IMPROVEMENT OF RESOLUTION IN MEASUREMENT OF ELECTROCARDIOGRAM RR INTERVALS BY INTERPOLATION

The measurement of successive RR intervals, obtained from the electroc ardiogram (ECG), is the basis of any subsequent method for the assessm ent of variations in heart rate, for example using intervalograms, his tograms, trend curves, spectral analysis, etc. The accuracy of measure ment directly depends on the sampling rate used for the acquisition of the ECG signal. Depending on specific applications, rates down to 128 Hz-are not uncommon. This considerably limits the resolution if RR in terval data are to be derived. Interpolation is often employed for sol ving problems of this tyke. Linear, cubic and spline interpolations, o btained directly from the MATLAB software product, were applied and co mpared for the purpose of RR interval measurement. The cubic method wa s found to combine the improvement of resolution (+/-1 ms) at sampling rates successfully dawn to 100 Hz, with a rapid operating speed. Comp arison examples are given. with ECG signals acquired with 1000-Hz, 16- bit sampling. (C) 1997 Published by Elsevier Science Ltd.