Deceleration Capacity--A Novel Measure for Autonomic Nervous System in Patients with Vasovagal Syncope on Tilt-table Testing

This study was to investigate the changes of autonomic nerve function and hemodynamics in patients with vasovagal syncope(VVS) during head-up tilt-table testing(HUT). HUT was performed in 68 patients with unexplained syncope and 18 healthy subjects served as control group. According to whether bradycardia, hypotension or both took place during the onset of syncope, the patients were divided during the test into three subgroups: vasodepressor syncope(VD), cardioinhibitory syncope(CI) and mixed syncope(MX) subgroups. Heart rate, blood pressure, heart rate variability(HRV), and deceleration capacity(DC) were continuously analyzed during HUT. For all the subjects with positive responses, the normalized low frequency(LFn) and the LF/HF ratio markedly decreased whereas normalized high frequency(HFn) increased when syncope occurred. Syncopal period also caused more significant increase in the power of the DC in positive groups. These changes were more exaggerated compared to controls. All the patients were indicative of a sympathetic surge in the presence of withdrawal vagal activity before syncope and a sympathetic inhibition with a vagal predominance at the syncopal stage by the frequency-domain analysis of HRV. With the measurements of DC, a decreased vagal tone before syncope stage and a vagal activation at the syncopal stage were observed. The vagal tone was higher in subjects showing cardioinhibitory responses at the syncopal stage. DC may provide an alternative method to understand the autonomic profile of VVS patients.

Serious response during tilt-table test in elderly and its prophylactic management

Objective: To evaluate the serious response during tilt-table test (TTT) and its prophylactic management. Method: Seventy-six elderly patients were tested at a tilt angle of 70 degrees for a maximum of 45 min and then subjected to isoprotere- nol-provocative tilt testing. ECG and blood pressure were monitored during the test and patients were kept at normal saline con- dition through a peripheral intravenous duct. Results: Fifty-one of 76 patients were defined as positive including 23 having serious response; 6 of the 23 patients had arteriosclerosis involving internal carotid arteries and 7 cases had bradycardia, two of which were associated with II°-I A-V block and the others with chronic atrial fibrillation. The serious response consisted of cardiac arrest for more than 5 s (6 cases), or serious bradycardia for more than 1 min (7 cases) or serious hypotension for more than 1 min (10 cases). Those with serious response were managed by returning to supine position, thus driving up legs and intravenous atropine, CPR (2 cases with cardiac arrest) and needing oxygen supplementation (11 cases). Only 2 hypotension patients recovered gradually by 10 min after emergency management, while others recovered rapidly with no complications. Conclusion: Although non-invasive, TTT may result in serious response, especially in elderly. Therefore proper patient selection, control of isoproterenol infusion and close observation of vital signs are decisive for a safe consequence.

Syncope as a health risk for soldiers: Influence of medical history and clinical findings on the sensitivity of head-up tilt table testing

Background: Syncope is a relevant health problem in military environments. Reliable diagnosis is challenging. Tilt table testing is an important tool for syncope diagnosis. The aim of this study was to determine whether signs such as prodromal symptoms, co-morbidity, frequency of syncopal events, body length, body mass index, and electrocardiography(ECG) abnormalities can be used to predict the success of tilt table testing at diagnosing syncope.Methods: Data from 100 patients with histories of syncope or pre-syncope, who were diagnosed using head-up tilt table testing, were retrospectively analyzed in a cross-sectional analysis. The diagnostic procedure was based upon a modified version of the Westminster protocol without any pharmacological provocation. Results: Patients showing pathological reaction patterns during tilt table testing suffered from prodromal symptoms, such as dizziness and sweating, significantly more often. The patients reported more injuries resulting from syncopal events and more previous syncopal events, and the prevalence of co-morbidity was greater among patients presenting negative findings during tilt testing. An asthenic-leptosomal physique was not confirmed as a risk factor for syncopal events as is the case for idiopathic arterial hypotension. However, patients with pathological reaction patterns during tilt table testing were significantly taller. This finding was detected for both females and males. No significant predictors were found in the ECG patterns of patients showing syncope during tilt table testing.Conclusions: Frequency of prior syncope and prodromal symptoms, and increased body length with an otherwise good state of health influence the predictive value of tilt table testing for syncope diagnosis. In particular, if these factors are present, tilt table testing should be considered part of the diagnostic algorithm for soldiers with recurrent syncope.

Syncope as a health risk for soldiers-influence of medical history and clinical findings on the sensitivity of head-up tilt table testing

Background:Syncope is a relevant health problem in military environments.Reliable diagnosis is challenging.Tilt table testing is an important tool for syncope diagnosis.The aim of this study was to determine whether signs such as prodromal symptoms,co-morbidity,frequency of syncopal events,body length,body mass index,and electrocardiography abnormalities can be used to predict the success of tilt table testing at diagnosing syncope.Methods:Data from 100 patients with histories of syncope or pre-syncope,who were diagnosed using head-up tilt table testing,were retrospectively analyzed in a cross-sectional analysis.The diagnostic procedure was based upon a modified version of the Westminster protocol without any pharmacological provocation.Results:Patients showing pathological reaction patterns during tilt table testing suffered from prodromal symptoms,such as dizziness and sweating,significantly more often.The patients reported more injuries resulting from syncopal events and more previous syncopal events,and the prevalence of co-morbidity was greater among patients presenting negative findings during tilt testing.An asthenic-leptosomal physique was not confirmed as a risk factor for syncopal events as is the case for idiopathic arterial hypotension.However,patients with pathological reaction patterns during tilt table testing were significantly taller.This finding was detected for both females and males.No significant predictors were found in the electrocardiogram patterns of patients showing syncope during tilt table testing.Conclusions:Frequency of prior syncope and prodromal symptoms,and increased body length with an otherwise good state of health influence the predictive value of tilt table testing for syncope diagnosis.In particular,if these factors are present,tilt table testing should be considered part of the diagnostic algorithm for soldiers with recurrent syncope.

The Changes of Heart Rate Power Spectral Density during Head-up Tilt Test

To study the role of autonomic nervous system in the period of developing syncope induced by head-up tilt test(HUT), we analysed the changes of heart rate power spectral density(HRPSD) in 50 patients with unexplained syncope, including 15 positive patients (Group 1) and 35 negative patients(Group 2), and 15 negative healthy persons(Group 3) in 5 minute periods before and after tilting and 5 minutes before the end of test. HRPSD and their changes in total(T), very low-frequence(VLF), low-frequence(LF), high-frequence(HF) and the ratio of low/high frequence(LF/HF) were similar (P>0.05) 5 minutes before and after tilting among three groups. Five minutes before the end of test, Group 1 had obvious increase of T, VLF, LF and LF/HF while Group 2 and 3 had not such significant changes. There was significant difference(P<0.01) compared Group 1 with Group 2, 3. The results showed that the abnormal regulatory function of autonomic nervous system played an important role in the mechanism of symcope induced by HUT, the positive group had abnormal increase of sympathetic tone and imbalance of sympathetic/parasympathetic neural tone before syncope appeared.

Age and Sex Distribution of Patients with Vasovagal Syncope Undergoing Head-up Tilt Table Test: 7-Year Audit

To investigate age and sex distribution of vasovagal syncope （VVS） patients undergoing head-up tilt table test （HUTT） at a tertiary hospital. The details of syncope patients who underwent HUTT at our department of cardiac function from January 2004 to December 2010 were reviewed. Of the 1 799 patients who underwent the HUTT, 854 tested positive, of which 558 （65.3%） were women, which were more than the women in the negative group （450, 47.6%） （p〈0.05）. VVS patients showed a bimodal age distribution between 11 and 20 years of age and in the fourth decade. In almost all age groups, mixed response was the highest compared with vasodepressor and cardioinhibitory. VVS patients who underwent HUTT indicate bimodal distribution peaking before the second decade and the fourth decade. The incidence of females was twice that of males before the sixth decade, and old age occupies a small percentage of VVS with no other comorbidities.

Predictive Value of Blood Pressure,Heart Rate,and Blood Pressure/Heart Rate Ratio in a Chinese Subpopulation with Vasovagal Syncope

Objective:The head-up tilt test(HUTT)is widely used but is time-consuming and not cost-effective to evaluate patients with vasovagal syncope(VVS).The present study aims to verify the hypothesis that ambulatory blood pressure(BP)monitoring(ABPM)and the simplistic tilt test may be potential alternatives to the HUTT.Methods:The study consecutively enrolled 360 patients who underwent the HUTT to evaluate VVS.BP),heart rate(HR),and BP/HR ratios derived from ABPM and the simplistic tilt test were evaluated to predict the presence,pattern,and stage of syncope during the HUTT.Results:Mixed response was the commonest pattern,and syncope occurred frequently with infusion of isoproterenol at a rate of 3μg/min.During the simplistic tilt test,the cardioinhibitory group had higher tilted BP/HR ratios than the vasodepressor group,while the vasodepressor group had a faster tilted HR and a larger HR difference than the cardioinhibitory group.The higher the BP/HR ratio in the tilted position,the higher the isoproterenol dosage needed to induce a positive response.During ABPM,BP/HR ratios were signifi cantly higher in the cardioinhibitory group than in the vasodepressor group.The higher the ABPM-derived BP,the higher the dosage of isoproterenol needed to induce syncope.There were signifi cant correlations in BP/HR ratios between ABPM and the supine position in the vasodepressor group,while signifi cant correlation was found only for the diastolic BP/HR ratio between ABPM and the tilted position in the cardioinhibitory group.The mixed pattern shared correlative features of the other two patterns.Conclusion:ABPM and the simplistic tilt test might be used as promising alternatives to the HUTT in VVS evaluation in clinical settings.

倾斜试验评价飞行员晕厥及立位耐力不良

晕厥（或称昏厥）是相对常见的临床症状，人群中大约3%的人在25年中至少体验过1次晕厥，其临床特点是突然短暂性意识丧失，无神经定位体征，肌张力低，能自行恢复。无论何种原因，晕厥发作时最基本的病理生理机制是血压和心率等生物调控功能之间的平衡障碍，导致一过性大脑低灌注。晕厥分3类：与心脏病无关的有原因晕厥（如低血糖反应等）、心源性晕厥和不明原因晕厥。

A multi-center study of hemodynamic characteristics exhibited by children with unexplained syncope

Background Syncope is common in children and adolescents, with 15% estimated to have had at least one syncopal episode by age 18. In recent years, an increasing number of children, especially girls at their school age, have developed unexplained syncope. The mechanism of an unexplained syncope exhibited by children is incompletely studied; the association between different hemodynamic patterns and clinical features is also not clear. The aim of the study was to investigate the hemodynamic patterns of children with unexplained syncope and to examine the clinical relevance. Methods Two hundred and eight children [87 boys, 121 girls, aged 3-19 years, mean （11.66±2.72） years] were selectively recruited from May 2000 to April 2006 when they presented syncope as their main complaint at the Multi-center Network for Childhood Syncope in Beijing, Hunan Province, Hubei Province, and Shanghai of China. All of the patients underwent head-up tilt tests; data were analyzed using SPSS version 10.0 for Windows. Continuous variables were expressed as the mean± standard deviation. Dichotomous variables were compared through a X^2 test. A value of P〈0.05 （two sided） was regarded as statistically significant. Results The age distribution of children with syncope was approximately normal. Head-up tilt tests was positive in 155 children, and the incidence of positive response of the baseline head-up tilt test for diagnosing unexplained syncope was 50.48%. The sensitivity value and diagnostic value of sublingual nitroglycerin head-up tilt test were both 74.52%. The hemodynamic pattern was normal in 53 children. The 155 children, who were positive in head-up tilt tests, showed signs of postural orthostatic tachycardia syndrome （60, 28.8%）, the vasoinhibitory pattern （72, 34.6%）, the cardioinhibitory pattern （5, 2.4%）, and the mixed pattern （18, 8.7%）. The gender distribution between the two age groups （age 〈 12 years vs age ≥ 12 years） was not different （P〉0.05）. The distribution of hemodynamic patterns between the children of the two age groups （age 〈 12 years vs age ≥ 12 years）, and the children with different complaints （dizziness vs syncope） was significantly different （P〈0.05）, while the distribution between the children of different sexes and different lasting time of syncope （≤ 5 minutes vs 〉 5 minutes） was not significantly different （P〉0.05）. Different hemodynamic patterns were differentiated by differing syncope inducements, presymptoms, and complicated symptoms during and after syncope. Conclusion The tested girls were more prone when compared with the boys to have unexplained syncope, and the peak age was around twelve years old. The incidence of positive response of head-up tilt tests was also relatively higher for the girls. The distribution of hemodynamic patterns for different ages was different. For children with unexplained syncope, we should use head-up tilttests to distinguish the hemodynamic patterns in order to adopt rational therapeutic measures.