直立倾斜试验中心率变异功率谱分析

为评价自主神经在诱发晕厥过程中的临床意义，分析了６例直立倾斜试验阳性及１０例阴性结果患者在直立倾斜试验前后，阳性反应前或试验结束前各４分钟的心率变异功率谱图。发现阳性组三个时间段的低频段逐渐增高，于阳性反应前达最高峰。高频段呈进行性降低，各时间段明显低于阴性组。低频段／高频段比值呈进行性显著增大，各时间段明显大于阴性组。结果表明，交感神经和副交感神经功能调节障碍在直立倾斜试验诱发晕厥的发生机制中起着重要作用；低频段／高频段比值是反映两者相互作用的准确、敏感而具有实用价值的指标。     

原因不明晕厥患者直立倾斜试验中血压和心率反应

本文采用倾斜试验加用或不加用异丙肾上腺素（Ｉｓｏｐｒｏｔｅｒｅｎｏｌ，ＩＳＯ）对１２０例原因不明晕厥患者行诱发试验，旨在观察阳性患者心率、血压的反应及心电图变化，并对其机制作初步探讨。资料与方法１９９４年６月至１９９７年３月来我院就诊的原因不明晕厥患...     

直立倾斜试验中的阳性反应和药物反应

目的 :区分直立倾斜试验 (HUT)中的阳性反应和药物所致的假阳性反应 (药物反应 )。方法 :将 96例不明原因的晕厥患者及 72例无晕厥病史的健康人分别分成基础倾斜试验 (BTTT)组和异丙肾上腺素分级递增倾斜试验 (MITTT)组。结果 :药物反应完全不同于阳性反应 ,其表现为血压缓慢下降持续数分钟 ,伴随心率代偿性增加或长时间明显血压下降后出现轻微心动过缓。排除药物反应后 MITTT对诊断迷走血管性晕厥的敏感性 67.5% ,特异性 93.2 % ,诊断价值 (78.8% vs60 .7% )明显高于 BTTT。结论 :正确区别阳性反应和药物反应 ,是提高 MITTT敏感性而又不降低其特异性的有效的方法。     

直立倾斜试验中药物假阳性反应的表现

目的：研究直立倾斜试验中药物假阳性反应的表现。方法：分析１００例临床表现为血管迷走性晕厥的患者和２１名无晕厥史的正常人直立倾斜试验的结果。结果：药物反应主要表现为①缓慢发展的血压下降，伴随代偿性心率增加；②长时间明显血压下降可出现轻微心动过缓，但心率减慢低于同阶段的３０％；③逐渐出现的症状如头晕、眼花、出汗等晕厥先兆与平时发作的症状不一样。排除药物反应后直立倾斜试验的敏感性为６２．０％，特异性为９０．５％；呈阳性反应者无１例心率≥１５０次／分。结论：正确区别突发的迷走神经反射亢进和药物反应，并且在试验过程中设置１５０次／分的心率上限，是提高直立倾斜试验敏感性又不降低试验特异性的有效方法。     

激发药物在直立倾斜试验中的应用

本文介绍了近年来在直立倾斜试验(HUT)中,应用激发药物评价血管迷走性晕厥(VS)的结果。     

倾斜试验中的直立性T波改变

我们从258例不明原因晕厥患者的倾斜试验(TTT)中检出62例直立性T波改变,旨在总结其特点、阐明其发生机理、临床意义及其与血管迷走性晕厥的相关性,以提高临床对该现象的认识。     

倾斜试验中晕厥患者自主神经功能的变化

目的　运用频谱法研究直立倾斜试验中血管性晕厥的发生机制。方法　对 2 7例不明原因晕厥患者行直立倾斜试验 ,运用频谱法计算低频 (LF)、高频 (HF)及LF/HF的变化。结果　 15例发生晕厥或先兆晕厥 (阳性组 ) ,12例未出现症状 (阴性组 ) ,倾斜前两组LF、HF和LF/HF差异无显著性 ;阴性组倾斜后即刻HF明显下降 ,LF/HF显著升高 ,平卧后恢复到倾斜前水平 ,阳性组晕厥或先兆晕厥发作时 ,HF突然升高 (10 4 7± 4 0 4→ 32 95± 10 4 8) ,明显高于倾斜前 (2 3 4 4± 4 2 0→32 95± 10 4 8,P <0 0 5 ) ,LF/HF显著下降 (3 2 8± 0 39→ 1 0 7± 0 31,P <0 0 1) ,试验终止平卧后 ,HF和LF/HF恢复 ,两组LF在倾斜前后不同阶段均无明显变化。结论　在平卧、静息状态下 ,阳性患者和阴性患者的自主神经功能差异无显著性 ,倾斜后阳性患者迷走神经兴奋性在抑制过程中突然过度增强 ,导致晕厥或先兆晕厥发生。     

血管迷走性晕厥直立倾斜试验反应类型研究

目的 观察首次直立倾斜试验阳性．并依据血流动力学特征表现为心脏抑制型和血管减压型晕鳜患者进行直立倾斜试验时血压和心率的反应。方法 对48例心脏抑制型性晕厥和20例血管减压型晕厥患者，间隔1～7d．在相同试验条件下再次行直立倾斜试验，观察血压和心率的再次反应。结果 ①48例心脏抑制型晕厥患者．40例诱发晕厥或晕厥前症状．阳性重复性为83.3％，其中30例仍表现为心脏抑制型晕厥，10例表现为血管减压型和／或混合型晕厥；②20例血管减压型晕厥患者，16例诱发晕厥或先兆晕厥症状，阳性重复性为80％．其中11例仍表现为血管减压型晕厥．5例表现为心脏抑制型和／或混合型晕厥。结论 心脏抑制型和血管减压型晕厥的反应类型可以改变．此类由心脏受体所激发的神经介质反应具有复杂性，有助于我们进一步阐明心脏血管神经源性晕厥的病理生理机制，为临床诊治提供了重要线索。     

不明原因晕厥患者在直立倾斜试验中的血流动力学研究

目的研究不明原因晕厥患者在直立倾斜试验中的血流动力学改变及其年龄、性别与血流动力学改变的相关性。方法93例不明原因晕厥患者进行基础倾斜试验及硝酸甘油激发试验，持续监测、记录心电、血压变化。分析患者的基本特征及其在倾斜试验早期和倾斜试验过程中的血流动力学反应。结果93例患者均可耐受及完成试验。阳性反应52例（55．9％），其中混合型18例（34．6％）、血管抑制型30例（57．7％）、心脏抑制型4例（7．7％）；阴性反应41例（44．1％），其中正常反应29例（70．7％）、直立体位性心动过速综合征（POTS）4例（9．8％）自主神经反应障碍8例（19．5％），直立位低血压0例。将所有病人按年龄分为3组：A组：≤30岁；B组：31～50岁；C组：≥51岁，随年龄增长，出现变时性不良的可能性增加（OR 0．94095％ CI 0．906-0．975 P=0．001），而随年龄减小，出现心率过度增加的可能性增加（OR 1．10695％ CI 1．034-1．182 P=0．003）。高龄与自主神经反应障碍和混合型血管迷走性晕厥的发生相关，而低龄与血管抑制型血管迷走性晕厥的发生相关（P〈0．01）。性别与倾斜试验的阴性及阳性结果差异元统计学意义（P=0.12）。结论倾斜试验中，年轻人主要表现为心率过度增加，而老年人则多为心率变化不明显。对倾斜试验中血流动力学变化的观察分析、研究年龄性别与血流动力学反应的关系，对明确晕厥原因，选择相应治疗方案具有重要意义。     

直立倾斜试验中血压、心率及血浆去甲肾上腺素变化意义的初步探讨

目的：研究直立倾斜试验（ＨＵＴ）中平均动脉压、心率及血浆去甲肾上腺素（ＮＥ）水平变化。方法：３５例不明原因晕厥患者及１５名正常对照者行ＨＵＴ时，观察平均动脉压、心率及ＮＥ的改变。结果：平卧位及直立倾斜后５分钟ＨＵＴ阳性（Ｉ组）、阴性（Ｉ组）和对照（ＩＩ组）３组平均动脉压、心率及ＮＥ无显著差异（Ｐ＞０．０５）。ＨＵＴ检查结束时，Ｉ组平均动脉压、心率较平卧位显著下降（Ｐ＜０．０１），而Ｉ、ＩＩ组较平卧位则上升（Ｐ＜０．０５）；Ｉ组与ＩＩ、ＩＩ组有显著性差异（Ｐ＜０．０１）。血浆ＮＥ水平３组均较平卧位有显著增加（Ｐ＜０．０５），但３组之间无显著性差异（Ｐ＞０．０５）。结论：ＨＵＴ时不能仅仅依据血浆ＮＥ水平来判断体内交感神经张力的高低。     

倾斜试验中血管迷走性晕厥患者血流动力学和神经激素的变化

目的探讨血管迷走性晕厥患者倾斜试验中血流动力学和神经激素的变化及晕厥触发机制.方法倾斜试验采用平卧10 min和倾斜80°直立30 min.试验阳性标准为晕厥先兆伴收缩期血压<90mm Hg(1 mmHg=0.133 kPa)和/或心率<60次/min.超声心动图于基础平卧,直立2 min和每隔3 min直至试验结束时连续记录左心室收缩末期内径(LVESD),左心室舒张末期内径(LVEDD),短轴缩短分数(SF)和心排出量(CO).同时测量儿茶酚胺血浆浓度.Ⅰ组为正常自愿者且倾斜试验阴性者8例,Ⅱ组为原因不明晕厥伴倾斜试验阴性者8例,Ⅲ组为原因不明晕厥伴倾斜试验阳性者16例.结果3组间年龄、性别以及基础状态下心率、平均动脉压、左心室内径、SF、CO和儿茶酚胺血浆浓度差别不明显.Ⅰ组和Ⅱ组完成了30 min直立试验,Ⅲ组出现阳性反应时间为(10±4)min.直立时各组发生的改变为(1)Ⅰ组和Ⅱ组虽心率明显增加,但血压稳定.Ⅲ组心率增快和血压逐渐下降,终止试验时心率由(110±22)次/min突然降至(82±16)次/min,平均动脉压由(78±14)mmHg降至(50±9)mm Hg,10例为血管抑制性晕厥,6例为混合性晕厥;(2)Ⅰ组和Ⅱ组左心室内径,CO和SF变化不显著;Ⅲ组LVEJDD由基础时(47±5)mm减至(36±6)mm,LVESD由(32±4)mm减至(22±5)mm;SF由(31±2)%增至(39±4)%,与前两组比较差别有显著性;(3)LVEDD和LVESD降低速率Ⅲ组明显大于Ⅰ组和Ⅱ组;(4)肾上腺素浓度在Ⅲ组明显高于前两组,由基础时(18±10)pg/ml达结束时(126±80)pg/ml,去甲肾上腺素在3组均有增高但组间比较无差别.结论血管迷走性晕厥患者倾斜试验中血流动力学和血浆儿茶酚胺浓度发生明显异常改变;左心室容量降低伴肾上腺素异常分泌和SF增强而激发迷走神经反射可能是触发晕厥的主要机制.     

血管迷走性晕厥患者倾斜试验过程中压力反射敏感性变化及其临床意义

目的：研究血管迷走性晕厥（VS）患发生晕厥时压力反射敏感性（BRS）的变化及其与神经内分泌因素的关系,以探讨BRS的变化在VS发生中的作用。方法：42例不明原因晕厥患,其中基础倾斜试验（HUT）阳性病人22例,阴性20例及20例健康人（HUT呈阴性反应）,进行HUT,在HUT前,HUT结束或阳性反应时,抽取肘静脉血分别测定血浆内皮素（ET）一氧化氮（NO）,去甲肾上腺素（NE）水平,并用新福林法测定（BRS）。结果：HUT（＋）组在晕厥发生时BRS较基础状态明显减弱,在倾斜试验结束时,HUT（＋）组,血浆ET,NO水平较基础水平明显升高,血浆NE水平较基础水平亦有升高趋势。（2）倾斜结束时,HUT（＋）组血浆ET,NO变化与BRS呈负相关,血浆NE浓度变化与BRS无相关。结论：VS患在发生晕厥时BRS减弱;血浆ET,NO水平异常与BRS减弱可能共同参与了VS的发生机制。     

血压与心率基础值对直立倾斜试验阳性结果的影响

目的探讨血压与心率基础值对直立倾斜试验阳性结果的影响。方法不明原因晕厥病人51例,行45min基础直立倾斜试验(head-uptilttest,HUT),阴性病人保持70°倾斜角,直接含服硝酸甘油0.25mg,继续20min试验;HUT阳性病人按晕厥反应类型分为血管抑制型组、心脏抑制型组与混合型组。比较基础血压和基础心率。按血压140/90mmHg与心率(60次/分)为界分别分为高血压组与非高血压组,心率偏慢组与心率正常组。结果HUT阳性组率为62.7%(32/51),其中血管抑制型21例;心脏抑制型5例;混合型6例;阴性19例。HUT阳性组病人的血压与心率基础值与HUT阴性者差异无统计学意义(P>0.05)。晕厥发生率:高血压组62%(8/13),血压正常组63%(24/38),差异无统计学意义;心率偏慢组3/5,心率正常组60%(29/46),差异无统计学意义。结论血压与心率基础值对HUT没有明显影响,不能作为HUT试验阳性的预测指标。     

Excessive myocardial contraction in vasovagal syncope demonstrated by echocardiography during head-up tilt test

The purpose of this study was to gain insight into the mechanism of vasovagal syncope and to test the efficacy of theophylline to prevent syncope. Twenty-six patients with vasovagal syncope underwent two-dimensional echocardiography and theophylline test during head-up tilt test. A standard parastemal short-axis view of echocardiography at the level of the papillary muscle was recorded to measure fraction shorting of the left ventricle, and left ventricular end-diastolic and end-systolic dimensions. Heart rate, blood pressure, and symptoms were recorded. There were three groups; Group 1: no syncope with and without isoproterenol (n = 5); Group 2: syncope only after the infusion of isoproterenol (n = 16); Group 3: syncope without isoproterenol (n = 5). Groups 2 and 3 proceeded to theophylline injection (250 mg). The study showed that the 80° tilt induced an increase in heart rate of 6.6 ± 4.0,12.4 ± 6.6, and 25.4 ± 4.5 beats/min in Groups 1,2, and 3, respectively (p < 0.05 in Groups 1 and 2, p < 0.05 in Groups 1 and 3). The addition of isoproterenol during posture change from supine to an 80° tilt made the significant change of fractional shortening from 0.4 ± 5% to 6 ± 13% in Group 2 (p = 0.05), compared with no significant change in Group 1. There were no significant differences in left ventricular end-diastolic dimension and end-systolic dimension in each group between baseline and isoproterenol infusion during posture change. Vasovagal syncope was associated with vigorous myocardial contraction, rather than with contraction against an empty left ventricle. The acute loading of theophylline was not effective in preventing vasovagal syncope.     

Reproducibility of head-up tilt test in patients with syncope

As the head-up tilt test (HUT) is employed to verify the efficacy of undertaking a treatment, we prospectively evaluated the reproducibility of positive and negative results, as well as that of the response type in 64 consecutive patients (mean age 34.6 ± 22.9 years) with syncope of unknown cause. Two HUTs (60 min, 75° ), separated by an interval of 9.77 ± 8.21 days, were performed on each patient. Positive responses were reproduced in the second HUT in 54.5% of the patients. A greater reproducibility (84.3%) was observed for negative responses. Of the 31 patients with a negative first test, 5 had a positive response during the second HUT. Using a multivariate analysis, no clinical variable correlated with the reproducibility of positive or negative results. Likewise, neither arterial pressure nor heart rate observed during the test were correlated with reproducibility. Of 18 patients who reproduced positive responses, 12 (66.6%) did so with the same response modality. In three patients with documented monomorphic sustained ventricular tachycardia, which was hemodynamically well tolerated, and in one patient with temporal spike wave activity in the electroencephalogram, HUT was also positive. It was concluded that the low reproducibility of HUT limits its usefulness as a tool for evaluating treatment efficacy. The variability of the type of response suggests a common mechanism leading to cardioinhibitory and vasodepressor reactions. A positive result in only the second study shows the rationale of performing two tests when the first one is negative.     

直立倾斜试验的严重反应类型及其预防和处理

目的总结直立倾斜试验的严重反应及其预防和处理。方法试验的倾斜角度为７５°，最长时间为４５分钟。整个过程中持续心电和血压监测，维持良好的静脉通路。身体用特殊护带保护以防意外。结果共有１８例患者接受了这一检查。其中１０例阳性，５例出现严重反应。５例中２例有颈内动脉粥样硬化，２例有慢性房颤。严重反应类型包括：心脏停搏５秒以上（２例），或严重心动过缓心室率慢于５０／ｍｉｎ达１分钟以上（２例），或严重低血压持续１分钟以上（１例）。所有患者在发生晕厥后立刻放回至平卧位，抬高下肢；心率慢者给阿托品静推。有１例做了胸外心脏按压。所有患者经处理神志很快转清，未发生并发症。结论直立倾斜试验虽然为一项无创性检查，但严重反应并不罕见。严格掌握适应证、术前充分准备和术中密切观察有助于避免意外的发生     

Correlation between results of head-up tilt test and clinical features in patients with syncope or presyncope

Background

Head-up tilt test (HUTT) is a well-established diagnostic tool in patients with suspected vasovagal syncope. Identification of factors that predict a positive HUTT result could simplify diagnostic steps. The aim of this study was to assess the correlation between clinical characteristics of patients with suspected neurocardiogenic syncope or presyncope and results of HUTT.

Materials and Methods

The study group consisted of 90 patients (55 men, 35 women; mean age, 43.2 ± 17 years) with a history of syncope or presyncope. Cardiological and neurologic test findings were normal in every patient. The patients were tilted to a 70° position for 45 minutes. If the first phase produced a negative response, the patients received 400 μg of sublingual nitroglycerin for the second phase and continued to be tilted for an additional 15 minutes.

Results

Sixty-four patients had a positive HUTT result, characterized by a vasodepressive response in 26 patients, mixed response in 24 patients, and cardioinhibitory response in 14 patients. In logistic regression analysis, the presence of prodromal symptoms was a predictor of a positive HUTT result (P = .002).

Conclusion

We showed that the prognostic performance of clinical features, including the time interval between the last episode and HUTT, the number of syncope or presyncope episodes, age, and sex, was not ideal. The presence of prodromal symptoms might be more likely to predict a positive response during HUTT.     

The yield of head-up tilt testing is not significantly increased by repeating the baseline test

Background and hypothesis: Head-up tilt is widely used in evaluating patients with syncope. Data suggest that baseline tilt without isoproterenol is associated with few ≤ 10%) positive results in normals. However, there is considerable day-today variability in patients with syncope, resulting in low reproducibility. We hypothesized that repeating the baseline tilt would increase the total number of positive responses. Methods: In all, 193 patients with syncope of unknown etiology prospectively underwent serial baseline tilt (Tilt-1 and Tilt-2) at 70° for 25 min on two consecutive days. Results: Of 193 patients, 39(20%) had a positive Tilt-1. Of these, 19 had a positive Tilt-2, (positive concordance rate: 19/39 = 49%). Of 154 patients with a negative Tilt-1, 145 had a negative Tilt-2 (negative concordance rate: 142/151=94%). Only 9 of 154 patients (6%) with a negative Tilt-1 had a positive Tilt-2. Thus, the yield increased from 20% (39/193) after Tilt-1, and to 25% (48/193) after Tilt-1 plus Tilt-2, p = NS. Conclusions: (1) Reproducibility of a positive Tilt-1 is moderate. (2) Reproducibility of a negative Tilt-1 is high. (3) Repetition of tilt in patients with a negative Tilt-1 does not significantly increase the number of positive results.