Quantification of fetal ST-segment deviations

Abstract

By fetal electrocardiogram (FECG) analysis it has been found that changes in the ST segment are associated with acid-base status, and thus fetus health state. Currently the most popular estimation of fetal ST-segment deviations is performed as ratio between T-wave height and QRS-complex amplitude using the STAN monitor. Thus, this evaluation is indirect because not directly derived from measurements on the ST segment. This study proposes a new procedure for an automated direct quantification of fetal ST-segment deviations, which are described in terms of ST-amplitude and ST-trend. Particularly, ST-amplitude corresponds to the maximum of the mean amplitude values obtained through a moving-average (15 ms) operation over the ST segment. Instead, ST-trend corresponds to the difference between the ST-segment amplitudes calculated in the first and the last of three intervals in which the ST segment is divided; thus, ST-trend sign indicates a ST-segment elevation (positive sign) or depression (negative sign). The procedure was evaluated on five direct FECG recordings (in https://physionet.org/physiobank/database/adfecgdb/). Mean values (over population) of ST-amplitude and ST-trend were 9.6 ± 5.5 μV and 1.4 ± 2.3 μV, respectively. All found values were validated by visual inspection of the magnified FECG plots.