Shi Bo, Motin Mohammod Abdul, Wang Xinpei, Karmakar Chandan, Li Peng
School of Medical Imaging, Bengbu Medical College, Bengbu 233030, China.
Department of Electrical and Electronic Engineering, University of Melbourne, Melbourne, VIC 3110, Australia.
Entropy (Basel). 2020 Dec 20;22(12):1439. doi: 10.3390/e22121439.
QT interval variability (QTV) and heart rate variability (HRV) are both accepted biomarkers for cardiovascular events. QTV characterizes the variations in ventricular depolarization and repolarization. It is a predominant element of HRV. However, QTV is also believed to accept direct inputs from upstream control system. How QTV varies along with HRV is yet to be elucidated. We studied the dynamic relationship of QTV and HRV during different physiological conditions from resting, to cycling, and to recovering. We applied several entropy-based measures to examine their bivariate relationships, including cross sample entropy (XSampEn), cross fuzzy entropy (XFuzzyEn), cross conditional entropy (XCE), and joint distribution entropy (JDistEn). Results showed no statistically significant differences in XSampEn, XFuzzyEn, and XCE across different physiological states. Interestingly, JDistEn demonstrated significant decreases during cycling as compared with that during the resting state. Besides, JDistEn also showed a progressively recovering trend from cycling to the first 3 min during recovering, and further to the second 3 min during recovering. It appeared to be fully recovered to its level in the resting state during the second 3 min during the recovering phase. The results suggest that there is certain nonlinear temporal relationship between QTV and HRV, and that the JDistEn could help unravel this nuanced property.
QT间期变异性（QTV）和心率变异性（HRV）都是公认的心血管事件生物标志物。QTV表征心室去极化和复极化的变化。它是HRV的主要组成部分。然而，QTV也被认为接受上游控制系统的直接输入。QTV如何随HRV变化尚待阐明。我们研究了从静息到骑行再到恢复的不同生理条件下QTV和HRV的动态关系。我们应用了几种基于熵的方法来检验它们的双变量关系，包括交叉样本熵（XSampEn）、交叉模糊熵（XFuzzyEn）、交叉条件熵（XCE）和联合分布熵（JDistEn）。结果显示，不同生理状态下的XSampEn、XFuzzyEn和XCE没有统计学上的显著差异。有趣的是，与静息状态相比，JDistEn在骑行期间显著降低。此外，JDistEn在恢复过程中从骑行到恢复的前3分钟也呈现出逐渐恢复的趋势，并在恢复的后3分钟进一步恢复。在恢复阶段的后3分钟，它似乎完全恢复到了静息状态的水平。结果表明，QTV和HRV之间存在一定的非线性时间关系，并且JDistEn有助于揭示这种细微的特性。
