Staff Scientist Children's National Hospital Children's National Hospital Washington, District of Columbia, United States
Background: Visualizing the fetal electrocardiogram (fECG), including waveforms and cardiac time intervals (CTIs) is important to manage high-risk pregnancies, diagnose and treat rhythm disorders, and decrease the risk of still birth. Currently, consistent and accurate measurement of fECG is impeded by filtering techniques and a low signal to noise ratio.
Objective: We present a novel automatic approach based on the frequency domain and an averaging technique to attenuate maternal ECG (mECG) and extract fECG with visible CTIs. We compared the quality score of the cardiac appearance as well as intra- and inter-observer variability of the current approach with a previously proposed time domain-based adaptive interference cancellation (AIC) technique.
Design/Methods: To evaluate our method, we manually selected 16 good quality datasets (obtained under IRB approval with patient consent) with three or more consecutive beats acquired by a device developed by the Johns Hopkins University Applied Physics Laboratory and the School of Medicine. This device records both mECG and abdominal ECG (aECG) signals (mixture of fECG and mECG). The data was acquired from singleton pregnant women trans-abdominally in gestational ages 16-41 weeks at Johns Hopkins Hospital and the Children’s National Hospital Cardiology Clinic. The coherent components between mECG and aECG were identified using spectral coherence and they were subtracted in the frequency domain, leaving fECG as residual. The fECG signal was then transformed back to the time domain and enhanced by averaging the cardiogram using 0.5s of data prior and 0.6s of data post to each R-wave (Figure 1). Two fetal cardiologists blindly reviewed the results of our new approach and the AIC method on two different days and assigned a scale value of 1-5 based on the quality of the QRS, PR, and QTc intervals (Table 1).
Results: The results in Table 2 show that the fECG signal obtained using the new approach yielded an average grade value of 3.89 ± 0.893 versus the AIC method with an average grade value of 3.156 ± 0.739 (Wilcoxon Rank Sum p-value <0.001). Conclusion(s): A novel methodology of frequency-based filtration with minimal averaging outperforms AIC (time-based approach) and provides fECG with an improved signal quality. Furthermore, it is automatic and produces more reproducible results. The method has potential for use in fECG acquisition and fetal CTI measurements in clinical applications.
Authors/Institutions: Pooneh Roshanitabrizi, Children's National Hospital, Washington, District of Columbia, United States; RB Govindan, Children's National Health System, Washington, District of Columbia, United States; Catherine Ingbar, Children's National Hospital, District of Columbia, District of Columbia, United States; Tyler Salvador, Children's National Hospital, Washington, District of Columbia, United States; Mary Donofrio, Children's National Medical Center, Washington, District of Columbia, United States; Kevin Cleary, Children's National Hospital, Washington, District of Columbia, United States; Anita Krishnan, Childrens National Medical Center, Washington, District of Columbia, United States
