Please take part of the latest US publication regarding ST Analysis: A Randomized Trial of Intrapartum Fetal ECG ST-Segment Analysis.

In 2005, the Food and Drug Administration (FDA) approved the STAN S31 device (Neoventa Medical) for use as an adjunct to conventional electronic fetal heart-rate monitoring for fetal ECG ST Analysis.

Following the FDA approval, the largest trial that took place in regards to the STAN method was the US RCT in which over 11,000 women participated.

The US RCT took place over a time span of four years and was supported by NICHD (National Institute of Child Health and Human Development). Neoventa did not participate in the monitoring of the study; and hence did not take part in the data collection, management, analysis or manuscript preparation process. The study consisted of a pilot phase and the randomized trial. It was conducted at 16 University-based clinical centers, each consisting of between 1 to 5 hospitals with delivery ward facilities; making up a total of 26 delivery wards in the study.

The providers were equipped with online training at the start of the pilot phase and most of the centers had 2 STAN monitors. As the study proceeded there is no knowledge of whether additional education was provided.

A total of 43,376 women were screened for inclusion, of whom 18,456 did not meet eligibility criteria and 13,812 declined participation. As a result a total of 11,108 women were randomly assigned to “open” (5532 women) or “masked” (5576 women) monitoring with fetal ST Analysis.

The cesarean section rate for the STAN arm of the US RCT was 16.9% and the masked arm (normal fetal heart monitor) was 16,2 %. In addition the operative delivery rate was 22.8% and 22.0%, respectively. Adverse events were rare and occurred with similar frequency in the two groups.

This result demonstrates that there was no significant difference between the two groups in the overall rates of cesarean delivery, or any operative delivery in a US population. Therefore the conclusion for this particular trial was that there was no benefit of the adjunctive use of ST Analysis in the US.

The first published response by Isis Amer-Wahlin and Anneke Kwee from the paper: Combined cardiotocographic and ST Analysis: A review

“There are some important differences between the study designs of the European trials and the US trials. In the FDA-approved US trial a simplified approach with a 3-category CTG classification system was chosen, thus assessing non reassuring FHR in one category instead of separating them into intermediary and abnormal as in the European 4-category guidelines. The aim was to simplify the interpretation of CTG & ST changes and reduce the risk for ambiguous data interpretation. However, major changes occurred in the US user guidelines affecting the decision to act based on ST-waveform changes as an adjunct to CTG analysis. The most obvious is that a 60′ rule has been included, stating that in case of an non re-assuring FHR for >60′ but no ST event, direct physician assessment of fetal state was required with intrauterine resuscitation, and if no improvement was observed, expeditious delivery was performed.

The statement in the US study protocol that could cause ST-analysis to be completely ignored was a paragraph stating the following: Do not rely solely on the appearance of an ST event marker to signal the need for obstetrical intervention. If you suspect, on the basis of FHR only and/or clinical data that the fetus is experiencing severe hypoxia, you should manage the patient accordingly despite the absence of an ST event marker. As a consequence, one would assume unnecessary interventions, especially in 2nd stage with the risk of neonates being affected due to emergency operative procedures. Furthermore, the following statement was also added in the US study protocol: In the presence of maternal fever and related infection, the fetus may have a blunted or no response to hypoxia, and ST events may fail to appear. Therefore, if the maternal temperature reaches 38.0C (100.4 F) or greater, management should be related to the FHR and the clinical situation. Thus the USRCT study protocol was substantially altered from the protocol approved by the FDA, and the guidelines at some decisive points different from those used in the previous STAN RCTs, making comparisons problematic.”

Abstract – Belfort et al.

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