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The Importance of Environmental Charges in Influencing Heart Rate Variability: Increased Heart Rate Variability on Weekends in Healthy Active Subjects
Attila Frigy1, MD, Pawel Zagozdzon2, MD, Marek Malik2, MD, PhD
1 3rd
Medical Clinic, University of Medicine and Pharmacy Targu-Mures
Romania
2Department of Cardiological Sciences, St.
George’s Hospital Medical School
London, United Kingdom
Abstract
Introduction
Material and Methods
Results
Discussion and Conclusions
References
Abstract
Background: Heart rate variability (HRV) analysis is widely recognised as
a powerful tool for characterising cardiac autonomic activity. However, the effect on HRV
of the environmental charges encountered during a regular weekly activity has not been
properly investigated. As HRV is likely to be influenced by charges in the external
environment, a weekly pattern may have implications for clinical use of HRV.
Methods: In order to evidence weekly behaviour of HRV we performed
24-hours Holter recordings in 10 healthy subjects (5 female, 5 male, mean age 33,4 years)
with regular weekdays working activity. The analysis was performed using a MARS 8000
system (Marquette Medical Systems). For each subject time domain (SDNN, SDANN, SDNNindex,
rMSSD, pNN50) and spectral HRV parameters (total, VLF, LF and HF power, LF/HF ratio) were
obtained from Tuesdays and Saturdays. The differences in the parameters were assessed
using paired t-test.
Results: Compared to weekday recordings HRV was increased on Saturdays,
the level of significance being reached by the MNN (771± 70.63 ms vs. 806± 66.03 ms,
p=0.04), pNN50 (13.79± 7.05% vs. 16.06± 8.16%, p=0.048) and the LF/HF ratio (3.706± 1.6
vs. 3.16± 1.8, p=0.034).
Conclusions: (1) The finding of the lower heart rate and the increased
parasympathetic parameters on Saturdays support the importance of weekly environmental
charges (e.g. psychosocial and physical) in influencing HRV. (2) When HRV, and
particularly changes in HRV, is analysed in outpatients, this weekly behaviour has to be
considered.
The effect on HRV of the environmental charges encountered during a regular weekly activity still has not been properly investigated. As HRV is likely to be influenced by charges in the external environment, a weekly pattern may have implications for clinical use of HRV.
TopMaterial and Methods: In order to evidence weekly behaviour of HRV we performed 24-hours Holter recordings in 10 healthy subjects (5 female, 5 male, mean age 33,4 years) with regular weekdays working activity (physicians and research nurses from our department). The analysis was performed using a MARS 8000 system (Marquette Medical Systems). For each subject time domain (MNN, SDNN, SDANN, SDNNindex, rMSSD, pNN50) and spectral HRV parameters (total, VLF, LF and HF power, LF/HF ratio) were obtained from Tuesdays and Saturdays. The differences in the parameters were assessed using paired t-test.
TopResults: Compared to weekday recordings, all the parameters revealed an increased HRV on Saturdays, the level of significance being reached by the MNN (771± 70.63 ms vs. 806± 66.03 ms, p=0.04), pNN50 (13.79± 7.05% vs. 16.06± 8.16%, p=0.048) and the LF/HF ratio (3.706± 1.6 vs. 3.16± 1.8, p=0.034)- fig.1.
Fig. 1. Variation of individual values of LF/HF TopDiscussion and Conclusions: It is a well known fact that in normal, healthy subjects HRV is related to age, gender, smoking, physical fitness and weight. Besides these "internal" factors, HRV also reflects the autonomic alarm state of the cardiovascular system induced by environmental charges of different nature. [ 4, 5, 6, 7]
The finding of the lower heart rate and the increased parasympathetic parameters on Saturdays support the importance of weekly environmental charges (mainly psychosocial) in influencing HRV. The relative sympathetic overactivity encountered during the working day could serves as an explanation for our results. This fact provides us practical considerations. When HRV, and particularly changes in HRV, is analysed in outpatients, this weekly behaviour has to be considered.
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