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Biomedical subjects

A B Houston

Publications and source records attributed to A B Houston.

At least 37 records · Page 2Linked to original sources
PubMed1991

Transoesophageal echocardiographic assessment of fixed subaortic obstruction in children.

OBJECTIVE: To evaluate the clinical usefulness of transoesophageal echocardiography in the assessment of children with fixed left ventricular outflow tract stenosis. PATIENTS AND METHODS: Eight consecutive children, aged over 5 years, with fixed subaortic stenosis and one child with fixed subpulmonary left ventricular outflow tract stenosis were prospectively assessed by precordial and transoesophageal echocardiography. RESULTS: Transoesophageal images of the left ventricular outflow tract were much clearer than precordial images in all patients except one with a prosthetic mitral valve. Improved visualisation provided further information on the nature of the lesion (additional chordal attachment of the mitral valve in one, accessory atrioventricular valve tissue with aneurysm formation in one), on the extent of the lesion (circumferential in three), and on the very close relation of a ridge to the aortic valve leaflets in one. Transoesophageal Doppler did not provide any additional information on aortic regurgitation and was unreliable for gradient estimation across the left ventricular outflow tract. CONCLUSIONS: Transoesophageal imaging provides an excellent means of visualising lesions in the left ventricular outflow tract and can be useful in a few children and adolescents in whom precordial echocardiography does not provide adequate information. The technique can also be used intraoperatively to define the full extent of the obstructive lesion and to assess residual lesions after surgery.

Adolescent↗
PubMed1990

Colour Doppler flow mapping in the diagnosis of traumatic ventricular septal defect.

The use of colour Doppler flow mapping allows noninvasive diagnosis and gives haemodynamic information on the severity of ventricular septal defects. We describe the case of a man with delayed presentation of a traumatic ventricular septal defect in whom colour Doppler flow mapping permitted conservative management after accurate noninvasive diagnosis.

Adult↗
PubMed1990

Anomalous origin of the left coronary artery from the pulmonary trunk: elucidation with colour Doppler flow mapping.

Four infants and children with anomalous connection of the left coronary artery to the pulmonary trunk were studied with colour Doppler flow mapping. In three the diagnosis was only suspected when the colour Doppler study showed dilated intraseptal and epicardial vessels and an abnormal flow signal into the pulmonary artery in diastole; this latter signal localised the exact site of communication, which was not apparent on angiocardiography. Two of these patients had previously had operations for severe mitral regurgitation, the diagnosis of anomalous left coronary artery having been previously considered in one but missed despite aortic root angiography. The colour study in the fourth was largely confirmatory, operation without catheterisation being undertaken on the basis of the echocardiographic images. By contrast in two infants subsequently seen with congestive cardiomyopathy the demonstration of flow direction in the left coronary artery confirmed that it was normally connected to the aorta. Colour Doppler flow mapping can show flow direction in the left coronary artery and from the mouth of an anomalous coronary artery into the pulmonary artery, thus simplifying the diagnosis and allowing the site of the connection of the left coronary artery to the pulmonary artery to be determined with precision.

Cardiomyopathy, Dilated↗
PubMed1990

Pulmonary artery sling: definitive diagnosis by colour Doppler flow mapping avoiding cardiac catheterisation.

Pulmonary artery sling is a rare abnormality that usually presents in infancy with wheeze or stridor. Diagnoses by cross sectional echocardiography, computed tomography, and magnetic resonance imaging have been described but pulmonary arteriography was regarded as essential for a definite diagnosis. The use of colour Doppler adds to the diagnostic certainty of cross sectional echocardiography and colour Doppler provided a definite diagnosis in an infant that allowed surgical repair without the need for cardiac catheterisation. Postoperative flow through the left pulmonary artery was also assessed by Doppler, and this avoided the need for repeat catheterisation or perfusion lung scanning.

Echocardiography, Doppler↗
PubMed1989

Variability of the Doppler gradient in pulmonary valve stenosis before and after balloon dilatation.

The variability of the valve gradient measured by Doppler in pulmonary stenosis was compared with the variability of the gradient measured at catheterisation in 42 infants and children undergoing catheterisation with a view to balloon dilatation of the pulmonary valve. The maximum value measured by Doppler when the patient was unsedated was significantly higher than that measured when the patient was sedated for catheterisation, and the maximum gradient was significantly higher shortly after than several days later. In a patient with pronounced infundibular obstruction after dilatation the Doppler signal clearly showed that the obstruction was dynamic, with a superimposed lower fixed signal that correctly predicted the final low gradient. The Doppler gradient in an alert and unsedated patient may be a better measure of the true physiological value. The highest Doppler value so obtained is a more appropriate indicator of the need for balloon dilatation than a single catheter measurement. The result of dilatation is best assessed by Doppler measurement at least a day after the procedure.

Adolescent↗
PubMed1989

Doppler flow characteristics in the assessment of pulmonary artery pressure in ductus arteriosus.

The Doppler spectral pattern of flow through the ductus arteriosus was studied in 117 patients. In 37 who underwent catheterisation, Doppler records and aortic and pulmonary artery pressure were available (21 simultaneously with two catheters) for review while the others had surgical ligation of the duct on the basis of the results of non-invasive tests. Four flow patterns were obtained: (a) continuous flow, maximum velocity in late systole with gradual fall throughout diastole; (b) continuous flow, high systolic flow with rapid fall to a very low early diastolic velocity maintained throughout diastole; (c) continuous low velocity, maximum in late diastole; and (d) bidirectional flow. Flow pattern (a) was associated with normal or slightly raised pulmonary artery pressure; (b) with raised pulmonary artery pressure; and (c) and (d) with pulmonary artery pressure at systemic values. Comparison of the Doppler and measured pressure differences between the great arteries was reasonably good for peak values but poor for the trough readings. Doppler ultrasound clearly showed ductal flow; the flow pattern gave an indication of the pulmonary artery pressure, but pressure measurement by application of the Bernoulli equation to the flow velocities cannot yet be regarded as reliable.

Adolescent↗
PubMed1989

Hypertrophic cardiomyopathy in identical twins.

Hypertrophic cardiomyopathy was diagnosed in identical twin boys in early childhood. One underwent myomectomy at the age of 12 years because of progressive severe exertional dyspnoea accompanied by considerable obstruction of the left ventricular outflow tract shown on both echocardiography and cardiac catheterisation. Seven years later, at the age of 19, he remains incapacitated to a moderate degree. By contrast, the other twin has led a relatively normal life to date and no left ventricular outflow obstruction has been shown.

Adult↗
PubMed1989

Congenital fistula between the left ventricle and coronary sinus: elucidation by colour Doppler flow mapping.

A fistula between the left ventricle and the coronary sinus was diagnosed by Doppler echocardiography and confirmed by cardiac catheterisation in a symptom free child who presented with clinical signs of mitral regurgitation. A similar abnormality has been reported after repeated mitral valve replacement and after myocardial infarction but a congenital fistula of this type has not been described before.

Child, Preschool↗
PubMed1988

Doppler assessment of the interventricular pressure drop in patients with ventricular septal defects.

Doppler ultrasound was used to assess the pressure drop between the ventricles in 109 infants and children (61 less than two years old) with a ventricular septal defect who underwent cardiac catheterisation. The pressure in both ventricles was measured at catheterisation in 103 patients either simultaneously through two catheters (41) or with a single catheter withdrawn across the septum or removed from one ventricle to the other (62). When pressure was measured simultaneously with two catheters (41 patients) the peak to peak and instantaneous gradients showed a maximum difference of 20 mm Hg with levels within 10 mm Hg of each other in 36. Comparison of the difference in the gradients with the average of the measurements demonstrated a tendency for Doppler to underestimate the difference when it was high (greater than 50 mm Hg) and overestimate it when it was low. A Doppler estimate of a low pressure difference between the ventricles indicates pulmonary arterial hypertension and a high one low pulmonary artery pressure, but in the intermediate group Doppler is as yet not sufficiently sensitive to allow selection of those patients who require further investigation and possible operation. Doppler ultrasound was found to be a sensitive method of detecting a very small ventricular septal defect. Thus although Doppler is a very useful means of assessing and following patients with a ventricular septal defect, further studies are required to determine its exact place in clinical practice.

Adolescent↗
PubMed1987

Aortic origin of right pulmonary artery: successful surgical correction in three consecutive patients.

Over a period of four years (1981 through 1984), 3 infants with aortic origin of the right pulmonary artery were seen in our surgical unit. Two infants had a persistent ductus arteriosus, which arose from the left subclavian artery in 1 of them who also had a right-sided aortic arch. There were no other associated abnormalities. Preoperative diagnosis was established by echocardiography in 2 infants. Anatomical surgical correction was undertaken in all 3 infants under cardiopulmonary bypass. There were no operative deaths. One child required reoperation at 15 months for anastomotic stenosis. All 3 children were well two to five years postoperatively with scintillographic evidence of normal ventilation and perfusion. Our experience indicates that this rare but severe congenital cardiac anomaly is easily diagnosed by echocardiography, and confirms that it is eminently amenable to surgical correction.

Cardiopulmonary Bypass↗
PubMed1987

Doppler ultrasound in the assessment of severity of coarctation of the aorta and interruption of the aortic arch.

Doppler ultrasound was used to investigate 48 infants and children (age 2 days-16 years, weight 1.0-58 kg) with aortic arch abnormalities. In only 38 of the 42 with an important coarctation was an increased blood flow velocity from the distal arch demonstrated. In three with interruption of the aortic arch an increased velocity recorded from the region of the distal arch was thought to represent ductal flow. There was little difference between the peak to peak and instantaneous maximum gradients in the 20 patients with important coarctation in whom direct pressure measurements both proximal and distal to the obstruction were made at catheterisation. There were poor agreements between Doppler and measured peak to peak and instantaneous gradients in the 17 patients found to have both an increased velocity and important coarctation. It is concluded that although an increased blood flow velocity in the distal arch is usually demonstrated in coarctation this may not occur with severe obstruction. Furthermore, the maximum velocity is not related to the anatomical severity of the obstruction and the Doppler estimate of pressure drop in coarctation may not even reliably predict that measured at catheterisation.

Adolescent↗
PubMed1986

Comparison of Doppler ultrasound velocity measurements with pressure differences across bioprosthetic valves in a pulsatile flow model.

Continuous wave Doppler ultrasound was used in vitro to assess the pressure differences across four different cardiac bioprosthetic valves in a pulsatile flow test apparatus. Valves were tested under four different flow conditions. Pressure differences were calculated from the maximum flow velocity measured by Doppler ultrasound and correlated well with the pressure differences measured directly in the flow model (r = 0.98). Thus Doppler ultrasound can accurately measure pressure differences across bioprosthetic valves in vitro.

Bioprosthesis↗
PubMed1986

Doppler ultrasound in the estimation of the severity of pulmonary infundibular stenosis in infants and children.

Pressure gradients estimated by Doppler echocardiography were compared with values obtained at cardiac catheterisation in 31 children (aged seven days to 16 years, mean 2 years 7 months) with pulmonary infundibular stenosis including 16 with tetralogy of Fallot. Various parasternal and subcostal positions were explored to obtain the maximum velocity of blood flow and the obstructive gradient was calculated from the modified Bernoulli formula. The gradient across the obstruction could be measured directly at the time of catheterisation in only 21 patients. The correlation coefficient for the Doppler and total measured gradients was r = 0.90 for catheter entry and r = 0.77 for catheter withdrawal. Doppler ultrasound, by measuring the total gradient from the right ventricle to the pulmonary artery, provides a non-invasive assessment of the severity of pulmonary stenosis, and in those with infundibular obstruction allowance need not be made for possible energy losses caused by the elongated obstruction or the presence of narrowing at more than one level.

Adolescent↗
PubMed1986

Non-invasive assessment by Doppler ultrasound of 155 patients with bioprosthetic valves: a comparison of the Wessex porcine, low profile Ionescu-Shiley, and Hancock pericardial bioprostheses.

One hundred and fifty five patients with 167 bioprosthetic valves (68 Wessex porcine, 54 Hancock pericardial, and 45 low profile Ionescu-Shiley pericardial valves) were studied by Doppler ultrasound. Valve gradients were calculated from the mitral and aortic flow velocities by the modified Bernoulli equation. Mean mitral gradients were significantly smaller across the Ionescu-Shiley valves than across the Wessex porcine or Hancock pericardial valves. Mitral pressure half time was, however, significantly longer in the Hancock pericardial than in the Wessex porcine or Ionescu-Shiley valves. No significant differences were seen among the groups of aortic bioprostheses, though the comparable size of Wessex porcine valves showed significantly higher gradients. Bioprosthetic regurgitation was detected in 13 of 103 mitral and 11 of 59 aortic valves, though it was suspected clinically in only 12 mitral and six aortic bioprostheses. Doppler ultrasound is a repeatable non-invasive method of acquiring haemodynamic information in vivo from a variety of bioprostheses and it can detect bioprosthetic regurgitation at an early stage.

Adult↗
PubMed1985

The severity of pulmonary valve or artery obstruction in children estimated by Doppler ultrasound.

Doppler echocardiographic estimation of pressure gradient has been compared to that measured at cardiac catheterisation in 37 children, 6 weeks to 15 years of age, with suspected pulmonary valve stenosis or a pulmonary artery band. Various parasternal and subcostal positions were explored to obtain the maximum velocity of blood flow and the valve gradient was calculated from the modified Bernoulli formula. The Doppler study was performed at the time of catheterisation in 19, the maximum velocity being measured during catheter withdrawal in 7, immediately after withdrawal in 7, and while simultaneous right ventricular and pulmonary arterial pressures were measured in 5. Five other patients were studied within 24 hours of catheterisation and the other 13 within 6 months. Comparison of Doppler and catheterisation gradients showed a close correlation, this being particularly good where simultaneous right ventricular and pulmonary arterial pressures were measured. Doppler now provides an accurate non-invasive measurement of the severity of pulmonary valve stenosis and the adequacy of a pulmonary artery band.

Adolescent↗