Heart rate variability (HRV) is a measure of regulatory systems’ energy reserves, their resistance to extreme factors, balanced in the branches of regulation, the quality of these systems’ protective and compensatory processes, resources for recovery from disease, and risk of catastrophic health disorders.
Analysis of heart rate variability is a method of assessing the state of regulation of physiological functions in the human body, namely regulatory mechanisms’ general activity, neurohumoral regulation of the heart. The HRV study is based on spectral analysis and mathematical modeling of the control of variability of the autonomic nervous system’s sympathetic and parasympathetic divisions.
The autonomic nervous system’s sympathetic and parasympathetic divisions result from the multi-circuit and multi-level response of the circulatory system. That is why they change their parameters to achieve the optimal adaptive response, reflecting the whole organism’s adaptive feedback.
Adaptive responses are individual and realize in different people with different degrees of involvement of functional systems, which, in turn, have feedback that is variable over time and has an inconsistent active organization. The method’s principle is based on measuring time intervals between R-R teeth of electrocardiograms, constructing a series of cardio intervals, and the subsequent analysis of the received numerical series by various mathematical methods.
Referring to research on Pubmed, a Smartphone algorithm to analyze the evolution of HRV “seems particularly suitable for performing daily HRV monitoring in field conditions. “The unique Welltory application allows you to make regular measurements of heart rate variability using the flash and camera of your iPhone. But the special application is not based on the principle of registration, but thanks to the most extensive database and self-learning machine algorithm that adapts to the personal rhythm of human life.
Importance of the HRV measurement.
– Assessment of autonomic regulation of heartbeat in almost healthy people (base level of autonomic regulation, autonomic reactivity, autonomic activity);
– Assessment of autonomic regulation of heart rhythm in patients with various diseases (changes in autonomic balance, the degree of preference of one of the autonomic nervous system departments). Obtaining additional information for the diagnosis of multiple forms of the disease;
– Assessment of the functional state of the regulatory organism based on an integrated approach to the circulatory system, as an indicator of the adaptive activity of the whole organism;
– Determining the type of autonomic regulation (weight, or norm, or sympathicotonia);
– Prognosis of the risk of sudden death and fatal arrhythmias in myocardial infarction and coronary heart disease, in patients with ventricular arrhythmias, in chronic heart failure due to cardiomyopathy, hypertension;
– Selection of risk groups for the development of life-threatening increased heart rate instability;
– Use as a control method when conducting various functional tests;
– Evaluation of the effectiveness of treatment and prevention and health measures;
– Assessment of stress levels, the degree of stress of regulatory systems in extreme and sub extreme effects on the body;
– Use as a method of assessing functional status in mass preventive (nosological) studies of various contingents of the population;
– Prediction of functional states (stability of the organism) in the professional selection and determination of professional suitability;
– Monitoring of HRV in surgery to objectify the severity of surgical stress and control the adequacy of anesthesia, as well as to choose the type and dosage of anesthetic protection and for control in the postoperative period;
– Objectification of reactions of the autonomic nervous system when exposed to electromagnetic waves, intoxications, and other pathogenic factors;
– The choice of the best drug therapy taking into account the background of autonomic regulation of the heart, monitoring the effectiveness of treatment, dose adjustment;
– Assessment and prediction of mental reactions based on the assessment of the autonomic background;
– Control of the functional state in sports;
– Control of the active state of the fetus in obstetrics. Use in the neonatal period of development of an organism;
– Assessment of autonomic regulation in the process of development in children and adolescents. Use as a control method in school medicine for socio-pedagogical and medical-psychological research.
For researchers and clinicians who use the method of HRV analysis, the physiological and clinical interpretation of the results is of paramount importance. It is crucial when evaluating the results of the study to compare the data with the norm. The idea of the norm as a statistical set of values obtained in the study of a reference group of specially selected people needs to be clarified.
Since it is not a question of estimating relatively stable parameters of homeostasis but of changing indicators of autonomic regulation, in this case, it would be correct to understand the concept of a norm as a functional optimum.
It implies that the organism’s norm does not always coincide with the average mark. The same type of adaptive reactions occurs differently following the conditions in which a person is and their functional reserves.
For example, in space medicine, the concept of a physiological norm has been developed, which indicates preserving a sufficient level of the organism’s functional capabilities for the environment in which the astronaut is forced to be. At the same time, homeostasis is provided at the minimum pressure of regulatory mechanisms. According to the value of most indicators, HRV should not exceed certain thresholds set for a particular gender, age, occupation, a regional group.
To the greatest extent, this condition is realized in a comprehensive assessment of HRV analysis results. It is where the self-learning principle of artificial intelligence data processing comes in handy.
There are also concepts of the clinical norm, which characterizes the value of indicators in persons without signs of the disease.
But it is known that the nosological approach is based on the assessment of changes mainly at the structural, metabolic, or energy-metabolic levels of the living system and minimally considers the state of regulatory systems. Thus, the problem of the norm regarding the assessment of HRV needs further in-depth development and study.