Heart Rate Variability in Healthy Subjects During Monitored, Short-Term Stress Followed by 24-hour Cardiac Monitoring

Area of Science:

• Cardiology
• Physiology
• Data Analysis

Background:

• Heart Rate Variability (HRV) provides insights into cardiac function.
• Detrended Fluctuation Analysis (DFA) is a non-linear method to analyze HRV by assessing correlations in RR intervals.
• Visual and mental stimuli can influence autonomic nervous system activity and heart rate.

Purpose of the Study:

• To investigate the impact of visual and mental stimulation on HRV using DFA in healthy adults.
• To determine if DFA can differentiate between distinct types of cognitive and sensory stimulation.
• To explore the effect of image presentation order (organized vs. random) on HRV metrics.

Main Methods:

• 70 healthy adults underwent repeated 2-min 18-sec visual stimulation followed by a 4-min math and recall task.
• Electrocardiogram (ECG) was recorded throughout the stimulation and task periods.
• A subset of 37 participants also underwent a 24-hour Holter monitoring.
• DFA alpha1 (DFA α1) was calculated from RR intervals to quantify HRV.

Main Results:

• DFA α1 significantly distinguished between the visual stimulation segments (0.96–1.08) and the mental task segments (1.17–1.26) (p < 0.0006).
• No significant difference in DFA α1 was found between the pure (organized) and mixed (random) image presentation groups.
• The average DFA α1 during the 24-hour Holter recording was 1.09 (SD = 0.14).

Conclusions:

• DFA α1 demonstrates a graded physiological response to short-term visual and mental stimulation.
• HRV, as measured by DFA, reflects the body's ability to adjust to changing external environments.
• DFA is a sensitive index for detecting short-term changes in autonomic regulation during cognitive tasks.