Revisiting Left Ventricular Ejection Fraction Levels: A Circadian Heart Rate Variability-based Approach
Abstract Analysis of heart failure is important in clinical practice to ensure coronary artery disease (CAD) patients will be provided with appropriate timely treatment. The current gold standard, echocardiography, although reliable, provides a once-off left ventricular ejection fraction (LVEF) measurement but does not provide information about heart function the during day / night cardiac cycles. The aim of this study was to investigate the ability of heart rate variability (HRV) features in classifying CAD patients into multiple LVEF groups through a new index, HRV ejection fraction (HRVEF) and its agreement to established norms. A total of 92 heart failure patients were included in this study. HRVEF groups optimized on hourly basis through Jenks natural breaks algorithm exhibited a consistent pattern with a goodness of variance fit (GVF) of more than 0.70 accuracy during the late-night to early-morning (01:00-08:00) and evening (17:00-23:00) time periods. At these hours, several HRV features were found significant in differentiating between HRVEF groups using statistical analysis of variance (ANOVA) test. These features include the successive differences between normal heartbeats (RMSSD), low and high frequency (LF, HF) power, standard deviation of normal heartbeats (SD2), short-term scaling exponent (alpha1), and percentage of normal heartbeats in alternation segments (PAS). This study paves the way towards new LVEF guidelines based on the association between LVEF and HRV features for a better demonstration of the circadian cardiac function at different LVEF levels in CAD patients.