Detection of End of T-wave in Fetal ECG Using Recurrence Plots

Automatic detection of fetal ECG features can assist in diagnosis of fetal cardiac complications and may reduce the time required for diagnosis. Detection of the end of the repolarization period wave in ECG has been proven challenging due to its low amplitude and low frequency range. The prolongation of end of T-wave is associated with sudden cardiac death, thus, methods that can accurately pinpoint it is highly desirable for early diagnosis of cardiac diseases. In this paper, a technique based on recurrence plots is developed for the detection of end of T-wave. The developed technique was tested on maternal ECG (mECG), fetal scalp ECG (fsECG) and non-invasive fetal ECG (nfECG) records. The technique was able to detect end of T-waves in all of the mECG beats, 75% of the non-invasive fECG beats (verified by simultaneously captured doppler ultrasound signals) and 78% of the fsECG beats. Detection of fECG signals were more challenging than mECG signals due to the noise and their low amplitude T-waves.