心率变异性分析在血管迷走性晕厥中的研究进展

血管迷走性晕厥（vasovagalsyncope,VS）被认为与植物神经功能异常密切相关,国内外众多学者应用心率变异性（hearratevariability,HRV）这一非侵入性技术,分析评估该病的发病机理、诊断及其防治。现将研究进展综述如下。1HRV研究的基本方法HRV分析是应用微机对动态心电图记录的心电信号回放处理,测量QRS波群周期之间的变化,从而揭示植物神经调节心脏的规律和趋势。它包括时域、频域和非线性分析三种,前二者是常用的定量分析方法。时域法常用指标有平均间期（MRR）、标准差（SD）、差值均方根（rMSSD）、爱丁堡指数（PNN50…     

血管迷走性晕厥193例临床特征分析

目的:通过对血管迷走性晕厥(VVS)患者临床资料的分析,为该病的防治提供依据。方法:选择本院193例经直立倾斜试验(HUTT)证实的VVS患者,回顾性收集患者发病诱因、晕厥先兆及动态心电图心率变异性(HRV)资料。提取HUTT检查阴性的晕厥患者的HRV数据。结果:193例VVS患者中女性多见,共114例(59.1%)。常见反应类型为血管抑制型(VD)101例(52.3%),其次为混合型(MX)77例(39.9%),心脏抑制型(CI)仅15例(7.8%)。153例(79.3%)患者晕厥前有诱因。156例(80.8%)患者有先兆症状,其中胸闷79例(50.6%)、头晕54例(34.6%)和全身出汗52例(33.3%)为最常见的3个先兆症状。VVS组最大频域功率小时显著低于对照组。3种不同反应类型组间比较时,CI组时域指标和频域指标均低于VD组和MX组,除r MSSD的CI组与VD组以及最大频域功率小时的CI组与VD组比较外,差异均有显著性;VD组和MX组组间比较,差异均无统计学意义。结论 :充分认识VVS的诱因和晕厥先兆表现,结合动态心电图检查,能帮助临床医生早期识别VVS患者。     

血管迷走性晕厥儿童心率变异性的年龄和性别差异

目的探讨血管迷走性晕厥(VVS)儿童心率变异性(HRV)的年龄和性别差异。方法2003—01～2007—05在中南大学湘雅二医院晕厥专科诊治的不明原因晕厥(UPS)儿童54例(晕厥组),其中<12岁儿童22例,直立倾斜试验(HUTF)全部为阳性反应。匹配48例健康儿童为对照(对照组)。晕厥组和对照组儿童均行24 h动态心电图(Holter)检查,数据经TLC3000A 12通道动态心电图分析系统自动分析结合人工干预生成HRV时域指标和频域指标。结果①晕厥儿童HRV性别比较:与男性儿童相比,女性儿童各项时域指标和频域指标均偏低,其中时域指标总体标准差(SDNN)、均值标准差(sDANN)和频域指标总功率(TP)、低频功率(LF)、极低频功率(VLF)降低显著(P<0.01或P<0.05)。②健康儿童HRV性别比较:女性儿童时域指标SDNN、差值均方根(rMSSD)、差值>50 ms的百分比(pNN50)和频域指标TP、VLF、LF低于男性儿童,其中差异有统计学意义的是频域指标VLF(P<0.01)和LF(P<0.05)。③晕厥儿童HRV年龄比较:与≥12岁儿童相比,<12岁儿童时域指标SDNN、SDANN、pNN50和频域指标TP、LF稍降低(均P>0.05)。④健康儿童HRV年龄比较:与≥12岁儿童相比,<12岁儿童时域指标rMSSD、pNN50和频域指标LF、高频功率(HF)偏高,其中差异有统计学意义的是HF(P<0.05),其余指标稍偏低(均P>0.05)。结论VVS儿童自主神经功能异常,其自主神经变化规律的年龄和性别差异与健康儿童不同。     

循环系统症状为主的血管迷走性晕厥误诊分析

目的　探讨非器质性疾病患者循环系统症状的原因。方法　对排除器质性心脏病的 47例患者进行倾斜试验。结果　在试验中 36例呈现阳性结果 ,占 76 .6 % ,均伴随其主诉症状的发生。结论　以循环系统症状为主而无客观证据的患者可能是一种特殊类型的血管迷走性晕厥。     

成年人直立性心动过速与血管迷走性晕厥的相关研究

目的探讨成年人直立性心动过速综合征与血管迷走性晕厥的相关性。方法选择直立性心动过速疑似患者,利用改良的基础倾斜试验方案予以确诊,随后进行含化硝酸甘油倾斜试验,若出现晕厥,口服心得安后再行倾斜试验全过程。结果93例疑似患者中78例发生直立性心动过速,阳性率83.65%;在随后的硝酸甘油倾斜试验中有63例出现晕厥,阳性率80.77%;上述两种阳性患者于第4天口服心得安30mg后再行试验无1例出现直立性心动过速和晕厥。结论改良的基础倾斜试验是诊断直立性心动过速的最佳方案,成年人直立性心动过速与血管迷走性晕厥的发生密切相关。     

血管迷走性晕厥患者行直立倾斜试验与治疗的护理

总结86例血管迷走性晕厥患者在作直立倾斜试验前后以及治疗过程中的护理经验，以减少意外伤害及再次发作的次数。护理要点：(1)试验前作好准备工作，包括环境、药物、监护仪器、患者的心理准备；(2)试验中密切观察患者的症状及生命体征，出现阳性反应及时处理，鉴别药物反应及阳性反应；(3)试验结束后，指导阳性患者服药或倾斜台治疗。经过有效的护理，本组无1例患者发生意外伤害。     

直立倾斜试验对恶性血管迷走性晕厥的诊断价值及治疗

晕厥是常见的综合征,30%～60%经各方面检查不能明确病因,可能属于神经介导的反射性的,短暂的低血压及心动过缓所致.神经介导的晕厥中常见的为血管迷走性晕厥.有人认为是心源性猝死的一种潜在原因.有报道心源性晕厥一年病死率为30%,非心源性晕厥者为12%,而不明原因者为6%.为了估价这种可能性和检测血管迷走性心源停搏的特征,本试验对32例原因不明晕厥者采用直立倾斜试验方法作诱发试验,以识别恶性血管迷走性晕厥,并进行药物治疗评价.     

24-Hour Heart Rate Variability in Patients with Vasovagal Syncope

Since alterations in the autonomic nervous system are thought to play a major role in the pathogenesis of vasovagal syncope, we characterized the chronic autonomic profile of 44 patients with syncope and 20 healthy subjects by means of heart rate variability using 24-hour Holter recordings (time- and frequency-domain indexes), and evaluated whether the different types of responses to tilting (vasodepressive versus cardioinhibitory) could be associated with different cardiac autonomic patterns. Twenty-three patients exhibited a positive response to tilting, which was vasodepressive in 11 patients and cardioinhibitory in 12 patients. All vasodepressive patients had a standard deviation of the averages of NN (SDANN) intervals in all 5-minute segments lower than 100 ms. Patients with vasodepressive syncope also had significantly lower values of RMSSD (the 24-hour square root of the mean of the sum of the squares of differences between adjacent normal RR intervals) than those with cardioinhibitory response, and lacked the day-night rhythm of the low frequency/high frequency ratio. However, only SDANN values correctly identified patients with vasodepressive response to tilting. We conclude that (1) the population of patients with vasovagal syncope is heterogeneous, (2) patients with vasodepressive syncope have a peculiar chronic autonomic profile as assessed by 24-hour heart rate variability analysis, and (3) the evaluation of the autonomic profile in 24-hour Holter recordings could be of value in the diagnosis of patients with syncope.     

Autonomic Imbalance Assessed by Heart Rate Variability Analysis in Vasovagal Syncope

In this prospective study, the autonomic modulation of the sinus node of 12 patients (mean age 28 ± 7 years) suffering from vasovagal syncope (VVS) was compared to that of 11 sex and age matched control patients (mean age 32 ± 4 years) by analysis of heart rate variability. Spectral indices (low frequency power [Plf], high frequency power [Phf], total power [Pt], sympathovagal balance [LF/HF]) and temporal indices, the mean of all coupling intervals between normal beats (mRR), the standard deviation about the mean (sdRR), the percentage of adjacent R to R intervals differing by more than 50 msec (pNN50), and the root mean square of variations in successive R to R intervals (rMSSD) were compared at baseline and during head-up tilt between and within groups. Baseline results were similar in both groups. During tilt testing, comparison of results between groups revealed only significantly higher sdRR and rMSSD and lower LF/HF ratio in VVS patients. Within WS patients, comparison of temporal and spectral analysis between baseline and tilt showed a significant increase of most indices (Plf, Phf, Pt, sdRR, and rMSSD) but a comparable LF/HF ratio; in contrast, control patients exhibited only a significant increase of LF/ HF ratio. In conclusion. VVS patients who developed vasovagal syncope during head-up tilt demonstrated a nonreciprocal modulation of the sinus node by the autonomic nervous system indicative of a pronounced physiological sympathetic surge along with a paradoxical vagal input to the cardiovascular system.     

Heart Rate Variability in Patients with Vasovagal Syndrome

The aim of this study was to assess the heart rate variability in patients with vasovagal syndrome (WS). Heart rate variability was expressed as: (1) the standard deviation (SD) of the mean RR interval; and (2) the SD as a percentage of the mean RR interval (%SD). Heart rate variability was measured in VVS patients and compared with control individuals. Eighteen patients (mean age 50 ± 14 years) with a history of recurrent syncope and positive tilt testing were included in the study. Fifteen asymptomatic individuals (mean age 53 ± 13 years) with no history of syncope and negative tilt testing were used as a control group. The SD and %SD (39 ± 38 and 5 ± 4 msec) in the WS group were statistically higher at the tenth minute of tilt testing than in the control group (20 ± 14 and 2.5 ±1.8 msec, P = 0.03 and P < 0.05, respectively). The mean RR interval (mean heart rate) was shorter after the 15th minute of tilt testing in the WS group than in the control group (RR-WS 687 ± 136 msec, RR-control 801 ± 131 msec, P < 0.05). It is concluded that heart rate variability, as expressed by the SD of the mean RR interval, and the SD as a percentage of the mean RR interval (%SD) are significantly higher in VVS patients than in control asymptomatic individuals.     

Abnormal Vasovagal Reaction, Autonomic Function, and Heart Rate Variability in Patients with Paroxysmal Atrial Fibrillation

The aim of this study was to evaluate the cardiovascular autonomic function and vasovagal reaction in patients with paroxysmal atrial fibrillation without significant structural heart disease. Twenty-eight patients with paroxysmal atrial fibrillation (9 patients were categorized to have autonomic-mediated atrial fibrillation while atrial fibrillation in other patients was nonautonomic mediated) and 19 normal control subjects were recruited. Cardiovascular autonomic function tests included measuring heart rate response to standing, deep breathing, Valsalva maneuver, baroreflex sensitivity, 24-hour heart rate variability, and also head-up tilt test. Compared with normal subjects, no significant autonomic dysfunction was found in patients with autonomic-mediated and nonautonomicmediated atrial fibrillation. All subjects had negative baseline tilt test. With isoproterenol provocation, six patients developed atrial fibrillation. Four of 9 patients and 3 of 19 patients with autonomic mediated and nonautonomic mediated atrial fibrillation had a positive tilt test respectively, while none occurred in the controls. A significant percentage (32%) of patients with paroxysmal atrial fibrillation had episodes of atrial fibrillation provoked by changes in autonomic tone, although there was no underlying abnormal cardiac autonomic function nor sympathetic-parasympathetic imbalance. A heightened susceptibility to vasovagal cardiovascular response may have important implications on the occurrence and symptomatology of patients with paroxysmal atrial fibrillation.     

DDD Pacing with Rate Drop Response Function Versus DDI with Rate Hysteresis Pacing for Cardioinhibitory Vasovagal Syncope

Background: The effectiveness of cardiac pacing in preventing vasovagal syncope remains controversial. However, DDI pacing with rate hysteresis has been reported to prevent the recurrence of Cardioinhibitory vasovagal syncope in up to 35% of affected subjects and to reduce the overall incidence of syncopal episodes in the others. Recently, DDD pacing with a new promising rate drop response function (Medtronic Thera-I model 7960) has become available in clinical practice. Aim of the study: The aim of the present open trial was to test the effectiveness of this new pacing modality in patients with Cardioinhibitory vasovagal syncope. Study population and methods: The study population included 20 patients (12 males and 8 females; mean age 61.1 ± 14 yrs) with recurrent syncope (mean number of prior episode = 6.8, range 5–11) and Cardioinhibitory responses during two head-up tilt tests: the first diagnostic and the second during drug therapy with either β-blockade or etilephrine. The study patients were randomized to receive either DDI pacing with rate hysteresis (8 patients) or DDD pacing with rate drop response function (11 patients). The head-up tilt test performed 1 month after pacemaker implantation was positive in 3 of 12 patients (25%) with DDD pacing with rate drop response function and in 5 of 8 patients (62.5%) with DDI pacing with rate hysteresis. The mean duration of follow-up was 17.7 ± 7.4 months. During follow-up no patients with a DDD pacemaker with rate drop response function had syncope, while 3 of 8 patients with a DDI pacemaker with rate hysteresis had recurrence of syncope (P < 0.05). Conclusions: These data suggest that DDD pacing with rate drop response function is effective in Cardioinhibitory vasovagal syncope and may be preferable to DDI pacing with rate hysteresis.     

不明原因晕厥的发病机制与脑血流的关系

晕厥在临床上是指各种原因引起的一过性脑供血不足 ,所致以意识丧失为主的临床症候群。是临床上常见的危急症状。关于晕厥的发病机制除了与心脏病相关及部分心脏外原因 ,大多数晕厥原因不明。原因不明的晕厥从广义上说是指所有神经介导性晕厥 ,而血管迷走型晕厥 (ＶＳＳ)最常见 ,故狭义上不明原因晕厥即指ＶＳＳ[1 ] 。目前ＴＴＴ(直立倾斜试验 )的广泛开展被公认为ＶＳＳ的诊断和评价的金标准[1 ] 。国际公认的ＶＳＳ临床诊断标准为 :ａ .有 1次以上的晕厥发作史。ｂ .新近所做的神经学检查正常。ｃ .没有应用引起体位性低血压的药物史。ｄ…     

Bedside Autonomic Function Testing in Patients with Vasovagal Syncope

The factors that determine the individual susceptibility to vasovagal syncope (VVS) are largely unknown, including the role of the autonomic nervous system. We therefore studied common vagal and sympathetic reflexes in 12 patients with WS (mean age 37 (18–75) years, 6 men). The Valsalva maneuver and deep breathing were performed to assess vagal responsiveness and mental arithmetic stress; the cold-pressor test and isometric handgrip were performed to assess sympathetic responsiveness. Standing up was performed to assess the combined responsiveness. With the exception of a subnormal response to deep breathing in one patient, all vagal tests were normal. In contrast, the response to mental stress, the cold-pressor test, and isometric handgrip was subnormal in 4 patients, 6 patients, and 4 patients, respectively. The response to standing up was normal in all patients. It is concluded that many patients with WS are characterized by normal vagal responsiveness, but sympathetic hyporesponsiveness. Sympathetic hy-poresponsiveness might explain the inadequate vasoconstriction, which plays an important, early role in WS.     

Possible Involvement of Cerebral Hypoperfusion as a Trigger of Neurally-Mediated Vasovagal Syncope

It is well known that some patients with neurally mediated syncope have a feeling of aura before the onset of syncope. A case is reported in which cerebral dysfunction recorded by EEG was present before the onset of a vasovagal reaction. The vasovagal reaction, bradycardia and/or asystole, was preceded by abnormal EEG findings when the patient complained of feeling a headache, photophobia, and nausea. These findings suggest that cerebral hypoperfusion, such as with cerebral vasospasms, before the onset of bradycardia might be involved in the mechanism of neurally mediated syncope in patients with an aura.     

Neural Monitoring of Vasovagal Syncope

Head-up tilt testing has become a valuable and widely accepted diagnostic tool for evaluation of patients with vasovagal syncope. This test has afforded clinical researchers the opportunity to focus on the hemodynamic, humoral, and neural changes that accompany syncope. We review the animal and clinical studies that provide insight into the possible pathophysiological mechanisms involved in vasovagal syncope. Hemodynamic measurements in patients with vasovagal syncope suggest that a relative decrease in ventricular size and increase in cardiac contractility may be seen in many patients with vasovagal syncope. Patients with vasovagal syncope have also demonstrated numerous "exaggerated" neurohumoral responses to syncope. Differential changes in plasma levels of epinephrine, renin, endothelin, vasopressin, cortisol, prolactin, beta endorphins, and substance P have been reported by some investigators either prior to or during a syncopal episode in patients with vasovagal syncope. The precise pathophysiological significance of these measurements is unknown at the present time. Measurements of autonomic tone may be accomplished indirectly with analysis of heart rate variability or baroreflex slope, or directly by sympathetic neural recordings of the peroneal nerve. We have demonstrated decreased baroreflex slopes in patients with vasovagal syncope. Using microneurography, we and others have demonstrated decreased sympathetic nerve activity occurring 11 ± 3 seconds prior to syncope during bead-up tilt table testing. A variety of other abnormal reflexes, including blunted forearm blood flow responses during exercise, have been demonstrated by others. These observations suggest that pacing instituted after the event may not be as helpful as the use of a hemodynamic sensor that will result in the initiation of pacing prior to sympathetic withdrawal or modify the decrease in sympathetic tone that occurs prior to syncope.