Correlation Between Poincare Plot Indices and Linear–Nonlinear Heart Rate Variability During Fasting and Postprandial States

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The beat-to-beat fluctuations in the electrocardiogram (ECG) are called heart rate variability (HRV). There are various linear and nonlinear methods for measurement of the HRV. Poincare plot is one of the nonlinear methods to evaluate HRV. Previous studies have shown strong correlation between Poincare plot descriptors SD1 and SD2 with linear and nonlinear HRV measures. The present study is aimed to verify the correlation during fasting and postprandial states. A total of 46 young adults participated in the study. 10 min of ECG lead II was recorded in supine position with minimum 8 h of fasting. The subjects were then given 75 gm of glucose. The ECG was again recorded after postprandial 1 h (PP1H) and postprandial 2 h (PP2H) intervals. The linear and nonlinear HRV indices were calculated. The correlation coefficient was obtained by Spearman’s correlation test and regression analysis. The strong correlation was verified for SD1 and SD2 with linear HRV measures; however, the degree of correlation was changing during fasting and postprandial states. SD1/SD2 was strongly correlated with LF/HF ratio, Detrended Fluctuation Analysis (DFA) (α1, α2), suggesting nonlinear characteristics of the parameters. The entropy measures were not statistically significant with any index of Poincare plot. It can be concluded that the correlations exist between linear and nonlinear HRV measures and degree of correlation changes during fasting and postprandial states. Therefore, in studies correlating linear and nonlinear HRV, the fasting and postprandial states must be specifically identified.