Cardiac electromechanical dissociation in the hypoxic fetal sheep may have clinical implications.
OBJECTIVE
Our purpose was to determine the sequence of fetal cardiac electrical and mechanical events associated with acute hypoxic acidemia and to correlate those events with terminal fetal heart rate patterns preceding fetal death.


METHODS
Eight acutely catheterized fetal sheep were rendered hypoxic by placental embolization with microspheres until fetal death occurred. The fetal electrocardiogram, Doppler cardiogram, left ventricular and aortic pressures, and fetal heart rate were continuously recorded.


RESULTS
All eight fetuses showed a terminal bradycardia consisting of two phases: an initial phase of falling ventricular pressures, culminating in mechanical asystole, and a subsequent phase after asystole during which the electrocardiographic signal persisted for an average duration of 15.2 +/- 8.7 minutes (range 3.1 to 32.4) and triggered a Hewlett-Packard 8040A monitor to show a heart rate pattern.


CONCLUSIONS
The phenomenon of cardiac electromechanical dissociation may be occurring during similar terminal bradycardias that are observed in human labor and explains the delivery of a fresh stillbirth in spite of the recording of an electrocardiographic signal from a scalp electrode.
Lewinsky
R M
RM
Department of Obstetrics and Gynaecology, Mount Sinai Hospital, University of Toronto, Ontario, Canada.
Oppenheimer
L W
LW
Morrow
R J
RJ
Adamson
S L
SL
Farine
D
D
Ritchie
J W
JW
D000818:Animals; D001696:Biomechanical Phenomena; D002245:Carbon Dioxide / Q000097:blood; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D005318:Fetal Heart / Q000503:physiopathology*; D005311:Fetal Hypoxia / Q000503:physiopathology*; D006340:Heart Rate, Fetal; D006863:Hydrogen-Ion Concentration; D010100:Oxygen / Q000097:blood; D011247:Pregnancy; D012756:Sheep
D002245:Carbon Dioxide; D010100:Oxygen