Heart Rate Variability – Noninvasive Monitoring of Autonomic Nervous System Function -

Monitoring of changes in heart rate is the commonest way of rapid assessment of cardiovascular function in everyday clinical practice. Analysis of the recordings of the heart electrical activity enabled the discovery that specific fluctuations of the length of consecutive heart cycles, which can not be measured in clinical examination, are associated with physiological conditions. That phenomenon, named heart rate variability, could be evaluated only by implementing special measurements, based on time domain analysis and frequency domain analysis which give many parameters that are related to the functioning of two branches of autonomous nervous system: sympathetic and parasympathetic system. Many observational and controlled clinical studies have shown reduced heart rate variability in different pathological conditions, so that it could be a useful tool in risk stratification after acute myocardial infarction, or coronary artery disease, in diabetic autonomic neuropathy, endocrine diseases, neurologic and psychiatric diseases. During anaesthesia, there are profound alterations in autonomic nervous tone, depending on the comorbidity and the agents that are used for induction and maintenance. Measurements of changes in autonomic function is very important, and could give a possibility for determination of the perioperative risk and timely correction of the dysfunction, especially in high risk patients. Some aspects of measurement of heart rate variability and changes of the values of parameters in different pathological conditions and in anaesthesia are reviewed.