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ECG analysis: the next generation in electronic fetal monitoring?
Dr. Devoe is Brooks Professor and Chairman of Obstetrics and Gynecology and Director of Maternal-Fetal Medicine at the Medical College of Georgia, Augusta, Ga.
As fetal electrocardiograph analysis comes of age, there's a growing body of research to suggest it can serve as a valuable adjunct to traditional EFM. Here's an expert review on the technology and the data supporting it.
It's been more than three decades since clinicians started using electronic fetal monitoring (EFM) to assist during deliveries. When the technology was first put into widespread use, we had hoped it would significantly reduce perinatal mortality and complications, especially neurologic damage. Unfortunately, clinical experience has proven otherwise; in fact, [since the introduction of EFM, rates of operative delivery have significantly increased.1 ]
In the mid-1990s, an expert panel convened by the National Institute of Child Health and Human Development (NICHD) developed a set of standard terms to help clinicians interpret FHR patterns.2 In the decade since that terminology was introduced, there has been little apparent improvement in any of the outcomes associated with EFM.3
To enhance the performance of EFM, several adjuncts have been developed, including intermittent fetal scalp blood (FSB) pH and, more recently, fetal pulse oximetry (FPO). While FSB pH improves the specificity of FHR pattern interpretation, it is rarely used in the United States.4 And a recent randomized trial comparing EFM and FPO to standard EFM alone has failed to show that FPO improved perinatal outcomes or lowered cesarean delivery rates.5
The science behind the STAN system
In adult medicine, myocardial hypoperfusion that's been induced by coronary artery insufficiency can be detected during a graded exercise test by ECG changes such as elevated T-waves or depressed ST segments. [In fetal medicine, FECG analysis provides a window into the response to the stress of labor and is based on a considerable amount of experimental animal data.7 ]
Development of the STAN clinical system
The development of the current STAN system is based on clinical studies conducted during the 1980s. These studies validate the basic physiologic findings explained above. Several technological advances over the years have allowed application of the experimental findings to the eventual development of the STAN monitors, including: