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Eur J Cardiothorac Surg 2003;24:1-10
© 2003 Elsevier Science NL
Congenital Heart Surgeons Society Data Center, 555 University Avenue, Toronto, ON, Canada M5G 1X8
Received 24 October 2002; received in revised form 21 March 2003; accepted 5 April 2003.
* Corresponding author. Tel.: +1-416-813-6419; fax: +1-416-813-7984
e-mail: bill.williams{at}sickkids.ca
| Abstract |
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Key Words: Transposition Outcome Functional assessment Neurodevelopment Reintervention Multi-institutional
| 1. Introduction |
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In this report we examine the 1217-year follow-up of all 829 neonates with repair of TGA in the 198589 era and entered into the CHSS study. We examine their intermediate survival, prevalence of re-intervention and functional outcomes.
| 2. Materials and methods |
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2.1. Death before repair
Neonates who died prior to definitive repair are excluded from this report (n=34), and this issue was considered in previous publications [1,2]. Among the neonates entering an institution with an arterial switch protocol, there were 13 deaths prior to that repair. These 13 deaths account for a 2.5% mortality prior to repair. The deaths occurred at a median age of 4 days (range 031 days). Among neonates admitted to an atrial repair protocol, there were 14 deaths prior to the repair, a mortality rate of 4.7%. Their median age at death was 9.5 days (range 0155 days) with five of the 13 deaths occurring beyond age one month. Mortality rate prior to repair was higher (15.2%) among those neonates who were candidates for a Rastelli repair. Two deaths prior to repair occurred in patients with important pulmonary stenosis and no ventricular septal defect.
2.2. Morphology and repair technique
The diagnostic categories of the 829 neonates included in the study are simple TGA in 631, TGA/VSD in 167, TGA/VSD/pulmonary stenosis (TGA/VSD/PS) in 30, and TGA/PS in one child. The operative management included an arterial switch (ASO) in 516, an atrial repair in 285 (Senning 175, Mustard 110), and a Rastelli operation in 28. Cross-tabulation of diagnosis and operation is shown in Table 1. There were 108 early deaths after repair (within 30 days of repair or prior to hospital discharge), and 43 children died later. Operative mortality for the ASO is 14.9%, for atrial repair 10.5% (Senning 14.2%, Mustard 3.6%) and for Rastelli, 7.1%.
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2.4. Informed consent
A parent or the child completed a two-page follow-up questionnaire that included information about medication, functional ability, development, pacing, and any voluntary comments. The form also includes a consent section requesting written permission to include the child in the study and to obtain pertinent medical records. Informed consent had not been requested nor even considered at the inception of this observational study. The institutional review board of the Hospital for Sick Children approved the research application of the CHSS data centre, and each participating institution sought approval for their participation from their own review board. The data centre contacted the majority of the patients (72%) and those institutions that preferred to do their own follow-up did so.
2.5. Data collection and analysis
For each patient, pertinent copies of the hospital chart for each admission, including reports of diagnostic and imaging studies, operations and catheter-based interventions, and any autopsy as well summaries of pre- and post-operative care were forwarded to the CHSS data centre. The data centre staff maintain strict confidentiality and created computerized records for each child.
All analyses were performed using SAS statistical software, version 8 (SAS Institute Inc., Cary, NC). Data are described as frequencies, medians with ranges, or means with standard deviations as appropriate. The number of non-missing values is given for descriptive analyses. Missing data that occurred sporadically and at random were managed in multivariable analysis by non-informative imputation of mean value and formation of an indicator variable that was used in analyses for determining if patients with missing values behaved differently with respect to outcome compared to patients with values present.
Time-related freedom from death and re-intervention focusing on late events was studied by hazard function analysis. Non-risk adjusted non-parametric estimates of time-related outcome events (death and re-operation) were obtained by the KaplanMeier method. Parametric estimates were obtained by modelling the hazard function and searching for multiple phases of risk and the characteristic equation for each phase.
Demographic, morphologic, institutional, and surgical risk factors associated with late-phase death or re-intervention including re-operation were sought by multivariable modelling of the parametric hazard function using the variables noted in Appendix A. Variables associated with fewer than five events were eliminated from consideration to minimize the risk of model over-determination. Bootstrap bagging was used for risk factor selection and model validation [4,5]. One thousand bootstrap datasets of the same size as the original dataset were analysed by automated stepwise regression with inclusion criterion of P<0.1.
Functional classification was assigned to each child from the annual follow-up questionnaire using the following criteria:
Multiple logistic regression analysis was used to identify risk factors for learning deficits.
| 3. Results |
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Survival estimates stratified by type of operation illustrate significant differences in overall survival at 17 years by univariate analysis (Mustard 94%, Rastelli 89%, Arterial switch 81% and Senning 74%) (Wilcoxon P=0.001). However multivariable analysis for late hazard risk of death revealed that only the Senning operation (P<0.001) and morphology other than simple TGA (P=0.003) is associated with an increased risk of late death
A comparison of all 516 children managed by an arterial switch operation with the 285 managed by an atrial repair reveals an almost identical 15-year survival of 81 and 82%, respectively (Fig. 2A) . However, the hazard function illustrates that while the early phase is higher for the arterial switch patients (in that era), the ongoing constant phase risk of death is higher for the atrial repair group. (Fig. 2B) There appears to be a crossover of mortality that will occur soon after 17 years.
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3.2.3. Pacemaker implant
Freedom from permanent pacing 15 years after repair is 98% for the arterial switch patients and 89% after an atrial repair. A pacemaker implant was more likely among children with a VSD (P=0.019). Pacemaker implant after an arterial switch was required in eight children (1.8% of operative survivors). Seven of these eight had a VSD. Pacemaker implant after an atrial repair was needed in 23 children (9%), and did not occur until after 1 year from repair, with a steady increase of pacemaker implantations from 1 to 11 years after atrial repair. Incremental risk factors for insertion of permanent pacemaker occurring after repair are a non-arterial type repair (P<0.001) and presence of a VSD (P=0.005).
3.3. Functional assessment
Overall changes in functional class are shown in Fig. 4
. Multivariable analysis showed a quadratic relationship with time, with functional status slowly decreasing and then improving in the adolescent years (P<0.001). Other significant independent variables affecting functional status include arterial switch repair and the presence of ventricular septal defect. The arterial switch patients had significantly greater functional status throughout compared to all other repair types (P<0.001). There was an interaction with time for patients with associated VSD alone, with initially poorer functional status that improved more than for patients with predominately simple TGA (P<0.001).
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Independent risk factors identified that increased the likelihood of learning disability are a longer duration of circulatory arrest, the presence of post-operative seizures, repair type other than arterial switch operation, and two specific institutions (one of which was protective).
| 4. Discussion |
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Neonates born today with simple TGA or TGA/VSD are managed by the arterial switch operation in the neonatal period. The era of this study was the transition away from an atrial type of repair to the arterial switch operation. The follow-up of these children provides a comparison of outcomes for different surgical management protocols from that era. The clinical series includes the initial experience with the arterial switch operation, the so-called learning curve, when the operative risk was 15%, considerably higher than in the present era. In contrast, the techniques of atrial repair were well established and the operative risk lower, especially for the Mustard operation, 3.6%. The early results and risk factors affecting survival have been presented in previous CHSS publications [1,2]. The operative survival of the arterial switch operation for neonates with TGA currently is superior to atrial repair techniques, an outcome that was predicted as early as the 1988 CHSS publication [2].
In comparing the survival outcome of these protocols for neonates born with TGA, it is important to consider deaths prior to an intended repair. Because the ASO is performed in the neonatal period, one would expect lower mortality risk prior to repair. However, even among the ASO group, there were 13 deaths prior to repair, and the mortality risk compared to the atrial group (2.5 versus 4.7%) is only 2.2% different.
Late survival of these children, 81% at 17 years, is a remarkable improvement over the natural history whereby 80% would die in the first month of life. There is a small immutable risk of late death, and the ongoing constant hazard for death after the arterial switch operation is significantly less than for atrial repair although survival at 17 years is identical either with an arterial or an atrial operation. (Fig. 2A,B).
There is ample literature demonstrating that systemic ventricular dysfunction late after an atrial repair is progressive [69]. There is also optimism that ventricular function is preserved late after an arterial switch [1012]. Late arrhythmia, including sudden unexpected death is also far less prevalent after the arterial switch than after an atrial repair [13]. It is not entirely clear to us why the functional class in our patients, as reported in the questionnaire completed by their parents, improved during adolescence, nor why the improvement was more impressive among the children with a VSD. For the atrial repair patients, the absence of a late rise in hazard for death and the functional improvement observed in adolescence, make it difficult to consider recommending either a switch conversion or a transplant within the first 17 years post repair.
In comparing the two atrial repair operations, early and late survival and the prevalence of re-operation is significantly better in the Mustard patients, either for simple TGA or TGA/VSD as reported previously by Wells [3]. These differences are not surprising given the historical sequence of the operations. Mustard's contribution followed Senning's by 5 years but was technically simpler and reproducible by other surgeons. By multivariable analysis, only the Senning operation and non-simple TGA morphology are identified as risk factors for late phase death. Other comparisons of these two operations from single institutions are confounded by the fact that the operative series were not concurrent.
Neonates with TGA/VSD/PS undergo intra-cardiac repair at an older age, and their mortality risk prior to repair is substantial (15.2%). Repair consists of connecting the left ventricle to the aorta via the VSD and construction of conduit between the right ventricle and pulmonary artery as described by Rastelli and modified by LeCompte and others [1416]. Only 28 children (3.4%) in our series, including three with VSD but no PS, underwent this type of repair and their survival is excellent. The prevalence of TGA/VSD/PS is under-represented in this series because children with these associated lesions may not present until after age 2 weeks. Pulmonary conduit failure requiring re-operation compromises their late result.
The prevalence of re-intervention is predictably higher for the Rastelli operation, given the necessity of conduit replacement. Baffle-related complications and arrhythmia are the usual indications for re-intervention after an atrial repair, and are more likely after a Senning than a Mustard repair. After an arterial switch operation, right ventricular outflow stenosis is the most common indication for re-intervention [17]. We have not observed late re-intervention for coronary artery stenosis after the arterial switch, but it may be overlooked without specific investigation including coronary angiography [18,19]. As in other studies, growth of the neo-aortic valve and new left ventricular outflow tract is usually normal [20]. Late neo-aortic valve insufficiency leading to re-operation is also rare and to date has occurred in only one child in our series, in whom a Ross operation 10 years after the TGA repair failed, and led to re-replacement of the aortic valve with an allograft.
In the annual follow-up questionnaire, some parents reported a decrease in their child's functional ability. The change in functional ability is much more evident among the atrial repair group, and by inference from the literature, is probably due to failing systemic ventricular function, arrhythmia and tricuspid valve regurgitation. But a decrease in functional ability is also seen to a lesser extent among the arterial switch patients and the mechanism accounting for this gradual change is not known. These observations parallel a study we conducted using a Child Health Questionnaire that was completed by a cohort of 310 of these children after TGA repair (Culbert et al., in preparation).
An alarming finding in this study is the high prevalence of psychosocial deficits as reported by the parents, especially learning difficulties. Studies from Boston I year after the arterial switch identified learning, speech and developmental delay in children who had been randomized to have circulatory arrest or hypothermic bypass with hemodilution to 20% and the alpha stat strategy [21,22]. Bellinger reported that the use of circulatory arrest was associated initially with worse motor coordination, but by 8 years of age, both groups had a lower than anticipated IQ. They correlated lower IQ and academic achievement with worse psychosocial health. Hovels-Gurich studied 33 children 34.6 years after an arterial switch and demonstrated that circulatory arrest and low flow bypass is associated with neurologic impairment [23]. Recent studies suggest that higher hematocrit and use of pH-stat perfusion techniques may reduce the incidence of developmental delay after circulatory arrest or continuous hypothermic bypass [24]. In our study, the pH strategy did not correlate with late developmental deficit, although institutional differences, both positive and negative were independent risk factors affecting the prevalence of learning disorders. The duration of circulatory arrest is also a predictor of learning deficit. Forbess found that arrest periods exceeding 39 min were associated with deficits of visual-motor and fine motor skills and possibly with full-scale IQ [24]. We could not identify a cut-point (i.e. a point at which any period of circulatory arrest was either safer or more dangerous) that affected this outcome. The use of circulatory arrest should be limited.
4.1. Limitations of the study
While the advantages of a multi-institutional enrolment of patients is evident in accumulating a large experience during a short interval, the Data Center relies on voluntary institutional patient enrolment. The Data Center did not audit the institutional enrolment but are grateful for the enormous cooperation the participating institutions provided. Once patients were identified, often prior to surgical intervention, all were followed to definitive therapy or death.
The age at admission to a CHSS institution was limited to <15 days. Therefore we have no information regarding the outcomes for babies with transposition who present later.
Although follow-up data was known by completed questionnaire for 83% of the children, and the recent status of another 4% was known, 13% of the cohort had less complete follow-up albeit a mean of 7.9 years after repair. Unknown events that may have occurred among these children could affect the analysis, although the statistical techniques of adjusting for this group lessen that impact.
Late functional assessment and psycho-social deficits were as reported by the parents of these children (n=562). While this data is not generated by objective testing, we are confident that the parents annual reports are reliable and we thank them for their cooperation in providing the information.
4.2. Conclusion
The protocol change to the arterial switch operation that occurred in this 198589 era for managing neonates with simple TGA or TGA/VSD is clearly supported by our outcomes data for children now 1217 years after TGA repair. Experience since that time has further improved early survival after the arterial switch. These improvements may also result in fewer long-term complications. Future improvement in care should focus upon protecting these children from neurologic injury during their early management.
| Acknowledgments |
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| Footnotes |
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| Appendix A. Demographic, morphologic, and procedural characteristics entered into multivariable analyses for risk factor determination |
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| Appendix B. Conference discussion |
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Dr Williams: Well, I feel somewhat embarrassed presenting this in Europe where the Senning originated, but I don't find it surprising. If you look at the history of the Senning operation, it preceded the Mustard operation by 5 years, and yet I think other surgeons had difficulty duplicating this very elegant operation. I think that the Mustard is a safer, simpler procedure that more surgeons could do. As time evolved and we realized there were problems with the Mustard operation, some surgeons went back to the Senning and got better results, but even during this study period of 1985 to 1989, outcomes are not as optimal as those for the Mustard. And I would stress that this is a multi-institutional study. There is no need for one institution to do one operation or the other. They did the procedure they thought was best, and invariably the people doing the Senning's felt it would be the best operation, but I think the data speaks for itself.
Dr K. Samir (Marseille, France): As I was from the new generation where we didn't have many chances to see the atrial switch operation, I want to ask you if there are still indications for the atrial switch operations in some of the transposition of the great arteries, especially for the unique intramural coronary artery.
Dr Williams: I think you have pointed out something that's important, and I would stress that this data included only children admitted in the first 14 days of life. I think the quandary of whether to still do atrial switch surgery is based on late presentation, and if we had the exceptional child presenting at a much older age, then the consideration of whether you do an arterial switch or an atrial switch is a different question not addressed by this data. I could give you my personal opinion, but it wouldn't be based on this particular information.
Dr F. Lacour-Gayet (Hamburg, Germany): I have a couple of questions. We tried to stratify the complexity of the arterial switch operation and there are many different factors involved. I would like to ask you what you call a non-simple TGA, and if the long-term results are less satisfactory in patients with additional cardiac lesions and associated procedures?
Dr Williams: Well, in the interest of time, I didn't show you the data for morphology, but the constant phase mortality for simple TGA is better than for other forms of TGA, that is, VSD, VSD/PS. But I would also stress that these data refer to the constant phase of mortality, not the early mortality. We have addressed that previously. And I think the coronary artery anatomy may well be important in the early survival, but that's not addressed in this analysis. We only looked at the constant or late phase.
Dr Lacour-Gayet: I have another question. At Marie-Lannelongue over 1000 arterial switches were followed, and it was absolutely clear that in patients with associated aortic arch obstruction, particularly TaussigBing, the risk of late RVOT obstruction was important. I want to ask you if you have seen that in your series.
Dr Williams: The prevalence of late RV outflow tract obstruction?
Dr Lacour-Gayet: The prevalence of reoperation for RVOT stenosis in patients with TaussigBing associated with aortic arch obstruction.
Dr Williams: Well, as you saw, the RV outflow tract obstruction was the most common reason for reoperation in the arterial switch group. In this paper we didn't look at the criteria affecting the reoperation for that subgroup. We have in a previous paper, and I think you're quite right, that the downstream obstruction affects outcome.
Dr C. Schreiber (Munich, Germany): Could you please clarify this swing in functional classes which you were showing. What were the reasons for that?
Dr Williams: A good question, to which the short answer is I don't know. The longer answer is that it did not mean that the children in poorer functional class were dying and therefore the proportion was greater. That didn't seem to be the case. I think one thing we did see was the effect of treatment. If children were having problems at 10 or 11 years of age and underwent treatment, whatever that might be, they improved and their functional class got better. Beyond that I don't know the explanation for it.
Dr Schreiber: They didn't show an impairment of ventricular function maybe due to coronary stenosis or e.g. aortic insufficiency?
Dr Williams: No, and we do not have that information about whether these children have coronary artery stenosis and we don't have a direct measurement of their ventricular function.
Dr G. Sarris (Athens, Greece): As a result of the data indicating a long-term adverse effect of circulatory arrest in these patients, has the Congenital Heart Surgeons Society come to a recommendation regarding avoidance of circulatory arrest and using full bypass during this operation?
Dr Williams: Well, I don't think this society has policies along that line, but I think management of these infants has evolved to points that we can avoid circulation arrest. Three-quarters of these patients were done with circulation arrest, and it didn't matter whether it was an arterial switch or an atrial repair, and I would think today that probably very few of us would use circulation arrest for an arterial switch operation. I wouldn't want to leave you with the impression that all of our patients or at least 31% of our patients today have learning deficits or will have learning deficits. I think it should be much less than that, but it's probably a long way from zero, and I think we need to focus on that area. We've dealt in the last 15 years with coping with mortality, and I think it's time to look at functional outcome rather than alive or dead basically.
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