Processing the abdominal fetal ECG using a new method

Abstract

The performance of the method described above has been assessed in clinical trials. Comparing the results with those obtained using the earlier techniques of abdominal ECG processing showed a mean increase in the detection rate of the fetal QRS complexes of about 60%. When compared to fetal heart frequency recordings using ultrasonocardiography or phonocardiography the new method shows an important improvement with respect to the evaluation of short term variations of heart frequency.In addition to a bad signal to noise ratio the analysed abdominal signal showed a high rate of coincidence between maternal and fetal QRS complexes. Using simple threshold logic the measurement is obtained if the maternal ECG is subtracted prior to the threshold analysis of the signal. However, the necessary reliability is only achieved when both the maternal ECG is eliminated and a correlation analysis of the residual signal is performed. Comparing the FHF computed simultaneously from the scalp-lead ECG (A) and the abdominal ECG (8) shows that in most cases there is no loss of information when using the new non-invasive technique. In conclusion, it can be stated that the reliability of 'beat-to-beat' measurement of the fetal heart frequency could be significantly improved by employing the new analysis procedure. the resulting FHF curve cannot be employed clinically. An improvement of the measurement is obtained if the maternal ECG is subtracted prior to the threshold analysis of the signal. However, the necessary reliability is only achieved when both the maternal ECG is eliminated and a correlation analysis of the residual signal is performed.