Upright tilt testing in evaluating syncope: a comprehensive literature review

Dysautonomia and activity in the early stroke recovery period

Maintaining cerebral perfusion in the early stages of recovery after stroke is paramount. Autoregulatory function may be impaired during this period leaving cerebral perfusion directly reliant on intravascular volume and blood pressure (BP) with increased risk for expanding cerebral infarction during periods of low BP and hemorrhagic transformation during BP elevations. We suspected that dysautonomia is common during the acute period related to both pre-existing vascular risk factors and potentially independent of such conditions. Thus, we sought to understand the state of the science specific to dysautonomia and acute stroke. The scoping review search included multiple databases and key terms related to acute stroke and dysautonomia. The team employed a rigorous review process to identify, evaluate, and summarize relevant literature. We additionally summarized common clinical approaches used to detect dysautonomia at the bedside. The purpose of this scoping review is to understand the state of the science for the identification, treatment, and impact of dysautonomia on acute stroke patient outcomes. There is a high prevalence of dysautonomia among persons with stroke, though there is significant variability in the type of measures and definitions used to diagnose dysautonomia. While dysautonomia appears to be associated with poor functional outcome and post-stroke complications, there is a paucity of high-quality evidence, and generalizability is limited by heterogenous approaches to these studies. There is a need to establish common definitions, standard measurement tools, and a roadmap for incorporating these measures into clinical practice so that larger studies can be conducted.

Syncope in the Young Adult and in the Athlete: Causes and Clinical Work-up to Exclude a Life-Threatening Cardiac Disease

Syncope is defined as a transient loss of consciousness due to cerebral hypoperfusion, characterized by a rapid onset, short duration, and spontaneous complete recovery. It is usually a benign event, but sometimes it may represent the initial presentation of several cardiac disorders associated with sudden cardiac death during physical activity. A careful evaluation is essential particularly in young adults and in competitive athletes in order to exclude the presence of an underlying life-threatening cardiovascular disease. The present review analyzes the main non-cardiac and cardiac causes of syncope and the contribution of the available tools for differential diagnosis. Clinical work-up of the athlete with syncope occurring in extreme environments and management in terms of sports eligibility and disqualification are also discussed.

Recognizing Syncope: Pitfalls and Surprises

Loss of consciousness and falling are the key features of syncope. Common accompaniments include tonic and myoclonic muscle activity, eye deviations, automatisms, vocalizations and hallucinations which may render the distinction from epileptic seizures difficult. Differential diagnosis is based on the specific features and not the mere presence of these phenomena. Recognition of syncope depends also on accurate information about precipitants, premonitory symptoms and postictal events: the absence of postictal confusion has been identified as the single most powerful factor discriminating syncope from epileptic seizures whereas incontinence and head injury are common in both conditions. Investigations such as electroencephalogram, tilt testing and postictal prolactin or creatine kinase levels may be helpful but are never diagnostic in isolation. Exceptionally, hypoxic and epileptic mechanisms interact within a single attack.

Cardiovascular and Cerebral Hemodynamics in Asymptomatic Healthy Subjects With/Without Abnormal Head-up Tilt Test Versus Recurrent Fainters

PURPOSE

The aim of this study was to compare hemodynamic and autonomic responses during head-up tilt test (HUTT) between healthy volunteers and patients with a history of fainting and confirmed vasovagal syncope. We hypothesize that the autonomic and hemodynamic physiologic responses remain intact during orthostatic stress in people without previous fainting and negative HUTT, but deteriorate similarly in patients with recurrent vasovagal syncope and in asymptomatic healthy subjects who develop a vasovagal response during HUTT.

METHODS

The study included 57 asymptomatic healthy volunteers (42% women, mean age 23.7 ± 3.6 years) categorized as negative HUTT (n = 41) and positive HUTT (n = 16). They were compared with 14 patients (50% women, mean age 24.2 ± 6.1 years) with previous spontaneous recurrent syncope and inducible vasovagal response during HUTT. Cerebral and cardiovascular hemodynamic variables were assessed noninvasively during the HUTT in each participant.

RESULTS

In all patients with recurrent syncope, tilt was positive after a mean delay of 15.6 ± 8.6 minutes and did not differ from the time to syncope observed after 19.6 ± 6.9 minutes in asymptomatic healthy subjects with a positive test. A significant decrease throughout the tilting was observed in the blood pressure, peripheral resistances, cerebral blood flow, and vascular efferent sympathetic regulation in both groups of subjects with a positive test.

CONCLUSIONS

This study shows that there are subjects, without a history of syncope, who have a positive HUTT with hemodynamic and autonomic responses alike to patients with confirmed vasovagal syncope, precluding them to be selected as controls in vasovagal syncope studies.

Epicardial Fat Thickness is Correlated with Vagal Hyperactivity in Patients with Neurally-Mediated Syncope

BACKGROUND

Epicardial fat tissue has unique endocrine and paracrine functions that affect the cardiac autonomic system. The head-up tilt test (HUTT) is a simple non-invasive measurement that assesses autonomic nervous system dysfunction. We investigated the association between epicardial fat thickness (EFT) and autonomic neural tone, such as vagal tone.

METHODS

A total of 797 consecutive patients (mean age 46.5 years, male: 45.7%) who underwent HUTT and echocardiography between March 2006 and June 2015 were enrolled. EFT was measured during the diastolic phase of the parasternal long axis view. We excluded patients with prior percutaneous coronary intervention, old age (* 70 years old), valvular heart disease, symptomatic arrhythmias and diabetes. We divided patients into two groups based on the HUTT (positive vs. negative).

RESULTS

There were 329 patients (41.3%) with a negative HUTT result and 468 patients (58.7%) with a positive result. The HUTT-positive patients showed a significantly lower waist circumference, body mass index and systolic and diastolic blood pressure, although a significantly higher EFT as compared to the HUTT-negative patients (HUTT-positive, 5.69 ± 1.76 mm vs. HUTT-negative, 5.24 ± 1.60 mm; p < 0.001). EFT > 5.4 mm was associated with a positive HUTT result with 51.7% sensitivity and 63.8% specificity (p < 0.001) on receiving operator characteristic analysis. Multivariate Cox regression analysis revealed that EFT (hazard ratio: 1.02, 95% confidence interval: 1.01-1.30, p = 0.004) was an independent predictor of HUTT-positivity.

CONCLSION

EFT was significantly correlated with positive HUTT, which suggests an association between EFT and autonomic dysregulation.

Neurological Complications of Cardiac Disease

This article focuses on the complex interactions between the cardiovascular and neurologic systems. Initially, we focus on neurological complications in children with congenital heart disease both secondary to the underlying cardiac disease and complications of interventions. We later discuss diagnosis and management of common syncope syndromes with emphasis on vasovagal syncope. We also review the diagnosis, classification, and management of children and adolescents with postural orthostatic tachycardia syndrome. Lastly, we discuss long QT syndrome and sudden unexpected death in epilepsy (SUDEP), reviewing advances in genetics and current knowledge of pathophysiology of these conditions. This article attempts to provide an overview of these disorders with focus on pathophysiology, advances in molecular genetics, and current medical interventions.

INGESTÃO DE ÁGUA NO SISTEMA NERVOSO AUTÔNOMO: UMA REVISÃO SISTEMÁTICA E META-ANÁLISE

RESUMO Verificar, por meio de uma revisão sistemática, o efeito da ingestão de água (IA) no sistema nervoso autônomo (SNA) e variáveis hemodinâmicas em indivíduos adultos. Foram analisados estudos publicados entre 2000 e 2015, tendo como referência a base de dados Medline via Pubmed, sendo utilizado na construção da frase de pesquisa o MeSH. Foram estabelecidos os seguintes critérios de inclusão: ensaios clínicos controlados e randomizados (ECCR) realizados em humanos, na língua inglesa. Como critério de exclusão: intervenções pouco claras, mal descritas ou inadequadas e na forma de resumos. Utilizou-se as seguintes variáveis para a seleção dos estudos: frequência cardíaca (FC), pressão arterial (PA), componente de alta frequência (AF) e resistência vascular periférica (RVP). Foi usada a sistematização PRISMA para a elaboração desta revisão e a realização de uma meta-análise com o objetivo de evidenciar matematicamente os resultados da frequência cardíaca após a ingestão de água em sete estudos que avaliaram esta variável. Fizeram parte desta revisão 10 ECCR envolvendo 246 indivíduos com idade entre 19 a 64 anos, sendo que 34,55% do sexo masculino. A maioria dos ECCR analisados apresentou alterações após a IA. As alterações comumente observadas foram: diminuição da FC (estatisticamente significativa p < 0,001), aumento da AF e RVP. Contudo, em relação à PA, os resultados demonstraram-se conflitantes, com estudos que evidenciaram aumento e outros que não observaram diferença significativa. Esta revisão evidencia os efeitos da IA no SNA, em especial na FC, AF e RVP, não obstante em relação às alterações hemodinâmicas expressas pela PA permanece ainda um óbice em relação à comunidade científica.

Syncope in Children and Adolescents

Syncope is an abrupt loss of consciousness and postural tone frequently due to disturbance of the normal autonomic nervous system reflexive mechanisms in regulating peripheral vascular resistance, blood pressure, and heart rate. This leads to a transient decrease in cerebral blood flow. It is a common presenting complaint in children and adolescents. In many cases, there is a characteristic preceding prodrome of dizziness, nausea, diaphoresis, and pallor. Although most cases of syncope are benign in etiology, it frequently causes stress and anxiety in regard to potential cardiovascular disease and possible sudden cardiac death. With careful screening by detailed patient history, comprehensive physical examination, and electrocardiogram (ECG), a significant majority of patients with serious underlying cardiac conditions will be identified. The routine use of echocardiography, ambulatory ECG, tilt-table tests, and exercise stress tests is expensive and frequently of low diagnostic yield. With benign forms of syncope, patient reassurance and education should be the first-line treatment.

Orthostatic hypotension: managing a difficult problem

Orthostatic hypotension (OH) leads to a significant number of hospitalizations each year, and is associated with significant morbidity and mortality among affected individuals. Given the increased risk for cardiovascular events and falls, it is important to identify the underlying etiology of OH and to choose appropriate therapeutic agents. OH can be non-neurogenic or neurogenic (arising from a central or peripheral lesion). The initial evaluation includes orthostatic vital signs, complete history and a physical examination. Patients should also be evaluated for concomitant symptoms of post-prandial hypotension and supine hypertension. Non-pharmacologic interventions are the first step for treatment of OH. The appropriate selection of medications can also help with symptomatic relief. This review highlights the pathophysiology, clinical features, diagnostic work-up and treatment of patients with neurogenic OH.

The Role of the Syncope Management Unit

Syncope is a common symptom, experienced by 15% of persons less than 18 years old and up to 23% of elderly nursing home residents, so it is important to consider optimizing strategies for the management of these patients. The strategy selected will inevitably differ from place to place. However, an organized structure offers more cost-effective care. This article discusses possible health care delivery models for syncope management and reviews the current status of the organization of syncope care, to show the value of a multidisciplinary approach to the organized management of patients with syncope.

Autonomic function testing: an important diagnostic test for patients with syncope

Syncope is a common problem with a large differential diagnosis. The initial history and physical examination often provide initial clues; however, some cases warrant further testing to determine the underlying cause. Autonomic function testing is a safe way to evaluate patients with syncope further, and to assess their parasympathetic and sympathetic nervous systems. Autonomic testing can help to diagnose several conditions, including orthostatic hypotension, delayed orthostatic hypotension, postural tachycardia syndrome and neutrally mediated syncope. Thus, when the cause of syncope is unclear, autonomic testing can help to assess the autonomic nervous system, stratify the risk of future episodes and to guide treatment decisions.

Evaluation of the effect of radiofrequency catheter ablation on autonomic function in patients with atrioventricular nodal reentrant tachycardia by head-up tilt table test

Background:

One of the recommended treatments for atrioventricular nodal reentrant tachycardia (AVNRT), is radiofrequency catheter ablation (RFCA). However, RFCA may affect the autonomic system. This study aims to evaluate the effect of RFCA on autonomic system in patients with PSVT by head-up tilt table (HUTT) test.

Materials and Methods:

In a before–after study, 22 patients with PSVT were enrolled. Data were collected with a data collection form that included two parts. Electrocardiogram (ECG), echocardiogram, 24-h Holter monitoring, HUTT test, heart rate variability (HRV) indexes, and symptoms of all patients were recorded 24 h before and 1 month after the ablation. Wilcoxon, McNemar, Mann–Whitney U, and Chi-square tests were used to analyze the data.

Results:

Of the total 22 patients, 31.8% were male and 68.2% were female. There were significant differences in heart palpitation (P < 0.0001) and non-specific symptoms (P = 0.031) and no significant difference in head-up tilt test results and HRV indices before and after RFCA. The results showed that there were no significant differences in specific and non-specific symptoms in patients with AVNRT with positive and negative HUTT before and after RFCA.

Conclusions:

The observed difference in heart palpitation and non-specific symptoms emphasized the role of AVNRT in causing these symptoms. Autonomic dysfunction is more probably an accompanying condition of AVNRT than causing symptoms. We could not find any significance in the results of HUTT after RFCA. HUTT cannot determine or predict the symptoms after RFCA.

Early hemodynamic response to the tilt test in patients with syncope

INTRODUCTION

Our aim was to evaluate the differences in the early hemodynamic response to the tilt test (HUTT) in patients with and without syncope using impedance cardiography (ICG).

MATERIAL AND METHODS

One hundred twenty-six patients (72 female/48 male; 37 ±17 years) were divided into a group with syncope (HUTT(+), n = 45 patients) and a group without syncope (HUTT(-), n = 81 patients). ECG and ICG signals were continuously recorded during the whole examination, allowing the calculation of heart rate (HR), stroke volume (SV), and cardiac output (CO) for every beat. The hemodynamic parameters (averaged over 1 min) were analyzed at the following points of the HUTT: the last minute of resting, the period immediately after the tilt (0 min), 1 min and 5 min after the maneuver. The absolute changes of HR, SV and CO were calculated for 0, 1, and 5 min after the maneuver in relation to the values at rest (ΔHR, ΔSV, ΔCO). Also, the percentage changes were calculated (HRi, SVi, COi).

RESULTS

There were no differences between the groups in absolute and percentage changes of hemodynamic parameters immediately after and 1 min after tilting. Significant differences between the HUTT(+) and HUTT(-) groups were observed in the 5(th) min of tilting: for ΔSV (-27.2 ±21.2 ml vs. -9.7 ±27.2 ml; p = 0.03), ΔCO (-1.78 ±1.62 l/min vs. -0.34 ±2.48 l/min; p = 0.032), COi (-30 ±28% vs. -0.2 ±58%; p = 0.034).

CONCLUSIONS

In the 5(th) min the decrease of hemodynamic parameters (ΔSV, ΔCO, COi) was significantly more pronounced in HUTT(+) patients in comparison to the HUTT(-) group.

Venepuncture during head-up tilt testing in patients with suspected vasovagal syncope – implications for the test protocol

BACKGROUND AND PURPOSE

Head-up tilt (HUT) testing is a widely used diagnostic tool in patients with suspected vasovagal syncope (VVS). However, no gold standard exists for this examination and the various protocols used have a limited sensitivity and specificity. Our aim was to determine the sensitivity of a sequential HUT testing protocol including venepuncture (VP) and sublingual nitroglycerin application.

METHODS

This was a retrospective analysis of the diagnostic gain of a sequential HUT testing protocol including VP applied 10 min after the start of HUT testing and sublingual application of nitroglycerin 20 min after the start of the test protocol in 106 patients with a final diagnosis of VVS. The sensitivity of the test protocol was compared between patients with positive and negative history for VP induced VVS.

RESULTS

Overall, pre-syncope or syncope occurred in 68 patients (64.2%). Only 17% of all patients fainted spontaneously within 10 min of passive HUT. Another 39.6% fainted within 20 min. Application of nitroglycerin after 20 min of HUT evoked syncope in another 7.5% until the end of 45 min of HUT. The sensitivity of the test protocol for evoking (pre-)syncope was 94.4% in patients with a positive history for VP associated VVS and 58% in patients with a negative history (P < 0.01**); 85.7% of patients with a positive history and 42.9% of patients with a negative history fainted within 20 min of HUT testing (P < 0.01**).

CONCLUSIONS

Implementation of VP in sequential HUT testing protocols allows the sensitivity of HUT testing to be increased, especially in patients with a positive history for VP associated VVS.

Utility of corrected QT interval in orthostatic intolerance

We performed this study to determine whether electrocardiographic corrected QT (QTc) interval predicts alterations in sympathovagal balance during orthostatic intolerance (OI). We reviewed 1,368 patients presenting with symptoms suggestive of OI who underwent electrocardiography and composite autonomic function tests (AFTs). Patients with a positive response to the head-up tilt test were classified into orthostatic hypotension (OH), neurocardiogenic syncope (NCS), or postural orthostatic tachycardia syndrome (POTS) groups. A total of 275 patients (159 OH, 54 NCS, and 62 POTS) were included in the final analysis. Between-group comparisons of OI symptom grade, QTc interval, QTc dispersion, and each AFT measure were performed. QTc interval and dispersion were correlated with AFT measures. OH Patients had the most severe OI symptom grade and NCS patients the mildest. Patients with OH showed the longest QTc interval (448.8±33.6 msec), QTc dispersion (59.5±30.3 msec) and the lowest values in heart rate response to deep breathing (HRDB) (10.3±6.0 beats/min) and Valsalva ratio (1.3±0.2). Patients with POTS showed the shortest QTc interval (421.7±28.6 msec), the highest HRDB values (24.5±9.2 beats/min), Valsalva ratio (1.8±0.3), and proximal and distal leg sweat volumes in the quantitative sudomotor axon reflex test. QTc interval correlated negatively with HRDB (r = −0.443, p<0.001) and Valsalva ratio (r = −0.425, p<0.001). We found negative correlations between QTc interval and AFT values representing cardiovagal function in patients with OI. Our findings suggest that prolonged QTc interval may be considered to be a biomarker for detecting alterations in sympathovagal balance, especially cardiovagal dysfunction in OH.

A clinical manifestation-based prediction of haemodynamic patterns of orthostatic intolerance in children: a multi-centre study

OBJECTIVE

At present, the haemodynamic diagnosis of orthostatic intolerance is based mainly on the head-up tilt table test, which is sometimes risky for patients. Thus, it is important to find objective and safe methods to differentiate haemodynamic patterns of orthostatic intolerance cases.

METHODS

In all, 629 children with orthostatic intolerance, either vasovagal syncope or postural orthostatic tachycardia syndrome, were included in the multi-centre clinical study. We analysed the association between the clinical manifestation and haemodynamic patterns of the patients.

RESULTS

Syncope after motion with a prodrome of chest distress or palpitations and the concomitant symptom(s) after a syncopal attack, with debilitation, dizziness or headache, were the most important variables in predicting the diagnosis of vasovagal syncope. The overall diagnostic accuracy was 71.5%.

CONCLUSION

Complaint of syncope after motion with prodromal chest distress or palpitation and the concomitant symptom after a syncopal attack, with subsequent debilitation, dizziness or headache, were the most important variables in the diagnosis of vasovagal syncope in children with orthostatic intolerance.

The usefulness of the head-up tilt test in patients with suspected epilepsy

PURPOSE

It is estimated that approximately 20-30% of patients diagnosed with epilepsy have been misdiagnosed, and neurocardiogenic syncope (NCS) might frequently be the real cause of transient loss of consciousness (TLOC) episodes. We assessed the role of the head-up tilt test (HUTT) in patients previously diagnosed with refractory epilepsy to evaluate the ability of this test to correctly diagnose patients with NCS.

METHOD

We retrospectively analysed the clinical records of 107 consecutive patients with a previous diagnosis of refractory epilepsy that were taking antiepileptic drugs and who were referred for HUTT between January 2000 and December 2010. During the subsequent follow-up, we recorded the treatments performed and the recurrence of symptoms.

RESULTS

Complete follow-up data were available for 94 (88%) patients, and the mean follow-up period was 80±36 months. The HUTT was positive in 54% of patients. Thirty-one (33%) patients were misdiagnosed with epilepsy, and 20 (21%) patients had a dual diagnosis of NCS and epilepsy. The recurrence of TLOC was reported in 55% of the patients, but it was significantly lower in the misdiagnosed group (42% versus 64%; P=0.039).

CONCLUSION

NCS is an important cause of epilepsy misdiagnosis. The HUTT is often critical for making an accurate diagnosis and subsequently selecting the appropriate treatment for patients presenting with TLOC. The diagnostic overlap between epilepsy and NCS is not uncommon, suggesting that electroencephalographic monitoring during a HUTT may play an important role in diagnosing patients with recurrent, undiagnosed TLOC episodes.

Management of vasovagal syncope: 2004

Vasovagal syncope is a common disorder that affects at least 20% of people at some time in their lives. Probably half of these patients faint recurrently; for many this causes physical trauma, a substantial reduction in quality of life, and difficulties with driving, employment and education. The last 15 years have seen striking advances in diagnostic approaches and prognostic understanding. A number of physiological, pharmacological and electrical therapies have been developed and tested to various degrees in patients. These include counterpressure manoeuvres, salt and fluid recommendations, and attempted treatment with fludrocortisone, midodrine, beta-blockers, serotonin reuptake inhibitors, and permanent pacemakers. This review highlights the most important of these advances and suggests strategies for managing this often difficult problem.

Effect of head-up tilt-table testing on left ventricular longitudinal strain in patients with neurocardiogenic syncope

Recent studies have shown conflicting data regarding left ventricular (LV) function in patients with neurocardiogenic syncope, with some investigators reporting a marked decrease in LV end-systolic wall stress and stress-corrected fractional shortening. We sought to determine the characteristics of resting LV deformation in patients with neurocardiogenic syncope by selective motion tracking of subendocardial and subepicardial regions using speckle tracking echocardiography. We assessed resting LV function in 82 patients undergoing head-up tilt-table (HUTT) testing. Patients were divided into 3 groups based on a positive HUTT test with associated co-morbid conditions (n = 30), no associated co-morbid conditions (n = 30), or negative HUTT results (n = 22). LV longitudinal, circumferential, and radial strains were obtained by speckle tracking echocardiography of subendocardial and subepicardial regions in each group and compared with resting LV deformation in 20 healthy control subjects. Compared with endocardial longitudinal strain in control subjects, that in patients with positive HUTT results was attenuated, irrespective of co-morbid conditions (p <0.05). Circumferential and radial strains did not differ among groups. On multivariate logistic regression analysis, endocardial longitudinal strain was an independent predictor (odds ratio, 1.16; p = 0.01) of positive HUTT test results. In conclusion, resting LV longitudinal strain is attenuated in patients with positive HUTT test results. Overall, these results may suggest that an increase in resting LV contractility is not a prerequisite for development of neurocardiogenic syncope.

Right insular atrophy in neurocardiogenic syncope: a volumetric MRI study

BACKGROUND AND PURPOSE

Alterations in the central autonomic network are hypothesized to play a role in the pathophysiologic mechanism underlying neurocardiogenic syncope; however, few data are available regarding the structural changes of the brain in this condition. We used voxel-based morphometry and regional volumetry to identify possible neuroanatomic correlates.

MATERIALS AND METHODS

We prospectively studied 32 patients with neurocardiogenic syncope with a positive response to the head-up tilt test and 32 controls who had no history of syncope. We used voxel-based morphometry to compare GM volumes between patients and controls. In addition, regional volumes of structures known to be included in the central autonomic network were measured and compared between the groups. Correlation analyses were also performed between clinical variables and anatomic data.

RESULTS

Voxel-based morphometry showed a significant GM volume reduction in the right insular cortex in patients with neurocardiogenic syncope compared with controls (corrected P = .033). Regional volumetry showed a significant reduction of right insular volumes in patients compared with controls (P = .002, MANCOVA). Smaller right insular volumes in patients with neurocardiogenic syncope were related to larger drops in systolic (P = .020) and diastolic (P = .003) blood pressures during the head-up tilt test.

CONCLUSIONS

We observed a novel finding of right insular atrophy in patients with neurocardiogenic syncope with a positive response to the head-up tilt test, implicating the role of right insular dysfunction in the pathophysiologic mechanism underlying neurocardiogenic syncope. Our findings further support the hypothesis that right insular dysfunction may cause a decrease in sympathetic activity and a reciprocal increase in parasympathetic activity, leading to syncope.

Modified Calgary score in differential diagnosis between cardiac syncope and postural orthostatic tachycardia syndrome-associated syncope in children

The present study was designed to analyse the usefulness of a modified Calgary score system during differential diagnosis between cardiac syncope and postural orthostatic tachycardia syndrome-associated syncope through a large sample sized clinical investigation. The study included 213 children, including 101 boys and 112 girls, with cardiac syncope or postural orthostatic tachycardia syndrome-associated syncope in the age group of 2-19 years (mean 11.8 ± 2.9 years). A modified Calgary score was created, which was analysed to predict differential diagnoses between cardiac syncope and postural orthostatic tachycardia syndrome-associated syncope using a receiver operating characteristic curve. The median of modified Calgary scores for cardiac syncope was -5.0, which significantly differed from that of postural orthostatic tachycardia syndrome (0.0; p < 0.01). The sensitivity and specificity of a differentiation score of less than -2.5 was 96.3% and 72.7%, respectively. Owing to the fact that the modified Calgary score was an integer, when less than -3.0 the diagnosis could be considered as cardiac syncope. The modified Calgary score could be used to make an initial differential diagnosis between cardiac syncope and postural orthostatic tachycardia syndrome-associated syncope in the clinic.

Tilt testing with combined lower body negative pressure: a "gold standard" for measuring orthostatic tolerance

Orthostatic tolerance (OT) refers to the ability to maintain cardiovascular stability when upright, against the hydrostatic effects of gravity, and hence to maintain cerebral perfusion and prevent syncope (fainting). Various techniques are available to assess OT and the effects of gravitational stress upon the circulation, typically by reproducing a presyncopal event (near-fainting episode) in a controlled laboratory environment. The time and/or degree of stress required to provoke this response provides the measure of OT. Any technique used to determine OT should: enable distinction between patients with orthostatic intolerance (of various causes) and asymptomatic control subjects; be highly reproducible, enabling evaluation of therapeutic interventions; avoid invasive procedures, which are known to impair OT(1). In the late 1980s head-upright tilt testing was first utilized for diagnosing syncope(2). Since then it has been used to assess OT in patients with syncope of unknown cause, as well as in healthy subjects to study postural cardiovascular reflexes(2-6). Tilting protocols comprise three categories: passive tilt; passive tilt accompanied by pharmacological provocation; and passive tilt with combined lower body negative pressure (LBNP). However, the effects of tilt testing (and other orthostatic stress testing modalities) are often poorly reproducible, with low sensitivity and specificity to diagnose orthostatic intolerance(7). Typically, a passive tilt includes 20-60 min of orthostatic stress continued until the onset of presyncope in patients(2-6). However, the main drawback of this procedure is its inability to invoke presyncope in all individuals undergoing the test, and corresponding low sensitivity(8,9). Thus, different methods were explored to increase the orthostatic stress and improve sensitivity. Pharmacological provocation has been used to increase the orthostatic challenge, for example using isoprenaline(4,7,10,11) or sublingual nitrate(12,13). However, the main drawback of these approaches are increases in sensitivity at the cost of unacceptable decreases in specificity(10,14), with a high positive response rate immediately after administration(15). Furthermore, invasive procedures associated with some pharmacological provocations greatly increase the false positive rate(1). Another approach is to combine passive tilt testing with LBNP, providing a stronger orthostatic stress without invasive procedures or drug side-effects, using the technique pioneered by Professor Roger Hainsworth in the 1990s(16-18). This approach provokes presyncope in almost all subjects (allowing for symptom recognition in patients with syncope), while discriminating between patients with syncope and healthy controls, with a specificity of 92%, sensitivity of 85%, and repeatability of 1.1±0.6 min(16,17). This allows not only diagnosis and pathophysiological assessment(19-22), but also the evaluation of treatments for orthostatic intolerance due to its high repeatability(23-30). For these reasons, we argue this should be the "gold standard" for orthostatic stress testing, and accordingly this will be the method described in this paper.

[Orthostatic hypotension: which initial cardiovascular and biological explorations? Which therapeutic solutions? The place of recommendations]

Orthostatic hypotension (OHT) is a common symptom that affects about 1% of the population. Its prevalence increases with age. In addition to the morbidity related to falls and syncope, OHT is a risk factor for cognitive decline and cerebrovascular morbidity and mortality. In most cases, its cause is easily found by the examination and some simple explorations. For severe and/or less obvious mechanism, some paraclinical methods of investigation can be proposed. These include head upright tilt-test and Valsalva maneuver. Both explore the entire baroreflex arc, and are realised by non-invasive measurements of heart rate and blood pressure. Other tests explore more specifically the parasympathetic outflow tract or sympathetic. In some situations cardiac MIBG scintigraphy and urinary catecholamines may be useful. The respective choice of these tests depends on the clinical setting and suspected type of dysautonomic lesion. Identifying the cause and assessment of functional impairment guide the therapeutic choices, which are primarily based on non-pharmacological approach.

Underlying diseases in syncope of children in China

Background

Syncope accounts for about 1–2% of emergency department visits, but the etiology in many patients with syncope is unclear. Recently, with the use of the head-up tilt test (HUT), the number of patients with unexplained syncope (UPS) has been decreasing; however, the spectrum of underlying diseases of syncope in children is unclear. This retrospective study aimed to analyze the spectrum of underlying diseases in children with syncope.

Material/Methods

This multi-center clinical study consisted of 888 children (417 males, 471 females, aged 5–18 yrs, median age 12.0±3.0 yrs) with syncope who came from Beijing city, Hunan province, Hubei province and Shanghai from August 1999 to March 2009. The clinical and laboratory data of children were studied and the spectrum of underlying diseases in children with syncope was analyzed.

Results

In 888 children with syncope, 175 (19.7%) had vasovagal syncope (VVS) with vasoinhibitory response, 35 (3.9%) had VVS with cardioinhibitory response, 73 (8.2%) had VVS with mixed response, 286 (32.2%) had postural orthostatic tachycardia syndrome (POTS), 19 (2.1%) had orthostatic hypotension, 7 (0.9%) had situational syncope, 13 (1.5%) had cardiogenic syncope, and 280 (31.5%) had unexplained syncope.

Conclusions

The data suggest that neurally-mediated syncope was the most common cause in children with syncope. POTS and VVS were the most common hemodynamic patterns of neurally-mediated syncope.

Head Up Tilt Testing: An Appraisal of Its Current Role in the Management of Patients with Syncope

Head up tilt testing (HTT) is now commonly used to investigate otherwise unexplained syncope and presyncope. This test has been used for over 20 years primarily to diagnose neurally mediated syncope, but HTT's exact role in the diagnostic process remains uncertain. Recognized limitations include poor reproducibility, lack of prognostic role, and insufficient randomized studies to guide therapeutic choice. In this review, we describe the indications and methods recommended by present guidelines on utilizing HTT. In addition, present criticisms and limitations of this test, along with future perspectives, are outlined.

Independent role of reduced arterial baroreflex sensitivity during head-up tilt testing in predicting vasovagal syncope recurrence

AIMS

The involvement of arterial baroreflex function in the pathophysiology of vasovagal syncope (VVS) is controversial, and there are no published data supporting its clinical usefulness. The aim of this study was to evaluate the role of arterial baroreflex sensitivity (BRS) at baseline and during head-up tilt testing (HUT) in predicting the recurrence of VVS.

METHODS AND RESULTS

The study involved otherwise healthy patients with a history of unexplained syncope who underwent diagnostic HUT by being tilted to 70 degrees after 10 min supine rest; the test was potentiated by the administration of 300 microg of nitroglycerine (NTG) after 20 min. Beat-to-beat heart rate and systolic blood pressure were continuously recorded, and the sequence method was used to measure arterial baroreflex control of heart rate. The 190 enrolled patients were followed up for 18 +/- 6 months, during which 34 experienced a total of 90 episodes of syncope recurrence. In a stepwise multivariate analysis, female gender [hazard ratio (HR): 2.74; P = 0.008], the presence of >or=3 syncope events before HUT (HR: 3.36; P = 0.004), and BRS below median value after the start of HUT or after the administration of NTG (HR: 3.79; P = 0.006) were significantly and independently associated with the recurrence of syncope. Moreover, when a BRS value of less than the median was added to the other independent factors in a stepwise model, a significant increase in discrimination (C-index: 0.77) and model fitting (P = 0.001) was observed.

CONCLUSION

Reduced BRS during HUT has independent and incremental value in predicting the recurrence of syncope, thus supporting its potential usefulness in the clinical management of patients.

Head-up tilt table testing in syncope: safety and efficiency of isosorbide versus isoproterenol in pediatric population

BACKGROUND

The aim of this study was to compare the diagnostic value and safety of sublingual isosorbid dinitrate (ISDN) with intravenous isoproterenol (ISOP) during head-up tilt table testing (HUTT) in pediatric patients with suspected neurocardiogenic syncope.

METHODS

One hundred thirty-six consecutive pediatric patients complaining of presyncope or syncope were submitted to HUTT for the first time. Those who did not develop syncope or presyncope during passive HUTT for 20 minutes underwent repeated HUTT with either 1.25 to 2.5 mg sublingual ISDN or intravenous ISOP (1-3 mug/min) for 20 minutes. There were 54 boys and 82 girls, aged 10 to 18 years with an average of 15.5 +/- 2.4 years and a median of 16 years. Among the patients with cardioinhibition or mixed responses, the severity of the bradyarrhythmia was scored 1 to 3 (restoration of effective rhythm within 10 seconds, 10-20 seconds, and >20 seconds while back to supine position, respectively).

RESULTS

During the passive period, 24 (17.6%) of 136 patients had a positive response to HUTT. Syncope was observed in another 44 patients during either ISDN or ISOP period (14/58 [24.1%] and 30/54 [55.5%] with ISDN vs ISOP, respectively, P < .05). The time to symptoms was shorter with both ISDN and ISOP compared with passive period (6.5 +/- 2.9, 6.3 +/- 5.9, and 10.3 +/- 4.4, minutes, respectively, P < .05). The severity score for cardioinhibition response was significantly higher with ISDN compared with the passive period and ISOP (2 +/- 0.8, 1.25 +/- 0.45, and 1.26 +/- 0.45, respectively, P < .01).

CONCLUSIONS

Sublingual ISDN is less sensitive and less safe compared to intravenous ISOP in assessing pediatric age patients with suspected neurocardiogenic syncope and with a negative result in tilt test without provocation. The simplicity of ISDN use should be weighed against the risk of longer symptoms with ISDN.

Tilt table testing in patients with suspected epilepsy

BACKGROUND

Approximately 20-30% of patients with epilepsy are misdiagnosed and syncope often seems to be the mistaken cause. We re-evaluated patients referred to an epilepsy clinic where suspicion of neurally mediated (reflex) syncope were raised using tilt table testing (HUT).

METHODS

HUT laboratory results and medical records of 120 consecutive patients were reviewed retrospectively over a period of 27 months.

RESULTS

HUT was positive in 59 (49%) patients. Seventeen of 38 (45%) patients previously diagnosed with epilepsy and taking antiepileptic drugs were found to be misdiagnosed. Four of 21 patients with epilepsy (19%) had dual diagnoses of reflex syncope and epilepsy.

CONCLUSION

HUT is an informative investigation when suspicions of reflex syncope are raised in patients referred to an epilepsy clinic. Reflex syncope is an important and common differential diagnosis of epilepsy.

Preliminary Observations on the Effect of Amitriptyline Treatment in Preventing Syncope Recurrence in Patients with Vasovagel Syncope

PURPOSE

Vasovagal syncope is a common and challenging problem that may result in injury and causes substantial anxiety among patients and their relatives. However, treatment of vasovagal syncope with standard pharmacologic approaches is not satisfactory. The aim of this study is to investigate the effect of amitriptyline, a tricyclic antidepressant drug, by using its anticholinergic effects in preventing syncopal episodes in patients with vasovagal syncope.

METHODS

In this study, 74 patients (mean age 24 +/- 1.9 years, 26 male) with a history of recurrent syncope and baseline positive head-up tilt table test (syncope or presyncope) were included. Oral amitriptyline treatment was given to all patients, with a starting dose of 10 mg once a day. Head-up tilt table test was performed in all patients 4 weeks after the treatment started. Patients were followed up clinically for 6 months.

RESULTS

After 4 weeks, during head-up tilt table test in 69 patients (93%), syncope or presyncope was not seen and test was assumed as negative. At the end of the 6th month, 67 patients (91%) were free of symptoms. Only two patients (0.3%) did not tolerate amitriptyline due to side effects.

CONCLUSIONS

Oral amitriptyline can be used in the prevention of recurrent episodes of vasovagal syncope safely. However, randomized controlled studies are essential to assess the real effectiveness of this therapy.

Provocation of neurocardiogenic syncope during head-up tilt testing in children: comparison between isoproterenol and nitroglycerin

OBJECTIVE

Although nitroglycerin- and isoproterenol-augmented tilt tests are of equal value in the diagnosis of neurocardiogenic syncope in adults, no data exist in children. We compared the sensitivity and specificity of the 2 tests in a pediatric population.

PATIENTS AND METHODS

We studied 85 patients (33 boys; mean age: 11.6 +/- 2.9 years). Of them, 56 had a diagnostic history of neurocardiogenic syncope, whereas 29 served as controls. After a negative passive phase, they were randomly assigned to either intravenous isoproterenol or sublingual nitroglycerin, and tilt was continued for 20 minutes.

RESULTS

Sensitivity was 0.78 for the isoproterenol test and 0.79 for the nitroglycerin test, but specificity was significantly higher for isoproterenol test compared with nitroglycerin test. In patients with a positive test, the duration of the recovery period was significantly longer after nitroglycerin (8.4 +/- 2.7 minutes) than after isoproterenol (5.1 +/- 1.6 minutes).

CONCLUSIONS

Nitroglycerin- and isoproterenol-augmented tilt tests are associated with equal sensitivity in the diagnosis of neurocardiogenic syncope in children and adolescents. However, nitroglycerin results in more false-positive tests and produces more prolonged vasovagal symptoms. Our data do not support the routine use of nitroglycerin in the evaluation of syncope in this age group.

Vasovagal syncope in patients with reduced left ventricular function

Vasovagal syncope (VVS) is mediated by arterial mechanoreceptors, resulting in reflexive changes in heart rate and vascular tone. The Bezold-Jarisch reflex was originally described as enhanced contraction and activation of left ventricular mechanoreceptors, but later studies implicated other triggers, including coronary, carotid, and cerebral arterial mechanoreceptors. VVS is uncommon in patients with left ventricular dysfunction. We hypothesized that VVS could occur in this subset and examined patient characteristics and hemodynamic responses during tilt table testing. From 1996 through 1998, 128 consecutive patients with ejection fraction <40% underwent tilt table testing (70 degrees , 45 min). A total of 15 patients (11.7%) had a positive neurocardiogenic response thought to be the cause of syncope. Clinical data and hemodynamic responses were reviewed. Mean patient age (+/-SEM) was 70.1 +/- 12.2 years. Nine patients were male. Mean ejection fraction was 27.7% +/- 7.1%. Thirteen had electrophysiologic studies with normal findings or abnormal findings insufficient to account for syncope. Hemodynamic analysis of 14 patients who had a vasovagal response during passive tilt table testing showed a mean time to positive response of 17.6 +/- 12.7 min. Cardioinhibitory responses (pauses >3 sec or heart rate < 40 beats/min for > or =10 sec) were not observed. Five responses were classified as mixed type (>10% decrease in heart rate without a cardioinhibitory response) and 9 as vasodepressor type (< or =10% decrease in heart rate). VVS occurs in patients who have clinically significant left ventricular dysfunction. Although this study had a small cohort size, the predominantly vasodepressor response without a cardioinhibitory component warrants further investigation into mechanisms of VVS in these patients.

Use of the implantable loop recorder in children and adolescents

INTRODUCTION

Recurrent but infrequent syncopes represent a diagnostic challenge, since they frequently remain unexplained despite extensive investigations. This applies specifically for patients who carry an increased risk of potentially lifethreatening arrhythmias, either due to congenital cardiac disease or primary electrical disorders. Implantable loop recorders permit long-term electrocardiographic monitoring. Experience with these devices is still limited in children.

PATIENTS AND METHODS

Between January 1999 and August 2005, 12 patients underwent implantation of a loop recorder in our tertiary referral centre. The mean age was 10.9 years, with a range from 2 to 17 years. Of the patients, 6 had structural disease, 3 had primary electrical abnormalities, and 3 had no cardiovascular disease.

RESULTS

Resyncope occured in 9 of the 12 patients. Arrhythmic origin of the syncope was diagnosed in 4 of these patients. The events recorded were ventricular fibrillation in 2, intermittent asystole in 1, and pacemaker-syndrome in the other patient. Malignant arrhythmia was ruled out in the remaining 5 patients. There were no complications related to implantation of the loop recorder, and the mean duration until explantation was 8.3 months.

CONCLUSIONS

Based on our experience, we suggest that implantation of a loop recorder represents an additional tool for a selected group of children. Due to its invasive nature, it should be restricted to patients at high risk, or those in which there is substantial clinical suspicion of the likelihood of serious arrhythmias when conventional testing has been inconclusive. In this cohort, implantation of the loop recorder either helps to establish the correct diagnosis, or to exclude an arrhythmic event, thus avoiding unnecessary escalation of therapy and providing reassurance for the family.

Norepinephrine Transporter Inhibition Prevents Tilt-Induced Pre-Syncope

OBJECTIVES

We tested the hypothesis that pharmacological norepinephrine reuptake transporter (NET) inhibition delays the onset of head-up tilt-induced presyncope in healthy subjects.

BACKGROUND

Treatment of neurally mediated syncope is unsatisfactory. In a previous study in a small number of healthy subjects, pharmacologic NET inhibition delayed the onset of head-up tilt-induced pre-syncope.

METHODS

We combined data sets from 3 substudies comprising 51 healthy subjects without a history of syncope. In a double-blind, randomized, cross-over fashion, subjects underwent 2 head-up tilt tests, once with placebo and once with a NET inhibitor (sibutramine or reboxetine). Tilt testing was prematurely ended when pre-syncopal symptoms such as dizziness, nausea, or visual disturbances occurred together with a decrease in blood pressure and/or heart rate.

RESULTS

The mean tolerated tilt test duration was 29 +/- 2 min with placebo and 35 +/- 1 min with NET inhibition (p = 0.001). The odds ratio for premature abortion of head-up tilt testing was 0.22 (95% confidence interval 0.09 to 0.55, p < 0.001) in favor of NET inhibition. Norepinephrine reuptake transporter inhibition elicited a pressor response and increased upright heart rate.

CONCLUSIONS

In healthy subjects, NET inhibition prevents tilt-induced neurally mediated (pre)syncope. Therefore, NET inhibition may be a worthwhile target of drug intervention for larger trials in highly symptomatic patients with neurally mediated syncope.

[Sensitization of tilt-table testing for syncope of unknown etiology: which drug to use?]

OBJECTIVE

The sensitivity of tilt-table testing in the diagnosis of vasovagal syncope is between 30% and 50% only. The most common method currently used to improve the sensitivity of the test is the administration of isoproterenol i.v. However, this method is difficult to perform and time consuming. The objective of our study was to compare sublingual trinitrin administration to i.v. isoproterenol during tilt-table testing.

METHODS

We analyzed the results of 257 consecutive patients referred for tilt testing. Patients who had a negative test received either a ten minutes infusion of i.v. isoproterenol at the dose of 4 mcg/kg/min, or 0.4 mg of trinitrin given sublingually.

RESULTS

Two hundred (and) fifty-seven patients underwent tilt-table testing. In the first group (isoproterenol group), 42 patients (39%) had a spontaneous positive tilt test, compared to 45 patients (31%) in the trinitrin group (P = NS). After sensitization, 24 additional patients (22%) had a positive test in the isoproterenol group vs 55 patients (37%) in the trinitrin group (P = NS). The total number of positive tests was 66 (61%) in the isoproterenol group compared to 100 (68%) in the trinitrin group (P = NS).

CONCLUSION

Sublingual trinitrin is at least as good as IV isoproterenol during tilt-table testing. Because trinitrin is simpler to use and because its administration is much faster than isoproterenol, it should be recommended as the drug of choice to improve the sensitivity of tilt-table testing.