Fetal heart rate detection in multivariate abdominal ECG recordings using non-linear analysis

A novel three-stage methodology for the detection of fetal heart rate (fHR) from multivariate abdominal electrocardiogram (ECG) recordings is introduced. In the first stage, the maternal R-peaks and fiducial points (maternal QRS onset and offset) are detected. Maternal fiducial points are used to eliminate the maternal QRS complexes from the abdominal ECG recordings. In the second stage, two denoising procedures are applied to enhance the fetal QRS complexes. The phase space characteristics are employed to identify fetal heart beats not overlapping with the maternal QRSs which are eliminated in the first stage. The extraction of the fetal heart rate is accomplished in the third stage, using a histogram based technique in order to identify the location of the fetal heart beats which overlap with the maternal QRSs. The methodology is evaluated on simulated and real multichannel ECG signals. In both cases, the obtained results indicate high performance; in the simulated ECGs the accuracy ranges from 74.21-100%, depending on the employed SNR, while in the real recordings the average accuracy is 94.08%.