Twenty-four hour variation in heart rate variability indices derived from fractional differintegration

Area of Science:

• Cardiology
• Physiology
• Complex Systems

Background:

• Heart rate variability (HRV) analysis is crucial for understanding cardiovascular health.
• Traditional HRV metrics may not fully capture the complex, dynamic nature of heart rate regulation.
• The fractional noise quantifier (fnQ) offers a novel approach to assess multifractality in RR time-series.

Purpose of the Study:

• To evaluate the circadian variation of the fractional noise quantifier (fnQ) in healthy individuals.
• To determine if fnQ, a measure of multifractality, exhibits diurnal patterns.
• To assess the potential of fnQ as a surrogate measure for multifractality in RR time-series.

Main Methods:

• Continuous 24-hour electrocardiogram (ECG) recordings from 69 healthy participants.
• Calculation of fnQ using fractional differintegration on RR time-series.
• Analysis of HRV in time-domain and assessment of circadian trends across 1-hour and 6-hour blocks.

Main Results:

• Most HRV variables, excluding fnQ, showed significant circadian variation.
• fnQ exhibited a non-significant trend towards higher values during evening and night periods (approx. 10% increase).
• Circadian trends in all analyzed variables were independent of gender.

Conclusions:

• The structure of RR time-series in healthy individuals may be most multifractal during evening and night.
• fnQ shows promise as a sensitive measure of multifractality in heart rate dynamics.
• Further research is warranted to confirm the statistical significance of fnQ's diurnal variation.