Requirements for optical recordings of cardiac beat to beat variabilities
Heart rate variability describes the variation in time intervals between consecutive heart beats and serves as a prognostic marker in cardiac and non-cardiac diseases. The experimental setup used for this study enables electrical as well as optical studies on the excitability of cardiac tissues or cells under control as well as treatment conditions. Whereas electrical recordings offer the detection of temporal intervals, optical methods give additional information about the tissue contraction from the amplitude domain of the recorded signals. In this study, we investigate the influence of optical drifts and power supply noise, both of which may degrade the recorded signals, on nonlinear parameters used for quantitating variabilities. Additionally, the appropriate frame rates for video recordings are evaluated.