心率變異度是測試自主神經系統功能的一種簡便而且非侵入性的方法。心率變異度的測量分析可以使用時域分析法或頻域分析法，時域分析法是將心跳間期的變異性作統計學上的計算，頻域分析法則是將心電圖中的RR間距轉換成頻譜，來作為心率變異度的分析。目前心率變異度在醫學上除應用在心血管疾病病患的研究外，也被廣泛應用於非心血管疾病，甚至健康正常人的研究。本文將針對心率變異度及其臨床應用做概略介紹。

Heart rate variability (HRV) is a convenient and non-invasive method for evaluation of autonomic nervous system. The measurement and analysis of HRV can be done by time domain analysis or frequency domain analysis. Time domain analysis is based on altered versions of the measurement of the standard deviation of the heart period. Frequency domain analysis transforms the RR interval to a power spectral analysis of heart rate variability. Studies of heart rate variability were used not only in the field of cardiovascular disease, but also for analysis of noncardiovascular disease and healthy individuals. We reviewed here the issues concerning heart rate variability, its measurement and clinical applications.