Chester B. Martin

INTERMITTENT FUNCTIONING OF THE UTEROPLACENTAL ARTERIES.

Abstract Repeated radioarteriographic placentograms carried out during uterine relaxation demonstrated alterations in the pattern of arterial entries visualized. Spurts appeared, or disappeared, independent of recorded myometrial activity or significant change in maternal blood pressure. The pattern of the variations was such that vasomotion of the arteries supplying the intervillous space seemed to be the most probable explanation for intermittent functional patency of the entries.

Normal Fetal Physiology and Behavior, and Adaptive Responses with Hypoxemia

The principal objective of antenatal testing is to detect fetal hypoxia before the fetus has suffered lasting harm. This article summarizes some of the mechanisms by which fetal oxygen consumption is maintained under normal conditions, and adaptations that occur in response to hypoxemia. Alterations in the fetal heart rate are prominent in the fetal response to hypoxemia and are the basis of some methods of antenatal testing. The principal mechanisms underlying these fetal heart rate changes are described. Adaptations in the distribution of blood flow that permit the fetus to deal with reduced oxygen levels are summarized. Developmental trends in fetal motility and behavior are outlined, and also how these are modified by fetal growth retardation and maternal diabetes. Fetal movements are suppressed during acute hypoxemia, but with gradually developing hypoxemia, normal movement patterns may continue until the fetus becomes acidemic. This may limit the use of these biophysical variables in antenatal testing.

Catheter‐directed thrombolysis for thromboembolic disease during pregnancy: a viable option

Anticoagulation with intravenous heparin has been the standard treatment for the management of gestational thromboembolic complications. Catheter-directed thrombolysis is an encouraging approach for the treatment of thromboembolic disease and has not been previously reported during pregnancy. One gravid woman with pulmonary embolism, critically ill, and hemodynamically compromised, and two gravid women with iliofemoral venous thrombosis, who failed to respond to standard treatment with intravenous heparin, were treated with catheter-directed urokinase. All three patients experienced rapid resolution of symptoms and successful pregnancy outcomes. In our three patients, catheter-directed thrombolysis for thromboembolic disease during pregnancy allowed rapid resolution of hemodynamic abnormalities and/or resolution of thrombus. Catheter-directed thrombolysis offered a reasonably safe alternative to prolonged medical management in these young, otherwise healthy, patients. Long-term, it may prevent the postphlebitic syndrome.

Spectral analysis of antepartum fetal heart rate variability from fetal magnetocardiogram recordings

Fetal heart rate variability was derived from fetal magnetocardiogram recordings in ten subjects at gestation ages 32-38 weeks. Maternal interference was negligible and R-wave detection was highly reliable. Oscillations suggestive of respiratory sinus arrhythmia (RSA) were prominent in many of the heart rate tracings. Spectral analysis was used to quantify heart rate variability and to examine the influence of the RSA-like oscillations on heart rate variability. The oscillations were associated with increased power in the frequency range 0.4-1.0 Hz (P < or = 0.05). Magnetic recording appears to offer significant advantages for investigation of beat-to-beat fetal heart rate throughout the latter stages of pregnancy.

Venous drainage of the placenta in rhesus monkeys: Radiographic studies

Abstract 1. 1. Drainage from the intervillous space of the placenta has been studied in 41 rhesus monkeys by serial and cineradioangiography following introduction of contrast medium into the maternal arterial bloodstream and directly into the intervillous space. 2. 2. When dye is injected into the intervillous space during uterine relaxation, it drains promptly through venous orifices into the uterine mural veins and thence to the pelvic veins (primarily the ovarian veins). 3. 3. During uterine contraction, there is partial or complete disappearance of dye from drainage channels, but the size and configuration of the placental blood pool is maintained. 4. 4. Inflow through arterial channels is halted during contractions, and any dye spurts which may have begun to form are arrested until the contraction peak has passed. 5. 5. The study indicates the controlling role played by arterial inflow in the maintenance of placental circulation. Continuing inflow provides the impetus whereby blood is eventually pushed toward orifices of exit and drained into uterine and pelvic veins. When intrauterine pressure is raised by myometrial contractions, both inflow and outflow are reduced or even halted though the volume of blood in the intervillous space appears to be maintained, thus providing for continued (though reduced) maternal-fetal exchange.

Assessment of fetal rhythm in complete congenital heart block by magnetocardiography.

We report high precision assessment of fetal rhythm in utero in a case of isolated congenital complete heart block using fetal magnetocardiography. The recordings reveal a remarkably strong tendency for the atria and ventricles to synchronize, which is manifested by the continual presence of ventriculophasic sinus arrhythmia and frequent episodes of accrochage and isorhythmic AV dissociation.

Atrial and ventricular fetal heart rate patterns in isolated congenital complete heart block detected by magnetocardiography

Atrial and ventricular fetal heart rate tracings from a patient with isolated congenital complete heart block treated with dexamethasone showed a remarkable degree of correlation and greater reactivity for the ventricular than the atrial fetal heart rate. Ventriculophasic sinus arrhythmia was present continually in the atrial fetal heart rate tracings.

Foetal magnetocardiogram amplitude oscillations associated with respiratory sinus arrhythmia

We show that oscillations at foetal breathing frequencies observed in foetal heart rate (FHR) tracings obtained from foetal magnetocardiogram (FMCG) recordings are often accompanied by synchronous modulation of FMCG signal amplitude. This implies an association between the FHR oscillations and foetal chest wall movements, corroborating the hypothesis that the oscillations are due to respiratory sinus arrhythmia.

Pharmacologic control of uterine contractility. In vitro human and in vivo monkey studies.

The exact cause and mechanism of the onset of labor are unknown but the theories are many. There is considerable evidence that prostaglandins are potent stimulants of uterine activity and may play a role in the onset of labor. Prostaglandin release may be the natural mediator of uterine contractions during labor. A group of anti-inflammatory compounds (aspirin-like compounds) that inhibit prostaglandin synthesis include indomethacin and fenoprofen. Inhibition of prostaglandin production is a reasonable approach to inhibiting premature labor. An excised muscle strip technique was used as a screening procedure for pharmacologic depression of human uterine activity in vitro, testing isoxsuprine, mesuprine, Alupent, ritodrine, indomethacin, and fenoprofen. The prostaglandin antagonists indomethacin and fenoprofen exhibited marked depressant activity. These drugs were further tested in an in vivo rhesus monkey preparation measuring uterine activity, maternal blood pressure, uterine blood flow, fetal heart rate, fetal blood pressure, and blood gases. Fenoprofen is effective in reducing uterine contractility without serious maternal or fetal side effects and shows promise as a clinically effective agent for pharmacologic control of premature labor.

A cyclic variation in thyroid-stimulating hormone in the fetal rhesus monkey

Morning and evening simultaneous fetal and maternal plasma samples were analyzed for thyroid-stimulating hormone. An a.m.-p.m. variation in fetal concentrations was identified, whereas the majority of the maternal values (28 of 32) were below the sensitivity of the assay. The importance of this cyclic fetal activity is discussed.