During tilt, patients with CFS developed significantly lower systolic BP, diastolic BP, and ETPCO2, and a significant rise in HR and RR (P <.01). In CFS patients, the postural tachycardia syndrome occurred in 44%, vasodepressor reaction in 41%, cardioinhibitory reaction in 13%, and hyperventilation in 31% of cases. One or more end points of the CHUTT were reached in 78% of patients with CFS but in none of the controls (P <.0001). Conclusions: In most patients with CFS, a spectrum of abnormal homeostatic reactions is diagnosed with the aid of the CHUTT. Data provided by the CHUTT may reinforce the clinical diagnosis by adding objective and unbiased criteria to the subjective assessment of CFS. Semin Arthritis Rheum 30:79-86. Copyright © 2000 by W.B. Saunders Company

The postural orthostatic tachycardia syndrome: a potentially treatable cause of chronic fatigue, exercise intolerance, and cognitive impairment in adolescents.

Head upright tilt table testing has become an accepted method to measure an individual's predisposition to autonomically mediated periods of hypotension and bradycardia severe enough to cause frank syncope. At the same time it has become increasingly apparent that less profound falls in blood pressure, while not sufficient to result in loss of consciousness, may cause symptoms such as near syncope, vertigo, and dizziness. We describe a subgroup of adolescents that have a mild form of autonomic dysfunction that exhibit disabling symptoms such as postural tachycardia and palpitations, extreme fatigue, lightheadedness, exercise intolerance, and cognitive impairment. During baseline tilt table testing at a 70 degrees angle, these patients demonstrated a heart rate increase of > or = 30 beats/min (or a maximum heart rate of > or = 120 beats/min) within the first 10 minutes upright (not associated with profound hypotension), which reproduced their clinical symptom complex. Similar observations have been made in the adult population and has been termed the postural orthostatic tachycardia syndrome (POTS). We report that POTS may also occur in adolescents and represents a mild, potentially treatable form of autonomic dysfunction that can be readily identified during head upright tilt table testing.

Preliminary observations on the use of midodrine hydrochloride in the treatment of refractory neurocardiogenic syncope.

Recurrent episodes of neurocardiogenic syncope that occur without warning are a common cause of recurrent syncope that can be identified during head upright tilt table testing. While the use of beta blockers, theophyllines, fludrocortisone, disopyramide, and serotonin reuptake inhibitors can be useful in the prevention of episodes, some patients are either unresponsive to or poorly tolerant of these agents. We investigated the use of the peripheral alpha stimulating agent midodrine in preventing both tilt-induced and spontaneous neurocardiogenic syncope. Twenty-five patients (16 women, 9 men, mean age 30 +/- 23 years) with severe recurrent syncope and a positive head upright tilt table study (refractory to or intolerant of standard therapies) were placed on midodrine 5-10 mg orally three times per day, (two patients required 15 mg/day). Of these, twelve became asymptomatic and five had a marked reduction in symptoms. We conclude that midodrine may be an effective therapy in patients with recurrent neurocardiogenic syncope refractory to other forms of therapy.