Biomedical subjects
Publications and source records attributed to D R Clarke.
Successful surgical repair of an 8 1/2-month-old infant weighing 8 kg with d-transposition of the great arteries associated with ventricular septal defect and left ventricular outflow tract obstruction was accomplished utilizing a recently described technique. To our knowledge, this is the first attempt to use this technique in an infant.
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Aortoventriculoplasty was performed in 16 children between July, 1980, and July, 1984. Indications for the procedure were 1) aortic stenosis or insufficiency, or both, necessitating replacement of an aortic valve whose anulus would not accept a 19 mm diameter valve, (2) replacement of a small valve prosthesis, or (3) recurrent tunnel subaortic stenosis. Patients were 5 months to 17 years old at operation, 14 had previous repairs, and four had prior aortic valve replacement. There were 13 long-term survivors followed up for 14 to 38 months; 12 are asymptomatic with normal exercise tolerance. Three had residual ventricular septal defects, two requiring repair. All patients were given warfarin with or without antiplatelet agents. There have been no thromboembolic episodes and no hemorrhagic complications. Aortoventriculoplasty is well tolerated in children and appears to be a viable surgical option in the management of young patients with a hypoplastic left ventricular outflow tract.
A newborn with critical aortic stenosis and anular hypoplasia was treated with an aortic valvotomy using inflow occlusion. Five months later, important valvular insufficiency and residual stenosis necessitated aortic valve replacement. An aortoventriculoplasty using a 19 mm St. Jude Medical Valve was successfully performed with a good hemodynamic response.
A total of 20 children with total anomalous pulmonary venous drainage (TAPVD) underwent complete repair within the past six years. The drainage was supracardiac in 11, infracardiac in seven, and into the coronary sinus in two. At repair mean age was nine weeks, and weight was 3.7 km. Operative technique in extracardiac types included complete mobilization of the common vein with division of anomalous channel when possible. The incision in the confluent vein was extended into the lobar veins when necessary to permit extensive incorporation of this structure into the posterior wall of the left atrium and resulted in a nonobstructing stellate-type anastomosis. Operative mortality was 10% (2 of 20). Deaths occurred only in the group of infants in whom severe obstruction to pulmonary venous return required emergency operation, and one of these patients has persistent neurologic deficit. Late cardiac catheterization has been performed in 11 of 18 survivors. Nine had no or only minor abnormalities and two required reoperation. There have been no late deaths with follow-up of 2-8 years (mean = 4 years). Currently, all of the survivors are without cardiac symptoms and only one requires cardiac medication. Our experience identifies pulmonary venous obstruction with critical symptoms as the major operative risk factor in patients with TAPVD. With early operation prior to onset of critical symptoms, mortality is low and functional results are excellent.
An enzyme linked immunosorbent assay (ELISA) technique was modified and used to detect heat-labile (LT) enterotoxigenic Escherichia coli (ETEC) from specimens of faeces sent to a routine diagnostic laboratory. Strains of LT ETEC were detected in eight of 250 (3.2%) diarrhoeal stools but were not found in 110 non-diarrhoeal stools. All eight patients found to have LT ETEC were travellers returning with diarrhoea. LT ETEC was the most common bacterial pathogen found (15.4%) in this group of patients, exceeding Campylobacter sp. (5.8%) and Salmonella sp. (7.7%). The ELISA technique was simple to perform and visual readings were found to be reliable.
Two consecutive infants with pulmonary artery sling underwent successful surgical repair utilizing a median sternotomy for surgical exposure and adjunctive aortopexy. Bronchoscopy demonstrated severe tracheomalacia in both patients which was corrected under direct bronchoscopic control. Median sternotomy (rather than recommended left thoracotomy) provided perfect exposure of the pulmonary artery at its bifurcation thus permitting easy reconstruction of pulmonary artery. Aortopexy eliminated postoperative respiratory symptoms. Both patients are well.
During the past 7 1/2 years, 36 infants (less than or equal to 6 months of age) underwent surgical relief of critical pulmonary valve stenosis. The results of closed and open (cardiopulmonary bypass, CPB) procedures were compared. Closed procedures included Brock valvotomy (two patients) and normothermic inflow stasis with transpulmonary valvectomy (10 patients). Twenty-two patients had open procedures with valvectomy alone (five patients) and right ventricular outflow tract (RVOT) reconstruction (17 patients). Two additional patients had staged operations (shunt followed by open procedure at 3 and 5 months postoperatively). Patients who had the closed procedures, as compared with CPB, were significantly younger (10 versus 61 days, p less than 0.01) and more critically ill with congestive heart failure and acidosis. In addition, the mean peak systolic right ventricular-left ventricular pressure ratios (RVP/LVP) were higher (1.6 versus 1.4, p less than 0.02) in the closed group. There were no deaths in the closed group in contrast to six deaths among those having RVOT reconstruction (0/12 versus 6/17 or 35%, p less than 0.04). Critical obstruction of the pulmonary valve, tricuspid valve regurgitation, and hypoplastia of the right ventricle occurred more frequently in the closed group. All operative deaths resulted from right heart failure. There were no late deaths in the entire series. Three patients in the closed group (mean follow-up 2.8 years) required operations for recurrent pulmonary valve stenosis approximately 2 years postoperatively, and none in the open group (mean follow-up 2.0 years). In conclusion, despite current advances in infant CPB and care, the results from our experience suggests that closed procedures, especially inflow stasis and pulmonary valvectomy, are superior to the use of CPB and RVOT reconstruction, even in the presence of pulmonary valve dysplasia.
Three cases of infant coarctation that could not be repaired by subclavian flap aortoplasty were repaired by alternative techniques. The principles of subclavian flap were considered and its major advantages preserved: in one case by using a common carotid artery flap and in two cases by constructing a free subclavian artery patch graft. Both of these alternatives worked well and should be considered for repair of infant coarctation when the anatomy is unsuitable for subclavian flap aortoplasty.
This study was undertaken in order to investigate the use of fluid perfusion to prevent the adhesion of erythrocytes to a porous foreign surface. Three pore sizes each of two different commercially available polyethylene and aluminum oxide (AI2O3) tubes were investigated. Tubes were perfused with Ringer's solution while immersed in a bath of whole canine blood. Control tubes were prepared in an identical fashion but were not perfused. After testing, tubes were fixed in glutaraldehyde and dehydrated with graded ethanol. Samples were then sectioned and prepared for erythrocyte adhesion analysis by scanning electron microscopy (SEM). Results indicate that fluid perfusion can be used as a means to prevent erythrocyte adhesion in the range of pore sizes (10-60 micrometer diameter) studied. Critical values of the fluid perfusion rate are 0.027, 0.073 and 0.21 ml/min. cm2 for 10 micrometer, 35 micrometer, and 60 micrometer pore polyethylene respectively. The critical values for the ceramic samples are 0.22, 0.16 and 0.72 ml/min cm2 respectively for 7, 11 and 31 micrometer pore diameter respectively.
Human thymocytes normally proliferate poorly in PHA-stimulated cultures, as measured by thymidine uptake. Their response increases when supernatant factors from mitogen-stimulated human lymphocyte cultures (SUP) are added. The cells that proliferate in PHA + SUP-stimulated cultures continue to divide if they are resuspended with fresh SUP every 3 to 4 days. PHA-stimulated thymocytes are deficient in the production of the T cell growth factor interleukin 2 (IL 2). The phenotype of thymocytes prior to stimulation was 90% T6+, 80% T4+, 83% T8+, and 12% T3+, whereas that of the cells after 3 days in culture with PHA + SUP was 1% T6+, 18% T4+, 66% T8+, and 80% T3+. Lysis of T3+ cells from the thymocyte preparation before culture greatly reduced the proliferative response to PHA + SUP. This suggests that the PHA-induced proliferation of more mature thymus cells is restricted by a lack of essential growth factors (either IL 1 or IL 2) and that the co-stimulating activity of SUP on human cells is predominantly on thymus cells that already are T3+.
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A case of chylothorax following a right-sided Blalock-Taussig shunt is presented. Chylopericardial tamponade eventually developed, because the mediastinal leakage of chyle was sealed off from the pleural cavity and diverted into the pericardium. Chylopericardium is a rare cause of an enlarged cardiac silhouette on a postoperative chest roentgenogram, but the importance of differentiating it from congestive heart failure is illustrated. When chylopericardial tamponade occurs, treatment consists of (1) aspiration for immediate relief and, if there is recurrence, (2) surgical evacuation of the pericardium with tube drainage or pericardiectomy and (3) ligation of the source of chylous drainage.
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Between May 1971 and December 1975, 39 infants had operations for correction of total anomalous pulmonary venous drainage. Fourteen of the 39 patients were under 1 month of age at the time of operation. Twenty-four patients had supracardiac, 7 intracardiac, and 6 infracardiac total anomalous pulmonary venous drainage, and 2 had a mixed type. The overall hospital mortality was 36 per cent. There have been no late deaths. The improvement in survival rate in this series is attributed to: (1) earlier recognition and prompt referral, (2) an aggressive approach to diagnosis involving complete cardiac catheterisation and angiocardiography, (3) vigorous preoperative care, (4) early complete correction including construction of a large anastomosis and enlargement of the left atrium when indicated, and (5) intensive postoperative management paying particular attention to fluid balance and treatment of pulmonary complications. Operative mortality was highest in patients with total anomalous pulmonary venous drainage directly to the superior vena cava, and in those with infradiaphragmatic drainage of whom all had pulmonary venous obstruction. Mortality was not closely related to age, body weight, or severity of pulmonary hypertension.
Ligation of a patent ductus arteriosus was carried out in 22 premature infants, 20 with concomitant respiratory distress. The duration of high-volume shunting is critical in determining the prognosis for these infants. Because of the low surgical mortality and morbidity and the high incidence of bronchopulmonary dysplasia in babies managed conservatively, infants with respiratory distress syndrome (RDS) who are respirator dependent should undergo ligation as soon as the presence of large left-to-right shunting is detetmined. Premature infants without RDS or those with mild RDS who are not respirator dependent can be managed medically or with elective ligation. Surgical intervention is strongly indicated in patients with persistent congestive heart failure and respiratory failure. Echocardiography offers an accurate and risk-free approach to the early diagnosis of a large left-to-right shunt through the ductus.
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