Analysis of heart rate variability and clinical implications

In the last decades analysis of heart rate variability has emerged as a new useful tool for assessing the changes in autonomic tone that influences cardiovascular function. High variability of oscillations and the integrated physiologic activities of heart and cardiovascular system isassociated with physiologic functioning. Irregularity of the length of consecutive heart cycles, designated as heart rate variability, reflects the ability of cardiovascular system to adapt to different situations in everyday life. Reduction of these fluctuations of the heart periods has been shown to be associated with pathological conditions in many experimental and clinical trials. The extent and consistency of the reduction of heart rate variability in the patients after acute coronary events, were shown to be related to mortality and cardiovascular dysfunction. In patients with diabetes mellitus who develop autonomic neuropathy, reduced heart rate variability is quite common. Reduced heart rate variability was shown in endocrine disorders, neurological and psychiatric diseases, with use of different drugs and many other conditions. The most common ways of measuring heart rate variability are measuring in time domain analysis and frequency domain analysis. Parameters calculated from the measurements are related to the functions of sympathetic and parasympathetic nervous system. Measurements of changes in autonomic function is very important in the follow up in different diseases and for determination of the efficacy of the therapy. In the field of surgery and anaesthesia, besides preoperative risk stratification, there are many studies on the effects of different anaesthetics on heart rate variability. In this paper, some aspects of measurement of heart rate variability and changes of the values of parameters in different pathological conditions and clinical implications are reviewed.