ABSTRACT
Physiological rhythms or oscillations are the manifestation of a complex physiological system. The clinical community has long recognized that alterations in physiological rhythms are associated with disease and therefore have clinical value. Oscillations in cardiovascular systems are reflected in electrocardiogram (ECG) time series variability. Methodological considerations form the crux of any research as they are a big part of using heart rate variability (HRV) as a tool in clinical practice. For HRV analysis, several pre-processing considerations have to be met. Noises in the recording and ectopic beats have to be removed. HRV analysis is a simple, sensitive, and noninvasive method for measuring cardiac rhythm and refers to the beat-to-beat variation in heart rate. It is the result of complex interactions between the autonomic nervous system, endocrine influences, and vasomotor and respiratory centers. The variation in cardiac rhythm has mainly been suggested to be of nonlinear deterministic nature rather than due to stochastic noise.
