通常，HRV 最明显的振荡成分是呼吸性窦性心律失常 (RSA)，其中迷走神经刺激在吸气过程中被切断，因此，HR 在吸气过程中增加，在呼气过程中降低（见下面的视频）。因此，HRV 的这种高频 (HF) 分量以呼吸频率为中心，并被认为在 0.15 至 0.4 Hz 的范围内。HRV 的另一个显着分量是低频 (LF) 分量，范围从 0.04 到 0.15 Hz。HF 成分几乎完全由 PNS 活动介导，而 LF 成分由 SNS 和 PNS 活动介导，并且还受压力反射活动 特别工作组 1996 年，   Berntson 等人的影响。1997 . 然而，LF 振荡的起源被认为由 SNS 主导，并且 LF 分量的归一化功率可用于评估交感神经传出活动 Pagani 等人。1997 年， 弗兰等人。2000 . 另一方面，低于 0.04 Hz 的波动没有像更高频率那样被研究。这些频率通常分为 极低频 (VLF, 0.003-0.04 Hz) 和 超低频 (ULF, 0-0.003 Hz) 频段，但在短期录音的情况下，ULF 频段通常被省略 Task Force 1996. 这些最低频率节律是 HRV 信号的特征，并且与例如体温调节过程和肾素-血管紧张素系统 Berntson 等人的体液因素有关。1997 年。

当试图评估心脏自主神经调节的功能时，心率变异性是一种常用的工具。它已被用于与心血管研究和不同人类健康应用相关的众多研究中，作为评估自主神经系统 (ANS) 功能和平衡的间接工具。

发现心率变异性有价值的主要临床场景之一包括急性心肌梗死特别工作组 1996后心源性猝死的风险分层 ，   Acharya 等人。2006 年， 莱蒂奥等人。2007 年， 普拉达潘等人。2014 年。此外，HRV 降低通常被认为是糖尿病心血管自主神经病变 工作组 1996 年，   Acharya 等人的早期预警信号。2006 年，在糖尿病Vinik 等人的前 5-10 年内发现 HRV 的最显着下降 。2013 年，   Tarvainen 等人。2014. 除了这两种主要的临床情况外，HRV 还与几种心血管疾病、肾功能衰竭、体育锻炼、职业和社会心理压力、性别、年龄、药物、酒精、吸烟和睡眠 相关研究 van Ravenswaaij-Arts 等人。1993 年， 马利克等人。1993 年，   1996 年工作组，   Pumprla 等人。2002 年，   Achten 等人。2003 年，   Acharya 等人。2006 年。

ABOUT HEART RATE VRIABILITY

Typically, the most conspicuous oscillatory component of HRV is the respiratory sinus arrhythmia (RSA), where the vagus nerve stimulation is being cut-off during inhalation, and thus, HR increases during inhalation and decreases during exhalation (see video below). This high frequency (HF) component of HRV is thus centered at respiratory frequency and is considered to range from 0.15 to 0.4 Hz. Another conspicuous component of HRV is the low frequency (LF) component ranging from 0.04 to 0.15 Hz. The HF component is mediated almost solely by the PNS activity, whereas the LF component is mediated by both SNS and PNS activities and is also affected by baroreflex activity Task Force 1996, Berntson et al. 1997 . The origin of the LF oscillations is however considered to be dominated by SNS and the normalized power of the LF component could be used to assess sympathetic efferent activity Pagani et al. 1997, Furlan et al. 2000. The fluctuations below 0.04 Hz, on the other hand, have not been studied as much as the higher frequencies. These frequencies are commonly divided into very low frequency (VLF, 0.003-0.04 Hz) and ultra low frequency (ULF, 0-0.003 Hz) bands, but in case of short-term recordings the ULF band is generally omitted Task Force 1996. These lowest frequency rhythms are characteristic for HRV signals and have been related to, e.g., humoral factors such as the thermoregulatory processes and renin-angiotensin system Berntson et al. 1997.

Heart rate variability is a commonly used tool when trying to assess the functioning of cardiac autonomic regulation. It has been used in multitude of studies, related to cardiovascular research and different human wellbeing applications, as an indirect tool to evaluate the functioning and balance of the autonomic nervous system (ANS).

One of the main clinical scenarios where heart rate variability has been found valuable include the risk stratification of sudden cardiac death after acute myocardial infarction Task Force 1996, Acharya et al. 2006, Laitio et al. 2007, Pradhapan et al. 2014. In addition, decreased HRV is generally accepted to provide an early warning sign of diabetic cardiovascular autonomic neuropathy Task Force 1996, Acharya et al. 2006, the most significant decrease in HRV being found within the first 5-10 years of diabetes Vinik et al. 2013, Tarvainen et al. 2014. Besides these two main clinical scenarios, HRV has been studied with relation to several cardiovascular diseases, renal failure, physical exercise, occupational and psychosocial stress, gender, age, drugs, alcohol, smoking and sleep van Ravenswaaij-Arts et al. 1993, Malik et al. 1993, Task Force 1996, Pumprla et al. 2002, Achten et al. 2003, Acharya et al. 2006.