WADY WRODZONE
Short-term results of neonatal arterial switch operation for simple and complex transposition of the great arteries. A single centre experience

Introduction
The aim of this study was to assess early and mid-term results of ASO in a single centre.
Transposition of the great arteries is one of the cyanotic congenital heart defects that can be treated successfully by a surgical approach. Frequency of TGA is around 5-7% of all CHD. In earlier years for treatment of TGA an atrial switch procedure was used (Mustard or Senning operation). Later this procedure was complicated with systemic vein obstruction, arrhythmias, and right ventricular insufficiency. In 1975, Jaten and colleagues [1] introduced the first arterial switch operation (ASO). Subsequently ASO became the treatment of choice in many centres for simple and complex TGA. Advantages of ASO instead of the atrial switch are that the left ventricle works in the systemic circulation and there are fewer problems with late arrhythmias [2-4]. Nevertheless, the ASO remains a complex surgical procedure with possible short- and long-term complications.

Material and Methods
Patients
From December 1997 to June 2009, 150 neonates (68 females, 82 males) underwent an ASO at our centre. Patients’ surgical reports and charts were retrospectively reviewed. Patients were divided into three groups for analysis according to the operation years.
Group I consisted of 54 patients from 1997/12 to 2001/12, Group II of 38 patients from 2001/12 to 2005/12, and group III of 58 patients from 2005/12 to 2009/06. In each group we calculated body weight, body surface area, aortic cross-clamp time, age, CPB time, coronary anatomy and thirty-day mortality; they are shown in Table I, Fig. 1 and Fig. 2.
Fig. 1 shows the thirty-day mortality in each group and Fig. 2 shows coronary anatomy following Leiden classification [5] in the mortality group.
Subsequently each group was divided into two subgroups A and B. Subgroup A consists of patients with simple TGA and an intact ventricular septum and subgroup B consists of patients with complex TGA: TGA/+VSD: CoA; HAA; Taussig-Bing heart.
Fig. 3. shows the thirty-day mortality in every subgroup.

Preoperative management
After admission and diagnosis continuous intravenous prostaglandin infusion was administered to all patients. Rashkind procedure was performed if it was necessary.

Surgical technique
After standard anaesthesia surgery for ASO was performed with systemic hypothermia (24°C) modified ultrafiltration and low flow. Complete circulatory arrest was used selectively, in patients with aortic arch problems. For coronary transfer the trapdoor technique was mainly used [6]. Reconstruction of the pulmonary artery was done with a quadrangular autologous pericardial patch.

Statistics
For check normal distribution was used the Shapiro-Wilk test. Parametric Student t tests were used for variables with a normal distribution. Otherwise, variables were tested by the U test (Mann-Whitney test). Nominal variables were evaluated by Fisher’s exact test. The following parameters were compared between groups: age, weight, body surface area, aortic crossclamp time, mortality. Values of p less than 0.05 were considered significant.
It was checked corelation between patients BSA, age, crossclamp time and mortality in our data. For statistical research depend of following paramters used test analisys tables time of life. Above tests needn’t normal distribution data. The results of survival rate show graphs. Statistic description results done with Statistica 7.0 (StatSoft).

Results

Total thirty-day mortality in group I was 20% (11), and in subgroups A and B was 12% (4) and 33% (7) respectively. In group II total mortality was 8% (3), and in subgroups A and B 6% (1) and 10% (2) respectively. In group III total mortality was 11% (6), and in subgroups A and B 5% (2) and 22% (4) respectively.
The majority of our patients were operated on before the 14th day of life. Regarding Fig. 2, in our study coronary anatomy was not considered as elevating risk. Higher risk for early mortality was associated with complex anatomy in other studies [7, 8], because of prolonged aortic cross-clamp time (Table II). Also it is noticeable that coronary transfer is the most important part of ASO. Failure of an anastomosis can induce myocardial infarction [9], resulting in death. Early post-operative follow-up showed good function of neo-aorta and no significant PA stenosis.

Discussion
Our study has shown that the arterial switch operation (ASO) can be performed safely in patients with simple TGA, regardless of associated intra- or extracardiac defects. This study is in agreement with previously published findings on ASO studies [10]. Our 30-day mortality in the last two groups is around 5% for simple TGA and compares favourably with other published large series, where an early mortality rate between 1.6% and 11% of the ASO has been reported [11]. However, the presence of a VSD, aortic arch obstruction and complicated coronary anatomy has been described as a significant risk factor. We did not observe differences in outcome regarding the coronary pattern. This might be due to improved surgical skills, progress in cardio-pulmonary bypass and cardiac intensive care.
Conclusion
The results indicate that ASO on patients with simple anatomy does not show high risk of mortality; the risk factor is higher with patients having complex TGA. The practice and development of operation skills gives better results. To conclude, ASO can be done with acceptable morbidity and mortality.
According to the research the greatest value of survival is for BSA 0.23 m², age 5 days, time of cross-clamp approximately 70 minutes.

References
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