Cardiac systolic time intervals and other parameters of myocardial contractility as indices of fetal acid-base status.
Electronic fetal heart rate monitoring has become the standard method for the assessment of fetal status during labour. Unfortunately, the hoped-for benefit from implementation of this technique has not been realized. The non-specific nature of FHR changes has led to undesirable side-effects, especially an increase in inappropriate operative interventions. Thus, there is an obvious need for methods which will improve upon the accuracy of FHR monitoring. There is substantial evidence for a tight coupling of fetal acid-base balance and myocardial contractility. This relationship has been established in experimental animal studies where fetuses were gradually rendered hypoxic and acidaemic while myocardial contractility was assessed by dP/dtmax and end-systolic elastance (Ees). Furthermore, the correlation between pH and indices of contractility extends over the entire range of clinical importance rather than being a terminal event. Systolic time intervals have long been recognized as good indicators of myocardial contractility. Recent advances in technology, have made their measurement in the human fetus by non-invasive means feasible. Substantial evidence has been accumulated, from both animal and human studies, to indicate that fetal STIs and especially the PEP and PEP/VET ratio are good predictors of fetal acid-base status. Other indices of fetal myocardial function, such as Doppler-derived aortic acceleration time and peak acceleration, have also emerged as having a potential benefit in monitoring the fetus before and during labour. Fetal STIs and other indices of myocardial contractility may be valuable adjuncts to FHR monitoring. During labour, STIs may prove to be of value both to elucidate equivocal FHR patterns and to detect fetal hypoxaemia and acidaemia. For this to occur, the sensitivity and specificity have to be determined by large-scale prospective clinical trials comparing STIs to current monitoring methods.
Lewinsky
R M
RM
Department of Obstetrics and Gynaecology, Bnai Zion Medical Center, Technion Institute of Technology, Haifa, Israel.
D000137:Acid-Base Imbalance / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D015148:Cardiotocography; D002986:Clinical Trials as Topic; D005260:Female; D005311:Fetal Hypoxia / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D006340:Heart Rate, Fetal; D006801:Humans; D009200:Myocardial Contraction; D011247:Pregnancy; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors