Instantaneous heart rate: should RR-intervals be resampled?

RR-interval sequences (tachograms) represent heart rate variability discretely. When time series representations of instantaneous heart rate (IHR) are required, tachograms are often resampled into a time series. This paper demonstrates that traditional RR-interval resampling is often inconsistent with the time domain constraints of the tachogram. A general technique, called frequency-modulated phase-interpolation (FMPI), is presented that preserves the time domain constraints. Results of FMPI in the synthesis of ECG signals with accurate event-interval reconstruction are shown. Discussion of the model against IPFM and the heart timing signal is presented. Consequences of the IHR reconstruction perspective to the spectral characterization of heart rate variability are also introduced.