Antepartal analysis of fetal heart rate variability by abdominal electrocardiography

Abstract

Antepartal analysis of fetal heart rate variability (FHRV) has been shown to be of value in predicting fetal distress in labor [8]. Abdominal fetal electrocardiograin (aFECG) is used äs a trigger signal in the statistical analysis of intervals and the differences between them [7]. The indices of variability thus obtained have a good correlation with indices calculated simultaneously from direct FECG [6,12]. Interval index (II) describes the long-term variability and differential index (DI) the short-term variability in this analysis. The main disadvantage of this analysis System is a fairly high failure rate of aFECG during the third trimester of pregnancy. Gestational age, the electrode position and the maternal position have been shown to affect the recordability of aFECG [l, 2, 3, 4, 9, 11]. On the other hand, maternal obesity, placental location and the state of the membranes have been shown not to have any effect on the quality of aFECG [l, 3, 9]. The aim of this study was to investigate how often FHRV analysis made by aFECG succeeds and what is the role of certain methodological factors in the recording procedure. Patients and methodsFHRV analyses were performed by a previously described method using an on-line microprocessor system [7]. The analysis was regarded äs a failure when less than 30% of the intervals detected were accepted in the analysis. Student's paired t-test (one-sided) was used to measure the significance of the results.2.2 Maternal position in FHRV analysis. The maternal supine vs. 90-degree lateral position was studied relating to the success rate and to the variability indices in 30 pregnancies. A five-minute analysis was fiist attempted in the supine position immediately followed by a 90-degree lateral position. The maternal supine and 15-degree lateral positions were similarly compared in 30 pregnancies.

Quantification of the Fetal Heart Rate Variability by Spectral Analysis in Growth-Retarded Fetuses

“…Using spectral analysis, it was demonstrated that a major part of HRV is caused by lowfrequency oscillators, whereas respiratory HRV is much lower in neonates than in adults [14][15][16]. Spectral estimates of the fetal HRV also show maximal power at the lower frequency bands [2,17,18].…”

“…The assessment of FHR variability and its significance in fetal well-being have re ceived increased attention in recent years [1][2][3]. Variations in heart rate are attributed to modulation of the depolarization rate of the sino-atrial node through a number of physiological mechanisms such as blood pressure control, thermoregulation or respi ration [4][5][6].…”

Heart rate variability and electrocardiogram changes in the fetal lamb during hypoxia and beta-adrenoceptor stimulation

“…[6] suggested that an epoch length of at least five minutes was necessary to obtain good estimates of short-term variability indices. However, KARINIEMI et al found a good correlation between one-minute and five-minute epochs for estimation of DI [18]. Long epochs are advantageous only if the indices can be assumed to be stationary throughout the epoch.…”

Analysis of neonatal heart rate variability by a microprocessor-based on-line system

“…We recently reported reference values for NHRV after normal labor and after elective cesarean section [7]. We have also shown previously that rejection logic limits have a considerable effect on the values of variability indices, albeit they are necessary in the quantitative analysis of a noisy signal as from an abdominal fetal electrocardiogram [6]. When reproducing the recorded neonatal electrocardiograms from magnetic tapes, we observed that, in addition to the infant's movements and crying, there are two further principal sources of error in neonatal heart rate tracings: the remote shadow trace caused by premature beats ( Fig.…”