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J Thorac Cardiovasc Surg 2007;133:1540-1546
© 2007 The American Association for Thoracic Surgery
Surgery for Congenital Heart Disease |
a Department of Cardiac Surgery, Children’s Hospital Boston, Harvard Medical School, Boston, Mass
b Department of Cardiology, Children’s Hospital Boston, Harvard Medical School, Boston, Mass.
Read at the Eighty-sixth Annual Meeting of The American Association for Thoracic Surgery, Philadelphia, Pa, April 29-May 3, 2006.
Received for publication April 26, 2006; revisions received December 6, 2006; accepted for publication December 13, 2006. * Address for reprints: Pedro J. del Nido, MD, Department of Cardiac Surgery, Children’s Hospital Boston, 300 Longwood Ave, Bader 273, Boston, MA 02115. (Email: pedro.delnido{at}tch.harvard.edu).
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Abstract |
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Methods: From January 2000 through June 2005, 210 patients underwent stage I palliation. To enlarge the aortic arch, 12 (6%) patients had a direct connection, 115 (55%) patients had an aortic homograft, 53 (25%) patients had a pulmonary homograft patch, and 30 (14%) patients had autologous pericardium. Independent of the technique for aortic enlargement, 55 (26%) children had coarctectomy.
Results: Eighty patients had a significant arch gradient, as determined by means of echocardiography, and of these, 50 required balloon angioplasty, surgical arch augmentation, or both. Preoperative aortic coarctation was consistently linked to neoaortic arch obstruction (P = .032). Patients having aortic arch enlargement by means of direct connection or with autologous pericardium were less likely to have neoaortic arch obstruction (P = .049). Coarctectomy resulted in a lower incidence of neoaortic arch obstruction, as determined by means of echocardiography (P = .015), or need for reintervention (P = .01).
Conclusions: Patients with hypoplastic left heart syndrome undergoing aortic arch enlargement with autologous tissue are less likely to require intervention for neoaortic arch obstruction compared with those having homograft patch reconstruction. Excision of all ductal tissue by means of coarctectomy reduces the risk of recurrent aortic arch obstruction. An aggressive approach to reconstruction of the arch and the use of autologous tissue at the time of stage I palliation is advocated.
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Introduction |
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HLHS involves a wide spectrum of underdevelopment of the left-sided heart structures, characterized by aortic and/or mitral valve atresia or severe stenosis with hypoplasia or absence of the left ventricle.2,3 Coarctation of the aorta is usually associated with the anomaly.4,5 The first successful palliative operation for this complex cardiac anomaly was reported by Norwood and colleagues in 1983.6 The surgical technique achieved reconstruction of the aortic arch by means of direct anastomosis between the pulmonary artery trunk and the diminutive aorta. Although this procedure has been advocated recently by some groups,7-10 it was abandoned by Norwood and others because surgical anatomy was not usually deemed suitable to carry out this approach, with recurrent arch obstruction and left pulmonary artery stenosis being frequently observed. Augmentation of the aorta and arch remains a critical step in the Norwood operation, and surgical technical problems have been reported as the leading cause of sudden circulatory arrest and death early after the Norwood operation.11,12 Neoaortic arch obstruction (NAO) is one of the key features affecting morbidity and mortality after the stage I palliation or Norwood operation, with a reported incidence ranging from 11% to 37%.13-17 Recurrent arch obstruction can result in decreased cardiac output, ventricular dysfunction, and tricuspid regurgitation. However, there is not a standard surgical approach for the reconstruction of the aorta at the time of stage I palliation. The aim of this study was to compare the various surgical techniques used to augment the aortic arch at the time of the stage I procedure with respect to recurrence of NAO and need for balloon dilation, repeat surgical reconstruction, or both.
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Materials and Methods |
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Surgical Procedure
The surgical procedure for coarctectomy entails resection of the aorta at the level of coarctation, wide resection of all the ductal tissue and the posterior shelf, extended counterincision distally in the anterolateral aspect of the descending thoracic aorta, mobilization of the supra-aortic trunks, and direct end-to-end anastomosis between the greater curvature of the native aortic arch and the descending aorta, along with patch augmentation of the aorta with autologous pericardium treated with glutaraldehyde 4% for 10 minutes or heterologous tissue.
Regardless of the surgeon’s preferences, in the vast majority of patients, our approach for HLHS entails deep hypothermic circulatory arrest, with pH-stat for less than 28°C and a hematocrit value of greater than 25%. One hundred forty-four patients in our series underwent delayed sternal closure.
Statistical Analysis
The 2 primary outcome variables were recurrence of NAO and need for balloon dilation, repeat surgical reconstruction, or both, and a secondary outcome variable was in-hospital mortality. Relationships between patient and surgical characteristics and outcomes were evaluated by using the Fisher exact test. Multivariate analyses were performed with logistic regression. As part of the multivariate analysis, interactions among variables included in the logistic regression model were explored.
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Results |
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At a median follow-up of 1.7 years (range, 4 days-5.7 years) 172 (82%) patients are alive, 170 (81%) patients have had a stage II palliation, and 84 (40%) patients have completed stage III of palliation. Twenty (10%) of the 210 patients died in the hospital. Interstage mortality was 6% (13 patients). Weight at the time of the operation of less than 3 kg was significantly associated with early postoperative death (P = .001); overall mortality for patients weighing 3 kg or greater was 4% (6/136), whereas it was 19% (14/73) in patients weighing less than 3 kg at the time of the stage I operation. There was also higher mortality in patients with aortic atresia–mitral stenosis (P = .030). In the multivariate analysis weight at the time of the operation of less than 3 kg (P = .002) and aortic atresia–mitral stenosis (P = .023) were risk factors for death, with odds ratios of 5.0 and 3.3, respectively.
The incidence of a significant gradient, as determined by means of echocardiography, across the aortic arch after stage I palliation was 38% (80/210). Of these patients, 50 (24%) had either balloon dilation, aortic arch augmentation, or both at follow-up. Factors significantly and inversely related to postoperative NAO on the basis of results of echocardiography or need for intervention were use of autologous material to enlarge the aortic arch and coarctectomy. In this latter group 20 patients received autologous pericardium for reconstruction of the aortic arch, 18 received a pulmonary homograft patch, 12 received an aortic homograft patch, and 5 underwent direct anastomosis between the aorta and the pulmonary trunk. Interestingly, shunt type or size was not related to development of NAO. Univariate and multivariate analysis are shown in Tables 1 and 2.
In multivariate analysis statistically significant interactions between aortic coarctation and resection of the posterior shelf were detected; resection of the posterior shelf was associated with outcome in patients with aortic coarctation and not associated with outcome among those without aortic coarctation. The effect of coarctectomy is shown in Table 3.
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Discussion |
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HLHS is marked by underdevelopment of the left-sided heart structures, including the aortic arch. The goal of the first stage of surgical palliation is to create a large and unobstructed pathway for systemic circulation. A wide variety of materials have been used to enlarge the aortic arch.13-17 Currently, the more common technique for arch augmentation in the Norwood operation includes the use of a heterologous tissue to augment the union of the native ascending aorta, transverse arch, and proximal pulmonary trunk.14,15 Pulmonary homografts are usually considered the best material to reconstruct the aortic arch because they can be trimmed with an aortic arch–like shape, and there is minimal surgical bleeding through suture holes. On the other hand, homografts are expensive, not easy to procure, and are prone to calcification and potentially stenosis. Autologous pericardium, however, is one of the most widely used materials for reconstruction in pediatric cardiac surgery. It is readily available, nonimmunoreactive, and reasonably hemostatic. When fixed with 0.6% glutaraldehyde, it is also easy to handle, and the risk of aneurysmal dilatation is reduced.
Recently, modification of the standard Norwood procedure without a homograft patch has been proposed as a superior alternative.7-10 Intuitively, it is attractive to assume that the elimination of patch material in aortic reconstruction might be associated with a lower incidence of late aortic arch obstruction because the immunoreactive material is not expected to grow and might lead to obstruction at the distal end of the patch. Interestingly, nearly all aortic arch obstruction after initial palliation of HLHS is detected in the first few months after repair.18,19 Moreover, previous studies on patients with aortic coarctation and a hypoplastic aortic arch have demonstrated that relief of obstruction at the site of coarctation allows transverse arch growth.18-20 These observations indicate that recurrent arch obstruction after the Norwood procedure is likely related to the technical adequacy of the reconstruction rather than to a lack of growth of the augmented aorta. In fact, Mahle and colleagues21 found that in patients undergoing a Norwood procedure, growth of the reconstructed aorta parallels the rate seen in the healthy population. Postmortem investigations revealed that all the growth of the reconstructed aorta occurs in the native tissue that makes up at least a portion of the circumference of the aorta at every level. Furthermore, residual coarctation of the aorta can develop as a result of failure to extend the homograft around the arch.
A small-caliber neoaorta has been associated with increased mortality because of hemodynamic instability in the short-term and aortic coarctation in long-term follow-up.12 In our study, however, the presence of aortic atresia–mitral stenosis was associated with increased early mortality but not with recurrent arch obstruction. This finding implies that with current techniques, we have been able to mitigate hypoplastic aortic arch as a risk factor for NAO.
The existence of juxtaductal coarctation or a coarctation shelf is reported in more than 80% of the patients with HLHS, especially when the shelf of the ductal-like tissue located opposite the ductus arteriosum is included.4,5 This tissue has the potential to cause late obstruction.22 However, no standard surgical approach to this defect has been widely accepted. Moreover, contradictory data regarding this issue have been reported. Burkhart and colleagues23 have recently reported lower arch obstruction rates in patients undergoing the Norwood procedure with a technique that includes resection of the posterior shelf. However, Griselli and associates24 have reported that the type of aortic arch reconstruction did not affect the incidence of need for arch intervention. In our study the presence of a preoperative posterior shelf was significantly associated with NAO and need for reintervention, reoperation, or both. Furthermore, coarctectomy significantly reduced the incidence of NAO. This association resulted in "effect modification"; that is, coarctectomy is particularly effective in patients with a preoperative diagnosis of coarctation. However, echocardiographic determination of coarctation at the level of the implantation of the ductus arteriosus is very challenging because of the presence of a large ductus and the subsequent turbulent blood flow at the ductal insertion into the descending thoracic aorta. Direct inspection might also play a role in deciding whether coarctectomy should be done. Moreover, other factors besides resection of coarctation could be involved in the development of NAO in HLHS. In fact, in our study the risk of NAO was higher in patients undergoing resection of coarctation when no preoperative diagnosis of a posterior shelf was made.
In summary, coarctectomy at the time of stage I palliation significantly reduces the incidence of NAO, especially in patients with a preoperative diagnosis of coarctation. Use of autologous tissue to reconstruct the arch is also associated with improved outcome. An aggressive approach to reconstruction of the aortic arch at the time of stage I palliation is advocated.
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