Assessment of autonomic nervous system activity by heart rate recovery response

The assessment of autonomic nervous system (ANS) activity is a tool for diagnosing or predicting cardiovascular diseases, while heart rate recovery response (HRRR) after exercise has been promoted as a process under the regulation of ANS (sympathetic and parasympathetic nervous systems). Therefore, assessment of ANS activity was performed by HRRR in this study. Firstly, HRRR signal was extracted based on wavelet decomposition and difference curve of coarse component from heart rate signal. Then, HRRR was divided into quickly descending interval (QDI) and slowly descending interval (SDI). Finally, 3 groups of indexes (Difference, Exponential and Quadratic Groups) from QDI and SDI were compared between 50 normotensive and 61 hypertensive subjects. The results showed that the indexes of Difference Group were better choices than others in analyzing the features of HRRR. Furthermore, parasympathetic activity is dominant in QDI, while sympathetic and parasympathetic activities affect SDI together. In conclusion, the proposed method was effective to assess ANS activity.