Head-up tilt for the evaluation of syncope of unknown origin in children

Different haemodynamic patterns in head-up tilt test on 400 paediatric cases with unexplained syncope

OBJECTIVE

To assess haemodynamic patterns in head-up tilt testing on 400 paediatric cases with unexplained syncope.

METHODS

Medical records of 520 children who underwent head-up tilt testing in the preceding year were retrospectively evaluated, and 400 children, 264 (66%) girls and 136 (34%) boys, aged 12.6±2.6 years (median 13; range 5-18), with unexplained syncope were enrolled in the study. Age, sex, baseline heart rate, baseline blood pressure, frequency of symptoms, and/or fainting attacks were recorded. The test protocol consisted of 25 minutes of supine resting followed by 20 minutes of 70° upright positioning. Subjects were divided into nine groups according to their differing haemodynamic patterns.

RESULTS

There were no statistically significant differences between the groups with regard to age, gender, baseline blood pressure, and frequency of syncope (p>0.05). The response was compatible with orthostatic intolerance in 28 cases (7.0%), postural orthostatic tachycardia syndrome in 24 cases (6.0%), asymptomatic postural orthostatic tachycardia syndrome in 26 cases (6.5%), orthostatic hypotension in seven cases (1.7%), vasovagal syncope in 38 cases (9.5%), and negative in 274 cases (69.2%). Vasovagal syncope response patterns were of type 3 in nine cases (2.2%), type 2A in 10 cases (2.5%), type 2B in two cases (0.5%), and type 1 (mixed) in 17 cases (4.25%).

CONCLUSIONS

In the 400 paediatric cases with unexplained syncope, nine different haemodynamic response patterns to head-up tilt testing were discerned. Children with orthostatic intolerance syndromes are increasingly referred to hospitals because of difficulty in daily activities. Therefore, there is need for further clinical trials in these patient groups.

Head-up tilt testing for diagnosing vasovagal syncope: a meta-analysis

BACKGROUND

A systematic evaluation focused on sensitivity and specificity of head-up tilt testing (HUT) for diagnosing vasovagal syncope has not been previously performed. We conducted a meta-analysis of studies comparing HUT outcome between patients with syncope of unknown origin and control subjects without previous syncope.

METHODS

We searched Pubmed and Embase databases for all English-only articles concerning case-control studies estimating the diagnostic yield of HUT, and selected 55 articles, published before March 2012, including 4361 patients and 1791 controls. The influence of age, test duration, tilt angle, and nitroglycerine or isoproterenol stimulation on tilt testing outcome was analyzed.

RESULTS

Head-up tilt testing demonstrated to have a good overall ability to discriminate between symptomatic patients and asymptomatic controls with an area under the summary receiver-operating characteristics curve of 0.84 and an adjusted diagnostic odds ratio of 12.15 (p<0.001). A significant inverse relationship between sensitivity and specificity of tilt testing for each study was observed (p<0.001). At multivariate analysis, advancing age and a 60° tilt angle showed a significant effect in reducing sensitivity and increasing specificity of the test. Nitroglycerine significantly raised tilt testing sensitivity by maintaining a similar specificity in comparison to isoproterenol.

CONCLUSIONS

The results from this meta-analysis show the high overall performance of HUT for diagnosing vasovagal syncope. Our findings provide useful information for evaluating clinical and instrumental parameters together with pharmacological stressors influencing HUT accuracy. This could allow the drawing of tilt testing protocols tailored on the diagnostic needs of each patient with unexplained syncope.

Syncope in children and adolescents: Evaluation and treatment

Syncope in children is most often neurally mediated and usually has a natural history of spontaneous resolution or improvement. Syncope is defined as the temporary loss of consciousness resulting from a reversible disturbance of cerebral function. It is characterized by a loss of consciousness due to a lack of cerebral blood flow, rapid or sudden onset, falling of the patient, if not supported, and transiency of the attack. In children, it is most often benign, but may sometimes herald a more serious, potentially life-threatening cause. The main purpose of the present paper is to propose an evaluation scheme that will allow the physician involved in the care of children to differentiate the life-threatening causes of syncope with potential for injury or sudden death from the common, more benign neurally mediated syncope. Secondarily, the present article facilitates the identification of the patient with neurally mediated syncope who may benefit from medical therapy and distinguishes syncope from the more frequent noncardiac 'spells' of childhood.

Early childhood gender differences in anterior and posterior cerebral blood flow velocity and autoregulation

OBJECTIVE

We aimed to describe gender differences in blood flow velocity and autoregulation of the anterior and posterior cerebral circulations in prepubertal children.

METHODS

A prospective observational cohort study was performed at Harborview Medical Center's Cerebrovascular Laboratory after institutional review board approval, consent, and assent procedures. Children underwent measurement of middle cerebral and basilar artery flow velocities and cerebral autoregulation testing of the middle cerebral and basilar arteries. Cerebral autoregulation was quantified using the autoregulatory index, and estimated cerebrovascular resistance was calculated. Autoregulatory index <0.4 reflects impaired cerebral autoregulation. Data are presented as mean +/- SD. Patients were healthy 4- to 8-year-old children.

RESULTS

Forty-eight children (24 boys and 24 girls) 4 to 8 years of age (mean: 6 +/- 2 years) were enrolled. Middle cerebral artery flow velocity was higher than basilar artery flow velocity (96 +/- 13 vs 65 +/- 11 cm/s). Girls had higher middle cerebral artery flow velocity (99 +/- 11 vs 91 +/- 13 cm/s) and basilar artery flow velocity (70 +/- 10 vs 61 +/- 9 cm/s) than boys. Cerebral autoregulation was intact in all children. There was no gender difference in autoregulation between the middle cerebral artery (boys: 0.97 +/- 0.07; girls: 0.94 +/- 0.11) or basilar artery (boys: 0.94 +/- 0.13; girls: 0.94 +/- 0.11).

CONCLUSIONS

Similar to older children and adults, girls between 4 and 8 years of age had higher middle cerebral and basilar artery flow velocity than age-matched boys. This difference may reflect inherent differences in cerebral metabolic rate and/or estimated cerebrovascular resistance between the genders.

Usefulness of the head-up tilt test in distinguishing neurally mediated syncope and epilepsy in children aged 5-20 years old

Many nonepileptic disorders may mimic epilepsy by history or clinical presentation. Neurally mediated syncope is one of the most important conditions that might be difficult to differentiate from epilepsy on clinical grounds. We investigated the value of the head-up tilt test (HUT) to diagnose syncope in epileptic children. We studied 40 patients (18 girls and 22 boys) between 5 and 20 years old (mean, 11.5 +/- 3.5) who had a previous diagnosis of epilepsy. All patients underwent a HUT test. The HUT test was positive in 26 patients (65%). No statistical difference was observed between the tilt positive and negative groups in sex, age, provocating factors, associated symptoms, family history of syncope and heart disease, findings in physical examination, and electroencephalogram result. There was a history in favor of true syncope in 58% of tilt positive patients compared to 14% of tilt negative patients (p < 0.05). Also, family history of seizure was more frequent in tilt positive patients (p < 0.05). After 18 +/- 6 months of follow-up, 18 of 26 patients with a positive tilt test were completely asymptomatic. Inadequate history taking and overemphasis on positive family history for seizures were important causes of misdiagnosis of epilepsy in our study. The HUT test is a simple, noninvasive diagnostic tool for distinguishing syncope and epilepsy in children and should be considered early in the diagnostic plan and for determining management of selected patients with a history of drop attack and loss of consciousness.

Gender differences in cerebral blood flow velocity and autoregulation between the anterior and posterior circulations in healthy children

There is little information on gender differences in cerebral autoregulation. The purpose of this study was to compare autoregulation of the anterior and posterior circulations using the tilt test method in healthy boys and girls who were 10-16 y of age. Transcranial Doppler was used to measure middle cerebral artery and basilar artery flow velocities (Vmca and Vbas). Cerebral autoregulation (ARI) of the middle cerebral (ARImca) and basilar arteries (ARIbas) was examined using the tilt test method. An ARI <0.4 indicates impaired autoregulation. Among the 13 boys and 13 girls, Vmca and Vbas were higher in girls. All children demonstrated intact autoregulation, but boys had higher ARImca than girls, whereas girls had higher ARIbas than boys. Girls demonstrated greater autoregulation in the basilar artery, whereas boys demonstrated greater autoregulation in the middle cerebral artery. Girls had higher flow velocities in both vessels. This study provides normative data on cerebral autoregulation of the posterior circulation in healthy, awake boys and girls.

Head-up tilt test without intravascular cannulation in children and adolescents

Previous studies of head-up tilt test have shown that testing at high degrees lacks specificity in children. We suspected that the high false positive rate might be related to the intravascular catheter and other maneuvers incorporated in the test and therefore studied the sensitivity and specificity of standing and HUT at 80 degrees without any invasive procedure and other maneuvers in children and adolescents. Twenty three patients (11.8+/-2.7 years) with recurrent typical neurally mediated syncope and 35 normal control children (11.6+/-3.0 years) underwent motionless standing for 15 min and tilting to 80 degrees for 30 min. Continuous finger arterial pressure monitoring and ECG were performed during the test. Eight (35%) of the 23 patients developed symptoms of near syncope during motionless standing. Thirteen (57%) of them had positive results at 80 degrees tilting for 30 min. The symptoms of syncope were not always corresponding to excessive haemodynamic changes. None of the controls developed any symptoms or excessive hemodynamic changes. Without intravascular instrumentation and other autonomic maneuvers, active motionless standing or HUT at 80 degrees for 30 min is highly specific but of limited sensitivity for the investigation of vasovagal syncope.

Neurally mediated cardiac syncope: autonomic modulation after normal saline infusion

OBJECTIVES

This study assessed the heart variability response to orthostatic stress during tilt table testing before and after normal saline administration.

BACKGROUND

The efficacy of sodium chloride and mineralocortoid in the treatment of neurally mediated cardiac syncope is attributed to intravascular volume expansion; however, their modulation of autonomic nervous system activity has not been evaluated.

METHODS

Heart rate variability analysis was performed on 12 adolescents with a history of syncope or presyncope (mean age 15.2+/-0.7 years) during tilt table testing. Subjects were upright 80 degrees for 30 min or until syncope. After normal saline administration, the patient was returned upright for 30 min. Heart rate variability analysis data were analyzed by an autoregression model (Burg method).

RESULTS

All subjects reproducibly developed syncope during control tilt table testing; median time to syncope was 9.4+/-2.1 min. After normal saline infusion, none of the subjects developed syncope after 30 min upright. In the control tilt, there was an initial increase followed by a progressive decrease in low frequency power until syncope. Repeat tilt after normal saline administration demonstrates that low frequency power increased but the magnitude of initial change was blunted when compared with control. In addition, low frequency power increased during normal saline tilt sequence compared with the control tilt, during which it decreased.

CONCLUSIONS

Normal saline blunted low frequency power stimulation and prevented paradoxical low frequency power (sympathetic) withdrawal. Increasing intravascular volume with normal saline alters autonomic responses that may trigger neurally mediated syncope reflexes.

[The tilt-table test in assessing syncope of unknown origin: do differences exist between children and adults?]

BACKGROUND AND OBJECTIVES

Little is known about the differences between children and adults in the results of head-up tilt test. This study sought to investigate the potential differences concerning: a) the clinical profile and circumstances of spontaneous syncope; b) the overall diagnostic performance of the test, and c) the type of positive response obtained.

MATERIAL AND METHODS

We studied 31 children and 123 adults with unexplained syncope. If baseline test (tilting at 70 degrees for 30 min) resulted negative, it was repeated under isoprenaline low-dose infusion.

RESULTS

There were no differences in either clinical profile, except for severe traumatism more frequent in adults (25% vs. 3% in children; p < 0.05), or overall diagnostic performance (39% in children vs. 33% in adults; p = NS). However, the way the test rendered positive (via basal tilting in 92% of children vs. 50% in adults; p < 0.05) and the rate of cardioinhibitory response (42% in children vs 8% in adults; p < 0.01) were significantly different.

CONCLUSIONS

In this study children, in contrast to adults, rarely have a positive response in tilting under isoprenaline infusion. They also present a much higher rate of cardio-inhibitory response than adults.

Specificity of head-up tilt testing in adolescents: effect of various degrees of tilt challenge in normal control subjects

OBJECTIVES

This study sought to determine the specificity of commonly used tilt protocols in children.

BACKGROUND

Tilt table testing is commonly utilized in the evaluation of children and adolescents with syncope despite a lack of uniformity in tilt protocols and a lack of studies of specificity in normal control subjects.

METHODS

Sixty-nine normal control volunteers (12 to 18 years old, 38 male, 31 female) with no previous history of syncope, presyncope or arrhythmia underwent tilting to 80 degrees, 70 degrees or 60 degrees for a maximum of 30 min on a motorized table with a footboard support. Autonomic maneuvers, including deep breathing, carotid massage, Valsalva maneuver and diving reflex, were performed before tilt testing to determine whether the response to these maneuvers could identify subjects prone to fainting during tilt testing.

RESULTS

Symptoms of presyncope and frank syncope were elicited in 24 of 69 subjects (13 male, 11 female): 6 (60%) of 10 were tilted at 80 degrees, 9 (29%) of 31 at 70 degrees and 9 (32%) of 28 at 60 degrees. Tilt testing at 80 degrees was terminated after the tenth subject by the institutional review board. The mean time to a positive test response was 10.5 min at 80 degrees, 14.2 min at 70 degrees and 13.2 min at 60 degrees. In the 80 degrees tilt, 4 of 10 subjects had a positive response within 10 minutes, whereas only 3 of 31 and 2 of 28 had a positive response within < 10 min at 70 degrees and 60 degrees tilt angles, respectively. Subjects with and without a positive response to tilt testing were similar with respect to age; gender; PR, QRS and QT intervals; and baseline heart rate and blood pressure. Likewise, responses to other autonomic function tests performed were similar in tilt-positive and tilt-negative patients. The power for detecting a significant difference between patients tilted at 80 degrees versus 60 degrees and 70 degrees was 0.45 and for detecting differences in autonomic tone between tilt-positive (n = 24) and tilt-negative (n = 45) subjects was 0.8.

CONCLUSIONS

Children appear to be more susceptible to orthostatic stress than adults. Therefore, tilt protocols commonly used in adults lack specificity in teenage patients. A specificity > 85% may be obtained by performing the tilt test at 60 degrees or 70 degrees for no longer than 10 min.

Comparison of sensitivity and specificity of tilt protocols with and without isoproterenol in children with unexplained syncope

Head-up tilt testing with or without isoproterenol is extensively used in the evaluation of patients with unexplained syncope. However, sensitivity and specificity of tilt protocols with and without isoproterenol have not been clarified in children, due to lack of age matched control subjects. This study was designed to assess and to compare the sensitivity and specificity of tilting alone and tilting in conjunction with isoproterenol. Thirty children with unexplained syncope (group I) and 15 age-matched control subjects (control group I) underwent successive 60 degrees head-up tilts for 10 minutes during infusions of 0.02, 0.04, and 0.06 microgram/kg/min of isoproterenol, after a baseline tilt to 60 degrees for 25 minutes. Also, 35 children (group II) with unexplained syncope and 15 healthy control subjects (control group II) were evaluated by head-up tilt to 60 degrees for 45 minutes without an infusion of isoproterenol. In response to tilt protocol with graded isoproterenol, 23 (76.6%) of the patients in group I and 2 of the 15 (13.3%) control subjects developed syncope. Accordingly, the sensitivity of tilt testing with isoproterenol was 76.6%, and its specificity was 86.7%. Tilt testing without isoproterenol was positive in 17 (48.5%) of the patients in group II but in only 1 of the 15 (6.6%) control subjects. Thus, sensitivity and specificity of tilt testing without isoproterenol were 48.5% and 93.4%, respectively. The mean heart rate and systolic blood pressure decreased significantly (P < 0.001) in all tilt positive patients during syncope. In conclusion, the head-up tilt test is a valuable diagnostic test in the evaluation of children with unexplained syncope, and isoproterenol is likely to increase the sensitivity of the test without decreasing its specificity.

Syncope in the pediatric patient

Syncope in the pediatric patient is a common and usually benign event that frequently causes concern and anxiety. This article describes three general categories of syncope in children and adolescents: cardiac, noncardiac, and neurocardiogenic. The discussion includes specific pediatric issues and dissimilarities when compared to adult patients with syncope. In addition, a focused approach to the diagnostic evaluation of syncope in childhood is described.

Prospective evaluation of high-dose or low-dose isoproterenol upright tilt protocol for unexplained syncope in young adults

The sensitivity of the passive head-up tilt test (HUT) in the evaluation of unexplained short-lasting syncope in young adults remains insufficient. The infusion of isoproterenol was proposed to improve the benefit. To evaluate the sensitivity-specificity relationship during isoproterenol dosing, we studied 76 young adults (aged 20.9 +/- 1.7 years) (group S) with recurrent (mean 3.8 +/- 1.6) losses of consciousness that remained unexplained after clinical and noninvasive assessment and 35 young healthy volunteers (aged 22.6 +/- 2.7 years) (group V). Subjects underwent either passive HUT (45 min, 60 degrees without drug dosing for 48 subjects in group S (S1) and 17 in group V (V1), or HUT with isoproterenol infusion at progressive doses (2 then 5 micrograms/min) after 30 minutes of passive tilting for 28 patients in group S (S2) and 18 in group V (V2). During passive HUT, the test was positive (asystole, bradycardia, or fall in systolic blood pressure) in 2 of 17 (11.8%) patients in group V1 and in 7 of 48 (14.6%) in group S1 before 30 minutes, and in 3 of 17 (17.6%) in group V1 compared with 10 of 48 (20.8%) in group S1 at the end of the 45-minute infusion, with no difference in delay before the appearance of a positive result. During HUT with isoproterenol dosing, the test was positive in 2 of 18 (11.1%) patients in group V2 and in 18 of 28 (64.2%) in group S2 before 45 minutes (2 micrograms/min; p < 0.01) in 7 of 18 (38.8%) in group V2 compared with 24 of 28 (85.7%) in group S2 before 60 min (5 micrograms/min; p < 0.01). In both cases the mean delay in evoking a positive response was significantly shorter. No asystolic response was observed in the volunteers regardless of the protocol used. The most characteristic response to isoproterenol injection was the appearance of a junctional escape rate with a fall in systolic blood pressure (61.5% of subjects in group S2). The infusion of isoproterenol considerably improves the sensitivity of the HUT with satisfactory specificity if low doses are used (< 3 micrograms/min). These results support the use of HUT with isoproterenol in the evaluation of unexplained syncope in young adults.

Usefulness of tilt table test with normal saline infusion in management of neurocardiac syncope in children

Head-up tilt test has been useful in evaluating children with neurocardiac syncope. In this study patients with positive baseline and isoproterenol tests had repeat tilt testing done after normal saline infusion. If the symptoms persisted, the test was then repeated with phenylephrine infusion. Of the 101 patients studied, 58 (57%) had a positive tilt sign. Normal saline infusion was given to 53 patients. Three patients were excluded because of structural heart disease. Fifty patients (aged 14 +/- 4 years) comprised the study group. Forty-two (84%) of 50 patients had a negative repeat tilt sign after normal saline infusion, and these patients were treated with 0.5 to 1 gm of salt three times a day and/or fludrocortisone (20 patients). Of the 8 (16%) patients who did not respond to normal saline infusion, 5 had negative results when given phenylephrine and were treated with pseudoephedrine. Follow-up data on 42 patients (range 4 to 40 months, median 18 months) showed that all 35 patients who responded to normal saline were either asymptomatic or had improved. Two patients were successfully treated with pseudoephedrine; however, two patients in this group required pacemaker therapy. We conclude that (1) normal saline infusion mitigates the hemodynamic effects of neurocardiac syncope, (2) high-salt diet treatment in these patients was economical and effective, and (3) failure to respond to normal saline test may indicate a less favorable prognosis.

Head-up tilt test: a highly sensitive, specific test for children with unexplained syncope

Unexplained syncope may cause diagnostic and therapeutic problems in children. The head-up tilt test has been shown to be a useful tool for investigating unexplained syncope, especially for diagnosis of neurally mediated syncope. In this study 20 patients aged 9-18 years (12.0 +/- 2.5 years) with syncope of unknown origin and 10 healthy age-matched children were evaluated by head-up tilt to 60 degrees for 25 minutes. The test was considered positive if syncope or presyncope developed in association with hypotension, bradycardia, or both. If tilting alone did not induce symptoms (syncope or presyncope), isoproterenol infusion was administered with increasing doses (0.02-0.08 mu g/kg per minute). During the tilt test, symptoms were elicited in 15 (75%) of the patients with unexplained syncope but in only one (10%) of the control group (p < 0.001). The sensitivity of the test was 75% and its specificity 90%. Three patterns of response to upright tilt were observed in symptomatic patients: vasodepressor pattern with an abrupt fall in blood pressure in 67%; cardioinhibitory pattern with profound bradycardia in 6%; and mixed pattern in 27%. In patients with positive head-up tilt, there were sudden decreases in systolic blood pressure (from 130 +/- 15 to 61 +/- 33 mmHg) and in mean heart rate (from 147 +/- 26 to 90+/-38 beats per minute) (p < 0.001) during symptoms. Treatments with atenolol 25 mg/day has shown complete suppression of syncope in positive responders during a mean follow-up period of 18 +/- 6 months. The head-up tilt test is a noninvasive, sensitive, specific diagnostic tool for evaluating children with unexplained syncope.

Tilt table evaluation for control pediatric patients: comparison with symptomatic patients

This study was designed to evaluate pediatric control patients during head-up tilt in comparison with symptomatic neurocardiogenic syncope patient head-up tilt responses. Twenty-three pediatric control (c) patients (13 females, 10 males; 11.9 +/- 3.1 years) were tested with head-up tilt (HUT) and compared with 66 symptomatic (s) patients. Baseline drug-free HUT (cHUT-1), a second drug-free HUT (cHUT-2), and a final HUT with isoproterenol infusion (cHUT-3) were each performed at 80 degrees tilt angle for 30 min or until positive. For comparison, 66 symptomatic patients (41 females, 25 males; 13.6 +/- 2.5 years) underwent drug-free HUT (sHUT-1); negative responders during sHUT-1 underwent follow-up HUT with isoproterenol (sHUT-2). HUT data were compared for both groups at both 30 and 20 min tilt duration. Twelve control patients (52%) had a symptomatic response during cHUT-1 at 18 +/- 8 min. During cHUT-2, 5 of 23 patients were positive at 13 +/- 5 min; each had previously tested positive during cHUT-1. Two patients, each positive in cHUT-1 and cHUT-2, refused cHUT-3. The only patient testing positive during cHUT-3 was test positive in cHUT-1 but negative for cHUT-2. In comparison, 43 of 66 (65%) symptomatic patients tested positive during drug-free sHUT-1 at 11 +/- 6 min. Subsequently, 20 of the 23 negative patients underwent HUT with isoproterenol (sHUT-2), with 8 of 20 testing positive. Thus, 51 of 66 symptomatic patients (77%) were called "true positives."(ABSTRACT TRUNCATED AT 250 WORDS)

Incidence and hemodynamic characteristics of near-fainting in healthy 6- to 16-year old subjects

OBJECTIVES

We studied the incidence and hemodynamic characteristics of near-fainting under orthostatic stress in healthy children and teenagers.

BACKGROUND

Orthostatic stress testing is increasingly used to identify young subjects with unexplained syncope. However, the associated incidence of syncope and hemodynamic responses in normal young subjects are not well known.

METHODS

Eighty-four healthy subjects 6 to 16 years old performed forced breathing, stand-up and 70 degrees tilt-up tests. An intravenous line to sample blood for biochemical assessment of sympathetic function was introduced between the stand-up and tilt-up tests. Finger arterial pressure was measured continuously. Left ventricular stroke volume was computed from the pressure pulsations.

RESULTS

Sixteen of the 84 subjects were excluded because of technical problems. The incidence of a near-fainting response in the remaining 68 subjects was 10% (7 of 68) for the stand-up test and 40% (29 of 68) for the tilt-up test. Baseline parasympathetic and sympathetic activity of nonfainting and near-fainting subjects was not different. Near-fainting was characterized by attenuated systemic vasoconstriction and exaggerated tachycardia that occurred as early as 1 min after return to the upright position. On tilt-up, plasma adrenaline levels increased by a factor of 2, with slightly higher increments in the near-fainting subjects.

CONCLUSIONS

Inadequate vasoconstriction is the common underlying mechanism of near-fainting in young subjects. The remarkably high incidence of near-fainting during the tilt-up test after intravascular instrumentation raises serious doubts about the utility of this procedure in evaluating syncope of unknown origin in young subjects.

Effects of aging on responses to isoproterenol tilt-table testing in patients with syncope

The diagnosis of neuromediated syncope is often established with isoproterenol head-up tilt-table testing. Previous work has demonstrated changes in autonomic nervous system function with progressive age, suggesting that responses to tilt-table testing may depend on the age of the patient. The purpose of this study was to assess the effects of age on the clinical and hemodynamic responses to isoproterenol tilt testing in patients with syncope of undetermined etiology. Accordingly, 85 patients with syncope of undetermined etiology underwent tilt testing with infusions of 0, 2, and 5 micrograms/min of isoproterenol in 3 successive stages. Of 85 patients tested, 66 had a positive outcome. The proportions of patients with a positive test and with tests ending in syncope declined significantly with age, with positive outcomes seen in 100%, 86%, 69%, and 61% of patients aged 12 to 20, 21 to 35, 36 to 60, and 61 to 88 years, respectively (p = 0.033, chi-square). Presyncope developed more slowly in patients aged 61 to 88 years (half-time to presyncope 2.5 minutes) than in younger patients (half-times to presyncope 0.7 to 0.9 minute). There were no significant age-related changes in peak and trough systolic blood pressures and rate-pressure products, but trough heart rate increased significantly with age (r = 0.40, p = 0.003). In conclusion, the likelihood of a positive outcome to isoproterenol tilt-table testing declines with age. Older patients take longer to develop presyncope, are less likely to develop syncope, and are less able to develop a relative bradycardia. These results guide interpretation of isoproterenol tilt-table testing.

Use of sertraline hydrochloride in the treatment of refractory neurocardiogenic syncope in children and adolescents

OBJECTIVES

The purpose of our study was to determine whether the serotonin reuptake inhibitor sertraline hydrochloride could prevent neurocardiogenic syncope in children and adolescents resistant to or intolerant of other therapies.

BACKGROUND

The serotonin reuptake inhibitor fluoxetine hydrochloride has been reported to be effective in preventing neurocardiogenic syncope in adults.

METHODS

Seventeen consecutive young patients (mean age 15 years, range 10 to 18; 7 male, 10 female) with recurrent syncope and a positive head-upright tilt table test, and in whom standard therapies (fludrocortisone, transdermal scopolamine, beta-adrenergic blocking agents, disopyramide) were ineffectual, poorly tolerated or contraindicated, were referred for study. Sertraline was administered orally at 50 mg daily for 4 to 6 weeks. A head-upright tilt table test was then reperformed, and the clinical effect was noted.

RESULTS

Three patients (18%, 95% confidence interval [CI] 1 to 44) were intolerant of the drug, and it was discontinued. Nine patients became asymptomatic and tilt negative (53%, 95% CI 26 to 76), and five remained tilt positive (36%, 95% CI 15 to 65). Over a mean follow-up period of 12 +/- 5 months, the tilt-negative patients remained symptom free while taking sertraline.

CONCLUSIONS

The serotonin reuptake inhibitor sertraline hydrochloride can be effective in preventing recurrent neurocardiogenic syncope in selected patients unresponsive to or intolerant of other therapeutic modalities.

Circulatory responses in children with unexplained syncope evaluated by continuous non-invasive finger blood pressure monitoring

Cardiovascular responses on active standing in children with unexplained syncope were investigated with continuous non-invasive finger artery pressure monitoring (Finapres). We examined 34 symptomatic patients (13 boys and 21 girls), aged 8-16 years, and 24 age-matched controls. Finger blood pressure and heart rate were monitored continuously for 5 min in the supine position and for 10 min while standing. Ten of 34 patients developed fainting symptoms with hypotension during upright posture (fainters). In the initial standing phase (0-30 s), two prominent abnormal blood pressure responses were found in patients: a marked decrease 45 +/- 18/23 +/- 8 mmHg and a prolonged recovery time (16.5 +/- 2.9 versus 27.7 +/- 13.6 s), which appeared to be based on impaired vasoconstriction. Either or both abnormalities were observed in 21 (62%) of the 34 patients and in 2 (8%) of the controls. In addition, fainters also had a more marked increase in heart rate during standing compared with non-fainters. Our findings suggested that more than half of children with syncope had abnormal cardiovascular reflexes in the initial phase which appeared to be associated with vasodepressor syncope. The active standing test with a continuous beat-to-beat blood pressure recording has a high sensitivity in detecting abnormalities of autonomic function in patients with unexplained syncope.

Upright tilt testing in evaluating syncope: a comprehensive literature review

BACKGROUND

Upright tilt testing is widely utilized for the evaluation of syncope. Recently, there have been concerns about the specificity and the lack of standard methodology for this test. The purpose of this study was to summarize the methodologies of upright tilt testing in patients with syncope of unknown origin, the responses in control subjects, and the reproducibility and selection of therapy.

METHODS

We used MEDLINE to search English language articles from 1966 to June 30, 1992. Studies were included for content review if they met our inclusion criteria. Data were extracted from each article by two trained reviewers using a predesigned data collection instrument.

RESULTS

Thirty-three articles were included for review. There was considerable variability in the methodologies of tilt testing. Overall positive responses were reported in 49% of patients in passive-only studies as compared with 66% of patients in studies using isoproterenol with tilt testing. The percentage of positive responses increased with increasing angle of testing for studies using isoproterenol. There was no relationship between the percentage of positive responses and the maximum dose of isoproterenol. When we compared the results of passive studies that tested patients for 60 minutes at 60 degrees with the results of isoproterenol studies that tested patients at 60 degrees, the positive rate for passive-only studies was 54% as compared with 52% for the isoproterenol studies. The percentage of positive response in control subjects with passive studies was 8.9% (range 0% to 100%), and with isoproterenol 27% (range 0% to 65%). Other groups of patients showed a wide range of positive responses (range 0% to 83%). Reproducibility ranged from 71% to 87%. Upon retesting while the patient was receiving therapy, 90% of 115 positive patients were negative. Eighty-nine percent of 105 positive patients who were receiving therapy and followed for a mean time of 12 months were free of syncope.

CONCLUSIONS

This review strongly suggests that isoproterenol may not have an effect on stimulating vasovagal syncope during upright tilt testing. We recommend protocols of passive tilt testing procedures at 60 degrees for 45 to 60 minutes since the overall specificity is higher with this method. The use of isoproterenol during tilt testing adds to the cost and complexity of the test, is associated with a higher rate of false-positive responses, leads to potential complications, and, thus, should be avoided.

Neurocardiogenic syncope in children with a normal heart

OBJECTIVES

The purpose of this study was to review the results of investigation and management of children with syncope and a structurally normal heart.

BACKGROUND

Syncope is a common clinical problem and has many etiologies. Autonomic testing and, in particular, the tilt/orthostatic test have helped to positively diagnose neurocardiogenic syncope in a high proportion of such patients.

METHODS

Patient case notes and autonomic test charts were reviewed in 162 children aged 1 to 20 years (mean age 12.8 years) with syncope. The autonomic test consisted of orthostatic maneuver, carotid sinus massage, diving reflex, Valsalva maneuver and dose response to intravenous boluses of isoproterenol and phenylephrine. Serum levels of epinephrine and norepinephrine were drawn during the orthostatic test. After confirmation of neurocardiogenic syncope, treatment was begun with fludrocortisone and salt, and beta-adrenergic blocking agents were used as a second line of therapy when indicated.

RESULTS

The orthostatic test was positive for neurocardiogenic syncope in 100 patients (62%) and negative in 62 (38%). Patients in the former group were older, were more often female and had a diminished response to carotid sinus massage, a higher Valsalva ratio and a higher supine epinephrine level. Both groups showed an increase in epinephrine and norepinephrine levels at 5 min of standing. In the orthostatic positive group at the time of syncope, norepinephrine levels decreased, whereas epinephrine levels increased. Patients in this group were also more sensitive to the vasodilating effect of isoproterenol but not to its chronotropic effects. Eleven patients had cardioinhibitory syncope (asystole > or = 3 s). Of these, three had pacemaker implantation. Fludrocortisone and salt used in 84 patients in the orthostatic positive group produced resolution of symptoms in 55 patients (65%) and improvement in 14 (17%). Ten patients received beta-blockers, with resolution in four and improvement in four.

CONCLUSIONS

Patients with orthostatic test-proved neurocardiogenic syncope show evidence of autonomic dysfunction. They also show beta-adrenergic hypersensitivity. Treatment initiated on the basis of the protocol was associated with amelioration of symptoms in the majority of patients.

Esmolol tilt testing with esmolol withdrawal for the evaluation of syncope in the young

BACKGROUND

Head-upright tilt (HUT) testing is valuable in evaluating syncope. Isoproterenol is used to increase sensitivity. However, isoproterenol is contraindicated or dangerous in undiagnosed heart disease and produces false-positives. We introduced esmolol withdrawal during esmolol HUT, hypothesizing that (1) acute withdrawal of the ultrashort-acting beta-blocker induces beta-adrenergic effects by unmasking endogenous catecholamines and may provoke syncope with fewer risks, and (2) response to esmolol/esmolol withdrawal may predict effective therapy.

METHODS AND RESULTS

Thirty-six patients with unexplained recurrent syncope/presyncope (7 to 35 years old, known heart disease or arrhythmia in 14) underwent 2 to 4 HUT tests (60 degrees, 49 minutes): (1) baseline, (2) esmolol (500 micrograms/kg plus 50 micrograms.kg-1.min-1), (3) esmolol withdrawal (HUT continued after esmolol stopped), and (4) isoproterenol if tests 1 through 3 were negative and isoproterenol was not contraindicated. A positive test reproduced symptoms with hypotension or bradycardia, requiring recumbency for recovery. Twenty-five had positive tests, and 11 had negative tests. In 5, only the baseline test was positive; in 15, esmolol/esmolol withdrawal tests were also positive, with 3 in whom esmolol withdrawal was positive although negative at baseline. Two isoproterenol tilts were positive. Esmolol withdrawal and isoproterenol tilts had the highest initial heart rate and similar maximal heart rate increment. Only isoproterenol caused hypertension. One isoproterenol test was false-positive, with hypertension-induced arterial baroreflex. Treatment was beta-blockers (8), Na/fludrocortisone (9), both (6), and DDD pacemakers (2). Esmolol/esmolol withdrawal accurately predicted therapeutic response in 15; isoproterenol predicted therapeutic response in none.

CONCLUSIONS

Esmolol withdrawal tilt testing is preferable to isoproterenol for provocative testing of syncope in the young, and it appears to be safer. Esmolol withdrawal testing has clinical utility before invasive testing as a first-line investigation for syncope in patients with or without heart disease.

Efficacy of alpha-adrenergic agonist therapy for prevention of pediatric neurocardiogenic syncope

OBJECTIVES

The purpose of our study was to determine whether alpha-adrenergic agonist therapy could prevent neurocardiogenic syncope in pediatric patients.

BACKGROUND

Recent reports from adult patients suggest that withdrawal of alpha-sympathetic stimulation contributes to neurocardiogenic syncope.

METHODS

Sixteen young patients (mean age 13.1 years, range 7 years 10 months to 17 years 10 months) with recurrent syncope and a positive baseline head-up tilt response were studied. After a positive baseline tilt response, phenylephrine was infused and repeat tilt was performed for 30 min or until the test result was positive. At discharge, patients were followed up on a regimen of oral pseudoephedrine to evaluate treatment effectiveness and side effects.

RESULTS

During baseline tilt, seven patients experienced vasodepressor syncope, seven had mixed vasodepressor-cardioinhibitory syncope and two had cardioinhibitory responses. All patients became symptomatic, reproducing their clinical symptoms. Baseline mean arterial pressure decreased slightly immediately on tilt testing and significantly at the end point (82 +/- 13 vs. 77 +/- 18 vs. 30 +/- 14 mm Hg, respectively, p < 0.0001). Although heart rate varied, the changes were not statistically significant (78 +/- 17 vs. 105 +/- 19 vs. 87 +/- 46 beats/min, respectively, p = NS). Phenylephrine was infused (mean 1.74, range 0.6 to 3.0 micrograms/kg per min) as patients underwent follow-up tilt testing. Fifteen patients remained asymptomatic without hemodynamic changes; the remaining patient manifested a blunted mixed response. During phenylephrine infusion, heart rate (64 +/- 12 vs. 81 +/- 17 vs. 76 +/- 16 beats/min, respectively, p = NS) and mean arterial pressure (96 +/- 15 vs. 83 +/- 19 vs. 80 +/- 18 mm Hg, respectively, p = NS) did not change. During outpatient oral pseudoephedrine treatment (mean 11.7, range 6 to 14) 15 of 16 patients reported that their clinical condition was controlled without side effects.

CONCLUSIONS

Alpha-adrenergic stimulation prevents pediatric neurocardiogenic syncope. Intravenous phenylephrine prevents neurocardiogenic syncope during head-up tilt, despite reflex vagal bradycardia. Oral pseudoephedrine alleviates symptoms in patients with neurocardiogenic syncope without causing significant side effects.

Spectral analysis of heart rate in vasovagal syncope: the autonomic nervous system in vasovagal syncope

Spectral analysis of heart rate fluctuations was used to investigate the role of the autonomic nervous system in the pathogenesis of vasovagal syncope. Nine adolescents with a history of at least three episodes of vasovagal syncope and nine age-matched healthy controls were studied. All subjects were tested in supine position and at a 60 degrees inclination for 60 min or less if syncope developed. Blood pressure and heart rate were measured, while the ECG and respiration traces were recorded on magnetic tape for later spectral analysis. Baseline heart rate was lower in control subjects than in patients, increased with tilt in both groups, and remained lower in the control subjects throughout the experiment. Baseline systolic and diastolic blood pressure was similar in both groups. Diastolic blood pressure initially increased with tilt in all subjects and decreased significantly thereafter in patients. Pulse pressure was lower in patients throughout the experiment. The heart rate power spectra displayed a higher baseline level of low frequency fluctuations in the control group. The high frequency fluctuations component was similar in all subjects. The results of the test, regarding haemodynamic parameters and autonomic control of the heart rate, as expressed by low and high frequency fluctuations, are consistent with a reduced sympathetic reserve in the individuals with previous episodes of syncope.

Head-upright tilt table testing in evaluation of recurrent, unexplained syncope

Recurrent syncope is one of the most common problems referred to the pediatric neurologist for evaluation. Traditional evaluations are time consuming and expensive, and leave 40% of patients without a precise diagnosis. Vasovagal syncope has been believed to be a common cause of syncope; however, no reliable diagnostic modality has been available to confirm this theory. Head-upright tilt table testing has recently emerged as a useful tool in the evaluation and management of recurrent, unexplained syncope. In this review, we present the pathophysiologic mechanisms of vasovagal syncope and relate them to the reflexes triggered during head-upright tilt table testing. Additionally, we review the clinical data on the uses of this test in unexplained syncope, suggest a practical testing protocol, and elaborate potential therapeutic modalities that can be employed to prevent further episodes. Head-upright tilt table testing will likely become a standard test employed by both adult and child neurologists.

The use of head-upright tilt table testing in the evaluation and management of syncope in children and adolescents

Recurrent syncope in an otherwise healthy child or adolescent is a common anxiety provoking disorder. Vasovagally mediated hypotension and bradycardia are believed common, yet difficult to diagnose, causes of syncope in this age group. Upright tilt table testing has been suggested as a potential method to test for vasovagal episodes. This study evaluated the utility of this technique in the evaluation and management of recurrent syncope in children and adolescents. Thirty patients with recurrent unexplained syncope were evaluated by use of an upright tilt table test for 30 minutes, with or without an infusion of isoproterenol (1 to 3 micrograms/min given intravenously), in an attempt to produce hypotension, bradycardia, or both. There were 15 males and 15 females, mean age 14 +/- 6 years. Each of the tilt positive patients received therapy with either fluorohydrocortisone, beta blockers, or transdermal scopolamine. Syncope occurred in six patients (20%) during the base line tilt and in 15 patients (50%) during isoproterenol infusion (total positives 70%). All initially positive patients were rendered tilt negative by therapy. Over a mean follow-up period of 20 months, no further episodes have occurred. We conclude that tilt table testing is a useful and effective test in the evaluation of unexplained syncope in childhood.

Variations in expression and treatment of transient neurocardiogenic instability

Whereas previous reports describe the head-up tilt test for the diagnosis of neurocardiogenic syncope, this study focuses on the events leading up to syncope. These events are part of a spectrum of neurocardiogenic instability; syncope is the extreme end point. This report is based on tilt studies of 108 patients, aged 4 to 22 years (mean 13), with histories of either unexplained syncope or episodes of visual blackout without loss of consciousness. The tilt study was positive in 74% of the patients. Five stages of neurocardiogenic instability were identified, ranging from excessive fluctuations in heart rate to full syncope. Uncommon reactions during the tilt study include dissociation of hypotension, bradycardia and vagal symptoms and extended asystole (greater than 6 seconds). Therapy with beta 1-selective blockers was highly successful in suppressing symptoms of neurocardiogenic instability. Repeat tilt testing with beta blockade has resulted in either normal or markedly improved stability in heart rate and blood pressure. Neurocardiogenic instability is a common condition occurring between age 10 and 20 years. It appears to be self-limited.