Leslie William Organ

The pre-ejection period of the fetal heart: Patterns of change during labor

Abstract The pre-ejection period (PEP) of the cardiac cycle, fetal heart rate, and uterine contractions were monitored in a series of unselected patients in labor to assess the practicality of our current Doppler ultrasound technique for detecting PEP and to relate any change in PEP to fetal status and fetal heart rate patterns. The results showed that with the dedicated efforts of a research team it is possible to obtain PEP patterns during labor, but that for general use PEP monitoring cannot yet be considered practical. However, its potential value was demonstrated with the observation that PEP changed clinically in a manner predicted in experiments with stressed fetal lambs—umbilical cord compression prolonged PEP and hypoxemia shortened it. These changes are essentially independent of heart rate and therefore PEP can be considered as an independent parameter for fetal assessment.

The pre-ejection period of the fetal heart: Detection during labor with Doppler ultrasound

Abstract The use of Doppler ultrasound, together with the fetal electrocardiogram, was investigated as a method of determining the pre-ejection period (PEP) of the fetal cardiac cycle during labor. The PEP, which is related to myocardial contractility, is defined as the period from the beginning of the QRS complex to the opening of the aortic valve. It was found that by suitably filtering the detected ultrasound signal, in the range of 750 to 1,000 Hz, a pulse corresponding to the aortic valve opening was obtained more often than for any other valvular movement (in 77 per cent of the subjects studied). The time of occurrence of this pulse was stable from beat to beat as well as over longer periods of time so that the calculation of PEP based on its onset was felt to be reliable. The average value of PEP was 73 msec., with a standard deviation of 10 msec. The intrapartum availability of the PEP to a degree greater than has been considered possible should allow its consideration as a parameter for following changing fetal status during labor.

A computer system for stereotaxic neurosurgery.

Abstract An interactive online computer system has been developed to process data collected during stereotaxic neurosurgical procedures, in order to facilitate more accurate localization of subcortical target sites. Responses evoked by electrical stimulation during thalamotomies are pictorially depicted on a template representative of the thalamic section being operated upon. This enables comparison of the evoked physiological responses with the accepted somatotopographic architecture of the thalamic area by visual inspection. New computer techniques are presented which minimize surgical complications due to the variability in brain dimensions between patients, and correct for errors due to misalignment of the stereotaxic apparatus.

Physiological Guidelines for the Localization of Lesions by Percutaneous Cordotomy

Spinothalamic tractotomy, theorectically, is an ideal operation for the relief of intractable pain. But not until the introduction of the percutaneous technique by Mullan et al. (1963) could its benefits be extended to the majority of cancer patients; for most of them are too ill for open surgery. Moreover the precision of the new technique increases its effectiveness and at the same time minimizes complications.

Measurement of the pre-ejection period during labor with the use of arterial pulse time.

A new fetal parameter, the arterial pulse time, is described. It is the time from the onset of the fetal electrocardiographic recording to the arrival of the arterial pulse wave recorded at the fetal head. Since arterial pulse time differs from the pre-ejection period by only an apparently constant value, it is proposed as a potential method for obtaining the pre-ejection period during labor.

Computerized Graphic Display of Results of Subcortical Stimulation During Stereotactic Surgery

An on-line computer programme is described and illustrated which is capable of displaying graphically in the form of Woolsey-type figurine charts stimulation-induced responses obtained during stereotactic surgery. Not only can these data then be optimally utilized for lesion localization but also the programme includes facilities for a variety of types of analysis of the tape-stored data pooled from all patients studied.