Characterization of Heart Rate Variability Dynamics in Heart Failure Patients Admitted to Intensive Care Unit

Introduction: The high mortality and difficulty of diagnosis make Heart failure $(HF)$ a severe burden for the healthcare system, especially in intensive care units $(ICU)$. Goal: This work proposes a method to characterize $HF$ patients using autonomic indices from electrocardiogram $(ECG)$ recordings in the $ICU$ Methods: We considered 52 $ICU$ patients from the MIMIC-III database subjected to brain natriuretic peptide (NT-proBNP) laboratory measurement during their stay, of which 41 showed a positive reading for likely $HF$ due to elevated levels of the peptide $(NT-proBNP > 300\ pg/mL)$. RR intervals from 1 hour $ECG$ recordings in the hour preceding NT-proBNP measurements were selected, and a point process framework was applied to extract time-varying estimates of indices related to autonomic nervous system activity. A general linear mixed-effects model was used to analyze the dynamics of the two populations.Results: Results showed an increasing average $RR$ interval in the negative population $(p < 0.001)$. In parallel, $RR$ variability increased in negative subjects $(p < 0.001)$ and decreased in positive patients $(p < 0.001)$. High frequency power $(p < 0.001)$ further showed different dynamics between the two populations. Conclusions: Results point at different autonomic cardiac control dynamics in patients with positive NT-proBNP test in the hour preceding the measurement.