Simultaneous acquisition of maternal and dual‐fetal electrocardiography with maternal haemodynamic monitoring in anaesthetized pregnant rats

Figures

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  FIGURE 1. Main equipment and custom‐built electrodes used for simultaneous maternal and dual‐fetal electrocardiography recording. (a) Main recording hardware, including the pressure control unit, preamplifier and PowerLab data‐acquisition system. (b) Custom‐built needle‐style electrodes used for maternal ECG and fetal ECG recordings. (c) The whole workstation with vibration control desks and Faraday cages.

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  FIGURE 2. LabChart Software interface used for maternal blood pressure, maternal ECG and dual‐fetal ECG acquisition and analysis. (a) LabChart interface, showing the blood pressure module (1), ECG analysis module (2) and HRV module (3). (b) Representative recording channels, showing maternal arterial blood pressure, maternal ECG, fetus‐A ECG and fetus‐B ECG.

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  FIGURE 3. Electrode placement for simultaneous maternal and dual‐fetal ECG recording in pregnant rats. (a) Schematic illustration of fetal electrode placement in two fetuses, one selected from each uterine horn. (b) Representative surgical images, showing electrode placement and lead routing. Abbreviations: E, earth; FA, fetus A; FB, fetus B; M, maternal; N, negative; P, positive.

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  FIGURE 4. Stability of maternal and dual‐fetal cardiovascular recordings during a 5 h acquisition period. (a) Representative recording of maternal arterial blood pressure (AP), maternal ECG and dual‐fetal ECG obtained from one dam and two fetuses. (a1) Expanded traces at 5:1 horizontal scaling for a 2 s recording at the beginning. (a2) Compressed traces at 100 000:1 horizontal scaling for a 5 h recording. (a3) Expanded traces at 5:1 horizontal scaling for a 2 s recording at the ending. (b) Group data showing mean arterial pressure (MAP) and HR of dams and fetuses at the first 30 min and last 30 min of recordings. n = 6 for dams and n = 12 for fetuses. HR was derived from the RR interval of the ECG.

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  FIGURE 5. ECG waveform analysis in dams and fetuses. (a) Representative ECG recordings showing the major waveform components, including the P wave and QRS complex, from the dam and two fetuses. (b) ECG analysis settings window. (c) ECG averaging view. (d) Representative ECG parameters obtained from one dam and her two fetuses. (e–g) Group data for heart rate, PR interval and RR interval. n = 6 dams or fetuses per group. Fetus A was selected from the right uterine horn and fetus B from the left uterine horn.

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  FIGURE 6. Power spectral density and heart rate variability analysis of maternal and fetal ECG signals. (a) Representative power spectral density/spectrogram settings (a1) and output (a2). (b) HRV settings window (b1) and representative report views from the dam (b2), fetus A (b3) and fetus B (b4). (c) Group data for representative HRV parameters, including RMSSD, HF power, LF/HF ratio and SDRR, obtained from maternal and fetal ECG. ECG: electrocardiogram; HF: high frequency power; HRV: heart rate variability; LF: low frequency power; RMSSD: root mean square of successive differences; SDRR: standard deviation of RR intervals.

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  FIGURE 7. Effects of maternal NA administration on maternal and fetal cardiovascular signals. (a) Representative recording (a1) of maternal arterial blood pressure, maternal ECG, and dual‐fetal ECG after intravenous NA (0.01 mg kg− 1), and group data (a2) showing HR and RR interval responses in dams and fetuses. (b) Representative power spectral density and spectrogram output (b1) and group data (b2) showing RMSSD and LF/HF ratio before, during and after NA administration. HR was derived from the RR interval of the ECG. n = 6 dams and n = 12 fetuses. Data are means ± SD. Abbreviations: HR, heart rate; NA, noradrenaline; NA effect, maximal NA effect; Post, after NA injection; Pre, before NA injection. LF/HF: low frequency power/high frequency power; RMSSD: root mean square of successive differences.

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  FIGURE 8. Effects of maternal verapamil administration on maternal and fetal cardiovascular signals. (a) Representative recording (a1) of maternal arterial blood pressure, maternal ECG and dual‐fetal ECG after intravenous Ver (0.1 mg kg− 1), and group data (a2) showing HR and RR interval responses in dams and fetuses. (b) Representative power spectral density and spectrogram output (b1) and group data (b2) showing RMSSD and LF/HF ratio before, during, and after verapamil administration. HR was derived from RR interval of ECG. n = 6 dams and n = 12 fetuses. Data are means ± SD. Abbreviations: HR, heart rate; Post, after Ver injection; Pre, before Ver injection; Ver, verapamil; Ver effect, maximal Ver effect.

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  FIGURE 9. Assessment of maternal cardiac electrical interference in fetal ECG channels. (a) ECG obtained with intentionally suboptimal earthing, showing maternal QRS‐related interference in the fetal channels (red arrows). (b) ECG recording with optimized earthing used for formal experiments: (b1) full recording; (b2, b3) magnified regions indicated by the dotted rectangles in (b1). Black, dark red and blue arrows indicate small maternal QRS‐related deflections superimposed on the P‐wave region, baseline and QRS‐wave region of the fetus A ECG.

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  FIGURE 10. Effect of adding the fetus A ECG recording channel on simultaneous dam and fetus B ECG recordings. (a) Full recording during activation of the fetus A ECG channel. (b, c) Magnified regions indicated by the dotted rectangles in (a). The asterisk indicates the transient artefact generated when the fetus A preamplifier was turned on. 1st and 2nd indicate the first two QRS complexes detected from fetus A after activation of the preamplifier. Pre and Post indicate dam and fetus B QRS complexes recorded before and after activation of the fetus A ECG recording channel.