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Published on: June 29, 2013
Parameters influence on acceleration and deceleration capacity based on trans-abdominal ECG in early fetal growth
Tamara Stampalija1, Daniela Casati2, Marcella Montico3
1Unit of Prenatal Diagnosis, Institute for Maternal and Child Health, IRCCS Burlo Garofolo, Trieste, Italy.
Insights
The parameter T=9 in phase-rectified signal averaging (PRSA) best distinguishes fetal heart rate patterns in intrauterine growth restriction (IUGR) fetuses. This method shows significant differences in very preterm fetuses compared to appropriate for gestational age (AGA) fetuses.
Area of Science:
- Fetal Medicine
- Cardiology
- Signal Processing
Background:
- Intrauterine growth restriction (IUGR) is linked to altered autonomic nervous system regulation of fetal heart rate variability (fHRV) due to chronic nutrient deprivation and hypoxemia.
- Phase-rectified signal averaging (PRSA) is an algorithm used to quantify fetal heart rate's average acceleration and deceleration capacity (AC/DC), identifying periodic patterns.
Purpose of the Study:
- To evaluate the influence of the parameter T on PRSA computation for trans-abdominally acquired fetal ECG (ta-fECG).
- To assess PRSA's effectiveness in differentiating early IUGR (<34 weeks) from appropriate for gestational age (AGA) fetuses across different gestational age epochs.
Main Methods:
- Calculated AC/DC using PRSA for T values ranging from 1 to 45 on fetal RR intervals derived from ta-fECG.
- Analyzed data from 22 IUGR and 37 AGA fetuses in two gestational age groups: very preterm (≥26 to <30 weeks) and preterm (≥30 to <34 weeks).
Main Results:
- Significantly lower AC/DC in IUGR compared to AGA fetuses for all T values ≥5 (p<0.05).
- T=9 yielded the highest area under the receiver operating characteristic curve (AUC) for identifying IUGR (AUC AC-T9: 0.87, AUC DC-T9: 0.89).
- AC/DC were significantly lower in very preterm IUGR fetuses compared to preterm IUGR fetuses (p<0.05), with no differences in AGA fetuses.
Conclusions:
- The PRSA parameter T=9 is optimal for discriminating fetal heart rate AC/DC between IUGR and AGA fetuses before 34 weeks of gestation.
- The diagnostic accuracy of PRSA with T=9 surpasses that of short-term variation methods.
- Observed significant differences in AC/DC were more pronounced in the very preterm gestational age epoch.
Objective:
Intrauterine growth restriction (IUGR) is characterized by chronic nutrient deprivation and hypoxemia that alters the autonomous nervous system regulation of fetal heart rate variability (fHRV). Phase-rectified signal averaging (PRSA) is a new algorithm capable to identify periodic and quasi-periodic patterns of HR, and which is used to quantify the average acceleration and deceleration capacity (AC/DC) of the heart. The computation of AC/DC depends on the parameters T and s, which we set so that s=T. T and s determine the periodicities that can be detected (the larger T the smaller the frequency of oscillations for which the method is most sensitive). The aim of the study was to evaluate the influence of the parameter T on PRSA computation, based on trans-abdominally acquired fetal ECG (ta-fECG), in early IUGR (<34 weeks of gestation) at two different gestational age epochs.
Study Design:
AC/DC were calculated for different T values (1÷45) on fetal RR intervals derived from ta-fECG in 22 IUGR and in 37 appropriate for gestational age (AGA) fetuses matched for gestational age, in two gestational age epochs: very preterm group (≥26÷<30 weeks), and preterm group (≥30÷<34 weeks), respectively.
Results:
AC/DC were significantly lower in IUGR than in AGA fetuses for all T≥5 values (p<0.05). The best area under the receiver operating characteristic curve (AUC) in identifying IUGR at time of recording was observed for T9 [AUC AC-T9 0.87, 95% confidence interval (CI) 0.77-0.96; and AUC DC-T9 0.89, 95% CI 0.81-0.98), and in range of T 7÷15. In the same T interval, AC/DC were significantly lower in very preterm than in preterm IUGR group (p<0.05), while there were no differences in AGA fetuses at two gestational age epochs (p>0.05), respectively. The AUCs of AC-T9 and DC-T9 significantly outperformed that obtained by short-term variation (AUC 0.77, 95% CI 0.65-0.90; p=0.009 and p=0.003, respectively).
Conclusions:
Our study shows that within the range of T parameter 1÷45, T=9 proved to be the best value to discriminate the AC and DC of the fetal heart rate of IUGR from AGA fetuses prior to 34 weeks of gestation. These significant differences are emphasized in very preterm gestational age epochs.
