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Biomedical subjects

R B Mee

Publications and source records attributed to R B Mee.

At least 55 records · Page 3Linked to original sources
PubMed1993

Transatrial-transpulmonary repair of atrioventricular septal defect with right ventricular outflow tract obstruction.

Twenty patients had a repair of an atrioventricular septal defect with tetralogy of Fallot (n = 13) or double outlet right ventricle (n = 7). Mean age was 3.5 years. Surgical technique included transatrial-transpulmonary resection of right ventricular outflow tract obstruction and transatrial two patch repair of the atrioventricular septal defect. Ten patients required a transannular patch and one patient had a right ventricle-pulmonary artery conduit placed. There was no hospital mortality, and mean hospital stay was 15 days. One patient had late sudden death of unknown cause. Six patients have required reoperation because of residual ventricular septal defect (VSD), mitral incompetence, residual right ventricular outflow tract obstruction, and/or conduit stenosis. No patient was reoperated on because of left ventricular outflow tract obstruction. Fifteen patients are asymptomatic, one has exertional dyspnea, and two have intermittent occasional bronchospasm. The transatrial-transpulmonary two patch repair and extensive relief of right ventricular outflow tract obstruction have given good immediate results. Reoperation rate has been high mainly due to residual VSD and mitral incompetence.

Actuarial Analysis↗
PubMed1993

Cardiopulmonary bypass in neonates weighing less than 2.5 kg: analysis of the risk factors for early and late mortality.

A low weight has been implicated as one of the major reasons for deferring cardiac surgical procedures on cardiopulmonary bypass (CPB), resorting instead to palliative procedures. The purpose of this study is to analyze the risk factors associated with an increased mortality for surgery using CPB in small infants, and to compare this group with infants weighing over 2.5 kg. Between 1979 and 1990, 60 infants weighing less than 2.5 kg underwent surgery on CPB at our institute. The mean age was 17.9 days (range 1 to 68 days, SD = 16.4) and the mean weight was 2.1 kg (range 1.2 to 2.5, SD = 0.35). Eight had univentricular and 52 had biventricular repairs. The hospital mortality was 16.5% (70% CL 11.5% to 22.7%). The actuarial survival over 100 months was 67.5% (including hospital mortality). Over the same period, 946 patients under the age of 6 months but weighing more than 2.5 kg underwent surgery on CPB with a lower hospital mortality of 7.1% (70% CL 6.3% to 8.0%, p < 0.006). The risk factors associated with an increased risk of early death in the group weighing less than 2.5 kg were analyzed using logistic regression. They were: (1) presence of preoperative metabolic acidosis; (2) univentricular versus biventricular repair; and (3) duration of CPB. Within the less than 2.5 kg group, low weight per se did not affect the outcome adversely. The main cause of late death was the presence of associated medical conditions, notably bronchopulmonary dysplasia and tracheo bronchomalacia.

Cardiopulmonary Bypass↗
PubMed1993

Extracorporeal membrane oxygenation life support: a new approach.

The use of extracorporeal life support (ECLS) is considered in children who (1) have an acute life-threatening heart or lung disease, (2) are normal before the illness and are likely to be normal if they survive, and (3) have an 80% chance of death. Our use of a constrained vortex pump (CVP) offers a number of potential advantages compared to a roller pump. The circuit is designed to provide the capability of changing over to a new circuit while maintaining full support and is primed to match the biochemistry of the patient as closely as possible. Since May 1989 at the Royal Children's Hospital, Melbourne, Australia, we have provided ECLS to 30 neonates (20 of whom survived) and 22 children (eight of whom survived). ECLS is a useful technique for supporting patients who are unable to be adequately ventilated or oxygenated or who have an inadequate cardiac output.

Blood Flow Velocity↗
PubMed1993

Recent results with the modified Fontan operation.

From Jan 1989 to December 1991, 61 patients had modified Fontan procedures for a variety of lesions, including tricuspid atresia (18), mitral atresia (3), double inlet ventricle (14), isomeric hearts (4) and others (22). The hospital mortality was 1.6% (70% CL.0.2-5.3%). There were 2 late deaths. The median age at operation was 3.7 years (mean 5.6, range 1.5 to 20.3 years). There were two late failures at 2 months and 30 months after the operation, requiring take down of the Fontan in one and heart transplantation in the other. The 89% of the patients followed up are in NYHA class I or II at a mean follow up of 21.5 months (range 3-35 months). This suggests that the modified Fontan operation performed with the current patient selection criteria can be performed with a low mortality and that the early results are encouraging in the majority of the patients.

Adolescent↗
PubMed1993

Transposition of the great arteries with intact ventricular septum. Arterial switch repair in patients 21 days of age or older.

Since 1985 we have performed arterial switch repair for infants with simple transposition of the great arteries (with intact or virtually intact ventricular septum) who were younger than 2 months of age. As of December 1990, a total of 118 arterial switch operations had been performed for transposition of the great arteries with intact ventricular septum. Although correction is usually performed in the first 14 days of life, 18 infants had operations at or after 21 days (range 21 to 118 days; mean 38 days). Fourteen of 18 patients had echocardiographic or catheter evidence (or both) of low left ventricular pressure at the time of operation. None of these patients had preliminary pulmonary artery banding. Mortality was 5.6% (1 of 18 patients, confidence limit 0.8% to 17%) for the older group versus 0% (0 of 100 patients; confidence limit, 0% to 1.8%) for patients less than 21 days of age. The single death occurred in a 22-day old, 1.8 kg premature baby, probably as a result of a problem with a coronary anastomosis. One patient required a left ventricular assist device for 2 days after the operation. These data suggest that with appropriate perioperative management and support, the arterial switch procedure can be safely carried out as a primary procedure for patients up to the age of 1 month and probably up to the age of 2 months.

Age Factors↗
PubMed1992

Interrupted aortic arch in infancy: a 10-year experience.

Fifty infants with interrupted aortic arch (IAA), admitted between 1979 and 1988, were reviewed. They usually presented early in severe cardiac failure or shock. In the initial 5-year period, 17 of the 21 infants underwent diagnostic or confirmatory cardiac catheterization, in contrast with the latter 5 years when only eight of the subsequent 29 patients underwent catheterization. Since 1987, all patients underwent surgery after cross-sectional echocardiography. Fifteen infants had a type A IAA and 35 had type B. All had associated cardiac anomalies. Four infants were not operated on. In the initial 5-year period, of 17 infants who were surgically treated, four had a one-stage total repair, the remaining had a two-stage repair with initial reconstruction of the arch and pulmonary artery banding. There was an overall surgical mortality of 65%, reflecting the precarious state of many of these infants before surgery with a significant contribution from unrelieved subaortic stenosis. In the latter 5-year period, 29 underwent surgery, 22 had a one-stage total repair. There were three deaths, all in infants whose active treatment was withdrawn. The outcome of the survivors has generally been good, subsequent surgery being mainly related to the associated anomalies (e.g., recurrent subaortic stenosis, conduit replacement). Over this 10 year period the greater accuracy of noninvasive diagnoses, and perioperative intensive care, have led to an improvement in the preoperative state of these infants. Single-stage total repair is our procedure of choice.

Aorta, Thoracic↗
PubMed1992

Absent pulmonary valve syndrome: operation in infants with airway obstruction.

From 1979 through 1991, 19 infants with absent pulmonary valve syndrome and airway obstruction were seen for surgical treatment. All patients underwent extensive pulmonary artery aneurysmorrhaphy using cardiopulmonary bypass. Fourteen patients had simultaneous transatrial ventricular septal defect (VSD) closure, infundibular resection, and placement of a short transannular patch; 2 had transventricular VSD closure and infundibular resection without a transannular patch; 1 underwent transventricular VSD closure and transannular patching; and 2 underwent pulmonary artery aneurysmorrhaphy alone with the VSD left open. All 19 infants had good hemodynamics when taken from the operating theater, but 3 died postoperatively of severe airway obstruction, despite further tracheobronchopexy procedures in 2 (hospital mortality rate, 16%; confidence limits, 7% to 29%). Among the 16 patients discharged from the hospital, there was one late death. Five other patients have required reoperation for branch pulmonary artery stenosis (n = 2), residual airway obstruction resulting from persistent pulmonary artery dilatation (n = 1), closure of VSD (n = 1), and homograft valve insertion for pulmonary incompetence and right ventricular dysfunction (n = 1). There are 15 long-term survivors. Eight of them have episodic bronchospasm of mild to moderate severity, and all are responsive to sympathomimetic bronchodilator aerosols. The remaining 7 are asymptomatic.

Airway Obstruction↗
PubMed1992

Tetralogy of Fallot: favorable outcome of nonneonatal transatrial, transpulmonary repair.

This report describes our experience with 366 patients who had a transatrial, transpulmonary repair of tetralogy of Fallot between December 1980 and December 1991. Included in this group are patients with tetralogy of Fallot plus atrioventricular septal defect as well as patients displaying all degrees of aortic override (in the presence of subaortic ventricular septal defect and right ventricular outflow tract obstruction). Median age was 15.3 months and median weight, 12.3 kg. Of the 366 patients, 72% required a pericardial patch to reconstruct the main pulmonary artery or right ventricular outflow tract. Serious coronary anomalies were seen in 11 patients, without influencing surgical approach. There were two hospital deaths (0.5%; 70% confidence limits, 0.2% to 1.2%). Actuarial survival was 97.5% at 42 months (95% confidence limits, 95% to 99%) reflecting four late deaths over 1,129 patient-years of follow-up. Postoperative cardiac catheterization studies were performed in 61 patients at a mean follow-up interval of 23 months. Mean right ventricular/left ventricular systolic pressure ratio after repair was 0.46 (standard deviation, 0.28), and mean gradient across the right ventricular outflow tract was 15 mm Hg (standard deviation, 24 mm Hg). Actuarial freedom from reoperation for any reason has been 95% (95% confidence limits, 92% to 97%) at 5-year and 10-year follow-up. These early and medium-term results encourage us to continue with transatrial, transpulmonary repair of tetralogy of Fallot. We believe that this approach has an operative risk similar to or lower than transventricular repair, and that it will result in better preservation of right ventricular function in the long term.

Child, Preschool↗
PubMed1992

Complete thoracic ectopia cordis with double-outlet right ventricle: neonatal repair.

A case of total thoracic ectopia cordis with double-outlet right ventricle and ventricular septal defect is presented. Prenatal diagnosis allowed single-stage correction immediately after birth. This approach proved to be technically feasible. Death occurred on the twelfth postoperative day owing to sepsis unrelated to the repair.

Abnormalities, Multiple↗
PubMed1992

Congenital heart surgery.

In reviewing selected publications on congenital heart disease management for 1990 and 1991, some topics have been chosen for discussion, including isolated patent ductus arteriosus, coarctation of the aorta, critical aortic stenosis in early infancy, hypoplastic left-heart syndrome, pulmonary artery banding, Fontan procedures, pulmonary atresia and intact ventricular septum, Ebstein's anomaly, tetralogy of Fallot, transposition of the great vessels, and others.

Aortic Valve↗
PubMed1992

Outcome of infants with birthweight 2000 g or less who undergo major cardiac surgery.

A retrospective study of all neonates with birthweight 2000 g or less undergoing major cardiac surgery at the Royal Children's Hospital, Melbourne over the last 5 years was performed in order to determine outcome and identify subgroups within this population that may have a poor prognosis. The mean length of stay in intensive care following surgery was 32 days, with non-survivors having a significantly longer duration of stay than survivors. Overall mortality was 43%, and for children with congenital heart disease as part of a recognizable syndrome the mortality was 100%. None of the survivors suffered incapacitating cardiac, neurological or respiratory handicap. These children in general have a poor prognosis and utilize significant resources; results of cardiac surgery in this group need to be closely followed in the future.

Cardiac Surgical Procedures↗
PubMed1992

Cardiac conduction abnormalities and rhythm changes after neonatal anatomical correction of transposition of the great arteries.

Seventy three infants who underwent neonatal anatomical correction for transposition of the great arteries with or without a ventricular septal defect were reviewed for evidence of conduction and rhythm abnormalities on preoperative and postoperative 12 lead electrocardiograms and during 24 hour Holter monitoring. There was a partial right bundle branch block pattern in 47% (29/62) of all patients and in 60% (24/40) of those with simple transposition. Complete right bundle branch block was noted in 21% including 5% with simple transposition. Holter monitoring showed sinus rhythm in all patients except three: one had episodes of supraventricular tachycardia, another an intermittent second degree heart block, and a third a complete heart block. Atrial extrasystoles were noted in 47% (29/62) of patients but were frequent in only three patients. Occasional unifocal ventricular extrasystoles were encountered in 37% (23/62) of patients and were frequent in a further 3% (2/62). Only one patient (2%) developed multifocal ventricular extrasystoles. The frequency of important cardiac arrhythmias after neonatal anatomical correction of transposition of the great arteries was 5%, significantly less than that reported after atrial inflow diversion for the same malformation.

Arrhythmias, Cardiac↗
PubMed1992

Repair of hypoplastic or interrupted aortic arch via sternotomy.

Herein we describe our experience with repair of interrupted aortic arch and coarctation plus hypoplastic aortic arch in 55 consecutive infants (1984 to 1990). Median age at operation was 6 days and median weight 3.1 kg. Associated severe intracardiac anomalies were the rule. All patients had significant congestive cardiac failure, and the majority required prostaglandin E1 resuscitation and inotropic support (with or without ventilation) before the operation. All operations were performed via sternotomy with core cooling and circulatory arrest. Isolated myocardial perfusion was used in 13 patients during arch repair. A complete intracardiac (biventricular) repair was performed except in patients expected to require a Fontan operation as definitive treatment. The operative mortality overall was 14.5% (confidence limits 10% to 22%). For arch repair plus biventricular intracardiac repair, the operative mortality was 9% (confidence limits 5% to 15%), and for arch repair plus palliative intracardiac repair, 40% (confidence limits 22% to 60%). The mortality in the isolated myocardial perfusion group was 0% (confidence limits 0% to 14%), which may be related to reduced myocardial ischemic time (p less than 0.05). Actuarial survival was 75% (confidence limits 65% to 83%) at 12 months, with no subsequent deaths over 1294 patient-months (mean 28 months) of follow-up. Actuarial freedom from recurrent arch obstruction was 69% (confidence limits 48% to 85%) at 46 months' follow-up. Primary repair of interrupted aortic arch and coarctation plus hypoplastic arch compares favorably with a staged approach and is recommended even when complex intracardiac anatomy is present.

Aorta, Thoracic↗
PubMed1991

Current status of cardiac surgery in childhood.

In the 50 years since Gross (1938) obliterated a patent ductus arteriosus, congenital cardiac surgery has come of age, synchronized with the world explosion in microtechnology and space age materials. The late 1960s and early 1970s saw Barratt-Boyes pioneering complete intracardiac repairs on infants with congenital heart disease employing modifications of the Kyoto technique (Shirotani) for profound hypothermia and circulatory arrest. The past 10-15 years have been marked by the more widespread dissemination of increasingly safe techniques, and the application of progressive incremental refinement to the entire management package of complex congenital heart disease. Many innovative methods and concepts have been added to the therapeutic armamentarium of the congenital heart team. Currently, transplantation adds the prospect of "second chance", and in the future may constitute preferred primary management in certain complex forms of congenital heart disease. In the Western world the concept of "frequency sensitivity" and the value of rationalizing congenital heart surgery facilities, such that a single unit manages a population of 8-12 million, is established, though not necessarily widely accepted and acted upon. High-volume, low-risk units emerge such that operative mortality, despite the high acceptance rate of complex problems and high rates of neonatal and infant complex repairs, has dropped below 5%. Paradoxically, the so-called simple closed surgery (neonatal coarctation, shunts and other palliative procedures in complex congenital heart disease) retain relatively high risk and must be regarded as one of the areas of challenge over the next 5-10 years.

Child↗
PubMed1991

Staged repair of pulmonary atresia with ventricular septal defect and major systemic to pulmonary artery collaterals.

Fifty-eight consecutive patients with pulmonary atresia, ventricular septal defect, hypoplastic pulmonary arteries with arborization defects, and major aortopulmonary collaterals were entered into a program for staged surgical repair between January 1979 and July 1989. Prerepair preparatory procedures were designed to (1) encourage native pulmonary artery growth by increasing blood flow and (2) unifocalize pulmonary blood supply by transplanting or ligating major collaterals. A total of 121 staging procedures were performed with an overall mortality of 10.3%. One hundred thirty-four major collaterals were either ligated or transplanted. Thirty patients eventually underwent hemodynamic repair with an early mortality of 3.3% and late mortality of 10.0%. Twenty-six current survivors of repair remain clinically well after a mean follow-up of 3.6 years. Ten patients are currently in various stages of preparation. Twelve patients (20.7%) failed to achieve minimum requirements for repair after staging and await further palliation or heart-lung transplantation. The principles of management have evolved over the years and are discussed.

Abnormalities, Multiple↗
PubMed1991

Operations for subaortic stenosis in univentricular hearts.

Optimal prevention and treatment of subaortic stenosis (SAS) in the univentricular heart with subaortic outlet chamber and high pulmonary blood flow remains controversial, especially when complicated by aortic arch obstruction. Herein we analyze our surgical results. Group 1 consisted of 11 infants (mean age, 10 days) with univentricular heart and SAS. Ten required repair of interrupted aortic arch (n = 7) or coarctation with hypoplastic arch (n = 7). Four patients had relief of SAS by either Damus-Kaye-Stansel connection (n = 2) or aortopulmonary window (n = 2), with three operative deaths and one late death. Six had one-stage arterial switch and atrial septectomy with arch repair (5/6) with one operative death and one late death. Two survivors have progressed to bidirectional cavopulmonary shunt, a third has had a Fontan operation, and a fourth awaits Fontan. In group 2, 11 children required operation for acquired SAS after pulmonary artery banding. Nine have progressed to Fontan operation with either staged (n = 3) or concurrent (n = 6) relief of SAS by Damus-Kaye-Stansel connection or subaortic resection. Fontan mortality was 11% (70% confidence limits, 2% to 32%). Group 3 consisted of 3 patients without pulmonary artery banding who had SAS diagnosed at Fontan evaluation. All 3 survived Fontan operation and relief of SAS by Damus-Kaye-Stansel connection or subaortic resection. Group 4 consisted of 1 patient with previous pulmonary artery banding (no SAS) who underwent Fontan operation but required Damus-Kaye-Stansel connection 30 months later for SAS.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Multiple↗
PubMed1991

Very small pulmonary arteries: central end-to-side shunt.

Between 1980 and 1989, 28 patients with pulmonary atresia, ventricular septal defect, and very small pulmonary arteries with major aortopulmonary collateral arteries underwent direct central end-to-side shunts as staging procedures. Age range was 2 months to 32 years, with 19 patients less than 1 year of age. Pulmonary artery diameters ranged from 1 to 4 mm, with 24 less than 3 mm. Two patients (7%; 70% confidence limits, 2% to 16%) died after the shunt, and there were two further deaths after subsequent staging or correction. Acute shunt complications included congestive cardiac failure (mild to moderate, n = 8; severe, n = 3) and endocarditis (n = 1). Proximal right pulmonary artery stenoses have occurred in 75% of patients and left pulmonary artery stenoses, in 50%. Satisfactory pulmonary artery growth was achieved, however, in 16 of 24 hospital survivors investigated postoperatively. Twelve patients have proceeded through unifocalization to biventricular repair (in 2 the ventricular septal defect patch was subsequently fenestrated) with one death (8.3%; 70% confidence limits, 1% to 25%). Eight patients are still in staging, and 4 have been excluded from the program because of inadequate unifocalization. The direct central end-to-side shunt has proven satisfactory in attaining pulmonary artery growth in patients with very small central pulmonary arteries.

Adult↗