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Biomedical subjects

L D Allan

Publications and source records attributed to L D Allan.

At least 73 records · Page 4Linked to original sources
PubMed1990

Structural cardiac abnormalities in the fetus: reliability of prenatal diagnosis and outcome.

The outcomes of 129 pregnancies in which the fetus was found to have a structural cardiac abnormality are reviewed. Over a 30-month period from January 1985 to June 1987, 1924 patients were referred to the British Heart Foundation Research Centre for Perinatal Cardiology at Guy's Hospital for fetal cardiac scanning. A total of 129 structural cardiac abnormalities was diagnosed; 53% of these patients were referred because of an abnormal 'four-chamber view' on ultrasound at the referring hospital; 47 of the pregnancies (69% of the 68 patients referred before 28 weeks) were terminated, and in the remaining 82 pregnancies outcome was poor with only 20 infants (16%) surviving longer than 11 months. The prenatal diagnosis was fully or partly correct in 96% of the 111 cases where it was possible to verify the diagnosis by post-mortem or postnatal diagnosis. In the 82 pregnancies not terminated, 13 of the 22 cases given a moderate or good prognosis survived more than 11 months (59% survival), but only seven of the 60 (12% survival) given a fatal, poor or uncertain prognosis. The benefits of a multidisciplinary approach are discussed.

Chromosome Aberrations↗
PubMed1990

Prenatal measurement of cardiothoracic ratio in evaluation of heart disease.

The cardiothoracic ratio was measured in 410 normal fetuses and in a group of 73 fetuses with functional or structural heart disease. In normal fetuses it was fairly constant throughout pregnancy, but of those with congenital heart disease it was raised in cases of Ebstein's anomaly, tricuspid dysplasia, atrioventricular septal defect, and complete heart block. In some forms of congenital heart disease, however, it was within the normal range. There was a significant positive correlation between the cardiothoracic ratio and fetal hydrops in the group of 15 fetuses with supraventricular tachycardias. In these fetuses the cardiac size decreased significantly once the fetus reverted to sinus rhythm after the mother had been treated. Measurement of the cardiothoracic ratio is essential in the evaluation of fetal hydrops, as an increased value may point to the diagnosis of an intermittent fetal tachycardia if the fetus is assessed during a period of sinus rhythm. The measurement of this index forms a part of the complete prenatal evaluation of structural heart disease. The degree of cardiomegaly may provide useful information about secondary lung compression or cardiac failure and therefore assist in giving an accurate prognosis for postnatal survival.

Female↗
PubMed1989

The accuracy of fetal echocardiography in the diagnosis of congenital heart disease.

The accuracy of the echocardiographic diagnosis of fetal heart disease in an experienced centre was evaluated by analysing the results achieved during 1987 at the Perinatal Cardiology Unit, Guy's Hospital. In this one year, 978 high-risk patients were referred for fetal echocardiography. Of these, 74 cases were found to have cardiac malformation, 69 of which were predicted from the prenatal study. Of the 69, the autopsy specimen was available for correlative purposes in 41 cases. A postnatal echocardiogram was performed by us in a further 15 cases. The result of autopsy or of a postnatal echocardiogram was obtained from another hospital in 7 cases. Postmortem was refused in 5 cases, while one further case remains alive but has not had a postnatal echocardiogram. Close correlation was achieved between the predicted echocardiographic diagnosis and the anatomical results. Some minor errors in the complete interpretation of a defect were found, particularly in those fetuses in whom image quality was poor, due to early (less than 20 weeks) or late (greater than 34 weeks) gestation or to maternal obesity. Difficulty in echocardiographic interpretation was also experienced in unusual defects. There was one false positive prediction of coarctation of the aorta. One major (total anomalous pulmonary venous drainage) and 5 minor abnormalities (two atrial and three ventricular septal defects) detected after birth were overlooked on the fetal study. Although the echocardiogram in prenatal life is not as accurate as it can be postnatally, with suitable experience a high degree of precision can now be achieved.

Autopsy↗
PubMed1989

The natural history of the hypoplastic left heart syndrome.

In a fetus, examined initially at 22 weeks gestation, we identified the echocardiographic features of a dilated, hypertrophied and poorly contracting left ventricle. The presumptive diagnosis was critical aortic stenosis. Subsequent scans at 32 weeks and at term showed that the left ventricle had not grown since the first study such that the left ventricle had developed the appearance of a hypoplastic and densely echogenic chamber. Thus, in some forms of the hypoplastic left heart syndrome, the left ventricle can be of normal size or even dilated in early pregnancy. This may mean that the more subtle sign of poor left ventricular contraction could be overlooked in a routine four-chamber view obstetric scan.

Aortic Valve Stenosis↗
PubMed1989

Evidence of redistribution of cardiac output in asymmetrical growth retardation.

Thirty-one fetuses with growth retardation were studied by Doppler estimation of the cardiac output from each side of the fetal heart. Asymmetrical growth retardation was diagnosed in 16 fetuses by a head to abdominal circumference ratio above the 95th centile. In the 15 fetuses with symmetrical growth retardation, the distribution of cardiac output was normal. The mean and maximum velocity of blood flow in the pulmonary artery and aorta were similar to values in normal fetuses, and there was a greater calculated output from the right heart than from the left. The right heart flow expressed as a percentage of the combined cardiac output was not statistically significantly different from that in normal fetuses. In contrast, all 16 fetuses with asymmetrical growth retardation had a higher mean and maximum velocity in the aorta than in the pulmonary artery. The calculated volume flow from each side of the heart showed a greater output from the left than the right heart in 15. The right heart flow expressed as a percentage of the combined cardiac output was statistically different from the value in normal fetuses. These findings are consistent with theories of the redistribution of fetal blood flow, where cerebral blood flow is preferentially 'spared'.

Cardiac Output↗
PubMed1989

Fetal diaphragmatic hernia: the value of fetal echocardiography in the prediction of postnatal outcome.

Nineteen pregnancies complicated by fetal congenital diaphragmatic hernia (CDH) referred for fetal echocardiography have been reviewed. Congenital heart disease was diagnosed prenatally in three fetuses; in one of these the pregnancy was terminated, the two other infants died in the neonatal period. The presence of the fetal stomach within the thorax or a hernia/heart area ratio greater than 1.7 was associated with a large diaphragmatic defect. Polyhydramnios was not associated with a poor postnatal outcome. Evidence of cardiac ventricular disproportion before 24 weeks gestation in isolated CDH was associated with 100% mortality. Development of ventricular disproportion during the third trimester was associated with a survival rate of 75%. In three fetuses, all of whom survived, no ventricular disproportion was detected during the third trimester examination.

Echocardiography↗
PubMed1988

Obstetric importance, diagnosis, and management of fetal tachycardias.

During 1980-7, 23 pregnancies of 22-38 weeks' duration were investigated for fetal tachycardia. Twelve were cases of supraventricular tachycardia, eight of atrial flutter, and three cases in which the rhythm varied between supraventricular tachycardia and atrial flutter. In 11 cases the fetus had developed non-immune fetal hydrops before referral; 12 cases were non-hydropic at referral but one of this group of fetuses became hydropic during treatment. No relation was found between the rate or type of arrhythmia and the presence or absence of intrauterine heart failure. One non-hydropic infant was delivered electively prematurely. Maternal antiarrhythmic treatment was instituted in the remaining 22 cases. Conversion of the arrhythmia was achieved with digoxin alone in five cases and with a combination of digoxin and verapamil in nine. Control of the arrhythmia was achieved in seven of the 10 non-hydropic fetuses, and all were delivered at term with no deaths. Of the 12 hydropic fetuses, control was achieved in seven. Only three of the hydropic fetuses were delivered close to term. There were two deaths, both in the hydropic group. Of the whole group, five neonates suffered severe complications of prematurity. In this series the main benefit of treatment appeared to be in prolonging gestation of those hydropic fetuses in which conversion was achieved.

Delivery, Obstetric↗
PubMed1988

Prenatal detection of congenital heart disease: factors affecting obstetric management and survival.

Our recent experience in the diagnosis and management of fetal congenital heart disease is presented. During an 18-month period from January 1985 to June 1986, 1757 fetal echocardiograms were performed on a total of 989 antenatal patients. Cardiac anomalies were accurately predicted in 74 cases, 34 of which were associated with extracardiac or chromosomal anomalies. Twenty-three pregnancies were electively terminated. Currently the survival rate for ongoing pregnancies is 17%. A false negative diagnosis was made in 16 cases, the majority involving minor anomalies with a good prognosis and a survival rate of 81%. Prenatal detection of congenital heart disease places the fetus at high risk for chromosomal and extracardiac anomalies. Congenital heart disease detectable during pregnancy is usually severe and associated with a poor long-term prognosis. Termination of the pregnancy may be a reasonable option if a severe anomaly is detected early in pregnancy.

Echocardiography↗
PubMed1988

Fetal echocardiography.

A limited form of fetal heart examination is feasible by the ultrasonographer involved in routine scanning, allowing selection of fetuses with major forms of heart disease in the overall pregnant population. Detailed and accurate prediction of cardiac malformation is possible in a specialized center studying pregnancies at increased risk of heart disease in the offspring, and those pregnancies selected by obstetric scanning. Fetal hemodynamics can be studied by Doppler echocardiography allowing new insights into the fetal circulation. Fetal arrhythmias can be documented and successfully treated before birth.

Arrhythmias, Cardiac↗
PubMed1988

Doppler assessment of the cardiac and uteroplacental circulations in normal and complicated pregnancies.

Blood flow velocity waveforms were recorded in four sites in the fetal circulation in a series of 271 normal and 71 complicated pregnancies. The sites were the umbilical artery, the uterine artery branches in the placental bed, and distal to the two arterial valves in the heart. The blood flow through the arterial valves was added to estimate combined cardiac output. Normal ranges for values in all sites were established in our own series, and were similar to other published results. Abnormality of the waveform in the umbilical artery proved the most useful predictor of perinatal morbidity. Reversal of the normal pattern of increasing diastolic flow in the umbilical artery with advancing gestation was an important prognostic finding in the pregnancies studied serially. The combined cardiac output did not fall until late in the course of fetal compromise, and low values were seen only with an abnormal umbilical artery tracing.

Blood Flow Velocity↗
PubMed1988

Atrioventricular septal defect in prenatal life.

In a series of more than 3500 pregnancies referred for fetal echocardiography, 29 cases of atrioventricular septal defect were detected in the fetus. There was a chromosomal anomaly in 14 of these cases, left atrial isomerism in 12, and right atrial isomerism in two. Complete heart block was found in 11 of the cases with left atrial isomerism. Many associated cardiac abnormalities were found, particularly in the fetuses with atrial isomerism; the most common were double outlet right ventricle or aortic arch anomalies. The prognosis was poor in all patients with atrioventricular septal defect detected prenatally. Fifteen pregnancies went to term but there are only four survivors. Two of those have trisomy 21, a further patient has inoperable defects, and only one remains well and is awaiting corrective surgery for a partial atrioventricular septal defect.

Abnormalities, Multiple↗
PubMed1988

Coarctation of the aorta in prenatal life: an echocardiographic, anatomical, and functional study.

In a prospective echocardiographic study of over 2000 pregnancies, 24 fetuses were found to have dilatation of the right ventricle and pulmonary artery when these structures were compared with those of the left heart. In 18 of these cases the diagnosis of coarctation or interruption of the aorta was correctly inferred from these findings. On direct echocardiographic examination of the aortic arch, arch hypoplasia or interruption of the aortic arch was recognisable prenatally in 10 of these 18 cases, most readily between 20-30 weeks' gestation. In 11 of 12 cases of aortic arch anomaly studied by Doppler echocardiography, a reduction in blood flow in the ascending aorta was demonstrated. The intracardiac appearances were suggestive of coarctation but the Doppler findings were within normal limits in two further cases which later proved to be normal. A diaphragmatic hernia was found in four fetuses and the intracardiac echocardiography and Doppler findings were the same as those found in fetuses with aortic coarctation. Five cases of coarctation were overlooked on the prenatal echocardiogram but these were found at follow up of the infants. Thus coarctation of the aorta can be diagnosed prenatally, although the condition may be missed or incorrectly predicted by the criteria examined in the present study. Reduced aortic blood flow is a demonstrable feature of aortic arch abnormalities but it is found in other conditions that are not associated with coarctation.

Aorta↗
PubMed1988

Measurements of the dimensions of the aortic and pulmonary pathways in the human fetus: a correlative echocardiographic and morphometric study.

Thirty normal hearts from fetuses aborted at 10-33 weeks' gestation were measured directly and the results were compared with echocardiographic measurements in 20 normal live fetuses of 23-27 weeks' gestation. The diameters of the aorta, aortic isthmus, pulmonary arteries, and arterial duct were measured at standard levels and expressed as a ratio of the diameter of the ascending aorta. The ratios for the isthmus, the duct, and the right pulmonary artery were: 0.63 (0.11), 0.51 (0.13), 0.56 (0.10) respectively for the direct measurement and 0.73 (0.07), 0.7 (0.08), 0.62 (0.06) respectively at echocardiography. These results show that in mid-gestation the isthmus of the human fetus is not as small as that reported in animal models. This indicates that the distribution of the fetal circulation may not be the same either.

Aorta↗
PubMed1988

Fetal complete heart block.

In a series of over 6000 patients referred for fetal echocardiography during an eight year period, 37 fetuses were found to have complete heart block. There were 16 cases of isolated heart block and 21 cases associated with structural heart disease. All mothers of fetuses with isolated complete heart block had evidence of circulating syndrome Sjögren A antibody (Ro). Only one mother had clinical evidence of connective tissue disease. In the 21 cases associated with structural heart disease there were 17 cases of atrioventricular septal defect, one case of secundum atrial and perimembranous ventricular septal defects, two cases of tetralogy of Fallot, and one case of pulmonary stenosis. All fetuses with atrioventricular septal defects and complete heart block had left atrial isomerism. Additional abnormalities of the great arteries were often found in this group; these were double outlet right ventricle, transposition of the great arteries, pulmonary atresia, coarctation of aorta, and stenosis of the pulmonary or aortic valves. Intrauterine congestive heart failure was a feature of four cases in the group with isolated complete heart block and 11 cases of the group with associated structural heart disease. The outcome in the fetuses with isolated complete heart block was better than in those with heart disease: 12 of the 16 fetuses are alive, two of them have a pacemaker. But only three of the group of 21 fetuses with cardiac malformation are alive, and two of them have a pacemaker.

Echocardiography↗
PubMed1988

Diagnosis of fetal cardiac abnormality.

Congenital heart disease can now be accurately diagnosed in specialist units from about 18 weeks gestation. By teaching ultrasonographers to examine the four-chamber view of the heart, malformation can be suspected on a routine scan. This will allow a much greater number of pregnancies to be screened effectively for congenital heart disease.

Echocardiography↗
PubMed1987

Doppler assessment of umbilical artery blood flow for the prediction of outcome in fetal cardiac abnormality.

In a series of 244 pregnancies referred for fetal echocardiography, the umbilical artery waveform was also studied by pulsed Doppler ultrasound. In 152 normal pregnancies diastolic flow in the umbilical artery was always detectable after 20 weeks gestation. In 4 of 58 normal patients examined before 20 weeks, diastolic flow was absent in some part of the recording. In 34 fetuses with congenital heart disease detected at between 18 and 37 weeks gestation, 10 were found consistently to have associated absent diastolic flow. Five of these fetuses died in utero between 5 and 21 days after the recording; three were aborted and the remaining two died in the neonatal period at 4 and 7 days after the examination. Fetal congenital heart disease with normal umbilical blood flow also had a poor prognosis in general, but the adverse outcome was much less immediate than in fetuses with absent diastolic flow. No correlation was found between the type of congenital heart disease and the characteristics of the umbilical artery waveform. Absent diastolic flow in the umbilical artery indicates a poor short-term prognosis for fetuses with congenital heart disease, particularly after 20 weeks, when fetal death is predictable.

Diastole↗