To the interpretation of frequency components of the heart rate variability

Assessing the sympathetic-vagal balance is an important task for predicting shifts in the functioning of the body when adapting to changing external conditions, as well as aging, various pathological processes and therapy. Today, the method of analyzing the spectrum of heart rate variability (HRV) for determining the sympathetic-vagal balance due to its simplicity and non-invasiveness has become widespread both in clinical practice and in experimental studies. The article analyzes the results of our own and literary studies of influence of various effects on hemodynamic parameters, the level of circulating catecholamines, sympathetic nervous activity, the baroreceptor reflex, and also on the components of the HRV spectrum (LF (low frequency), HF (high frequency) and LF/HF). Often different authors under the same impact register different changes. Reasons for this include different doses of drugs, nature/strength of exposure (for stress and exercise), time between drug administration and registration. In addition, the effect of some drugs can be enhanced in the case of pathology, such as hypertension. Based on the comparison of the vectors of changes in the studied parameters, we concluded that, using the frequency analysis of HRV, it is necessary to draw a conclusion about the sympatho-vagal balance with great care due to the ambiguous nature of LF component, but HF component gives information of the tone of the vagus with sufficient accuracy.