Asian Cardiovasc Thorac Ann 2003;11:14-17
© 2003 Asia Publishing EXchange Ltd
Arterial Switch Operation in Neonates With Complex Congenital Heart Defects
Michal Wojtalik, MD,
Girish Sharma, MD,
Wojciech Mrowczynski, MD,
Aldona Siwinska, MD1,
Jacek Henschke, MD,
Rafal Bartkowski, MD,
Malgorzata Pawelec-Wojtalik, MD2,
Maciej Piaszczynski, MD
Department of Paediatric Cardiac Surgery
1 Department of Paediatric Cardiology
2 Department of Paediatric Radiology, Karol Marcinkowski University of Medical Sciences, Poznan, Poland
For reprint information contact: Wojciech Mrowczynski, MD Tel: 48 61 849 1277 Fax: 48 61 847 5228 email: schant{at}main.amu.edu.pl Department of Paediatric Cardiac Surgery, Karol Marcinkowski University of Medical Sciences, ul. Szpitalna 27/33, Poznan 60-572, Poland.
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ABSTRACT
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The aim of the study was to analyze short-term results of the arterial switch operation in 29 neonates with simple transposition of the great arteries (group A) and 18 (group B) with complex heart defects: transposition with a ventricular septal defect (10), coarctation of the aorta (5), or Taussig-Bing anomaly (3). The operations were usually performed on the 7th day of life (2nd–30th day), after a Rashkind procedure when necessary. The mean weight was 3,530 ± 780 g, body surface area was 0.219 ± 0.032 m2. Delayed sternal closure was necessary in 7 patients from group A (24%) and 8 from group B (44%) because of hemodynamic instability after weaning from extracorporeal circulation; these neonates had significantly lower body weights and smaller body surface areas. Perioperative mortality was 13.8% (4 patients) in group A and 27.8% (5 patients) in group B. Correction of complex transposition tends to be associated with a higher operative risk than simple transposition, but the difference was not significant.
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INTRODUCTION
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Anatomical correction of transposition of the great arteries (TGA) was described by Jatene and colleagues1 in 1975, who performed an arterial switch operation (ASO) in a neonate with TGA and a ventricular septal defect (VSD). Subsequently, an ASO became the treatment of choice for children with simple TGA. In contrast to atrial inversion, the ASO avoids the risks of supraventricular arrhythmia and thrombotic obstruction of intraatrial tunnels. Allocating the left ventricle to the systemic circulation provides better long-term results. The ASO can also be performed in patients with the Taussig-Bing variant of double-outlet right ventricle. Anatomical correction of TGA was introduced into our department in 1997. The aim of this study was to assess our early results of the ASO in neonates.
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PATIENTS AND METHODS
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From November 1997 to June 2001, 47 neonates (19 females, 28 males) underwent an ASO. The mean weight was 3,530 ± 780 g, and body surface area was 0.219 ± 0.032 m2. Patients were divided into two groups for analysis. Group A was 29 babies (62%) with simple TGA. Group B was 18 babies with complex defects: 10 cases of TGA and VSD (21%); 5 of TGA, VSD, and coarctation of the aorta (11%); and 3 cases of doubleoutlet right ventricle (6%). Normal coronary artery anatomy was observed in 33 patients; an intramural course of the left coronary artery was detected in one case. The circumflex artery arose from the right coronary in 11 patients, and 3 had a single coronary artery. Other variants were not observed.
Continuous intravenous prostaglandin E1 infusion was administered to all babies, starting during transport to the hospital or after admission and diagnosis. Rashkind septostomy was performed in cases of restrictive foramen ovale. Standard anesthesia and hypothermic (24°C) cardiopulmonary bypass (CPB) with flow reduction and modified ultrafiltration were employed. During the ASO, the coronary arteries were transferred to the excised (not incised) neoaorta. The trapdoor technique was used once. Sternal closure was delayed in cases of hemodynamic instability after weaning from CPB.
Parametric Student t tests were used for variables with a normal distribution. Otherwise, variables were tested by the Mann-Whitney U test. Nominal variables were evaluated by Fisher’s exact test. The following parameters were compared between groups: age, weight, body surface area, CPB time, aortic crossclamp time, mortality, and delayed sternal closure. Values of p less than 0.05 were considered significant.
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RESULTS
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There were no significant differences between the two groups in terms of age, weight, body surface area, mortality, or need for a Rashkind septostomy (Table 1
). Table 2 shows the perioperative data for both groups. The most common cause of death was low cardiac output syndrome despite inotropic support (extracorporeal membrane oxygenation was not available). Delayed sternal closure was necessary in 15 neonates (32%), extending up to 8 days. Table 3 summarizes the differences between patients according to the timing of sternal closure. Postoperative echocardiography revealed pressure gradients of 25 to 36 mm Hg across the neo-pulmonary valve in 1 patient in group A and 3 in group B, and across the neo-aortic valve (25 mm Hg) in 1 patient in group B. There was insufficiency (grade I–II) of the neo-pulmonary valve in 7 patients in group A and 3 in group B, and of the neo-aortic valve in 3 patients in each group.
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DISCUSSION
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Treatment of TGA by an ASO in the neonatal period is the standard method of correcting this defect. Only a few variants of TGA with complex coronary artery anatomy require procedures at the atrial level. In this study, all patients had favorable conditions for performing an ASO. Anatomic correction of simple TGA has a low risk comparable to procedures at the atrial level.2 Our perioperative mortality in patients with simple TGA was 13.8%; some results from other centres were 7%, 7%, 7.6%, and 14%.2–5 In the first Polish report on the ASO in 1992, perioperative mortality reached 29%.6 One center in Central Europe introducing the ASO reported mortality as high as 23%.7
The ASO enables correction of TGA with a coexisting VSD and/or aortic arch anomalies, and the Taussig-Bing variant of double-outlet right ventricle.8,9 It has been observed that simultaneous correction of TGA and concomitant defects does not significantly increase operative risk.10 Complex TGA was associated with perioperative mortality of 27.8% in this series, which is higher than other reports of 8%–21%.4,8 A coexisting defect tends to confer additional operative risk, but the difference in mortality between groups A and B was not significant.
There is general agreement that the ASO should be performed before the 21st day of life because of left ventricular weakening.5,9,11 The strategy of early correction was feasible because of the close cooperation between neonatologic departments. All children in this study, except 3 with complex TGA, were treated before the 14th day of life. The ASO can be carried out under deep or moderate hypothermia, with flow reduction during CPB or total circulatory arrest; both methods give comparable perioperative results.12 We used CPB with flow reduction in all cases, and mean CPB and aortic crossclamp times in neonates with simple TGA did not differ significantly from results in other centers.2,6,8 The longer CPB and aortic crossclamp times in group B were due to the additional corrections in neonates with complex morphology.2,8 Prolongation of the operation can be associated with higher operative risk, reflected in the higher perioperative mortality observed in this group. Coronary artery transfer is the most important part of the ASO. Failure of an anastomosis can induce myocardial infarction, resulting in death.3 Diagnosis of myocardial ischemia is very difficult in neonates.3 To prevent mechanical obstruction of the coronary ostia, the coronary arteries were transferred to the excised part of the neoaorta. Complicated coronary artery anatomy can make the operation difficult. One of our patients had an intramural course of the left coronary, but despite this additional risk, the ASO result was good.
Delayed sternal closure seems to be performed frequently in children with TGA.13,14 The benefit of this practice is derived from decompression of the chest with an edematous heart and lungs. Myocardial and lung edema results from increased parenchymal fluid due to prolonged CPB.13 Delaying closure of the sternum (15 patients) enabled the survival of 11 neonates with hemodynamic instability and low cardiac output syndrome. The significantly lower body weight and body surface area in these babies might have predisposed them to disproportion between chest volume and the total volume of the heart and lungs after CPB. Thus, delayed sternal closure can enhance the survival of neonates with simple TGA and low weight, which is in accordance with previous reports.3 Echocardiographic monitoring is needed in these patients, especially if they have a pressure gradient across the neo-pulmonary valve. Stenosis of this valve is frequent after an ASO.15 This complication can be treated surgically or by balloon valvuloplasty.
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Footnotes
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Presented at the 15th Biennial Congress of the Association of Thoracic and Cardiovascular Surgeons of Asia, December 6–9, 2001, Mumbai, India.
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REFERENCES
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ABSTRACT
INTRODUCTION
