Electrocardiographic changes following umbilical cord occlusion in the midgestation fetal sheep.
BACKGROUND
Clinical studies show that analysis of the fetal electrocardiographic (FECG) ST waveform at term gives important information on the myocardial response to intrapartum asphyxia. However, it is not known whether the preterm fetus responds in a similar fashion. The objective of the present study was to evaluate the FECGST response to umbilical cord occlusion in the preterm fetal sheep.


METHODS
Fetal sheep at midgestation were subjected to 25 min umbilical cord occlusion (n = 7) and compared to controls (n = 5). Changes in the FECGST waveform were recorded together with arterial blood pressure, heart rate, and acid base status during the occlusion and for 3 days afterward.


RESULTS
Umbilical cord occlusion resulted in immediate bradycardia (control: 187 +/- 7 bpm versus occlusion: 102 +/- 7 bpm), hypertension (control: 43.2 +/- 1.1 mmHg versus occlusion: 59.8 +/- 2.2 mmHg), and an initial increase in the T/QRS ratio (control: 0.10 +/- 0.02 versus occlusion: 0.60 +/- 0.10, P < 0.001), followed by hypotension (21.7 +/- 1.2 mmHg), normalization of the T/QRS ratio, and in some cases the development of negative T waves toward the end of the occlusion.


CONCLUSIONS
These studies show that the midgestation fetal sheep has the capacity to react to umbilical cord occlusion with a significant increase in the amplitude of the ST waveform together with an augmentation of blood pressure, which then subsides as the occlusion continues. The appearance of negative ST segment appears to signify significant cardiac dysfunction. The characteristic progression of ST-waveform changes in response to umbilical cord occlusion in midgestation fetal sheep, suggests that monitoring the ST waveform may contribute clinically important information also in the preterm individual.
Welin
Anna-Karin
AK
Department of Obstetrics and Gynecology, Perinatal Center, University of Göteborg, SE-416 85 Göteborg, Sweden. anna-karin.welin@telia.com
Blad
Sofia
S
Hagberg
Henrik
H
Rosén
K G
KG
Kjellmer
Ingemar
I
Mallard
Carina
C
D000818:Animals; D001237:Asphyxia / Q000150:complications / Q000196:embryology* / Q000503:physiopathology*; D001795:Blood Pressure Determination; D003251:Constriction, Pathologic; D004195:Disease Models, Animal; D004562:Electrocardiography; D005260:Female; D005323:Fetal Monitoring / Q000379:methods*; D006340:Heart Rate, Fetal; D006439:Hemodynamics; D017202:Myocardial Ischemia / Q000175:diagnosis / Q000196:embryology / Q000209:etiology; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012307:Risk Factors; D012680:Sensitivity and Specificity; D034561:Sheep, Domestic; D014470:Umbilical Cord / Q000473:pathology