Chronotype of Lung Fluid Levels in Patients with Chronic Heart Failure

Background: The variation in lung fluid levels dependent on chronotype in patients with chronic heart failure is unclear. Remote dielectric sensing (ReDS™) is a novel non-invasive system to quantify the lung fluids, which may correlate to intracardiac filling pressures. We aimed to understand the variation in ReDS measurements by chronotype in patients with chronic heart failure. Methods: The patients who were hospitalized for heart failure exacerbations between November 2021 and March 2022 were prospectively included. ReDS values were measured at clinically stable conditions at the following three time points during the day: 5:00 (morning), 12:00 (noon), and 21:00 (night) (manufacture-recommended reference of ReDS value: between 25% and 35%). Results: Twelve patients were included. The median age was 84 (75, 90) years and four patients (33%) were men. The median plasma B-type natriuretic peptide was 235 (178, 450) pg/mL. The median ReDS value was 38% (23%, 41%) in the morning. The ReDS value decreased significantly at the noon measurement, down to 28% (23%, 29%) (p = 0.005) and again increased significantly at the night measurement, up to 31% (27%, 42%) (p = 0.002). The patients were clinically stabilized during the observational period. Conclusions: the lung fluid level varied considerably in patients with chronic heart failure following clinical stabilization.