Influence of third-generation oral contraceptives on the complexity analysis and symbolic dynamics of heart rate variability

ABSTRACT

Objective To evaluate the influence of oral contraceptives (OCs) containing 20 μg ethinylestradiol (EE) and 150 μg gestodene (GEST) on the autonomic modulation of heart rate (HR) in women.

Methods One-hundred and fifty-five women aged 24 ± 2 years were divided into four groups according to their physical activity and the use or not of an OC: active-OC, active-non-OC (NOC), sedentary-OC, and sedentary-NOC. The heart rate was registered in real time based on the electrocardiogram signal for 15 minutes, in the supine-position. The heart rate variability (HRV) was analysed using Shannon's entropy (SE), conditional entropy (complexity index [CInd] and normalised CInd [NCI]), and symbolic analysis (0V%, 1V%, 2LV%, and 2ULV%). For statistical analysis the Kruskal-Wallis test with Dunn post hoc and the Wilcoxon test (p < 0.05 was considered significant) were applied.

Results Treatment with this COC caused no significant changes in SE, CInd, NCI, or symbolic analysis in either active or sedentary groups. Active groups presented higher values for SE and 2ULV%, and lower values for 0V% when compared to sedentary groups (p < 0.05).

Conclusion HRV patterns differed depending on life style; the non-linear method applied was highly reliable for identifying these changes. The use of OCs containing 20 μg EE and 150 μg GEST does not influence HR autonomic modulation.

KEYWORDS:

• Heart rate variability
• Non linear analysis
• Third generation oral contraceptives
• Exercise

ACKNOWLEDGEMENTS

This study was supported by CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico – Process no. 370448/2007-3) and FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo – Process no. 2006/56788-1). We are indebted to Dr Alberto Porta and his team of the Department of Technologies for Health, Galeazzi Orthopaedic Institute, University of Milan, Milan, Italy, for providing the programme for the nonlinear analysis of HRV.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and the writing of the paper.