Non-invasive evaluation of opening and closing timings of the cardiac valves in the fetal cardiac cycle

In this study, we propose a non-invasive system to recognize the timings of fetal cardiac events on the basis of analysis of fetal ECG and Doppler ultrasound signal together. Fetal ECG was extracted from transabdominal ECG (10 normal subjects, 38-41 weeks of gestation) using blind source separation with the reference signal. Multiresolution wavelet analysis enabled the frequency contents of the Doppler signals to be linked to the opening(o) and closing(c) of the heartpsilas valves (Aortic (A) and mitral(M)). M-mode, B-mode and pulsed Doppler ultrasound were used to examine and verify the timings of opening and closure of aortic as well as mitral valves. The time intervals from Q-wave of QRS complex of fetal ECG to opening and closing of aortic valve, i.e. Q-Ao and Q-Ac were found to be 75.0plusmn11.9 (msec) and 221.6plusmn29.0 (msec) respectively. As for the mitral valve, Q-Mc and Q-Mo were found to be 45.0plusmn18.9 (msec) and 301.6plusmn20.7 (msec) respectively.