A new computer technique for continuous measurement of the pre-ejection period in the human fetus: physiologic significance of pre-ejection period patterns.

A new interactive computer graphics system was developed for continuous online or offline measurement of the pre-ejection period (PEP) in the human fetus during both the antepartum and the intrapartum period. A significant feature is the system's ability to accurately measure PEP from the onset of QRS complex to the beginning of aortic opening with a resolution of less than 2 milliseconds. Normal patterns of PEP prolongation were observed with fetal movement and occlusion of the umbilical cord, whereas progressive shortening of PEP was noticed with late decelerations associated with acute hypoxia. A pathologic pattern of PEP prolongation associated with late decelarations and poor heart rate variability was observed with chronic hypoxia and acidosis. These patterns suggest that continuous monitoring of PEP may be a useful adjunct to current monitoring methods when attempting to assess fetal cardiac performance and well-being.