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Biomedical subjects

J C Fouron

Publications and source records attributed to J C Fouron.

At least 55 records · Page 3Linked to original sources
PubMed1995

Reversible steroid-induced hypertrophic cardiomyopathy with left ventricular outflow tract obstruction in two newborns.

Dexamethasone is now frequently used in the treatment of bronchopulmonary dysplasia. We report on two premature babies receiving dexamethasone who developed symptomatic myocardial hypertrophy and left ventricular outflow tract obstruction, as documented by M-mode echocardiography and Doppler studies. A normal heart was recorded on echocardiography before and after dexamethasone treatment. The patients had no known risk factors associated with the development of obstructive hypertrophic cardiomyopathy.

Bronchopulmonary Dysplasia↗
PubMed1994

Flow velocity profile of the fetal aortic isthmus through normal gestation.

Experimental and clinical evidence have demonstrated that an increase in resistance to placental blood flow causes changes in aortic isthmic diastolic flow profile before any significant modification is observed in umbilical artery Doppler waveforms. To identify these abnormal flow profiles, the objective of this study was to document the normal flow profile in the aortic isthmus throughout pregnancy. The study included 81 normal fetuses from 17 to 39 weeks of gestation. On the isthmic flow profile, an index, named the balance index, was calculated: (peak systolic--end-diastolic velocities/forward--reverse flow velocity integrals). Before 20 weeks of gestation, a forward flow was recorded throughout the cardiac cycle and the diastolic deceleration phase was gradual and smooth. After 20 weeks, an incisura appeared at end-systole that progressively increased, and by 30 weeks of gestation a brief reverse diastolic flow was constantly recorded. The balance index increased slightly throughout gestation. Color flow mapping demonstrated that the reverse flow observed late in gestation in the isthmus was coming from the ductus arteriosus. In conclusion, the morphology of the Doppler flow velocity waveform of the fetal aortic isthmus changes with gestation. The proposed balance index may be useful in identifying fetuses with disturbed peripheral hemodynamics.

Analysis of Variance↗
PubMed1994

Hypoxemia and increased fetal hemoglobin synthesis.

Fetal hemoglobin (HbF) synthesis in children with congenital cyanotic heart disease was compared that in normal children. Children with hypoxemia had higher levels of hemoglobin, total HbF, and HbF synthesis. In these children there was also an inverse correlation between HbF synthesis and oxygen content, as well as between HbF synthesis and hemoglobin concentration. Thus hypoxemia increases HbF synthesis.

Child↗
PubMed1994

Myocardial, erythropoietic, and metabolic adaptations to anemia of prematurity.

We determined the effects of anemia of prematurity on myocardial, metabolic, and erythropoietic functions. Twelve anemic (hemoglobin range, 65 to 78 gm/L) infants without symptoms (gestational age, (mean +/- SD) 28 +/- 2 weeks; birth weight, 1178 +/- 326 gm) were studied at a postconceptional age of 35 +/- 1.6 weeks. All measurements were done before and 36 to 48 hours after a transfusion of packed erythrocytes. Cardiac output, heart rate, and myocardial function were assessed. Oxygen consumption, carbon dioxide production, resting energy expenditure, arterial oxygen pressure for 50% hemoglobin saturation, and the concentrations of erythropoietin and 2,3-diphosphoglycerate were also determined. After transfusion, increased hemoglobin level (75 +/- 4 to 150 +/- 16 gm/L) and decreased oxyhemoglobin affinity (20.8 +/- 1.7 to 23.6 +/- 2.1 gm/L; p < 0.05) caused a decrease in plasma erythropoietin concentration (from 21.1 +/- 6.2 to 5.8 +/- 1.5 mU/ml; p < 0.01). There was a decrease in heart rate (from 155 +/- 10 beats/min to 146 +/- 7 beats/min) and cardiac output (from 281 +/- 73 ml/kg per minute to 199 +/- 62 ml/kg per minute; p < 0.05). Myocardial function indexes, weight gain, and metabolic demands were normal before and after transfusion. These results suggest that oxygenation is adequately maintained in symptom-free infants with anemia of prematurity.

Anemia, Neonatal↗
PubMed1994

Doppler echocardiographic assessment of changes in the central circulation of the fetal sheep induced by maternal oxygen administration.

Eleven fetal sheep were studied to investigate if Doppler echocardiography could document redistribution of blood flow during maternal oxygen administration. Velocities through the pulmonary valve, aortic valve, common brachiocephalic trunk, aortic arch, descending aorta, umbilical and carotid artery were recorded before, during and after oxygen was delivered to the ewe by face mask. Indices of cardiac performance (shortening fraction, velocity of fiber shortening and systolic time intervals) were also obtained. The aortic arch was the only recording site where significant changes in mean velocity related to oxygen administration and withdrawal were demonstrated (p < 0.01). Changes in the velocity waveform suggesting an increase in cerebral vascular resistance during oxygen administration were found in the carotid artery. Thus, using Doppler velocimetry, the carotid artery and the aortic arch (equivalent to the human aortic isthmus) appear to be suitable sites to document changes induced by maternal oxygen administration.

Animals↗
PubMed1993

Reference values for Doppler velocimetric indices from the fetal and placental ends of the umbilical artery during normal pregnancy.

A range-gated Doppler ultrasound system combined with a real-time imaging system was used to determine arterial blood velocity values from the fetal and placental ends of the umbilical cord in 269 normal pregnancies between 17 and 40 weeks, menstrual age. The systolic-diastolic ratio (S/D), pulsatility index (PI), and resistance index (RI) were higher at the fetal end compared to the placental end of the cord. The individual differences in these Doppler indices, obtained between the fetal and placental recording sites, were inversely related to menstrual age: S/D: r = -0.38, p < 0.001; PI: r = -0.25, p < 0.001; and RI: r = -0.15, p < 0.01. After normalization for the angle of insonation, the peak systolic velocity was higher and the end-diastolic velocity was lower at the fetal than at the placental end of the cord. It is concluded that routine recordings for Doppler velocimetric indices should take into account the recording site on the umbilical cord in order to reduce methodological sources of variance, especially during midgestation. Furthermore, the data presented here in the form of the median and percentile values are proposed as normal reference values to facilitate this procedure.

Blood Flow Velocity↗
PubMed1993

Fetal central blood flow alterations in human fetuses with umbilical artery reverse diastolic flow.

Blood flow velocimetry studies in animal fetuses with reverse diastolic flow in the umbilical artery have shown marked changes in the fetal central circulation characterized by a retrograde diastolic flow in the descending aorta, and as far as the aortic arch, along with a significant forward diastolic flow in the arteries going to the brain. Documentation and the implications of this phenomenon in human fetuses, to date, have not been reported. Doppler echographic evaluations of the diastolic patterns in the umbilical artery, descending aorta, the aortic arch, and the common carotid artery were performed on 5 fetuses in whom reverse diastolic flow was observed in the umbilical artery. In all five cases reverse diastolic flow was observed not only in the umbilical artery but also in the aortic arch. In the carotid artery, however, a forward diastolic flow was always recorded. It can be concluded, by inference, that in these fetuses, the area of lowest resistance was no longer the placenta, as seen in normal conditions, but the cerebral circulation. Furthermore, in four fetuses the retrograde component of the flow profiles was more prominent in the aortic arch compared with the descending aorta, suggesting that, in diastole, blood was coming from the pulmonary artery through the ductus arteriosus.

Adult↗
PubMed1993

Determinants of the Doppler flow velocity profile through the mitral valve of the human fetus.

OBJECTIVE: A normal fetal flow velocity profile through the atrioventricular valves early in gestation is characterised by a higher late peak (A) than early peak (E) velocity waveform, whereas the E/A ratio is known to increase throughout pregnancy. This study aims firstly to identify which of the two variables, E or A, is the contributory factor to the increased E/A ratio and secondly to assess the relative influence of gestational age, heart rate, and stroke volume on the flow velocity profile through the fetal mitral valve. DESIGN: Eighty normal fetuses from 18 to 38 weeks of gestation were examined by Doppler echocardiography. The variables measured were E and A waves, the early and late flow velocity integrals (EI and AI), and the total filling velocity integral (TI). The ratios E/A and EI/AI were also calculated. Transvalvar flow was obtained by multiplying TI by mitral area. Associations between Doppler variables and gestational age, heart rate, and stroke volume were assessed by multifactorial Anova and simple or multiple stepwise regression analyses. RESULTS: The results showed that the heart rates found did not affect flow velocity variables. There were only weak correlations between both A and AI values and gestational age (negative) and volume load (positive). With the advance in gestation, a significant increase in the early filling E wave was found. The E wave was also positively correlated with stroke volume. CONCLUSION: Contrary to the accepted concept that changes in fetal E/A ratio are related to an improvement in ventricular compliance, this study shows that only the E wave changes. Although these results cannot establish whether changes in the ventricular relaxation process or volume load are responsible for the progressive increase of the E wave, indirect evidence suggests that ventricular relaxation is in fact the most important contributory factor.

Blood Flow Velocity↗
PubMed1993

Quantitative assessment of circulatory changes in the fetal aortic isthmus during progressive increase of resistance to umbilical blood flow.

BACKGROUND: This study investigated the effects of impairment to placental flow on flow patterns through the aortic isthmus because in the fetus, this vascular segment is the link between the parallel vascular systems perfused by the left and right ventricles. METHODS AND RESULTS: A progressive increase in resistance to blood flow through the placenta was created in seven exteriorized fetal lambs by mechanical umbilical vein compression. Blood flows were measured in the ascending aorta, pulmonary artery, aortic isthmus, and umbilical artery at baseline and at each compression level. The severity of the levels of compression was determined by changes in the flow profile through the umbilical artery. An increase in placental resistance causing a fall in umbilical blood flow of approximately 50% was associated with a retrograde diastolic flow through the aortic isthmus even though the diastolic flow through the umbilical artery remained forward. Because of the systolic predominance, however, the net flow in the isthmus was forward. With a more severe increase in placental resistance corresponding to a decrease of 75% in umbilical blood flow, the net flow through the isthmus approached zero. A strong positive correlation was found between the umbilical blood flow and the net flow through the aortic isthmus (r = .89). CONCLUSIONS: Variations in Doppler blood flow velocity waveforms and integrals of the aortic isthmus can be used as a sensitive indicator of the state of the umbilical circulation.

Animals↗
PubMed1993

Effects of increased resistance to umbilical blood flow on fetal hemodynamic changes induced by maternal oxygen administration: a Doppler velocimetric study on the sheep.

A fetal lamb model was used to investigate whether the effects of maternal O2 administration on fetal blood gases and hemodynamics were modified when the fetoplacental circulation was compromised by stepwise compression of both umbilical veins. At basal state, O2 administration increased O2 saturation (SaO2) and the pulsatility index (PI) of the carotid artery Doppler wave form (p < 0.01). The first compression decreased left ventricular output (-21 +/- 16%, mean +/- 1 SD, p < 0.01) and umbilical mean velocity (-22 +/- 28%, p < 0.01) but did not modify carotid pH, SaO2, or the PI in any of the arteries studied. At this level of compression, O2 administration increased carotid SaO2 (p < 0.01) but did not affect carotid PI. After a second compression, left ventricular output and umbilical mean velocity were even more reduced [-39 +/- 21% (p < 0.01) and -53 +/- 23% (p < 0.01), respectively]. With this compression, carotid pH, SaO2, and PI decreased, whereas umbilical and descending aorta PI increased. O2 administration at this level of compression increased carotid SaO2 (p < 0.01) but did not modify carotid PI. Throughout the three stages of the experiment, O2 administration did not affect umbilical PI, descending aorta PI, or umbilical mean velocity. A good linear relationship (r = 0.77, p < 0.001) was demonstrated between left ventricular O2 delivery and carotid PI. Thus, at basal state, O2 administration induced velocity changes compatible with an increase in cerebral vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Pulmonary atresia with intact ventricular septum and hypoplastic right heart in sibs: a single gene disorder?

We report on 2 sisters with hypoplastic right heart and pulmonary atresia. The first sib was found to have pulmonary atresia, intact ventricular septum, and hypoplastic right heart after delivery. Fetal echocardiography at 22 weeks of gestation during the second pregnancy documented the same cardiac abnormalities. Autopsy findings in the fetus confirmed the echocardiographic findings. No other malformations were detected in either case, and no other affected relatives were identified. We suggest that this rare congenital heart defect may, in some cases, be an autosomal recessive trait.

Adult↗
PubMed1992

Ebstein anomaly: report of a familial occurrence and prenatal diagnosis.

The Ebstein anomaly is a rare congenital heart disease involving the position and structure of the tricuspid valve. Although most cases are sporadic, familial occurrence has been documented. We report on 2 sisters, born to consanguineous parents, who were diagnosed prenatally with severe Ebstein anomaly.

Adult↗
PubMed1992

Intrauterine diagnosis and evolution of a cardiomyopathy in a fetus with Noonan's syndrome.

We report on a newborn infant with a typical form of Noonan's syndrome. Because of the presence of a fetal cystic hygroma and normal karyotype the diagnosis was suspected before birth. A progressive hypertrophic cardiomyopathy was also found following fetal echocardiographic scanning. We conclude that in addition to cystic hygroma with normal karyotype, the presence of functional or morphological evidence of myocardial abnormality should be included also as prenatal features of Noonan's syndrome.

Cardiomyopathy, Hypertrophic↗
PubMed1992

Effect of hypoxemia on fetal hemoglobin synthesis during late gestation.

This study was carried out to investigate the effect of fetal hypoxemia, as a result of acute intermittent maternal hypoxia, on the switchover from fetal to adult type Hb as well as Hb oxygen affinity and 2,3-diphosphoglycerate levels in the near-term fetus. These experiments were carried out using 10 fetal lambs with gestational ages ranging from 132 to 140 d. After the installation of appropriate fetal catheters, five of the ewes were exposed to an air mixture containing 10% O2 for 90 min/d for 4 consecutive d. Blood samples were withdrawn before the beginning of the hypoxic experiments and between the 5th and 6th d after the first episode of hypoxia. These samples were for the determination of 2,3-diphosphoglycerate concentration, arterial O2 pressure at which Hb is 50% saturated, and Hb type synthesis. Blood gases were monitored during each hypoxic episode. During the hypoxia, fetal arterial O2 pressure decreased from 2.43 +/- 0.36 kPa (18.2 +/- 2.7 mm Hg) to 1.57 +/- 0.17 kPa (11.8 +/- 1.3 mm Hg). These values returned to their initial levels after cessation of the maternal hypoxia. Five control animals of the same gestational age were also followed. During the interval of the study, a decrease of fetal Hb synthesis was noted (71.7 +/- 12.1 to 57.4 +/- 10.2%, p less than 0.001) in the control group. However, the level of fetal Hb synthesis did not significantly change in the hypoxic group (85.1 +/- 11.1 versus 80.6 +/- 18.9%).(ABSTRACT TRUNCATED AT 250 WORDS)

2,3-Diphosphoglycerate↗
PubMed1992

Cardiac two-dimensional imaging and reference values for blood flow velocities in the ovine fetus.

Since the ovine model is the most commonly used for foetal haemodynamic investigation it was felt important 1) to investigate the technical difficulties involved with ultrasound fetal cardiac imaging in this species and 2) to establish normal reference values for ovine cardiac and umbilical blood flow velocity measurements. Both two-dimensional and pulsed Doppler techniques were used for this assessment in 25 unsedated ewes. All morphological features described in human features to identify the ventricular cavities could be found in the ovine fetus with the two-dimensional echocardiogram. Specific differences included a flatten thorax as visualized from the lateral position, the mesocardial position of the heart, and a large left azygos vein behind the left atrium draining blood into a dilated coronary sinus. The mean peak velocities (cm/sec) of the early diastolic wave (E) and the atrial wave (A), along with their calculated ratio, were not statistically different between the two atrio-ventricular valves (E: 30.6 +/- 6.6, 31.2 +/- 6.1; A: 43.0 +/- 8.3, 41.6 +/- 8.0; E/A: .72, .76 for mitral and tricuspid valves respectively). A significant difference was observed between the acceleration times of the blood ejected into the aorta and the pulmonary artery, with the time interval being shorter in the pulmonary artery (Aorta: 0.052 +/- 0.011; Pulmonary artery: 0.037 +/- 0.009 s). A mean pulsatility index of the umbilical artery of 0.89 was recorded. The data recorded in this study should serve as a reference base for further non-invasive studies of the ovine foetal circulatory system using the ultrasound technique.

Animals↗