Carrillo Andres E, Cheung Stephen S, Flouris Andreas D
FAME Laboratory, Centre for Research and Technology Thessaly, Trikala, Greece.
Aviat Space Environ Med. 2013 Jul;84(7):722-5. doi: 10.3357/asem.3573.2013.
Heart rate variability (HRV) indices (LF, HF, LF/HF, RMSSD, and pNN50) under combined heat and orthostatic stress leading up to and during accidental syncope (EXP group: one man, two women; age: 23.7 +/- 2.9 yr) were compared with data collected from subjects who did not experience syncope (CON group: one man, two women; age: 22.3 +/- 1.5 yr).
Minute averages of HRV indices were collected during 5 min at baseline (Base), 5 min leading up to syncope (PRE), and 5 min during syncope (Syncope) (i.e., 2 min leading up to, 1 min during, and 2 min post-syncope). Data were individually analyzed as 1-min means during Syncope as well as 5-min means during Base, PRE, and Syncope.
Between-group results revealed that LF and LF/HF were significantly higher and HF was significantly lower in EXP compared to CON subjects at minutes 1, 2, and 3 during Syncope. Further, RMSSD (CON: 161.1 +/- 37.0 ms; EXP: 17.5 +/- 13.3 ms) and pNN50 (CON: 26.4 +/- 36.3%; EXP: 1.3 +/- 1.2%) were significantly lower in EXP compared to CON subjects at minute 3 during Syncope. During Syncope, 5-min averages of LF (CON: 46.1 +/- 13.9 nu; EXP: 77.5 +/- 6.6 nu) and LF/HF (CON: 1.0 0.5; EXP: 3.8 +/- 1.7) were significantly higher, and HF (CON: 53.9 +/- 13.9 nu; EXP: 22.5 +/ 1 6.6 nu) was significantly lower in EXP subjects compared to CON.
Our findings show that autonomic nervous system modulation leading up to and during accidental syncope induced by heat and orthostatic stress is characterized by an exaggerated suppression of parasympathetic and elevation of sympathetic activity. Thus, elevated LF and LF/HF, and lower HF, RMSSD, and pNN50 may represent risk factors for accidental syncope.
将在热暴露和直立位应激联合作用下直至意外晕厥发生时及晕厥期间的心率变异性（HRV）指标（低频功率（LF）、高频功率（HF）、LF/HF、相邻RR间期差值的均方根（RMSSD）和50%相邻RR间期差值大于50毫秒的心搏数所占百分比（pNN50））（实验组：1名男性，2名女性；年龄：23.7±2.9岁）与未发生晕厥的受试者（对照组：1名男性，2名女性；年龄：22.3±1.5岁）收集的数据进行比较。
在基线期（Base）5分钟、晕厥前5分钟（PRE）以及晕厥期间5分钟（即晕厥前2分钟、晕厥期间1分钟和晕厥后2分钟）收集HRV指标的每分钟平均值。数据分别作为晕厥期间的1分钟平均值以及基线期、晕厥前和晕厥期间的5分钟平均值进行分析。
组间结果显示，在晕厥期间的第1、2和3分钟，与对照组相比，实验组的LF和LF/HF显著升高，HF显著降低。此外，在晕厥期间的第3分钟，与对照组相比，实验组的RMSSD（对照组：161.1±37.0毫秒；实验组：17.5±13.3毫秒）和pNN50（对照组：26.4±36.3%；实验组：1.3±1.2%）显著降低。在晕厥期间，实验组的LF（对照组：46.1±13.9归一化单位；实验组：77.5±6.6归一化单位）和LF/HF（对照组：1.0±0.5；实验组：3.8±1.7）的5分钟平均值显著升高，而HF（对照组：53.9±13.9归一化单位；实验组：22.5±6.6归一化单位）显著降低。
我们的研究结果表明，在热暴露和直立位应激诱发的意外晕厥发生时及发生期间，自主神经系统调节的特征是副交感神经受到过度抑制，交感神经活动增强。因此，LF和LF/HF升高，以及HF、RMSSD和pNN50降低可能代表意外晕厥的危险因素。
