Background: ECGs from neonates have a higher frequency content than adult ECGs. However, it is arguable if a diagnostic electrocardiograph needs a bandwidth >0.05-150 Hz for neonatal ECG recording.
Goal: The aim of the study was to determine the effect of using different filter bandwidths on neonatal ECGs initially sampled at a rate of 8000 samples per second (sps) (which permits the use of a signal bandwidth much higher than 150 Hz) and to consider implications for routine ECG recording.
Methods: 48 ECGs were recorded from healthy neonates (0-48 hours postnatal) at Princess Royal Maternity Hospital, Glasgow on a Burdick 8500 electrocardiograph. The frequency response of the machine was carefully checked. All 8 independent leads, I, II, V1 – V6 with V4R replacing V3, were sampled at 8000 sps. Average peak-peak QRS amplitudes during the 10sec recording were measured in all 8 leads using specially developed software with results obtained at the full bandwidth of the ECG machine regarded as the reference.
Results: The full bandwidth of the 8500 was verified as 0.05 – 540Hz. It was found that, at the bandwidth most commonly used, namely 0.05 -150 Hz (after the full bandwidth signals were processed by a 150-Hz FIR low-pass filter at 8000 sps), the number of QRS amplitudes <95% of the reference for 48 records was leads I(7), II(8), V4R(1) and V6(3).
Thus 4.9% (19/384) of the average beats were <95% of the reference. The lowest amplitude is 89.3%. The gross QRS amplitude was 98.80% ± 1.81%.
Conclusion: If the usual ECG recording bandwidth of 0.05 – 150 Hz is used, 4.9% of ECG amplitudes are reduced by 5-11% compared to the reference of 0.05 – 540Hz. It remains to determine if this attenuation is clinically significant.