PO-01-207 VERNIX CASEOSA DISTRIBUTION MODULATES NON-INVASIVE FETAL ECG SIGNAL: A COMPUTATIONAL STUDY

Abstract

Non-invasive fetal ECG (FECG) shows promise as a diagnostic method to monitor fetal health. However, extracting the fetal cardiac signal remains a challenge due to low signal-to-noise ratio. An important factor is a low-conducting layer which forms around the fetus from week 28 of gestation called the vernix caseosa (VC). We developed an anatomically detailed and biophysically accurate computational model of a pregnant torso to investigate the effects of the VC on the FECG. The model was constructed by combining geometries of a pregnant woman with a 24 week infant and a torso with ventricles (a). Ionic current properties of the maternal heart is modelled using the Ten Tusscher human ventricular cardiomyocyte model, while a modified version adapted to match fetal electrophysiology is used for the fetal heart. 22 distribution patterns of the VC was generated using combinations of 3 regions and 4 thickness. No VC case was used as control. Electrical propagation was simulated using the pseudo-bidomain formulation. Sinus rhythm was simulated with a baseline cycle of 500 ms and 450 ms for the maternal and fetal hearts, respectively. When VC was represented as homogeneous, changing the VC thickness from 0.5 mm to 3 mm resulted in reduction of QRS maximum amplitude from 6 x 10-5 to 6 x 10-6 mV (c). However, in the heterogeneous VC models, there is no significant difference in signal as thickness was changed (d). The location of the VC significantly affected the signal (e). VC only covering the head was almost identical to control with a relative difference measure of only 1.35%. However, introduction of VC on the back resulted in greatest difference in potential distribution with a relative difference measure ranging between 34.5 and 49%. We have developed a novel, highly-detailed computational model of a pregnant torso that shows how VC distribution affects the FECG. This model can be used to improve techniques in extracting FECG at different gestational stages.