Alterations in the fetal electrocardiogram as a sign of fetal asphyxia--experimental data with a clinical implementation.

Although considerable progress occurred with the introduction of electronic fetal monitoring it is now clear that the fetal heart rate alone does not provide optimal information about the fetus. Thus, a question arises whether additional information could be gained by further analyzing the fetal ECG as this is likely to be the parameter presently most easily accessible during labor. For the past 10 years work by our group in Göteborg has been focused on the evaluation of ST waveform changes in the fetal ECG as a method for fetal surveillance. Fetal hypoxemia results in a reproducible pattern of changes with the progressive increase in T wave amplitude as the main response. The ratio between the amplitude of the T wave and QRS complex, the so called T/QRS ratio, quantifies this T wave alteration. Considerable information has been gained, using this parameter, by conducting experiments on the fetal lamb and guinea-pig. The closest relationship was found between the rate of breakdown of myocardial glycogen and the increase in T wave amplitude. This utilization of myocardial glycogen during hypoxia is stimulated by beta-adrenoreceptors. The data also indicate a close link between the adrenaline surge and the appearance of high T waves in the fetal ECG. Relating T wave changes to other biochemical parameters shows a relationship during marked asphyxia with the appearance of a metabolic acidosis which is a result of an increase in blood lactate concentration.(ABSTRACT TRUNCATED AT 250 WORDS)