Discrimination Amongst Various Degrees of Left Ventricular Ejection Fraction in CAD Patients Using Circadian Heart Rate Variability Features

This study explored how 24-hour Heart Rate Variability (HRV) features differentiate amongst Coronary Artery Disease (CAD) patients with 'at risk', 'borderline', and 'normal' Left Ventricular Ejection Fraction (LVEF). Hourly segmentation of heart rate signals was completed by Cosinor Analysis fitting. Time, frequency, and non-linear HRV features were estimated for each hour and averaged across all CAD patients for each group. Statistical analysis to identify differences between the groups was based on one-way ANOVA test, followed by a multiple comparison analysis (Tukey test). The results showed a statistically significant difference between the three groups when using as discriminative features the normalized low frequency (0.04 to 0.15 Hz) HRV (LF-HRV) power and the sample entropy (SE) occurring only between 2:00-3:00, 18:00-19:00, and 19:00-20:00. In addition, the averaged normal-to-normal values show variation during the night time (from 23:00 to 5:00) between the three groups. These results pave the way for further investigation of the interaction of the sympathetic and parasympathetic nervous systems (as reflected in LF - HRV) and the cardiovascular autonomic regulation (as reflected in SE) in LVEF.