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.

The Changes of Baroreflex Sensitivity During Head-up Tilt Test and Its Clinical Significance in the Patients with Vasovagal Syncope

Objective To study thechanges of baroreflex sensitivity (BRS) during head - up tilt test (HUT) in patients with vasovagal syncope (VS), and to examine the relationship between baroreflex sensitivity and neurohormonal factors. Furthermore, to investigate the effects of the changes of BRS on VS. Methods Forty - two patients with unexplained syncope (Among the 42 patients, there were 22 patients with positive HUT and 20 patients with negative HUT respectively) and 20 healthy volunteers (with negative HUT) underwent passive head - up tilt testing, Ante-cubital vein blood samples were taken before and after HUT, or at syncope. The fasting plasma endothelin , serum nitric oxide (NO), serum NE were measured, the BRS was assessed on the basis of the linear regression slope the RR interval versus systolic arterial blood pressure during the increment in blood pressure after intravenous administration of phenylephrine. Results (1) During the syncope, the BRS significantly reduced in HUT(+) group than baseline. At the end of tilt, the level of plasma ET, serum NO in patients with positive HUT significantly increased compared with baseline or normal controls, and the plasma concentration of NE also had the trend of increase. (2) By multiple regression analysis, a significant negative correlation was found between baroreceptor sensitivity and the plasma ET, NO at the end of HUT in patients with positive HUT, but there was no relationship between BRS and NE. Conclusions During the syncope occure, the BRS in patients with VS decreased significantly compared with normal controls. The abnormal plasma ET, NO concen-tration might contribute to the mechanism of VS.

Evaluation of cilazapril in vasovagal syncope treatment

Objective: to evaluate cilazapril in vasovagal syncope treatment. Method: eighty\|six cases of VVS patients found positive in TTT tilt were medicated with 2.5 mg cilazapril daily for three months and followed up by TTT. Results: seven cases quit due to cough or unexplained reason; 79 VVS patients had no more fainting spells; 75.95% of TTT results of patients changed to negative after 3 months therapy. The before and after cilazapril treatment average blood pressures (taken in lying position) were 121/73 mm Hg (1 mm Hg= 0.133kPa) and 120/76 mm Hg respectively ( P > 0.05); and mean heart rates were 68.63±12.37/min and 70.13±13.15/min respectively with no significant changes ( P > 0.05). Conclusion: Cilazapril was effective in treatment of VVS; did not affect normal blood pressure and heart rate; was safe; and had little side effect.

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.

Different treatments for different mechanisms in vasovagal syncope

The treatment of vasovagal syncope has been by far unsatisfactory. Beta-blockers may prevent vasovagal syncope, but they exacerbates heart asystole. Cardiac pacing prevents syncope but notpresyncope. The frequent, serious vasovagal syncope attacks of a 63- year-old woman patient were completely prevented by administration of 100 mg metoprolol (b.i.d) for 3 months until the patient experienced a complete heart block. A DDD pacemaker implantation abolished syncope but not the presyncope, which was eventually prevented in a follow-up period of 24 months by adding 75 mg atenalol twice a day. This case suggests a different mechanism involved in vasovagal syncope.

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.

Minimal Vasovagal Dysautonomia in Patients with Rare or Unique Syncope

Introduction: It is common to find people sent to perform a Head Up Tilt Test (HUT) who suffered a single syncope, or syncopes that occur during certain periods and never appear again. We wonder how these people are different from those who have never had syncope. Methods: We found 300 patients who suffered only one (unique) or a maximum of 5 vasovagal syncopes during their life. And their HUT was positive for vasovagal dysautonomia. We compared them, with 120 healthy volunteers who have never had syncope. We try to explain how some constitutional predisposing factors act in these patients, and are associated with environmental triggers to precipitate the syncope. Results: We found differences between cases and controls in predisposing factors such as: heredity, joint hypermobility, baroreflex failure, venous compliance and some neurological diseases. Then an environmental factor acts as a trigger for syncope: prolonged standing, stress, pain and emotions, dehydration, use of certain drugs, abundant food. Conclusions: There are people with minimally expressed vasovagal dysautonomia who have an organic predisposition to present vasovagal syncopes (heredity, joint hypermobility, baroreflex failure, venous compliance, some neurological diseases, etc.). But this predisposition is not enough by itself to produce syncopes. One or more environmental factors must be added, acting as a trigger that would be the reason why these episodes are so infrequent.

Tilt table test today-state of the art

A tilt table test(TTT) is an inexpensive, noninvasive tool for the differential diagnosis of syncope and orthostatic intolerance and has good diagnostic yield. The autonomic system malfunction which underlines the reflex syncope is manifested as either hypotension or bradycardia, while an orthostatic challenge is applied. The timing of the response to the orthostatic challenge, as well as the predominant component of the response help to differentiate between various forms of neurocardiogenic syncope, orthostatic hypotension and non-cardiovascular conditions(e.g., pseudosyncope). Medications, such as isoproterenol and nitrates, may increase TTT sensitivity. Sublingual nitrates are easiest to administer without the need of venous access. TTT can be combined with carotid sinus massage to evaluate carotid sinus hypersensitivity, which may not be present in supine position. TTT is not useful to access the response to treatment. Recently, implantable loop recorders(ILR) have been used to document cardioinhibitory reflex syncope, because pacemakers are beneficial in many of these patients, especially those over 45 years of age. The stepwise use of both TTT and ILR is a promising approach in these patients. Recently, TTT has been used for indications other than syncope, such as assessment of autonomic function in Parkinson's disease and its differentiation from multiple system atrophy.

血管迷走性晕厥手术治疗的现状与展望

血管迷走性晕厥作为晕厥中最常见的一种形式,心脏抑制型晕厥患者经随机临床试验证实有效的药物疗法有限,可建议使用永久性起搏器治疗。本文梳理了起搏器治疗血管迷走性晕厥中曲折发展经历并总结了原因,根据指南整理了目前适用于起搏治疗的患者类型以及应用的局限性,心脏神经消融术可能成为血管迷走性晕厥患者的另一种选择,但尚需要大样本随机对照试验证实其安全性、有效性以及适用人群。

直立倾斜试验操作医师累计工作量对血管迷走性晕厥诊断结果的影响性分析

目的:探讨直立倾斜试验操作医师累计工作量对诊断报告结果的影响。方法:回顾性连续纳入中国医学科学院阜外医院自2016年1月1日至2022年12月31日进行直立倾斜试验检查的操作医师和患者资料。根据从本院开展倾斜试验至研究结束这一阶段医师的累计工作量,将医师分为低累计工作量组(累计50~100例)、中等累计工作量组(累计101~350例)、高累计工作量组(累计1000~4000例;无医师累计工作量在351~999例),以及按医师的的性别、学历、职称分别进行分组,分析不同分组内和不同分组间医师倾斜试验报告诊断率的差异。结果:共纳入22名医师操作的6122例患者,22名医师个体之间的阳性、可疑阳性和阴性报告率差异均具有统计学意义(P均<0.001)。中等累计工作量组平均可疑阳性报告率显著高于低累计工作量组和高累计工作量组(3.21%vs.1.09%vs.1.62%,P=0.001),女性医师可疑阳性报告率高于男性医师(2.25%vs.1.07%,P=0.017),本科学历医师可疑阳性报告率高于研究生学历医师(2.46%vs.1.52%,P=0.013),初级职称医师可疑阳性报告率高于中级和高级职称医师(3.40%vs.1.75%vs.2.53%,P=0.024)。多因素Logistic回归分析显示,不论以阴性还是阳性作参照,中等累计工作量均是可疑阳性报告的影响因素(P均<0.05)。结论:不同操作医师个体之间的倾斜试验诊断报告率存在一定差异,中等累计工作量组操作医师更易出具可疑阳性诊断报告。

血管迷走性晕厥患者晕厥先兆的影响因素分析

目的分析血管迷走性晕厥患者的临床特点,探讨其晕厥前是否有晕厥先兆的影响因素。方法回顾性纳入2017年1月—2022年6月首都医科大学附属北京天坛医院诊治的血管迷走性晕厥患者为研究对象。采集其一般资料、直立倾斜试验结果及血流动力学指标,采用多因素logistic回归分析探讨患者发生晕厥先兆的影响因素。结果研究共纳入血管迷走性晕厥患者1211例。根据其发生晕厥前是否有先兆症状进行分组,其中无先兆组582例(48.06%),有先兆组629例(51.94%)。有先兆组患者的年龄(t=6.006,P<0.001)、女性比例(χ^(2)=11.749,P=0.001)、BM I(t=2.562,P=0.011),以及既往有高血压(χ^(2)=12.643,P<0.001)、糖尿病(χ^(2)=9.129,P=0.003)、脑血管病(χ^(2)=4.060,P=0.044)的比例与无先兆组比较,差异有统计学意义。两组患者直立倾斜试验结果比较差异无统计学意义(χ^(2)=6.205,P=0.102)。多因素logistic回归分析发现,年龄≤60岁(OR=1.727,95%CI 1.347~2.214,P<0.001)和女性(OR=1.440,95%CI 1.122~1.847,P=0.004)是血管迷走性晕厥患者发生晕厥先兆的危险因素。结论年龄≤60岁和女性血管迷走性晕厥患者更易发生晕厥先兆,这可能与自主神经调节功能有关。

氯米帕明联合硝酸甘油激发直立倾斜试验对血管迷走性晕厥的诊断价值

目的:探讨氯米帕明联合硝酸甘油激发直立倾斜试验(HUTT)对血管迷走性晕厥(VVS)的诊断价值。方法:选取2020年1月—2022年10月于绵阳市第三人民医院疑诊为VVS的病人120例,随机分为硝酸甘油激发HUTT组(试验1组)、氯米帕明激发HUTT组(试验2组)、氯米帕明联合硝酸甘油激发HUTT组(试验3组),每组40例。选取同期60名健康者,随机分为硝酸甘油激发HUTT组(对照1组)、氯米帕明激发HUTT组(对照2组)、氯米帕明联合硝酸甘油激发HUTT组(对照3组),每组20名。比较各组试验阳性率、阳性反应出现时间、并发症发生率、去甲肾上腺素(NE)、肾素活性(RA)、血管紧张素Ⅱ(AngⅡ)、醛固酮(ALD)、催乳素(PRL)、皮质醇(Cor)水平。结果:试验3组诊断的阳性率为87.50%(35/40),各组诊断的阳性率、阳性反应出现时间比较差异均无统计学意义(P>0.05)。120例疑诊为VVS病人的并发症发生率为40.00(48/120),高于健康者的20.00%(12/60),差异有统计学意义(χ^(2)=6.669,P<0.05);试验3组并发症发生率低于试验1组、试验2组,对照3组并发症发生率低于对照1组、对照2组。各组HUTT试验后NE、RA、AngⅡ、ALD和PRL、Cor水平均高于试验前,差异均有统计学意义(P<0.05);试验3组HUTT试验后NE、RA、AngⅡ、ALD、PRL、Cor水平高于试验1组、试验2组。受试者工作特征曲线(ROC)分析显示,硝酸甘油、氯米帕明激发HUTT诊断VVS的曲线下面积(AUC)分别为0.714,0.795,硝酸甘油联合氯米帕明激发HUTT诊断VVS的AUC为0.817,诊断准确性高于硝酸甘油、氯米帕明激发HUTT。结论:对于VVS病人氯米帕明联合硝酸甘油激发HUTT阳性的敏感性高,有利于临床医生提高VVS的诊断准确率。

硝酸甘油与异丙肾上腺素直立倾斜试验诊断血管迷走性晕厥对比研究

目的:比较舌下含服硝酸甘油与静脉泵入异丙肾上腺素直立倾斜试验诊断血管迷走性晕厥的价值。方法:回顾性分析我院行直立倾斜试验的326例患者。其中行基础加舌下含服硝酸甘油直立倾斜试验129例(硝酸甘油组),行基础加静脉泵入异丙肾上腺素直立倾斜试验197例(异丙肾上腺素组),比较两种药物直立倾斜试验阳性率、诱发阳性反应时间、血压心率变化和不良反应。结果:硝酸甘油组阳性率高于异丙肾上腺素组(46．9％vs 30．7％,P<0．01)。硝酸甘油组诱发阳性反应时间(7．8±3．6)分钟高于异丙肾上腺素组(5．6±1．5)分钟,但无显著差异(P>0．05),而总试验时间硝酸甘油组明显短于异丙肾上腺素组[(37．8±3．6)分钟vs(72．6±7．3)分钟,P<0．01]。硝酸甘油组不良反应发生率较异丙肾上腺素组低(0．9％vs 11．7％,P<0．01)。结论:硝酸甘油直立倾斜试验有较高的阳性率,操作方便,完成试验时间短,不良反应少。

直立倾斜试验对不明原因头晕与晕厥患者诊断比较

目的探讨直立倾斜试验(HUTT)对不明原因头晕与晕厥患者诊断上的差异。方法对头晕组(n=35)进行HUTT检查,并选择同期晕厥组(n=303)的HUTT结果为对照,HUTT采用基础直立倾斜试验(BHUT)及舌下含服硝酸甘油倾斜试验(SNHUT)。结果①头晕组与晕厥组患者在BHUT、SNHUT时收缩压、舒张压、心率比较差异无显著性意义(P>0.05),阳性结果反应类型比较差异亦无显著性意义(P>0.05)。②阳性率:HUTT时头晕组31.43%(11/35),晕厥组42.90%(130/303)。其中BHUT时头晕组28.57%(8/28),晕厥组33.82%(70/207);SNHUT时头晕组42.86%(3/7),晕厥组62.50%(60/96)。阳性率在头晕组和晕厥组比较差异无显著性意义(P>0.05)。两组SNHUT阳性率较BHUT均明显提高(P<0.05)。③出现阳性结果时间:BHUT时头晕组(29.13±11.01 min)仅比晕厥组(23.52±12.80 min)稍长,SNHUT时在舌下含服硝酸甘油后也是头晕组(6.00±3.61 min)比晕厥组(4.98±3.51 min)稍长(P均>0.05)。结论临床上部分不明原因头晕患者由VVS所致,但并不出现晕厥发作,这类患者应重视倾斜试验检查。

年龄和性别对直立倾斜试验诊断血管迷走性晕厥结果的影响

目的：探讨年龄和性别对疑似血管迷走性晕厥（VVS）患者进行直立倾斜试验（HUTT）诊断结果的影响。方法：收集2008-08至2012-12在阜外心血管病医院进行HUTT检查的患者共1 223例,其中男性549例。患者年龄7-79岁,按年龄依次分为≤20岁组、21-40岁组、41-60岁组和〉60岁组。HUTT包括30 min的基础试验阶段和（或）20 min的药物（硝酸甘油）试验阶段。根据阳性患者血压和心电学的变化,VVS分为血管抑制型、心脏抑制型和混合型。结果：HUTT阳性率为51%（624/1 223例）,女性阳性率高于男性（60.1%vs 39.9%,P=0.001）。四组阳性率依次为68.3%、49.1%、48.6%和47.9%。阳性患者中混合型占51.4%（321例）,血管抑制型占28.7%（179例）,心脏抑制型占19.9%（124例）。HUTT阳性类型的分布受年龄因素的影响（男性：χ2=15.65,P=0.016;女性：χ2=18.84,P=0.004）,性别间差异无统计学意义（P〉0.05）。基础试验阶段74.8%的阳性反应出现在试验开始后22.5（17.5-27.5）min,但无年龄性别差异（P〉0.05）;药物试验阶段81.9%的阳性反应出现在试验开始后7.5（5-10）min,女性发生阳性反应的时间比男性提前（7.5 min vs 10 min,P=0.004）,无年龄差异。结论：HUTT诊断VVS的阳性率、阳性分型和发生阳性反应的时间存在年龄和性别差异。

不同年龄和性别不明原因晕厥患者直立倾斜试验的诊断比较

目的:探讨直立倾斜试验(HU TT)在不同年龄和性别的不明原因晕厥(UPS)患者诊断中的意义。方法:诊断为血管迷走性晕厥(VVS)的U PS患者14 9例,年龄4～70岁,平均(2 6 .78±16 .34)岁;男5 7例,女92例。采用电动倾斜床取头高脚低位直立倾斜70°后,每5 min自动测量血压和心电变化,评价HUTT结果。用SPSS11.0软件微机数理统计。结果:HU TT阳性率38.2 6 % (5 7/14 9例) ,女性占82 .4 6 % (47/5 7例)。直立倾斜(2 2 .74±14 .0 7) min时出现晕厥发作,≤18岁与>18岁两个亚组间〔分别为(2 0 .0 7±14 .10 ) m in与(2 5 .31±13.10 ) min〕差异未见显著性(P>0 .0 5 ) ,反应类型中血管抑制型为6 6 .6 7% (38/5 7例) ,心脏抑制型为2 2 .81% (13/5 7例) ,混合型为10 .5 2 % (6 /5 7例) ,且与年龄无关(P>0 .0 5 )。血管抑制型在女性较常见(5 7.9% ,P<0 .0 0 5 )。阳性组较阴性组HU TT结束时终末心率、终末收缩压及终末舒张压均显著降低(P<0 .0 5或P<0 .0 1)。阳性组男性患者终末心率、终末收缩压及终末舒张压较女性降低明显(P均<0 .0 5 )。将≤18岁亚组与>18岁亚组进行比较,阳性组前者起始收缩压及起始舒张压均降低(P均<0 .0 1) ,终末收缩压与终末舒张压亦降低(P均>0 .0 5 ) ,起始与终末心率稍增加(P均>0 .0 5 ) ;

不明原因晕厥相关性躯体意外伤害

目的探讨不明原因晕厥相关性躯体意外伤害情况。方法对不明原因晕厥患者（n=351）详细询问病史，包括晕厥发作时躯体意外伤害事件的发生情况，并行倾斜试验（HUTT）检查明确诊断。结果①31例（8．8％）患者有晕厥相关性躯体意外伤害，HUTT阳性患者中19例（11．5％）存在晕厥相关性躯体意外伤害；②晕厥致躯体意外伤害大多较轻，少数患者会发生严重伤害；③发生晕厥相关性躯体意外伤害者男性较多，年龄段以9～13岁居多；④躯体意外伤害患者HUTT反应类型以血管抑制型为主。混合型次之，心脏抑制型最少。结论晕厥相关性躯体意外伤害事件的发生是随机的，大部分患者伤害较轻，个别患者会发生严重意外伤害。强调对不明原因晕厥患者重视HUTT检查。对确诊的血管迷走性晕厥（VVS）患者实施早期干预，将躯体意外伤害事件的发生降至最低限度。

血管迷走性晕厥10年临床研究

目的 研究血管迷走性晕厥（VVS）10年临床情况.方法 2000-01～2010-07在我院诊治不明原因晕厥或先兆晕厥患者1782例,根据检查年限分为A组（2000-01～2004-12,n=280）和B组（2005-01～2010-07,n=1502）,根据年龄分为儿童组（〈18岁,n=1180,男450例,女730例）和成人组（≥18岁,n=602,男182例,女420例）.儿童组平均年龄（9.77±3.92）岁,按照年龄段分为4～6岁、7～10岁和11～18岁三个年龄段;成人组平均年龄（40.78±14.05）岁.结果 ①HUTT阳性率：HUTT总阳性率47.7%,其中儿童组和成人组分别为44.3%和54.3%;在儿童和成人中B组较A组均增加（45.7% vs33.3%,61.4% vs33.1%,P〈0.05）.②HUTT阳性率性别比例变化：儿童组和成人组女性均高于男性（32.2% vs12.1%,42.7% vs11.6%,P〈0.05）;在儿童和成人中B组男性和女性均高于A组（分别为12.5% vs9.3%、33.2% vs24.0%,9.8% vs7.3%、51.7% vs25.8%,P〈0.05）.③HUTT反应类型变化：儿童组和成人组血管抑制型〉混合型〉心脏抑制型（P〈0.05）,其中儿童组血管抑制型B组高于A组（33.8% vs19.4%,P〈0.05）;成人组血管抑制型和混合型B组均高于A组（40.1% vs20.5%,18.4% vs9.9%,P〈0.05）.④儿童组HUTT阳性率年龄变化：儿童组11～18岁组〉7～10岁组〉4～6岁组（P〈0.05）.在各年龄段中,4～6岁及11～18岁B组均高于A组（6.2% vs3.9%,23.3% vs21.7%,P〉0.05）,7～10岁组中B组明显高于A组（16.2% vs7.8%,P〈0.05）.结论 VVS患者的阳性率、反应类型在近10年不断发生变化,提示VVS的发生受社会因素、精神因素、生活方式等多种因素的影响.

一氧化氮和内皮型一氧化氮合成酶与血管迷走性晕厥发病的关系

目的探讨一氧化氮和内皮型一氧化氮合成酶与儿童血管迷走性晕厥发病的关系。方法血管迷走性晕厥患儿14例(A组),其他原因引起晕厥患儿10例(B组),健康志愿者20例(C组)。于倾斜试验(HUT)前和倾斜不同时间测定A组与B组患儿的血浆一氧化氮(NO)水平,同时对3组儿童进行内皮型一氧化氮合成酶(eNOS)基因G894T多态性检测。结果①A组患儿出现阳性反应时血浆NO水平较平卧时显著升高(76.7±9.6vs 90.0±11.4μmol/L,P<0.05);②A组患儿在症状好转后血浆NO水平较试验前显著降低(82.7±9.2 vs61.5±6.9μmol/L,P<0.01);③B组患儿倾斜时血浆NO水平较平卧时差异无显著性;④A,B两组患儿的血压、心率变化与NO水平无显著相关性;⑤A组患儿eNOS基因G894T突变型基因频率显著高于B组与C组(42.9%vs10%,P<0.05)。结论倾斜体位时血浆NO水平异常升高可能参与了血浆血管迷走性晕厥的发病机制,而其升高水平可能与eNOS基因G894T多态性表达有关。[中国当代儿科杂志,2008,10(4):478-480]

心率变异性对儿童不明原因晕厥的诊断价值

目的:通过测定不明原因晕厥儿童的心率变异性(heart rate variability,HRV),研究其对不明原因晕厥儿童的诊断价值。方法:对49例不明原因晕厥儿童行直立倾斜试验(head up tilt test,HUT)诊断及动态心电图监测,分析HUT阳性患儿与阴性患儿HRV的差异。采用受试者操作特征(receiver operating characteristic,ROC)曲线分析HRV对不明原因晕厥患儿的诊断价值。结果:49例不明原因晕厥患儿经HUT诊断后,32例(65.3%)诊断明确,HUT的诊断阳性率为65.3%。HUT阳性组的SDNNi、rMSSD、TP、ULF、VLF、LF以及HF均明显高于HUT阴性组(P<0.05)。HUT阳性组的SDNN、pNN50以及三角指数与HUT阴性组相比,差异均无统计学意义(P>0.05)。SDNNi、rMSSD、TP、ULF、VLF、LF和HF对HUT的诊断预测具有一定价值。分别以ULF、LF和HF 12 947.00、9 462.50和9 509.00作为界值时,对诊断阳性率的预测效果较好,灵敏度分别为75.0%、68.8%和68.8%,特异度分别为64.7%、64.7%和64.7%。结论:HRV中的ULF、LF和HF可作为HUT诊断自主神经介导性晕厥的预测指标,界值分别为12 947.00、9 462.50和9 509.00,具有较好的灵敏度和特异度。