Head-up tilt test in complicated neurocardiogenic syncope in children.

To confirm the usefulness of head-up tilt test (HUT) in neurocardiogenic syncope (NCS) with complicating clinical features, retrospective analysis were done on 12 selected children. The age at onset was 12.7 +/- 1.9 (mean +/- SD) years. Associated clinical features were postoperative congenital heart disease (PO CHD) in 3, coexistent arrhythmia in 8 (persistent ventricular arrhythmia during exercise in 3, premature ventricular contractions in 2, ventricular couplets in 1, sinoatrial exit block in 1 and resting sinus bradycardia in 1) and ST segment depression during exercise in 1. Four of them had a history of exercise-related syncope. All 3 patients with PO CHD had arrhythmia (ventricular tachycardia in 1, sinus bradycardia in 1 and atrioventricular block in 1). HUT provoked NCS in 8 (2 during baseline tilt, 6 during isoproterenol infusion). In one each, ventricular tachycardia and loss of consciousness without hypotension and bradycardia were induced. Atenolol was tried in 5 with improvement of NCS in 4 and aggravation of dizziness in 1. During follow-up, 7 became asymptomatic (2 with atenolol) and 5 were stationary. In conclusion, HUT was valuable in diagnosing NCS even in children with complicating clinical features such as arrhythmias or PO CHD. HUT could be done as apart of initial diagnostic tests if the past history suggests NCS, regardless of associated clinical features. In some cases, the unexpected results of the test turned out useful in managing children with syncope or dizziness.     

The effect of beta adrenergic stimulation on QT and QTc interval in syncope children with or without coexisting ventricular arrhythmias

We investigated the effect of beta-adrenergic stimulation on the heart rate and QT interval in syncope children with or without coexisting ventricular arrhythmias (VA). Of the 24 children who presented with syncope or presyncope and showed negative tilt test, 13 were classified into a group with VA and the remaining 11 without VA. The provocative test was performed in bolus infusion and continuous infusion. RR, QT, and QTc intervals on routine 12-lead surface electrocardiogram were obtained during each stage of isoproterenol infusion. In all cases, malignant ventricular arrhythmia and syncope were not induced by isoproterenol provocative test. RR and QT intervals were shortened and QTc intervals were prolonged as the isoproterenol dose was increased in both groups and methods. The QTc interval reached its peak level after the bolus injection of 1.0 microgram and during the continuous infusion of 0.03 microgram/kg/min. The two groups showed no significant difference in the QTc interval change according to the infusion methods. This study indicates that changes in the heart rate and QT interval by beta-adrenergic stimulation were not different according to the coexisting ventricular arrhythmias in syncope children with negative head-up tilt test.     

Seizure-Like Activities during Head-Up Tilt Test-Induced Syncope

Purpose

Some patients with neurally mediated reflex syncope may be misdiagnosed as epilepsy because myoclonic jerky movements are observed during syncope. The seizure-like activities during the head-up tilt test (HUT) have been rarely reported. The purpose of this study was to assess the characteristics of these seizure-like activities and evaluate whether there are differences in the clinical characteristics and hemodynamic parameters of patients with neurally mediated reflex syncope with and without seizure-like activities during HUT-induced syncope.

Materials and Methods

The medical records of 1,383 consecutive patients with a positive HUT were retrospectively reviewed, and 226 patients were included in this study.

Results

Of 226 patients, 13 (5.75%) showed seizure-like activities, with 5 of these (2.21%) having multifocal myoclonic jerky movements, 5 (2.21%) having focal seizure-like activity involving one extremity, and 3 (1.33%) having upward deviation of eye ball. Comparison of patients with and without seizure-like activities revealed no significant differences in terms of clinical variables and hemodynamic parameters during HUT.

Conclusion

Seizure-like activities occurred occasionally during HUT-induced syncope in patients with neurally mediated reflex syncope. The seizure-like activities during HUT might not be related to the severity of the syncopal episodes or hemodynamic changes during HUT.     

Parent and child psychological factors in pediatric syncope and other somatic symptoms

The authors examined associations among parental and child adjustment, child syncope, somatic, and school problems. Participants were children (N = 56) ages 7-18 years with syncope. Measures included syncope severity, parental distress, and children's internalizing symptoms. For children diagnosed negative for neurocardiogenic syncope (NCS), their fathers' and their own psychological symptoms were positively associated with the severity of syncope, whereas their mothers' functioning was negatively associated with the severity of syncope. Also, for the negative NCS group, fathers' psychological functioning was associated with children's nonsyncope somatic complaints but not with their school problems. For the positive NCS group, few significant father-child associations were found, but several significant positive associations were revealed between mothers' psychological symptoms and their children's syncope as well as somatic and school problems.     

Provocation of bradycardia and hypotension by isoproterenol and upright posture in patients with unexplained syncope

Neurally mediated hypotension and bradycardia are believed to be common causes of syncope. We used the "upright-tilt test" (duration, less than or equal to 10 minutes) with or without an infusion of exogenous catecholamine (isoproterenol [1 to 5 micrograms per minute], given intravenously) to elicit bradycardia, hypotension, or both in 24 patients with recurrent syncope and in 18 control subjects. A conventional electrophysiologic test performed before the tilt test was positive in 9 of the 24 patients, revealing arrhythmias that may have caused recurrent syncope, but was negative and thus nondiagnostic in 15 patients. The tilt test alone (i.e., without isoproterenol) induced symptomatic bradycardia or hypotension in 1 of the 9 patients with positive electrophysiologic tests (11 percent), 4 of the 15 patients with negative electrophysiologic tests (27 percent), and none of the controls. When the isoproterenol infusion was administered during the tilt test, 9 of the 11 patients with negative electrophysiologic and tilt tests had syncope, marked slowing of the heart rate, and hypotension. In contrast, isoproterenol was associated with tachycardia and only a slight decline in arterial pressure in the 8 remaining patients with positive electrophysiologic tests and the 18 control subjects, and syncope developed in only 1 of the 8 patients with positive electrophysiologic tests and negative tilt tests (13 percent) and 2 of the 18 control subjects (11 percent). We conclude that an isoproterenol infusion administered in conjunction with the upright-tilt test may be useful for identifying susceptibility to neurally mediated recurrent syncope.     

一种基于近似熵特征分类的冠心病诊断方法

对104例冠心病人心电Holter信号进行心率变异性的分析,计算RR间期序列的近似熵指标的24h分段变化趋势图,并于健康对照组作比较,验证了近似熵这个心率变异性非线性参数的意义.通过LDA(线性鉴别分析)的模式识别方法对病人及健康人的24h变化趋势图进行模式识别和分类,平均正确分类率达99.03%.分类的结果表明,冠心病患者与健康人相比在白天,尤其在早上6点到中午12点间,近似熵指标的降低更明显,利用此时间段作分类正确率更高.     

Delaying orthostatic syncope with mental challenge: a pilot study

At orthostatic vasovagal syncope there appears to be a sudden decline of sympathetic activity. As mental challenge activates the sympathetic system, we hypothesized that doing mental arithmetic in volunteers driven to the end point of their cardiovascular stability may delay the onset of orthostatic syncope. We investigated this in healthy male subjects. Each subject underwent a head up tilt (HUT)+ graded lower body negative pressure (LBNP) up to presyncope session (control) to determine the orthostatic tolerance time, OTT (Time from HUT commencement to development of presyncopal symptoms/signs). Once the tolerance time was known, a randomized crossover protocol was used: either 1) Repeat HUT+LBNP to ensure reproducibility of repeated run or 2) HUT+LBNP run but with added mental challenge (2 min before the expected presyncope time). Test protocols were separated by 2 weeks. Our studies on five male test subjects indicate that mental challenge improves orthostatic tolerance significantly. Additional mental loading could be a useful countermeasure to alleviate the orthostatic responses of persons, particularly in those with histories of dizziness on standing up, or to alleviate hypotension that frequently occurs during hemodialysis or on return to earth from the spaceflight environment of microgravity.     

Association of parental psychological and behavioral factors and children's syncope.

The authors examined the associations between parental variables and child syncope (fainting). Children ages 7 to 18 years undergoing tilt-table testing for neurocardiogenic syncope (NCS) at a pediatric cardiac center served as participants (N = 56). Results revealed that fathers' shortness of breath and overall psychological distress were significantly related to syncope frequency and emergency room (ER) visits for girls. Mothers' overall psychological distress, depressive symptoms, and shortness of breath were associated with boys' frequency of syncope and ER visits. Fathers' psychological factors were highly correlated with syncope for the children diagnosed negative for NCS. The frequency of children's syncope was higher in stepfamilies than in homes with both biological parents, and the correlations between children's syncope and the stepfathers' psychological symptoms were greater than for the children and their biological fathers in intact families. The role of parental psychological factors on child syncope is supported.     

癫痫脑电信号符号动力学分析

癫痫是大脑神经元异常放电所引起的常见神经系统疾病,其发作具有突然性和反复性特点,因此,提前预测发作以便对患者及时采取措施具有重要意义。本文引入符号动力学方法分析癫痫大鼠失神性发作时脑电(EEG)信号的特性,并对影响符号统计量的关键参数的选取进行讨论,计算癫痫发作不同时期EEG信号的符号熵和时间不可逆转性。研究发现正常发作间隙期,符号熵和时间不可逆转性指标值较大;从发作间隙期向发作期的转化阶段,即发作前期,二者明显减小;发作时维持较低水平。研究结果表明符号动力学方法能够揭示癫痫EEG动力学特征变化,符号熵和时间不可逆转性两个指标是表征癫痫发作不同阶段的敏感特征量,具有重要的潜在临床应用价值。     

R-R interval-blood pressure interaction in subjects with different tolerances to orthostatic stress

In addition to the gain, the time delay in the input-output response in a feedback system is crucial for the maintenance of its stability. Patients with posturally related (vasovagal) syncope have inadequate control of blood pressure and one possible explanation for this could be prolonged latency of the baroreflex. We studied 14 patients with histories of syncope and poor orthostatic tolerance (assessed by a progressive orthostatic stress test) and 16 healthy controls. We performed spontaneous sequence analysis of the fluctuations of R-R period (ECG) and systolic arterial pressure (SAP, Finapres) recorded during a 20 min supine period and during 20 min 60 deg head-up tilt (HUT). The baroreflex latency was determined by identifying the lag between the changes in SAP and in R-R interval from which the highest correlation coefficient was obtained. During the supine period, 74% of sequences in control subjects and 54% in patients occurred with zero beats of delay (i.e. R-R interval changed within the same R-R interval). The remaining sequences occurred with delays of up to four beats. HUT shifted the baroreflex delay to be approximately one heartbeat slower and again patients showed more sequences with prolonged response. The delay in heartbeats was transformed into delay in time. In control subjects, 75% of baroreflex responses occurred within 1 s. In patients, 75% of baroreflex responses took more than 2 s to occur. The results showed that syncopal patients with poor orthostatic tolerance have increased baroreflex latency. This may lead to instability and inadequate blood pressure control and may predispose to vasovagal syncope.     

心电RR间期序列的延迟时间研究

目的:探究心电RR间期序列的延迟时间的计算方法,并研究RR间期序列的延迟时间与其复杂度及年龄的关系。方法:以年轻(21~34岁)与年老(68~81岁)二组健康人的心电RR间期时间序列为实验数据,采用等概率符号分析方法计算其互信息,再按互信息极小原则确定其延迟时间。结果:年老组的延迟时间明显大于年轻组的(P0.015),并使用统计检验对其延迟时间与近似熵的分析,得出二者呈很强的负相关性(P-0.6)。结论:结果表明,RR间期序列的延迟时间直接反应了心电RR间期序列的复杂性特征,其大小与心率变异活动性和心血管的复杂程度负相关。     

Baroreflex analysis in diabetes mellitus: linear and nonlinear approaches

The aim of our study was to employ novel nonlinear synchronization approaches as a tool to detect baroreflex impairment in young patients with subclinical autonomic dysfunction in Type 1 diabetes mellitus (DM) and compare them to standard linear baroreflex sensitivity (BRS) methods. We recorded beat-to-beat pulse interval (PI) and systolic blood pressure (SBP) in 14 DM patients and 14 matched healthy controls. We computed the information domain synchronization index (IDSI), cross-multiscale entropy, joint symbolic dynamics, information-based similarity index (IBSI) in addition to time domain and spectral measures of BRS. This multi parametric analysis showed that baroreflex gain is well-preserved, but the time delay within the baroreflex loop is significantly increased in patients with DM. Further, the level of similarity between blood pressure and heart rate fluctuations was significantly reduced in DM. In conclusion, baroreflex function in young DM patients is changed. The quantification of nonlinear similarity and baroreflex delay in addition to baroreflex gain may provide an improved diagnostic tool for detection of subclinical autonomic dysfunction in DM.     

二进制序列在心率变异性分析中的应用及推广

目的：探究二进制序列在心率变异性分析中的应用。方法：提出了一种将RR间期序列转化成二进制序列的方法一阈值法，并利用这种方法分别将年轻组和老年组各20名健康受试者RR间期的原始序列转化成为二进制序列，计算了这两组健康受试者RR间期的原始序列和转化成二进制序列的近似熵与样本熵。结果：通过计算，得到转化后两组二进制序列的近似熵分别为0．5923±0．1071、0．3270±0．2057，样本熵分别为0．5315±0．1528、0．2238±0．1993。对这两个指标分别进行t检验表明：年轻组的近似熵与样本熵均明显大于老年组（P〈0．001，P〈0．001），经与原始序列的t检验结果对照发现，二进制序列的t检验效果更好．结论：经过讨论，本文介绍的经阈值法转化为二进制序列在心率变异性分析中有较明显的优点。     

Gender Difference in Patients with Recurrent Neurally Mediated Syncope

Purpose

The gender difference of neurally mediated syncope is not well defined in a large patient population. The aim of this study was to evaluate the gender difference of clinical manifestations in patients with neurally mediated syncope who underwent head-up tilt test.

Materials and Methods

The medical records of 1,051 consecutive patients with two or more episodes of syncope, who were diagnosed as having neurally mediated syncope by head-up tilt test, were retrospectively reviewed.

Results

Of 1,051 patients, 497 (47.3%) patients were male and 554 (52.7%) patients were female. Female patients were experiencing syncopal episodes for longer periods of their lives (8.2 ± 9.5 years vs. 6.8 ± 9.2 years, p = 0.002) and more episodes of syncope prior to head-up tilt test (HUT) (7.2 ± 9.4 vs. 5.0 ± 6.4, p = 0.001) than male patients. Micturition syncope (20.0% vs. 5.2%, p < 0.001) was observed more frequently in male patients than in female patients. To the contrary, however, defecation syncope (16.3% vs. 9.3%, p < 0.001) was observed more frequently in female patients than in male patients.

Conclusion

Female patients were experiencing syncopal episodes for longer periods of their lives and more episodes of syncope than male patients. Gender difference was also noted with regard to frequency of situational syncope.     

Adaptive computation of approximate entropy and its application in integrative analysis of irregularity of heart rate variability and intracranial pressure signals

The present study introduces an adaptive calculation of approximate entropy (ApEn) by exploiting sample-by-sample construction and update of nearest neighborhoods in an n-dimensional space. The algorithm is first validated with a standard numerical test set. It is then applied to electrocardiogram R wave interval (RR) and beat-to-beat intracranial pressure signals recorded from 12 patients undergoing normal pressure hydrocephalus diagnosis. The ApEn time series are further processed using the causal coherence analysis to study the interaction between ICP and RR interval. Numerical validation demonstrates that the proposed algorithm reproduces the known time-varying patterns in the test set and better tracks abrupt signal changes. It is also demonstrated that occurrences of large-amplitude ICP oscillation are associated with decreased ICP ApEn and RR ApEn for all 12 patients. The causal coherence analysis of ApEn time series shows that coherence between RR ApEn and ICP ApEn, after mathematically decoupling RR effect on ICP, is enhanced for the oscillatory ICP state and so is the amplitude of transfer function between ICP and RR interval. However, no enhanced coherence is observed after mathematically decoupling ICP effect on RR interval. In conclusion, the adaptive ApEn algorithm can be used to track nonstationary signal characteristics. Furthermore, interactions between dynamic systems could be studied by using ApEn time series of the direct observations of systems.     

Role of Baroreflex Sensitivity in Predicting Tilt Training Response in Patients with Neurally Mediated Syncope

PurposeAn association between baroreflex sensitivity (BRS) and the response to tilt training has not been reported in patients with neurally mediated syncope (NMS). This study sought to investigate the role of BRS in predicting the response to tilt training in patients with NMS.ResultsAfter tilt training, 52 patients (91.2%) achieved three consecutive negative responses to the HUT. In the supine position before upright posture during the first session of tilt training for responders and non-responders, the mean BRS was 18.17±10.09 ms/mm Hg and 7.99±5.84 ms/mm Hg (p=0.008), respectively, and the frequency of BRS ≥8.945 ms/mm Hg was 45 (86.5%) and 1 (20.0%; p=0.004), respectively. Age, male gender, frequency of syncopal events before HUT, type of NMS, phase of positive HUT, total number of tilt training sessions, and mean time of tilt training did not differ between the study groups. In the multivariate analysis, BRS <8.945 ms/mm Hg in the supine position (odds ratio 23.10; 95% CI 1.20-443.59; p=0.037) was significantly and independently associated with non-response to tilt training.ConclusionThe BRS value in the supine position could be a predictor for determining the response to tilt training in patients with NMS who are being considered for inpatient tilt training.     

模糊区间信息熵用于充血性心衰患者的检测

目的传统心率变异性图形化指标（直方图和散点图）检测区分充血性心衰患者和健康人时难以量化,针对这一问题,本文提出一种新的心率变异性图形化分析方法——RR间期序列归一化直方图及其量化指标,用于检测区分充血性心衰患者和健康人。方法首先定义RR间期序列归一化直方图,在此基础上定义基于模糊理论的量化指标——模糊区间信息熵FuzzyRIEn,最后利用120例临床试验数据（60例充血性心衰患者和60例健康人）分析对比指标FuzzyRIEn和前期研究提出的3个量化指标：中心一边缘比（center—edgeratio,CER）、累积能量（cumulativeenergy,CE）和区间信息熵（range information entropy,RIEn）在两组问的统计学差异。结果对比结果显示,CER（P=0．418）,CE（P=0．262）和RIEn（P=0．068）在两组间均无显著统计学差异,而FuzzyRIEn（P=0．023）在两组间统计学差异显著。结论利用模糊区间信息熵FuzzyRIEn检测区分充血性心衰有较高的临床诊断价值。     

Association of corrected QT interval with long-term mortality in patients with syncope

Introduction

The electrocardiographic parameters QRS duration, QRS-T angle and QTc can predict mortality in patients with cardiovascular disease. The prgnostic value of these parameters in hospitalized patients with syncope needs investigation.

Material and methods

We retrospectively studied 590 consecutive patients hospitalized with syncope. After excluding patients with baseline abnormal rhythm, QT- prolonging medications, and missing data, 459 patients were analyzed. Baseline demographic characteristics, co-morbidities, medication use, San Francisco Syncope Rule (SFSR) and Osservatorio Epidemiologico sulla Sincope nel Lazio (OESIL) score and data on mortality were collected. The categorical variables and continuous variables of the 2 groups of patients with prolonged QTc and normal QTc interval were analyzed by Fischer''s exact test and Mann-Whitney Test. A stepwise Cox regression model was used for time to death analysis.

Results

Of 459 patients, prolonged QTc interval was observed in 122 (27%). Mean follow-up was 41 months. Patients with prolonged QTc interval had higher prevalence of cardiovascular disease, OESIL score, high risk SFSR, hypertension, dyslipidemia, coronary artery disease, congestive heart failure, and increased mortality. Stepwise Cox regression analysis showed that significant independent prognostic factors for time to death were prolonged QTc interval (p = 0.005), age (p = 0.001), diabetes mellitus (p = 0.001) and history of malignancy (p = 0.006). QRS duration and QRS-T angle were not independent predictors of mortality.

Conclusions

A prolonged QTc interval is an independent predictor of long-term mortality in hospitalized patients with syncope.     

An approach to the patient with a history of local anesthetic hypersensitivity: experience with 90 patients.

We have studied the utility of skin testing and progressive challenge to detect local anesthetic hypersensitivity in patients with histories of reactions to local anesthetics. The likelihood of previous immediate hypersensitivity reactions was determined by history in 90 referrals. Fourteen had histories compatible with immediate hypersensitivity reactions, 24 did not, and the history was uncertain in 52. Of the 14, 12 were negative to lidocaine skin test and challenge, although 5 gave histories of immediate hypersensitivity reactions to it. The other 76 patients also underwent skin testing and progressive challenge. No skin tests were positive with 1:100 local anesthetics but 10 patients had positive intradermal skin tests to undiluted 1% local anesthetics. Proof of false positivity was confirmed in 4 of 10 cases by uneventful challenge to the local anesthetic giving the positive skin test. At least 1 local anesthetic was cleared for use in each of the 90 patients. Skin testing as part of a progressive challenge protocol is a useful approach to the management of alleged local anesthetic hypersensitivity. True immediate hypersensitivity reactions to local anesthetics are rare. Positive skin tests to dilutions of 1:100 local anesthetics are also rare and may suggest the possibility of true immediate hypersensitivity to the agent tested.     

T波峰-末间期与室性心动过速的关系探讨

目的：探讨T波峰-末间期（Tpeak-Tendinterval,Tpe）与室性心律失常发作之间的关系。方法：通过对动态心电图检查中的128例患者是否出现室速分为两组：室速组60例,无室速组68例。对检查过程中记录的同步12导心电图各导联的T波峰-末间期进行手工测量,并计算心率校正的T波峰-末间期（Tpe/√RR）。分别对研究对象各导联Tpe间期、Tpe/√RR以及12导联平均Tpe间期、Tpe/√RR进行两组之间比较的统计分析。结果：①除V1导联外其余各导联的Tpe间期及Tpe/√RR在室速组较无室速组显著延长（P〈0.05）。②12导联平均的Tpe间期及Tpe/√RR在室速组较无室速组亦显著延长（P〈0.05）。③在室速组较无室速组Tpe/√RR延长的显著性要高于Tpe间期。结论：室速发作前比无室速发作的Tpe间期延长具有统计学意义,Tpe间期有望成为预测室性心律失常事件的临床指标。