S. Vyas

Pulsatility index in internal carotid artery in relation to transdermal oestradiol and time since menopause

The protection afforded by postmenopausal oestrogen replacement against cardiovascular disease is not fully explained by changes in plasma lipoproteins. To investigate the effect of oestrogen on arterial tone, Doppler ultrasound was used to assess blood flow characteristics in the internal carotid arteries of 12 postmenopausal women. Patients were studied pretreatment and at weeks 4, 6, 9, and 22 of therapy with transdermal oestradiol 50 micrograms/day. The pulsatility index (PI), which is thought to represent impedance to blood flow distal to the point of sampling, was measured from the flow velocity waveform. 11 of the 12 patients were within 5 years of menopause; 1 was 8 years postmenopausal but had experienced bleeding 4 years after menopause. In the 11 women there was a highly significant correlation (r = 0.77) between time since menopause and baseline PI. A similar correlation (r = 0.74) was observed when the episode of postmenopausal bleeding was redefined as time of menopause in the twelfth patient. For all 12 patients, there was a significant negative correlation (r = -0.70) between change in PI during transdermal oestradiol therapy and mean of baseline plus week 22 PI value. For all correlations between changes in PI and time since menopause, the longer the time the greater the fall in PI. These results, and previous observations of a reduction in uterine artery PI with oestradiol treatment, suggest that oestrogen has a generalised effect on the arterial system.

Middle cerebral artery flow velocity waveforms in fetal hypoxaemia

Summary. In 81 small‐for‐gestational age fetuses (SGA) colour flow imaging was used to identify the fetal middle cerebral artery for subsequent pulsed Doppler studies. Impedence to flow (pulsatility index; PI) was significantly lower, and mean blood velocity was significantly higher, than the respective reference ranges with gestation. Fetal blood sampling by cordocentesis was performed in all SGA fetuses and a significant quadratic relation was found between fetal hypoxaemia and the degree of reduction in the PI of FVWs from the fetal middle cerebral artery. Thus, maximum reduction in PI is reached when the fetal PO2 is 2‐4 SD below the normal mean for gestation. When the oxygen deficit is greater there is a tendency for the PI to rise, and this presumably reflects the development of brain oedema.

Doppler examination of the middle cerebral artery in anemic fetuses

In 24 red cell isoimmunized pregnancies the fetal middle cerebral artery mean blood velocity increased with anemia. The blood velocity was not related to fetal blood PO2 and the relation of increased velocity to anemia was not affected by the pulsatility index. These findings suggest that the hyperdynamic circulation is a consequence of decreased blood viscosity.

Maternal abdominal pressure alters fetal cerebral blood flow

The aim of this study was to examine systematically the effect of fetal head compression caused by the ultrasound transducer on flow velocity wavaforms from the middle cerbral and internal carotid arteries. Minimal transducer pression should be exerced during doppler examination of foetal head to avoid an artefactual increase of impedence to blood flow, and thus, a high false negative rate in the detection of foetal hypoxia.

The use of color Doppler imaging for prenatal diagnosis of umbilical cord anomalies: Report of three cases

Color Doppler imaging could easily and rapidly detect the absence of an umbilical artery, despite the presence of oligohydramnios in one case and multiple cord loops involving a normal cord in the other case. In the third case, which on gray-scale imaging appeared as an indeterminate cystic structure of the cord, color Doppler imaging demonstrated a complex abnormal vascular pattern suggestive of an angiomyxoma.

Cerebral and renal artery blood flow velocity before and after birth

OBJECTIVE To document perinatal changes in cerebral and renal artery haemodynamics in premature growth-retarded and normal term infants. DESIGN Longitudinal study of individual infants. Doppler ultrasound measurements of blood flow velocity (BFV) in the middle cerebral and renal arteries were obtained before delivery, soon after delivery and during the first week of postnatal life. SETTING Teaching hospital obstetric and neonatal units. SUBJECTS 13 severely growth retarded infants born at 28-36 weeks gestation, and eight normally grown infants born at term. RESULTS In both groups, BFV in the cerebral artery was significantly lower in the first few hours after birth than in fetal life, but subsequently increased to reach pre-delivery values by the end of the first week. In contrast, BFV in the renal artery during the first postnatal day was not significantly different from fetal values, but it also increased during the subsequent week. In six of the preterm growth-retarded infants, fetal blood gases were measured in samples obtained by cordocentesis, and in these cases an increase in blood oxygen content at birth was documented. CONCLUSIONS Cerebral artery BFV falls at birth and is relatively low during the time that premature infants are at the greatest risk of developing periventricular haemorrhage.

Relations between the fetal circulation and pituitary-thyroid function.

Objective— To study the relation between changes in the fetal thyroid hormone and thyroid stimulating hormone (TSH) concentrations and alterations in the fetal circulation as assessed by Dopplcr ultrasound.