Sampling frequency of the electrocardiogram for spectral analysis of the heart rate variability

A model is developed under nonrestrictive assumptions to describe the error made in the measurement of the R-R intervals from digitized ECGs. The first- and second-order statistics of the error are given in closed form as functions of the ECG sampling frequency only. The error contribution to the spectrum of the heart-rate variability (HRV) is found to be additive and mostly at high frequency. The relative spectral balance between HRV and error is important for correctly interpreting the results of any kind of HRV analysis and can be expressed in terms of the signal-to-noise ratio. A test is proposed to identify possibly dangerous situations. The test is simple and computationally efficient since it requires only the HRV variance