自主神经在多阶段倾斜试验诱发血管迷走性晕厥中的作用

为评价自主神经在多阶段静滴异丙基肾上腺素倾斜试验（MITTT）诱发血管迷走性晕厥（VS）过程中的作用，分析了10例基础倾斜试验阳性（基础阳性组）、24例HITTT阳性（ISO阳性组）和11例MITTT阴性（对照组）结果患者在基础倾斜前后，阳性反应前或MITTT结束前各4分钟的心率功率谱图。结果显示，基础倾斜前4分钟，三组低频（LF）成分无明显差别（P＞0．05）；基础阳性组高频（HF）成分明显低于另两组（P均＜0．05），LF／HF比值显著高于另两组（P均＜0．05）。基础倾斜后和阳性反应前或MITTT结束前，三级LF成分均增高，但组间比较无明显差别；基础阳性组和ISO阳性组HF成分进行性降低，LF／HF比值进行性显著增大。对照组HF成分在这两个时间段无明显变化，虽然LF／HF比值较基础倾斜前明显增大，但后两个时间段比较并无差别。结果表明，交感神经和副交感神经功能调节障碍在MITTT诱发VS的发生机制中起着重要作用，LF／HF比值能更确切地反映两者在诱发VS中的相互作用。

The role of the autonomic nervous system in vasovagal syncope induced by multistage isoproterenol tilt table test

The role of the autonomic nervous system is studied in vasovagal syncope induced by multistage isoproterenol tilt table test (MITTT). We analysed the spectral characteristics of heart rate variability during the 4-minute periods just before and after basal tilt test and during the 4-minute just before the occurrence of vasovagal syncope of the end of MITTT in 10 subjects with positive basal tilt table test (basal positive group), 24 subjects with positive MITTT (ISO positive group) and 11 subjects with negative MITTT (control group). Low-frequency (LF) components was not signific antly different in three groups during 4-minute period before basal tilt,but high-frequency (HF) components was significantly lower than those of the other two groups,and the ratio of LF to HF (LF/HF ratio) was significantly higher than those of the control group. Just after basal tilt and just before the occurrence of vasovagal syncope or the end of MITTT,three groups had a significant increase in LF components but no difference in them. Basal positive group and ISO positive group had a progressive decrease in HF components and had a significant increase in LF/HF ratio. HF components did not significantly change in control group during these periods. Though LF/HF ratio in control group was significantly higher than what was just be fore basal tilt,they did not differ in these two periods. These results suggest that the imbalance of sympathetic and parasympathetic neural tones play an important role in the vasovagal syncope induced during MITTT. The LF/HF ratio is a practical measure which reflects the accuracy and sensibility of interaction of sympathetic and parasympathetic neural tones.