Vukasovic J L, Florenzano F
Departamento de Cardiología, Universidad de Chile, Santiago.
Rev Med Chil. 1995 Nov;123(11):1412-7.
The analysis of heart rate variability studies the normal oscillatory changes of the cardiac cycle. These changes are periodical or incidental and are controlled by humoral, sympathetic and parasympathetic stimuli. Frequency domain and time domain are the methods most used to assess heart rate variability. Time domain analyses variations of cardiac cycle using the standard deviation of RR intervals in 24 hours (SDRR) and the percentage of difference between adjacent normal RR intervals of more than 50 ms (pNN50). Frequency domain, converts beat to beat fluctuation of heart rate into different components of frequency by a fast Fourier transformation. They are classified, according to their magnitude, in high frequency (> 0.15 Hz), low frequency (0.04-0.15 Hz), very low frequency (0.003-0.04 Hz) and extremely low frequency (< 0.003 Hz). The high frequency fluctuations are predominantly related to parasympathetic activity whereas the low frequency fluctuations are related to sympathetic and parasympathetic activity. The physiology of very low and extremely low frequency fluctuations remains unclear. Many reports have shown that a decrease in heart rate variability after myocardial infarction may independently identify patients at risk for sudden death. However, the physiopathologic basis of these findings is not yet elucidated.
心率变异性分析研究心动周期的正常振荡变化。这些变化是周期性的或偶发的，受体液、交感神经和副交感神经刺激的控制。频域和时域是评估心率变异性最常用的方法。时域使用24小时RR间期的标准差（SDRR）和相邻正常RR间期差值超过50毫秒的百分比（pNN50）来分析心动周期的变化。频域通过快速傅里叶变换将逐搏心率波动转换为不同频率成分。根据其大小，它们被分为高频（>0.15赫兹）、低频（0.04 - 0.15赫兹）、极低频（0.003 - 0.04赫兹）和超低频（<0.003赫兹）。高频波动主要与副交感神经活动有关，而低频波动与交感神经和副交感神经活动有关。极低频和超低频波动的生理机制尚不清楚。许多报告表明，心肌梗死后心率变异性降低可能独立识别猝死风险患者。然而，这些发现的病理生理基础尚未阐明。
