Biomedical subjects
Publications and source records attributed to M L Rigby.
The cross-sectional echocardiographic and postmortem appearances of the heart from a patient with the rare association of aortic valve atresia, aortopulmonary window, and interrupted aortic arch are described. Differentiation of this anomaly from truncus arteriosus with interrupted aortic arch is important.
Congenital aneurysms of the interventricular septum were found in a 29 year old man and his four year old son. Both were symptom free. In both, M mode and cross sectional echocardiography showed an aneurysm in the mid-muscular trabecular portion of the ventricular septum with considerable paradoxical motion of the aneurysmal segment. Otherwise the chamber dimensions, intracardiac structures, and cardiac function were normal for age. Congenital aneurysm of the interventricular septum is rare and these familial cases may be unique.
Interventional balloon catheterisation is now the recommended procedure for several congenital heart defects. The overall complication rate in the first 160 children (median age 3 years) to undergo balloon intervention (excluding balloon atrial septostomy) at the Brompton Hospital was 24% (14% excluding haemorrhage and including three deaths (1.9%]. Most complications were related to vascular problems at the site of cardiac catheterisation. Complications were more common in the younger patient, especially neonates, and also in procedures that were ultimately unsuccessful. Most complications were transient and usually had no long term effects. Improvements in equipment design and technical expertise may reduce morbidity from these procedures.
OBJECTIVE: To examine left ventricular function after surgical resection of subaortic stenosis during childhood. DESIGN: Left ventricular performance was measured non-invasively in all patients who responded to an invitation for formal assessment. SETTING: Outpatient study, tertiary referral centre. PATIENTS: Twenty three (12 male and 11 female) patients (age range 3 to 31 years) of 43 consecutive patients with fixed subaortic stenosis undergoing surgical resection between 1975 and 1989 reattended for formal assessment 16 months to 15 years (median 4 years 4 months) after operation. MAIN OUTCOME MEASURES: Left ventricular dimension, left ventricular wall thickness, left ventricular Doppler inflow velocities, and left ventricular diastolic pressure (measured from apexcardiograms). Results were compared with those in controls individually matched for age and sex. RESULTS: All patients were symptom free. Left ventricular cavity dimensions were normal, as was the mean fractional shortening. Posterior wall thickness tended to be greater in the patients and there was a significant increase in septal thickness. Normalised peak rate of posterior wall thinning was significantly lower in the patients and the isovolumic relaxation time was significantly shorter. Doppler inflow velocity measurements showed that early diastolic mitral flow acceleration time was normal but deceleration time was significantly shorter in the patients. The ratio of mitral flow in early diastole (E) to E plus mitral flow in late diastole (A) was significantly higher in the patients and in two patients there was complete absence of A wave flow despite large A waves on the apexcardiogram. CONCLUSIONS: Systolic function was well preserved in patients after operation for subaortic stenosis. A restrictive pattern of left ventricular filling was common, however, and presumably reflected a response to the chronic pressure load and to surgery in the paediatric heart.
OBJECTIVE: To assess whether regional abnormalities of ventricular function are present in patients after the Fontan operation and to explore the implications of any such abnormalities for ventricular filling. DESIGN AND PATIENTS: Prospective study in which 25 patients after the Fontan operation were compared with 25 healthy controls and 12 patients with a univentricular atrioventricular connection, before the Fontan operation. INTERVENTIONS: Doppler echocardiography, with simultaneous electrocardiogram, phonocardiogram, and respirometer. RESULTS: Isovolumic relaxation time was significantly longer in patients after the Fontan operation than in normal children (p less than 0.001) or the preoperative patients (p = 0.001). Systolic intraventricular flow was detected in 60% of patients after the Fontan operation and in 42% of preoperative patients. After the Fontan operation 80% of patients showed intraventricular flow during isovolumic relaxation compared with 8% of normal children and none of the preoperative patients. CONCLUSIONS: Incoordinate ventricular relaxation is common after the Fontan operation. This may have important implications for ventricular diastolic filling, pulmonary blood flow, and cardiac output in these patients.
The influence of palliation on survival was studied in 191 consecutive infants, presenting at under 1 year of age, with double-inlet ventricle (1973 to 1988, median follow-up 8.5 years). Palliative operations were performed on 154 occasions in 121 patients (63%). Survival after a systemic-pulmonary arterial shunt (n = 57) and banding of the pulmonary trunk (n = 35) was comparable (84% and 77% at 1 year, 62% and 45% at 5 years), but those who underwent repair of aortic arch obstruction fared worse (n = 18, 44% and 22% at 1 and 5 years, p less than 0.001). The remainder did not undergo an operation because of balanced physiology (n = 17, 9% of entire group), complex anatomy (n = 32, 15%), or irreversible low output (n = 19, 12%). Palliative surgery, overall, had a deleterious effect on immediate survival (greater than 1 month relative risk 6.6, p less than 0.001), but, in the survivors, medium-term outcome was improved (greater than 6 months, 0.68, p less than 0.05). This effect was most marked for those undergoing a systemic-pulmonary artery shunt (less than 1 month, 2.52; greater than 6 months, 0.43); by contrast, after banding of the pulmonary trunk, with or without additional repair of the aortic arch repair, medium-term risk was not altered (greater than 6 months, 1.13 and 0.91, respectively). These data will assist the clinician in making decisions concerning the management of infants with double-inlet ventricle and in the judicious use of palliative surgery.
The cross-sectional echocardiographic findings were analysed retrospectively in 26 patients with Ebstein's malformation in the light of studies of autopsied specimens from different patients showing this lesion. The salient anatomical feature in diagnosis is the finding of the hinge point of the septal and mural leaflets of the valve within the inlet component of the right ventricle rather than at the atrioventricular junction. The other important feature is the nature of the distal attachment of the leaflets, particularly the anterosuperior one, which can either be in focal or linear fashion. The hinge point of the septal leaflet was noted echocardiographically to be displaced in 19 patients but, significantly, the leaflet was absent in the other seven. Also significant was that the hinge point of the mural leaflet at the crux had been visualized in only 15 of the patients. The anterosuperior leaflet had a distal linear attachment in 20 of the patients, with the anteroseptal commissure becoming a keyhole in six of these through which blood passed to the functional right ventricle. The valve remained a competent structure, even though closing at the junction of atrialized and functional components of the right ventricle rather than at the atrioventricular junction. Cross-sectional echocardiography is the technique of choice with which to display the salient morphological features of Ebstein's malformation.
Survival before definitive operations was studied in 191 infants with double-inlet ventricle presenting before 1 year of age (1973 to 1988, median follow-up 8.5 years). The morphologic spectrum was broad, with a great prevalence of associated lesions. The actuarial survival rate before definitive repair was 57% at 1 year, 43% at 5 years, and 42% at 10 years, worse than prior reports because of the younger age at entry into our series. Analysis of univariate risk factors established that right atrial isomerism (18% of the group, relative risk 2.9), common atrioventricular orifice (42%, 2.0), pulmonary atresia (20%, 3.4), obstruction of the systemic outflow tract (18%, 2.5), and extracardiac anomalous pulmonary venous connection (13%, 3.1) were strongly associated with poorer survival. Pulmonary stenosis (40%, 0.35), balanced pulmonary blood flow (9%, 0.40), and presentation at an older age (3%, 0.42 to 0.18) were beneficial (p less than 0.05 to 0.0001). Multivariate analysis allowed the creation of patient-specific curves for prediction of survival for different anatomic and physiologic variants of double-inlet ventricle. A simple additive index was then derived from the multivariate Cox coefficients to enable stratification of risk for these morphologic subgroups of patients and so assist in the making of clinical decisions in infancy.
The fate of 191 infants with double-inlet ventricle was studied to determine the influence of morphologic characteristics at presentation and subsequent management on the potential for, and timing of, definitive repair by the Fontan operation or ventricular septation. At presentation, 136 patients (71%) were potential candidates for a Fontan procedure. Actuarial survival was better than for those deemed unsuitable for either definitive option (n = 55; 68% versus 28% at 1 year; p less than 0.001), but still, only 78 patients (57%) were known to be alive and suitable candidates at 2 years of age. This was largely due to death after presentation with low cardiac output (n = 19) and at palliative operation (20 of 98 surgically treated patients). The adverse events of late sudden death (n = 14) and the development of new features precluding a Fontan operation (n = 18) mostly occurred before 4 years of age (n = 22). Patients requiring no operation and those who underwent a systemic-pulmonary arterial shunt fared better than those who underwent isolated banding of the pulmonary trunk (9/13 and 25/42 alive and suitable versus 14/33; p less than 0.05), and than those who required aortic arch repair together with banding (1/12; p less than 0.01), because of the development of subaortic stenosis in the latter group. In contrast, only 43 patients (23% of all 191 patients) had morphologic features that were additionally compatible with future ventricular septation. Actuarial survival free of adverse events for these 43 patients was similar to that of the 136 patients considered suitable for a Fontan operation. Thus management in infancy must be aimed at maintaining potential for a future Fontan operation, which itself should not be delayed, for most patients, beyond 3 years of age, because of the prevalence of adverse events with increasing age.
Twenty asymptomatic school children who had undergone Mustard's operation for simple complete transposition (concordant atrioventricular and discordant ventriculo-arterial connexions) were catheterised electively 6-13 years later. The studies were carried out under general anaesthesia in air and in 100% O2. Oxygen consumption was measured and end-tidal gases were monitored using respiratory mass spectrometry. There was significant left ventricular outflow tract obstruction in 2 patients. Cardiac output in air was normal in 15 and decreased in 5 patients. The pulmonary vascular resistance was normal in 18 of 19 cases, but grossly elevated in one patient. Baffle dysfunction was present in 11 patients: 10 with important gradients between the venous pathways and the systemic venous atrium, and 5 with a leak identified either by a left-to-right shunt or by the course of the catheter. Balloon dilatation was attempted in the inferior caval venous channel in 6 and in the superior caval venous channel in 2. Mean gradient before the dilatation fell after the procedure. No pulmonary venous obstruction was identified. Even in this group of children selected as asymptomatic, approximately half had a detectable haemodynamic abnormality.
Plasma atrial natriuretic peptide was measured in 10 children undergoing the Fontan procedure and 3 children undergoing total cavopulmonary connexion. There was no significant difference in pre-operative plasma levels, but post-operative levels were significantly higher 48 hours after cardiopulmonary bypass in the Fontan group. There was no significant difference in plasma arginine vasopressin levels either pre- or post-operatively. Post-operative pleural effusions occurred in only 2 of the 10 patients undergoing the Fontan procedure, but were present in all 3 of those undergoing total cavopulmonary connexion. The release of atrial natriuretic peptide is an appropriate homeostatic response to volume loading and the impairment of this response in the early post-operative period may be of clinical importance.
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In 22 cases of left atrial isomerism studied at the Brompton Hospital, four cases were found to have an unusual arrangement of the abdominal vessels. There was persistence of an inferior caval vein, partially anomalous hepatic venous connection and additional continuation of part of the venous return from the lower body through the azygos venous system. This venous pattern had surgical implications in our index case, since redirection of the inferior caval venous return was necessary.
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Over a 5 year period open valvotomy was performed on 13 patients under the age of one year with critical aortic stenosis. All 13 survived operation. There were two late deaths--one 38 days after operation, associated with an unrelated neurosurgical procedure and the other 2 years 6 months after when aortic root enlargement and replacement of the aortic valve were performed. During this period two other infants presented with aortic stenosis. One, who was very ill before transfer, died before operation could be performed. The second patient had a hypoplastic left ventricle with a small mitral valve ring and was, therefore, considered to be part of a different subgroup. All the surviving children have been followed up (median length of follow up 2 years and 11 months, range 7 months-5 years). Left ventricular function, in terms of percentage systolic wall thickening, was shown to be significantly impaired in all age groups. Peak diastolic thinning was abnormal in those children aged from 3 to 5. The aortic valve gradient, as assessed by peak instantaneous continuous wave Doppler, was less than 40 mm Hg in five patients and between 40 and 70 mm Hg in seven patients. One patient, with appreciable restenosis, has undergone successful percutaneous balloon dilatation of the aortic valve.
Ventricular pressure-volume diagrams were obtained from the right ventricle in patients before and after relief of right ventricular pressure load, in patients with volume loaded right ventricles, and from the left ventricle in patients after the Mustard procedure for transposition of the great arteries. The patterns of ejection during pressure development and decline were similar in patients after relief of pressure load and in those with isolated volume load. A right ventricular pressure load, however, reduced ejection during the two "isovolumic" periods, and the overall shape of the pressure-volume loop resembled that of the normal left ventricle. Pressure-volume diagrams obtained from the left ventricle after the Mustard procedure were indistinguishable from the normal right ventricle, which accords with the hypothesis that the normal right ventricular contraction pattern is a consequence of loading conditions rather than a reflection of an intrinsic property of the myocardium.
Transposition of the great arteries is frequently complicated by the early onset of pulmonary vascular disease. It is difficult to measure pulmonary blood flow by the Fick principle because the pulmonary arteriovenous oxygen content difference is small and bronchial blood flow is increased in this condition. In eight patients (mean age 7.7 years, range 3 months to 29 years) with transposition of the great arteries mass spectrometry was used to measure oxygen uptake and predict pulmonary end capillary blood oxygen content. The effects of the bronchial circulation were studied by computer modelling. There was close agreement between pulmonary end capillary and pulmonary vein blood oxygen contents but the resultant percentage difference in arteriovenous content difference was significant (mean (SE of difference)) (14.5(3.8)%). The effect of the bronchial circulation was to give spuriously high estimates of pulmonary blood flow. The error was greatest when oxygen consumption was low and aortic blood was very desaturated.
Indices of the severity of coarctation derived from non-invasive Doppler echocardiography were compared with measurements derived from cardiac catheterisation and angiography. In 24 Doppler studies from 17 children instantaneous peak systolic and diastolic gradients and time to half peak systolic and diastolic velocities were compared with the ratio of the coarctation diameter to the diameter of descending aorta at the level of diaphragm obtained from angiographic systolic frames of the aorta. A high peak systolic gradient (greater than 40 mm Hg) or long time to half peak diastolic velocity (greater than 100 ms) (that is, maintenance of flow in diastole) were both highly specific (100%) in detecting coarctation of the aorta where the angiographic ratio was less than or equal to 0.5. Diastolic measurements, however, were more sensitive (79% both for peak diastolic gradient and for time to half peak diastolic velocity) than systolic (57% for peak systolic gradient and 64% for time to half peak systolic velocity). Even higher sensitivity (93%) was obtained when the peak systolic gradient was greater than 40 mm Hg or the time to half peak diastolic velocity was greater than 100 ms. Examination by continuous wave Doppler echocardiography is an effective non-invasive method of assessing the severity of coarctation of the aorta, particularly when systolic and diastolic events are considered together. This approach overcomes the relatively low sensitivity of peak systolic gradient alone.