Graphical and statistical techniques for cardiac cycle time (phase) dependent changes in interbeat interval

Cardiac cycle time effects refer to the relative lengthening or shortening of a single cardiac cycle as a function of when in the cycle brief sensorimotor events occur. These effects may provide short-latency measures of cardiac sensitivity to psychological events. Conventional representations have, however, failed to clearly separate changes in interbeat interval due to cycle time--i.e., phase dependent changes--from other types of change. This paper advocates a particular technique of plotting to solve these representation problems. Heartbeat timing is represented in real time and in the context of beats both preceding and following the event of interest. The plot, a phase-sensitive plot, conceptualizes phase-sensitive (cardiac cycle time) effects as a change in linear or higher order trend. Thus, an adaptation of trend analysis is proposed as an efficient statistical analysis that follows directly from the proposed representational technique.