Differences in QRS locations due to ECG lead: Relationship with breathing

Abstract

Results of heart rate variability analysis depend on the accuracy of the RR time series that is measured only in one lead of the ECG. RR time series can subtly change from lead to lead. We have obtained the ECG of 21 healthy subjects in a quiet measurement, sampled at 5 kHz and from the I and II standard leads. For each subject a total of 60 minutes was measured. The QRS complexes in both leads have been detected using a conventional QRS detector plus a further refinement using a matching template. Differences between the locations of the QRS complexes have been quantified and compared with the breathing signal of each subject as well as the derived RR time series. The typical uncertainty in the fiducial points and RR time series is usually below 1 ms and the errors are modulated by breathing. © Springer International Publishing Switzerland 2014.