Profound hypotension and associated electrocardiographic changes during prolonged cord occlusion in the near term fetal sheep.
OBJECTIVE
To determine whether the onset of fetal hypotension during profound asphyxia is reflected by alterations in the ratio between the T height, measured from the level of the PQ interval, and the QRS amplitude (T/QRS ratio) and ST waveform.


METHODS
Chronically instrumented near-term fetal sheep received complete occlusion of the umbilical cord for either 8 (n=6) or 15-min (n=9).


RESULTS
Cord occlusion led to sustained bradycardia and severe acidosis. Mean arterial blood pressure initially rose and then fell to a nadir of 32.6 +/- 2.6 mm Hg in the 8-min group and 9.3 +/- 1.0 mm Hg in the 15-min group (P < .001). The T/QRS ratio rose initially in parallel with mean arterial blood pressure and then reduced as mean arterial blood pressure fell but remained significantly above baseline. Biphasic ST waveforms during occlusion occurred in only 2 fetuses, but biphasic and negative waveforms occurred during reperfusion in the 15-min group, with a significant rise in troponin T levels (0.58 +/- 0.46 versus 0.02 +/- 0.01 ng/mL at 6 h, P < .01).


CONCLUSIONS
Elevation of the T/QRS ratio does not identify fetal hypotension during severe hypoxia, but abnormal waveforms in the recovery phase may indicate developing cardiac injury.
Wibbens
Bert
B
Department of Physiology and Obstetrics and Gynecology, University of Auckland, Auckland, New Zealand.
Westgate
Jenny A
JA
Bennet
Laura
L
Roelfsema
Vincent
V
De Haan
Harmen H
HH
Hunter
Christian J
CJ
Gunn
Alistair J
AJ
D000138:Acidosis / Q000209:etiology / Q000503:physiopathology; D000818:Animals; D001794:Blood Pressure; D003250:Constriction; D004195:Disease Models, Animal; D004562:Electrocardiography; D005311:Fetal Hypoxia / Q000503:physiopathology*; D005333:Fetus / Q000098:blood supply; D006340:Heart Rate, Fetal; D006439:Hemodynamics; D007022:Hypotension / Q000209:etiology*; D012756:Sheep; D020107:Troponin T / Q000032:analysis; D014470:Umbilical Cord
D020107:Troponin T