Usefulness of 7-day Holter monitoring for heart rate variability nonlinear dynamics evaluation

Although a number of studies have addressed the clinical usefulness of Heart Rate Variability (HRV) as a marker of the autonomic activity, there are few studies about the short-term day-to-day reproducibility of HRV nonlinear indices. A database of 31 7-Day Holters (7DH) from Chronic Heart Failure patients was used to analyze the reliability of nonlinear dynamics and to evaluate the usefulness of 7DH recordings against the 24-hour recordings. On the one hand, scaling exponents α1 and α2 from De-trended Fluctuations Analysis, and Sample Entropy, were compared at two randomly selected days; day and night periods were also analyzed separately. On the other hand, the values obtained for each single day were compared to the ones for the 7DH. Intraclass Correlation Coefficients showed strong correlation for the indices between two random days, specially in the night period, hence suggesting that this could be the more suitable period to perform the calculations in terms of reliability. Significant differences were found for every single day of the week compared to the 7DH for α2. Therefore, 7DH can improve the understanding of long-term fractal correlation properties given by nonlinear indices.