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Transposition Complexes With Systemic Obstruction
Transposition Complexes With Systemic Obstruction Christo 1. Tchervenkov and Stephen J. Korkola The arterial switch operation is currently the procedure of choice for transposition of the great arteries and double-outlet right ventricle with subpulmonary ventricular septal defect. While the results of surgical repair have improved tremendously in recent years, the presence of associated lesions continues to make this a surgically challenging malformation. The association of these so-called transposition complexes with systemic obstruction has recently received increased attention. Systemic obstruction may occur at the subaortic level, in the aortic arch, or at both levels. Valvar aortic stenosis or atresia is extremely rare. Resection of hypertrophied muscle bundles with or without pericardia I patch augmentation is frequently enough to deal with obstruction at the subaortic level, which becomes the subpulmonary area following arterial switch operation. Aortic arch obstruction associated with intracardiac defects has traditionally been addressed with a staged approach, dealing first with the arch obstruction followed later by intracardlac repair. The results with this approach have been disappointing. At the Montreal Children's Hospital, we have obtained superior results using a single-stage approach. Therefore, we have advocated the use of pulmonary homograft patch aortoplasty for aortic arch reconstruction at the time of intracardiac repair to completely remove any anatomic afterload. Since 1989, in 22 consecutive patients undergoing single-stage anatomic repair of transposition complexes associated with aortic arch obstruction, we have had no early deaths, one late death of a noncardiac cause, and one recoarctation requiring balloon dilatation. In the last 2 years, we have been able to perform all our aortic arch reconstructions avoiding the use of circulatory arrest. Copyright © 2001 by W.B. Saunders Company Key words: Transposition complexes, subaortic arch obstruction, aortic arch obstruction.
T
he arterial switch operation (ASO) has become the procedure of choice for transposition of the great arteries (TGA) with intact ventricular septum (JVS) or with ventricular septal defect (VSD).1 It also is considered the procedure of choice for infants with double-outlet right ventricle with a subpulmonary VSD or the Taussig-Bing heart (TBH).2.3 Because of similarities in the surgical management of these malformations, they are considered together under the heading "transposition complexes." Patients with corrected transposition will not be considered here. From the Department of CardIOvascular Surgery" The Afontrial ChIldren's HospItal, JlcG,/l Cniz'em~)' Health Center, Montrial, Canada. Address reprint requests /0 Chnsto I. Tchm'enkol', JID, Department of CardlO"ascular Surge,)'. Room C-829, The .Uontrial Chzldren's Hospital. JfcGdl ['ml'l'TJl~)' Health Cent". 2300 Tupper St, Montrial, Quibec. Canada H3H-IP3. COp")'nghl © 2001 ~)' II'.B. Saundm Compa'!.), 1092-9126/0 I /040/-0008135.00/0 dOl: IO.J053/pcw.200J.23736
Since the first successful ASO for TGA in 1975 by Jatene et aI,4 there have been remarkable improvements in the surgical outcome following this operation. 5- IO However, the presence of some associated lesions still present a formidable surgical challenge and constitute areas of ongoing controversy with respect to the surgical approach and the appropriate timing of intracardiac repair. For example, the surgical treatment of TGA in the presence of left ventricular outflow tract obstruction has been covered extensively in the surgical literature. II - 18 However, in recent years the importance of systemic obstruction has become increasingly apparent. The optimal surgical approach in the presence of subaortic obstruction (SAO), aortic arch obstruction (MO), or both has been evaluated in comparatively few series. Traditionally, in the presence of AAO, a twostage approach has been used. At the first stage, the coarctation with or without the
Pediatnc Cardzac SurgtT) Annual of th~ Seminars in ThoraCIC and Cardiovascular SUTgery, Vol 4, 2001: pp 71-82
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hypoplastic aortic arch was repaired through a thoracotomy and the cardiac malformation was palliated with a pulmonary artery band. At a later stage, debanding and repair of the intracardiac malformation was performed via a sternotomy incision. This approach has been associated with a high mortality.l9-22 Compared with the traditional two-stage approach, Planche et aJ19 have shown improved results with a single-stage repair of the aortic arch with ASO. Since 1989, we have consistently used the single-stage approach at the Montreal Children's hospital for intracardiac defects, including TGA complexes, with AAO with excellent results which were published in 1997 and 1998. 23 ,24 This chapter will present an overview of the anatomy, pathophysiology, natural history, surgical treatment, and outcomes of patients with transposition complexes and systemic obstruction. Our approach of single-stage ASO and aortic arch repair using the technique of pulmonary homograft patch aortoplasty will be highlighted and the recently introduced technique of aortic arch reconstruction without circulatory arrest will be discussed.
Anatomic Considerations Obstruction to systemic blood flow in patients with transposition complexes significantly impacts the pathophysiology and natural history of these lesions and influences the timing and nature of the surgical approach. The obstruction may occur at the subaortic level, the aortic valve, the level of the aortic arch, or at multiple levels. 25•29 While valvar aortic stenosis and aortic atresia are extremely rare, AAO is relatively common and is frequently accompanied by SAO, particularly in the patient with the TBH. Aortic arch obstruction occurs in the form of coarctation, tubular hypoplasia of the aortic arch, or both. Infrequently there is interrupted aortic arch. In TGA-VSD malalignment of the infundibular septum has important consequences with respect to SAO. Its anterior and rightward displace-
ment may result in narrowing of the subaortic area and impaired flow through the aorta relative to the pulmonary artery. While malalignment of the infundibular septum may contribute directly to subaortic stenosis and systemic obstruction, hypertrophied septoparietal trabeculations, prominent ventriculoinfundibular fold, and abnormal insertions of the atrioventricular valves may contribute as wel1. 28 •30 The unequal partitioning of aortic and pulmonary outflow tracts allows blood flow to be directed preferentially through the pulmonary artery, ductus arteriosus, and descending aorta. This often leads to developmental abnormalities of the aortic arch in the form of coarctation, tubular hypoplasia, or interruption of the aortic arch. 31 •32 In the TBH, the subaortic infundibulum is frequently hypoplastic, as it is commonly wedged between the tricuspid valve and the subpulmonary infundibulum. As in TGA with anterior malalignment VSD, this often results in SAO as well as AAO. The surgical importance of aortic arch obstruction associated with these anomalies seems obvious, yet it has received relatively little attention until recently. 'Vhile the diagnoses of aortic coarctation and interrupted aortic arch are relatively straightforward, tubular hypoplasia of the aortic arch may be less so. While tubular hypoplasia may be present in 62% of cases of isolated coarctation, it may occur in up to 93% of cases of coarctation occurring in association with complex intracardiac lesions. 33 Hypoplasia of the aortic arch may significantly complicate and alter the surgical approach and, if not addressed, may leave behind residual systemic obstruction.
Incidence of Systemic Obstruction in Transposition Complexes While SAO is rare in TGA-IVS,26 it occurs in 20% to 40% of cases of TGA_VSD. 19,26 Subaortic stenosis is common in the TBH, occurring in about 30% to 50% of cases. 3,30.34.3S
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Likewise, aortic arch obstruction occurs in only 2% to 3% of cases of TGA-IVS.7,25,26 It is more common in cases of TGA-VSD (l0% to 36%) 7,25-28 and is disproportionately distributed to those hearts with anterior malalignment VSD, occurring in up to 88% of these cases_ 14 Aortic arch obstruction is reported in at least 50% of cases of the TBH.2,29,34 Milanesi et al 28 studied 57 autopsy specimens of TGA-VSD. Nineteen cases (33%) had AAO which was in the form of coarctation in 15 cases, tubular hypoplasia in two cases, and aortic arch atresia in two cases. Fourteen of these 19 specimens had subaortic stenosis from rightward displacement of the infundibular septum combined with hypertrophied septoparietal trabeculations or huge ventricular infundibular fold. Pigott et a}26 reported on 129 autopsy specimens of TGA from the Cardiac Registry of the Children's Hospital of Philadelphia_ Of the 69 cases with TGA-IVS, only two (3%) had coarctation of the aorta and none had evidence of SAO. Conversely, in the 60 patients with a VSD, aortic arch obstruction was much more common, especially in the 29 cases with a malalignment type of VSD. Twenty-two of the 29 cases of malalignment VSD were associated with subaortic stenosis, 18 of which had some form of AAO in the form of coarctation, hypoplasia, or interruption. Several studies have documented AAO in association with the TBH.2,3,29,30,34-37 Parr et al 29 found aortic coarctation in six of nine patients with TBH in their clinical series and in 56 of 105 (53%) autopsy specimens. Conversely, they found aortic coarctation in none of 17 TGA-VSD patients in their clinical experience and in eight of 126 (6%) autopsy specimens. Aoki et al 2 reported on 73 patients undergoing biventricular repair for double-outlet right ventricle_ Of the 27 patients with double-outlet right ventricle and subpulmonary VSD in their series or the TBH, 14 (52%) had MO.
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Pathophysiology The pathophysiology of the transpOSItIOn complexes can be understood by considering the systemic and pulmonary circulations as existing in parallel rather than in series. 38 The clinical picture is largely dependent on the degree of mixing between these two circulations through defects in the atrial and/or ventricular septum and the patent ductus arteriosus. Lesions with poor mixing such as TGA-IVS present in the first few hours of life with rapidly progressive cyanosis. Mixing may be improved with prostaglandin infusion to keep the ductus arteriosus open and with the creation of an atrial septal defect by balloon atrial septostomy. Lesions with good mixing (TGA-VSD or TBH) usually present later in the first month of life. The natural decrease in pulmonary vascular resistance leads to pulmonary overcirculation and signs and symptoms of congestive heart failure with milder cyanosis. In the presence of severe obstruction, the systemic circulation is ductal-dependent. Closure of the patent ductus arteriosus is accompanied by a rapidly progressive downhill course with poor systemic perfusion accompanied by metabolic acidosis, acute renal failure, and necrotizing enterocolitis. Unless the patent ductus arteriosus can be promptly reopened with the infusion of prostaglandins, the clinical course is uniformly fatal. In milder forms of obstruction, the systemic circulation may not be ductal dependent. Nevertheless, the clinical picture is characterized by pulmonary overcirculation with severe congestive heart failure and pulmonary edema.
Natural History Successful surgical treatment of complex congenital heart disease has occurred only recently. The era before successful surgery for TGA gives us insight into the importance of surgical intervention at an early age. The natural history of TGA without surgical cor-
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rection is early death. Patients with poor mixing (ie, TGA-NS) die rapidly of hypoxia. Patients with good mixing but pulmonary overcirculation die of severe congestive heart failure. When the spectrum of TGA is considered together, survival at 1, 6, and 12 months is 55%, 15%, and 10%, respectively.38 However, survival depends on the particular subgroup being considered. While 80% of patients with TGA-IVS are alive at 1 week of life, survival is only 17% at 2 months and 4% at 1 year. When a significant VSD is present, survival is somewhat better at 91 %, 43%, and 32% at 1 month, 5 months, and I year, respectively. While the Taussig-Bing malformation is physiologically similar to TGAVSD, the natural history is often worse, likely secondary to the early development of pulmonary vascular obstructive disease and/or the high incidence of associated systemic obstruction. While associated left ventricular outflow tract obstruction may be protective in TGAVSD leading to survivals of 70% at 1 year and 29% at 5 years, subaortic or aortic arch obstructions are associated with a particularly poor prognosis. Although, the natural history of the TGA complexes associated with systemic obstruction has not been specifically highlighted, one can speculate that in the presence of severe obstruction and a ductaldependent systemic circulation the outcome is universally fatal without surgical treatment. In the milder forms, when the systemic circulation is not ductal dependent, the prognosis is expected to be at best similar to that of TBH.
Surgical Considerations The nature of the ASO used to treat the TGA complexes is such that the subaortic area and the aortic arch are incorporated into different parts of the circulation after the repair. While the aortic arch remains part of the systemic circulation, the subaortic area becomes the subpulmonary area. This means that residual AAO is a problem
faced by the left heart, with resultant left heart failure and inadequate systemic perfusion. On the other hand, inadequate relief SAO results in residual obstruction in the right heart and the pulmonary circulation after the ASO. There are few published reports dealing specifically with AAO in patients with TGA complexes. In a multi-institutional study by the Congenital Heart Surgeons Society on neonatal coarctation, the overall mortality was 19% for patients with TGA-NS and TGA-VSD and 50% for those ''''ith the TBH.20 Although, the surgical approach used is unclear, it is likely that most patients underwent a staged repair.
Staged Approach Versus Single-Stage Anatomic Repair The association of AAO with complex congenital heart disease presents a formidable surgical challenge and has been associated with a high mortality. Traditionally, these patients were repaired in two stages. At the first stage the AAO is repaired through a left thoracotomy with the intracardiac malformation palliated with a pulmonary artery band. The intracardiac repair was delayed by several months or years. In published reports, total mortality with the two-stage approach has ranged between 31 % and 64%.19,20,22,33 Several factors may have contributed to these discouraging results. The frequent association of tubular hypoplasia of the aortic arch in patients with coarctation and complex congenital heart disease has only been recognized recently.33 Furthermore, the deleterious effects of pulmonary artery band have become increasingly apparent. 19 Finally, outcome assessment of the two-stage approach must take into account not only the mortality of the initial palliation, but also the interval mortality and the mortality of intracardiac repair. There is increasing evidence that a single-stage anatomic repair may be the preferred treatment modality in patients with TGA complexes and AAO.19,23,24 Despite the increased com-
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plexity of the procedure and the smaller size of the baby at the time of repair, there appears to be a lower associated operative mortality in the group undergoing single-stage anatomic repair. 19,23,24,30,33 The single-stage repair for TGA and AAO was first reported by Pigott et al 26 in five patients. Four of the five patients were corrected in a single stage as neonates. They reported one early death from coagulopathy and one reoperation for distal AAO. In 1993, Planche et al 19 from Marie-Lannelongue Hospital in Paris, showed that the singlestage approach was superior when compared with a staged approach. They compared 40 patients with TGA-VSD and AAO having either single-stage (I4 patients) or two-stage repair (26 patients). Of the 14 patients in the single-stage group, there were two early deaths (14.2%) and one late death. Actuarial survival rate and rate of freedom from reoperation at 3 years were 78.5% and 81.5%, respectively. Conversely, in the 26 patients undergoing two-stage repair, there were eight early deaths (three after aortic arch repair and five after VSD closure and arterial switch) for an early mortality of 30.7%. Actuarial survival rate and rate of freedom from reoperation at 5 years were 57.5% and 49.9%, respectively. They noted how the placement of a pulmonary artery band may worsen the malalignment of the infundibular septum that is often present, leading to worsening or unmasking of SAO. Conte et aP3 updated this report with additional patients in 1995 with similar conclusions. From the same institution, Serraf et aF reported on a large series of 432 patients with TGA undergoing ASO. Twenty-three of their patients had associated coarctation of the aorta. Eighteen of these patients were repaired using a single-stage approach with a mortality of 13.3%, which was higher than the mortality of 7.6% in TGA-IVS patients and 8.5% in TGA-VSD patients undergoing ASO without associated AAO. By contrast, Tchervenkov et al 24 have not experienced an increased risk in a single-stage ASO with
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concomitant aortic arch repair with no operative mortality in 18 consecutive patients with TGA complexes and AAO. More recently, other investigators have reported good results with the single-stage approach as well. 3o ,33,39,4o In the most recent report from Marie-Lannelongue Hospital published in 1997, Lacour-Gayet et apo described their results with biventricular repair of 103 patients with conotruncal anomalies associated with aortic arch obstruction. Ninety-one of 103 patients in their series had a transposition complex (TGA-NS in 15, TGA-VSD in 44, and TBH in 32) as the conotruncal anomaly. The AAO was in the form of coarctation of the aorta in 88 cases and interrupted aortic arch in 15 patients. In the patients with coarctation, 64 of 88 had associated hypoplasia of the aortic arch. They performed biventricular repair and aortic arch reconstruction using either a two-stage or single-stage approach. The hospital mortality for the singlestage group was 12% (7 of 58), while it was 20% (9 of 45) for the group having two-stage repair. The investigators now reserve the two-stage approach for the patient with multiple VSDs, neurologic disorders, and multiorgan failure.
Surgical Techniques Subaortic Obstruction The ASO is currently the procedure of choice for TGA and double-outlet right ventricle with subpulmonary VSD.l The presence of SAO makes the surgical repair more challenging. The subaortic stenosis common in TGA-VSD and TBH is usually secondary to malalignment of the infundibular septum with hypertrophy of the subaortic conus. When repair is performed by ASO, this subaortic area becomes the subpulmonic area. The obstruction can usually be dealt with by division and resection of the obstructing bands of muscle,3o followed by primary closure of the right ventricular outflow tract. In some cases, it may be necessary to augment the right ventricular outflow tract with a
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Tcheroenk.ov and Kork.ola
patch of autologous pericardium 26 ,3o or to bypass the obstruction with a valved homograft conduit. 26 These techniques are applicable in the majority of cases, but there are instances in which the subaortic area is extremely hypoplastic and/or when anomalous coronaries cross the right ventricular outflow tract. In these cases, we have performed an anatomic repair by combining the salient features of the Rastelli and Norwood operations. 23 The left ventricle is tunneled through the VSD into the proximal pulmonary artery, which is then transected and incorporated into the systemic circulation. The ascending aorta is anastomosed to the proximal main pulmonary artery and the entire ascending aorta and arch is reconstructed using a pulmonary artery homograft patch. The right ventricular outflow tract is then reconstructed using a valved pulmonary artery homograft after oversewing the subaortic conus to render the aortic valve atretic.
Aortic Arch Obstruction Aortic arch obstruction manifesting as interrupted aortic arch, tubular hypoplasia, or coarctation may occur in isolation or in combination with subaortic stenosis. Traditional techniques to deal with coarctation with or without tubular hypoplasia of the aortic arch include resection and primary end-ta-end anastomosis, extended end-ta-end anastomosis, subclavian flap angioplasty, and patch (synthetic or homograft) aortoplasty. Coarctation of the aorta in association with transposition complexes is most commonly addressed with resection of the coarctation and primary end-to-end anastomosis. 3o ,37,39,4o Hypoplasia of the aortic arch is a frequently associated lesion and can be managed by extended end-to-end anastomoses of the descending aorta to the undersurface of the aortic arch as necessary. Advantages of this option are that it can be performed through a thoracotomy (staged approach) or median sternotomy (single-stage repair). This involves resection of the coarctation
and periductal tissue and does not involve the use of patch material. However, there may be significant tension on the suture line and proximal obstructions in the proximal arch and ascending aorta may be left unattended. Subclavian flap aortoplasty has been advocated by some for its relative ease to perform, requiring limited dissection with a p0tential for growth,4J \Vhile this simplifies the operation, this approach does not address the aortic arch hypoplasia that is often present, with the potential for leaving systemic obstruction. This technique is not applicable during single-stage repairs through a sternotomy. Synthetic patch aortoplasty has fallen out of favor because of the risk of sudden rupture and aneurysm formation.-t246 Replacement of the aorta with a tube graft is not practical in the neonate because of the obvious lack of growth potential. At the Montreal Children' Hospital we advocate the almost exclusive use of pulmanary homograft patch aortoplasty (Fig I) for our combined neonatal aortic arch reconstructions and intracardiac repair for a number of reasons. This technique is relatively straightforward and reproducible. It achieves three important objectives for adequate repair: (I) the arch repair can be extended proximally and distally as needed to make the aorta an adequate size throughout, regardless of the initial dimensions, (2) it corrects the often marked size discrepancy between the proximal neoaorta and the distal aorta, which is often present in patients with TGA, VSD, or the TBH; and (3) it results in a single tension-free anastomosis between the proximal neoaorta and the enlarged distal aorta. While the extended end-ta-end anastomosis results in excision of the coarctation shelf and avoids the use of foreign material, it accomplishes none of the three previously mentioned objectives. Some have expressed concern over the use of nonviable material crossing ductal tissue leading to recoarctation in the future. u Since 1988, we
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Figure 1. Technique of pulmonary homograft patch aortoplasty. Note the flexible arterial cannula advanced and snared in the innominate artery allowing continuous low-flow cerebral perfusion during reconstruction of the aortic arch. have performed single-stage anatomic repair of 22 patients with transposition complexes and aortic outflow tract obstruction using pulmonary homograft patch aortoplasty. In this group, we have observed one recoarctation (4.5%) requiring balloon dilatation and no aneurysm formation. Interrupted aortic arch in patients with TGA complexes can be repaired by direct anastomosis, as in patients with isolated interrupted aortic arch. Recently, Liddicoat et al described a new technique of repairing interrupted aortic arch associated with TGA complexes. 36 Anatomic single-stage repair was performed in two patients combining an ASO with bypass of the hypoplastic aortic arch by anastomosing the ascending aorta directly to the descending aorta and sewing
the neoaorta to the undersurface of the new aortic arch. Mavroudis et al used a similar technique to perform a single-stage repair of a TBH with SAO, a small ascending aorta, and coarctation. Great artery transection and coronary transfer were performed followed by coarctation resection. The ascending and descending aorta were then joined together in a manner similar to that described previously. A valved homograft was used to reconstruct the right ventricular outflow tract after subvalvar resectionY
Aortic Arch Reconstruction Without Circulatory Arrest Traditionally, reconstruction of the aortic arch in the neonate has required the use of deep hypothermic circulatory arrest. It has
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Tchm'tllkov and Korko/a
increasingly rccognized in recent yc~ars that deep hypotlwrmic circulatory arrest may be associatt'{l with significant neuI'Ologk morbidity:i7 As a consc'qlwnce, we and (It hers ha\'(' devised techniques to avoid or limit tl\(' Us(' of circulatory '\I·rt~styl-j:1 I;'or pati('nts with transposition complexes and AAO undt'rgoing simultaneous arch reconstruction and biventriculur repair, we have usc'd two main techniqu('s to avoid circulatory arn'st. The first technique involves Cllntinuoll!! low-flow c(~ rc'bral perfusion via the innominate artc'ry during arch reconstruction with tile' ardl vCl'lS(·ls snared and dcsl'C~nding aorta dump(~d (Fig I). The aorta is then augml'ntc'd with a patch of' pulmonary homograft as previously described.:'?:1 Arterial switch is pl'rrorm(~d in the usual manner with tilt' augm(~nt(·d ascending aorta being s('wn to the Iwoaorta. The other techniqUt: we have used to avoid circulatory arrcst is the applkation of the aortic cross clamp bctw('c'n the innominate artery and the left ('arotid artery. This allows continuous perfusion of the myocardium and cerebral circulation via the innominate artery. Single-stage reconstruction of the aortic arch with biventricular repair or complex intracardiac defects can be accomplished consisll'ntly without the use of circulatory arrest or direct cannulation ofthc arch vessels. Further expaiem'(~ with long-term follow-up is required to assess impact on neurologic outcomes.
bt~com(~
Experience At The Montreal Children's Hospital At the Montreal Children's lIospital, we adopted in 19HH an aggressive approach of thc single-stage anatomic repair uf congenital cardiac defects associated with AAO, consistent with our surgical philosophy of carly primary intracardiac repair. Since then we haw performed single-stage anatomic repairl'l in 4!) out or 50 eonseclitive patients with ('ardial' defrets associated with AAO with a ,~% m()rtality.2'~ A single-stage ASO
with or without VSD closure and concomitant aortic arch reconstruction was performed in 22 patients with TGA complexes and AAO.23,24 When present, subaortic stenosis was relieved by an outflow pericardial patch, except in one patient with the TBll. In this patient, severe tubular SAO and the presence of a major coronary artery across the outflow tract precluded the use of a transannular patch. This patient underwent a single-stage biventricular anatomic repair applying features of the Rastelli and Norwood operations using a right ventricle-topulmonary artery conduit. In this series of patients, we have had no early deaths and only one late death from a hepatoblastoma at 39 months. The only patient in this series nut having a single-stage repair was the first patient, a neonate with the TBll that became unstable after the induction of anesthesia. He underwent coarctation resection and extended end-to-end anastomosis through a left thoracotomy and a pulmonary artery banding. Because of persisting severe congestive heart failure, 12 days later he underwent an ASO, VSD closure, and debanding. As previously mentioned, in our experience, the presence of MO in patients with TGA complexes has not been associated with increased mortality following the ASO. Similar to our own experience, Comas et al found that AAO in association with TBII did not adversely affect outcome. 34 We believe that the appreciation for the presence of tubular hypoplasia of the aortic arch has led us to have a low threshold for enlarging the aortic arch at the time of ASO. We use criteria suggested by Karl et altO to define aortic arch hypoplasia requiring intervention. If the transverse aortic arch diameter by echocardiography is less than the patient's weight in kilograms plus one, it is considered hypoplastic. For example, in a 3-kg baby, if the aortic arch is less than 4 mm (ie, 3 + I), we consider it hypoplastic and would enlarge it surgically. We believe that a degree of hypoplasia of the aortic arch that
Transposition Complexes
may be well tolerated fonowing coarctation repair in an otherwise normal heart will not be tolerated by a heart that has been subjected to a complex intracardiac repair with a significant duration of myocardial ischemia and cardiopulmonary bypass. The decision to enlarge or not what appears to be a hypoplastic aortic arch is not always an easy and straightforward one. Therefore, a word of caution is advised. We have experience with a 5-week-old baby (3.96 kg) with TGA-VSD and tubular hypoplasia of the aortic arch measuring 5 mm on preoperative echocardiogram, just over the cutoff we use to consider augmentation (weight in kg + I = 4.96 mm). After ASO and VSD closure, the patient was weaned twice from cardiopulmonary bypass. Each time, about 45 minutes later, there was a rapidly progressive hypotension, necessitating reinstitution of cardiopulmonary bypass. In the face of well-perfused and clearly distended coronary arteries, the etiology of the patient's deterioration was thought to be secondary to a borderline aortic arch. The pulmonary and aortic anastomoses were taken down and the aortic arch was enlarged with a pulmonary homograft patch aortoplasty. Despite a total myocardial ischemia time of more than 3 hours and cardiopulmonary bypass time of more than 10 hours, the patient was then weaned successfully from cardiopulmonary bypass with relative ease and went on to recover without further problem. Conversely, in three patients, despite the aortic arch being suspected as being hypoplastic on preoperative echocardiogram, intraoperative probing of the internal diameter showed an adequate size, precluding surgical enlargement. A very large patent ductus arteriosus compressing the aortic arch was thought to have given the appearance of hypoplasia on the preoperative echocardiograms. However, one of these patients has returned 5 months after the neonatal ASO for TGA-IVS with discrete coarctation of the aorta. On routine follow-up, the patient was found to have absent femoral pulses secondary to a discrete
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coarctation confirmed by echocardiogram and magnetic resonance imaging. He underwent uneventful coarctation resection and primary end-to-end anastomosis through a left thoracotomy. The other two patients have no evidence of aortic arch obstruction on follow-up.
Conclusions The importance of systemic obstruction in association with transposition complexes has become apparent in recent years. Aortic arch obstruction and subaortic stenosis occur frequently in association with the TBH and TGA-VSD with anterior malalignment VSD and, rarely, in TGA-IVS. Since 1989 we have adopted a single-stage intracardiac repair with concomitant aortic arch reconstruction with excellent outcomes. The technique of pulmonary homograft patch aortoplasty has achieved an unobstructed systemic circulation, has allowed for correction of the frequently observed great vessel discrepancy with a tension-free anastomosis, and has been associated with a low recoarctation rate. Recently, the use of low-flow cerebral perfusion techniques has allowed the performance of all our aortic arch reconstructions to avoid the use of deep hypothermic circulatory arrest. The implications of these techniques will be become apparent in the next few years as the survival and functional status of these patients continues to improve.
References 1. Kirklin JW, Blackstone EH, Tchervenkov CI, et al: Clinical outcomes after the arterial switch operation for transposition. Patient support, procedural and institutional risk factors. Circulation 86: 1501-1515, 1992 2. Aoki, M, Forbes SJM, Jonas RA, et al: Results of biventricular repair for double-outlet right ventricle. J Thorac Cardiovasc Surg 107 :338-350, 1994
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3. Tchervenkov GI, MareHi D, Beland MJ, et al: Institutional experience with a protocol of early primary repair of doubleoutlet right ventricle. Ann Thorac Surg 60:S61O-S613, 1995 4. Jatene AD, Fontes VF, Paulista PP, et al: Anatomic correction of transposition of the great arteries. J Thorac Cardiovasc Surg 72:364-370, 1976 5. Idriss FS, Ilbawi MN, DeLeon SY, et al: Arterial switch in simple and complex transposition of the great arteries. J Thorac Cardiovasc Surg 95:25-36, 1988 6. Di Donato RM, Wernovsky G, Walsh EP, et al: Results of the arterial switch operation for transposition of the great arteries with ventricular septal defect. Surgical considerations and midterm follow-up data. Circulation 80: 1689-1705, 1989 7. Serraf A, Lacour-Gayet F, BruniauxJ, et al: Anatomic correction of transposition of the great arteries in neonates. J Am CoIl Cardiol 22: 193-200, 1993 8. Davis AM, Wilkinson JL, Karl TR, et al: Transposition of the great arteries with intact ventricular septum. Arterial switch repair in patients 21 days of age or older. J Thorac Cardiovasc Surg 106: 111-115, 1993 9. Wernovsky G, Mayer Jr JE,Jonas RA, et al: Factors influencing early and late outcome of the arterial switch operation for transposition of the great arteries. J Thorac Cardiovasc Surg 109:289-30 I, 1995 10. Haas F, Wottke M, Poppert H, et al: Long-term survival and functional follow-up in patients after the arterial switch operation. Ann Thorac Surg 68: 1692-1697, 1999 11. Rastelli GC, McGoon DC, Wallace RB: Anatomic correction of transposition of the great arteries with ventricular septal defect and subpulmonary stenosis. J Thorae Cardiovase Surg 58:545-552, 1969 12. Moulton AL, de Leval MR, Macartney Fj, et al: Rastelli procedure for transpo-
sition of the great arteries, ventricular septal defect, and left ventricular outflow tract obstruction: Early and late results in 41 patients (1971 to 1978). Br Heart J 45:20-28, 1981 13. LeCompte Y, N'eveux JY, Leca F, et al: Reconstruction of the pulmonary outflow tract without prosthetic conduit. J Thorae Cardiovasc Surg 8-l:727-733, 1982 14. Kurosawa H, Van Mierop LH: Surgical anatomy of the infundibular septum in transposition of the great arteries with ventricular septal defect. J Thorac Cardiovasc Surg 91: 123-132, 1986 15. jex RK, Puga Fj, Julsrud PR, et al: Repair of transposition of the great arteries with intact ventricular septum and left ventricular outflow obstruction.j Thorac Cardiovasc Surg 100:682-686, 1990 16. Vouche PR, Tamisier D, Leca F, et al: Transposition of the great arteries, ventricular septal defect, and pulmonary outflow tract obstruction. Rastelli or LeCompte procedure? J Thorac Cardiovase Surg 103:428-436, 1992 17. Sohn YS, Brizard CP, Cochrane AD, et al: Arterial switch in hearts with left ventricular outflow and pulmonary valve abnormalities. Ann Thorac Surg 66:8-l2848, 1998 18. Kreutzer C, De Vive J, Oppido G, et al: Twenty-five year experience with Rastelli repair for transposition of the great arteries. J Thorac Cardiovasc Surg 120: 211-223, 2000 19. Planche C, Serraf A, Comas]V, et al: Anatomic repair of transposition of the great arteries with ventricular septal defect and aortic arch obstruction. Onestage versus two-stage procedure.j Thorae Cardiovasc Surg 105:925-933, 1993 20. Quaegebeur JM, jonas RA, \Veinberg AD, et al: Outcomes in seriously ill neonates with coarctation of the aorta. 1 Thorae Cardiovasc Surg 108:8-l1-854, 1994 21. Vogel M, Freedom RM, SmallhornJF, et al: Complete transposition of the great
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arteries and coarctation of the aorta. Am] Cardiol 53:1627-1632, 1984 22. Vouche PR, Trinquet F, LeCompte Y, et al: Aortic coarctation with hypoplastic aortic arch. J Thorac Cardiovasc Surg 96:557-563, 1988 23. Tchervenkov CI, Tahta SA, Jutras L, et al: Single-stage repair of aortic arch obstruction and associated intracardiac defects with pulmonary homograft patch aortoplasty. J Thorac Cardiovasc Surg 116:897-904, 1998 24. Tchervenkov CI, Tahta SA, Cecere R, et al: Single-stage arterial switch with aortic arch enlargement for transposition complexes with aortic arch obstruction. Ann Thorac Surg 64: 1776-1781, 1997 25. Moene RJ, OttenkampJ, OppenheimerDekker A, et al: Transposition of the great arteries and narrowing of the aortic arch. Emphasis on right ventricular characteristics. Br Heart J 53:58-63, 1985 26. PigottJD, Chin AJ, Weinberg PM, et al: Transposition of the great arteries with aortic arch obstruction. Anatomical review and report of surgical management. J Thorac Cardiovasc Surg 94:82-86, 1987 27. Milanesi 0, Thiene G, Bini IU.1, et al: Complete transposition of the great arteries with coarctation of the aorta. Br Heart J 48:566-571, 1982 28. Milanesi 0, Ho SY, Thiene G, et al: The ventricular septal defect in complete transposition of the great arteries: Pathologic anatomy in 57 cases with emphasis on subaortic, subpulmonary, and aortic arch obstruction. Hum Pat hoI 18: 392-396, 1987 29. Parr GVS, \Va1dhausenJA, Bharati S, et al: Coarctation in Taussig-Bing malformation of the heart. Surgical significance. J Thorac Cardiovasc Surg 86:280287, 1983 30. Lacour-Gayet F, Serraf A, Galletti L, et al: Biventricular repair of conotruncal anomalies associated with aortic arch
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obstruction. 103 patients. Circulation 96:328-334, 1997 (suppl 2) 31. Van Praagh R, Bernhard WF, Rosenthal A, et al: Interrupted aortic arch: Surgical treatment. Am J Cardiol 27:200-211, 1971 32. Rudolph AM, Heymann MA, Spitznas V: Hemodynamic considerations in development of narrowing of the aorta. Am J Cardiol 30:514-525, 1972 33. Conte S, Lacour-Gayet F, Serraf A, et al: Surgical management of neonatal coarctation. J Thorac Cardiovasc Surg 109: 663-675, 1995 34. Comas]V, Mignosa C, Cochrane AD, et al: Taussig-Bing anomaly and arterial switch: Aortic arch obstruction does not influence outcome. Eur J Cardio-thorac Surg 1O:11l4-1119, 1996 35. Goor DA, Ebert PA: Left ventricular outflow tract obstruction in Taussig-Bing malformation. Anatomic and surgical implications. J Thorac Cardiovasc Surg 70:69-75, 1975 36. Liddicoat JR, Reddy VM, Hanley FL: New approach to great-vessel reconstruction in transposition complexes with interrupted aortic arch. Ann Thorae Surg 58: 1146-1150, 1994 37. Mavroudis C, Backer CL, Muster AJ, et al: Taussig-Bing anomaly: Arterial switch versus Kawashima intraventricular repair. Ann Thorac Surg 61: 13301338, 1996 38. Kirklin JW, Barratt-Boyes BG: Complete transposition of the great arteries, in Cardiac Surgery, vol 2 (ed 2). New York, NY, Churchill Livingstone, 1993, pp 1403-1483 39. Sandhu SK, Beekman RH, Mosca RS, et al: Single-stage repair of aortic arch obstruction and associated intracardiac defects in the neonate. Am J Cardiol 75: 370-373, 1995 40. Karl TR, Sana S, Brawn W, et al: Repair of hypoplastic or interrupted aortic arch via sternotomy. J Thorac Cardiovasc Surg 104:688-695, 1992
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41. Moulton AL, Roberts G, Ali S, et al: Subclavian flap repair of coarctation of the aorta in neonates: Realization of growth potential? ] Thorac Cardiovasc Surg 87:220-235, 1984 42. Del Nido P, Williams W, Wilson G, et al: Synthetic patch angioplasty for repair of coarctation of the aorta: Experience with aneurysm formation. Circulation 74:3236, 1986 (suppl 1) 43. Bromberg BI, Beckman RH, Rocchini AP, et al: Aortic aneurysm after patch aortoplasty repair of coarctation: A prospective analysis of prevalence, screening tests and risks. ] Am Coli Cardiol 14:734-741, 1989 44. Kumar A, Miller R, Finley]P, et al: Follow-up after patch aortoplasty for coarctation of the aorta. Can] CardioI9:751753, 1993 45. Mendelsohn AM, Crowley DC, Lindauer A, et al: Rapid progression of aortic aneurysms after patch aortoplasty repair of coarctation of the aorta.] Am Coil Cardiol 20:381-385, 1992 46. Venturini A, Papalia U, Chiarotti F, et al: Primary repair of coarctation of the thoracic aorta by patch graft aortoplasty: A three-decade experience and follow-up in 60 patients. Eur] Cardio-thorac Surg 10:890-896, 1996 47. Bellinger DC,]onas RA, Rappaport LA, et al: Developmental and neurologic status of children after heart surgery with hypothermic circulatory arrest of low-
flow cardiopulmonary bypass. N Engl ] Med 332:549-555, 1995 48. Asou T, Kado H, Imoto Y, et al: Selective cerebral perfusion technique during aortic arch repair in neonates. Ann Thorac Surg 61: 1546-1548, 1996 49. McElhinney DB, Reddy VM, Silverman NH, et al: Modified Damus-Kaye-Stansel procedure for single ventricle, subaortic stenosis, and arch obstruction in neonates and infants: Midterm results and techniques for avoiding circulatory arrest.] Thorac Cardiovasc Surg 114:718726, 1997 50. Imoto Y, Kado H, Shiokawa Y, et al: Norwood procedure without circulatory arrest. Ann Thorac Surg 68:559-561, 1999 51. Ishino K, Kawada M, Irie H, et al: Single-stage repair of aortic coarctation with ventricular septal defect using isolated cerebral and myocardial perfusion. Eur ] Cardio-thorac Surg 17:538-542, 2000 52. Pigula FA, Nemoto EM, Griffith HP, et al: Regional low-flow perfusion provides cerebral circulatory support during neonatal aortic arch reconstruction.] Thorac Cardiovasc Surg 119:331-339, 2000 53. Tchervenkov CI, Chu VF, Shum-Tim D, et al: The Norwood operation without circulatory arrest: A new surgical technique. Ann Thorac Surg 70: 1730-1733, 2000
T
he arterial switch operation (ASO) has become the procedure of choice for transposition of the great arteries (TGA) with intact ventricular septum (JVS) or with ventricular septal defect (VSD).1 It also is considered the procedure of choice for infants with double-outlet right ventricle with a subpulmonary VSD or the Taussig-Bing heart (TBH).2.3 Because of similarities in the surgical management of these malformations, they are considered together under the heading "transposition complexes." Patients with corrected transposition will not be considered here. From the Department of CardIOvascular Surgery" The Afontrial ChIldren's HospItal, JlcG,/l Cniz'em~)' Health Center, Montrial, Canada. Address reprint requests /0 Chnsto I. Tchm'enkol', JID, Department of CardlO"ascular Surge,)'. Room C-829, The .Uontrial Chzldren's Hospital. JfcGdl ['ml'l'TJl~)' Health Cent". 2300 Tupper St, Montrial, Quibec. Canada H3H-IP3. COp")'nghl © 2001 ~)' II'.B. Saundm Compa'!.), 1092-9126/0 I /040/-0008135.00/0 dOl: IO.J053/pcw.200J.23736
Since the first successful ASO for TGA in 1975 by Jatene et aI,4 there have been remarkable improvements in the surgical outcome following this operation. 5- IO However, the presence of some associated lesions still present a formidable surgical challenge and constitute areas of ongoing controversy with respect to the surgical approach and the appropriate timing of intracardiac repair. For example, the surgical treatment of TGA in the presence of left ventricular outflow tract obstruction has been covered extensively in the surgical literature. II - 18 However, in recent years the importance of systemic obstruction has become increasingly apparent. The optimal surgical approach in the presence of subaortic obstruction (SAO), aortic arch obstruction (MO), or both has been evaluated in comparatively few series. Traditionally, in the presence of AAO, a twostage approach has been used. At the first stage, the coarctation with or without the
Pediatnc Cardzac SurgtT) Annual of th~ Seminars in ThoraCIC and Cardiovascular SUTgery, Vol 4, 2001: pp 71-82
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hypoplastic aortic arch was repaired through a thoracotomy and the cardiac malformation was palliated with a pulmonary artery band. At a later stage, debanding and repair of the intracardiac malformation was performed via a sternotomy incision. This approach has been associated with a high mortality.l9-22 Compared with the traditional two-stage approach, Planche et aJ19 have shown improved results with a single-stage repair of the aortic arch with ASO. Since 1989, we have consistently used the single-stage approach at the Montreal Children's hospital for intracardiac defects, including TGA complexes, with AAO with excellent results which were published in 1997 and 1998. 23 ,24 This chapter will present an overview of the anatomy, pathophysiology, natural history, surgical treatment, and outcomes of patients with transposition complexes and systemic obstruction. Our approach of single-stage ASO and aortic arch repair using the technique of pulmonary homograft patch aortoplasty will be highlighted and the recently introduced technique of aortic arch reconstruction without circulatory arrest will be discussed.
Anatomic Considerations Obstruction to systemic blood flow in patients with transposition complexes significantly impacts the pathophysiology and natural history of these lesions and influences the timing and nature of the surgical approach. The obstruction may occur at the subaortic level, the aortic valve, the level of the aortic arch, or at multiple levels. 25•29 While valvar aortic stenosis and aortic atresia are extremely rare, AAO is relatively common and is frequently accompanied by SAO, particularly in the patient with the TBH. Aortic arch obstruction occurs in the form of coarctation, tubular hypoplasia of the aortic arch, or both. Infrequently there is interrupted aortic arch. In TGA-VSD malalignment of the infundibular septum has important consequences with respect to SAO. Its anterior and rightward displace-
ment may result in narrowing of the subaortic area and impaired flow through the aorta relative to the pulmonary artery. While malalignment of the infundibular septum may contribute directly to subaortic stenosis and systemic obstruction, hypertrophied septoparietal trabeculations, prominent ventriculoinfundibular fold, and abnormal insertions of the atrioventricular valves may contribute as wel1. 28 •30 The unequal partitioning of aortic and pulmonary outflow tracts allows blood flow to be directed preferentially through the pulmonary artery, ductus arteriosus, and descending aorta. This often leads to developmental abnormalities of the aortic arch in the form of coarctation, tubular hypoplasia, or interruption of the aortic arch. 31 •32 In the TBH, the subaortic infundibulum is frequently hypoplastic, as it is commonly wedged between the tricuspid valve and the subpulmonary infundibulum. As in TGA with anterior malalignment VSD, this often results in SAO as well as AAO. The surgical importance of aortic arch obstruction associated with these anomalies seems obvious, yet it has received relatively little attention until recently. 'Vhile the diagnoses of aortic coarctation and interrupted aortic arch are relatively straightforward, tubular hypoplasia of the aortic arch may be less so. While tubular hypoplasia may be present in 62% of cases of isolated coarctation, it may occur in up to 93% of cases of coarctation occurring in association with complex intracardiac lesions. 33 Hypoplasia of the aortic arch may significantly complicate and alter the surgical approach and, if not addressed, may leave behind residual systemic obstruction.
Incidence of Systemic Obstruction in Transposition Complexes While SAO is rare in TGA-IVS,26 it occurs in 20% to 40% of cases of TGA_VSD. 19,26 Subaortic stenosis is common in the TBH, occurring in about 30% to 50% of cases. 3,30.34.3S
Transposition Complexes
Likewise, aortic arch obstruction occurs in only 2% to 3% of cases of TGA-IVS.7,25,26 It is more common in cases of TGA-VSD (l0% to 36%) 7,25-28 and is disproportionately distributed to those hearts with anterior malalignment VSD, occurring in up to 88% of these cases_ 14 Aortic arch obstruction is reported in at least 50% of cases of the TBH.2,29,34 Milanesi et al 28 studied 57 autopsy specimens of TGA-VSD. Nineteen cases (33%) had AAO which was in the form of coarctation in 15 cases, tubular hypoplasia in two cases, and aortic arch atresia in two cases. Fourteen of these 19 specimens had subaortic stenosis from rightward displacement of the infundibular septum combined with hypertrophied septoparietal trabeculations or huge ventricular infundibular fold. Pigott et a}26 reported on 129 autopsy specimens of TGA from the Cardiac Registry of the Children's Hospital of Philadelphia_ Of the 69 cases with TGA-IVS, only two (3%) had coarctation of the aorta and none had evidence of SAO. Conversely, in the 60 patients with a VSD, aortic arch obstruction was much more common, especially in the 29 cases with a malalignment type of VSD. Twenty-two of the 29 cases of malalignment VSD were associated with subaortic stenosis, 18 of which had some form of AAO in the form of coarctation, hypoplasia, or interruption. Several studies have documented AAO in association with the TBH.2,3,29,30,34-37 Parr et al 29 found aortic coarctation in six of nine patients with TBH in their clinical series and in 56 of 105 (53%) autopsy specimens. Conversely, they found aortic coarctation in none of 17 TGA-VSD patients in their clinical experience and in eight of 126 (6%) autopsy specimens. Aoki et al 2 reported on 73 patients undergoing biventricular repair for double-outlet right ventricle_ Of the 27 patients with double-outlet right ventricle and subpulmonary VSD in their series or the TBH, 14 (52%) had MO.
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Pathophysiology The pathophysiology of the transpOSItIOn complexes can be understood by considering the systemic and pulmonary circulations as existing in parallel rather than in series. 38 The clinical picture is largely dependent on the degree of mixing between these two circulations through defects in the atrial and/or ventricular septum and the patent ductus arteriosus. Lesions with poor mixing such as TGA-IVS present in the first few hours of life with rapidly progressive cyanosis. Mixing may be improved with prostaglandin infusion to keep the ductus arteriosus open and with the creation of an atrial septal defect by balloon atrial septostomy. Lesions with good mixing (TGA-VSD or TBH) usually present later in the first month of life. The natural decrease in pulmonary vascular resistance leads to pulmonary overcirculation and signs and symptoms of congestive heart failure with milder cyanosis. In the presence of severe obstruction, the systemic circulation is ductal-dependent. Closure of the patent ductus arteriosus is accompanied by a rapidly progressive downhill course with poor systemic perfusion accompanied by metabolic acidosis, acute renal failure, and necrotizing enterocolitis. Unless the patent ductus arteriosus can be promptly reopened with the infusion of prostaglandins, the clinical course is uniformly fatal. In milder forms of obstruction, the systemic circulation may not be ductal dependent. Nevertheless, the clinical picture is characterized by pulmonary overcirculation with severe congestive heart failure and pulmonary edema.
Natural History Successful surgical treatment of complex congenital heart disease has occurred only recently. The era before successful surgery for TGA gives us insight into the importance of surgical intervention at an early age. The natural history of TGA without surgical cor-
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rection is early death. Patients with poor mixing (ie, TGA-NS) die rapidly of hypoxia. Patients with good mixing but pulmonary overcirculation die of severe congestive heart failure. When the spectrum of TGA is considered together, survival at 1, 6, and 12 months is 55%, 15%, and 10%, respectively.38 However, survival depends on the particular subgroup being considered. While 80% of patients with TGA-IVS are alive at 1 week of life, survival is only 17% at 2 months and 4% at 1 year. When a significant VSD is present, survival is somewhat better at 91 %, 43%, and 32% at 1 month, 5 months, and I year, respectively. While the Taussig-Bing malformation is physiologically similar to TGAVSD, the natural history is often worse, likely secondary to the early development of pulmonary vascular obstructive disease and/or the high incidence of associated systemic obstruction. While associated left ventricular outflow tract obstruction may be protective in TGAVSD leading to survivals of 70% at 1 year and 29% at 5 years, subaortic or aortic arch obstructions are associated with a particularly poor prognosis. Although, the natural history of the TGA complexes associated with systemic obstruction has not been specifically highlighted, one can speculate that in the presence of severe obstruction and a ductaldependent systemic circulation the outcome is universally fatal without surgical treatment. In the milder forms, when the systemic circulation is not ductal dependent, the prognosis is expected to be at best similar to that of TBH.
Surgical Considerations The nature of the ASO used to treat the TGA complexes is such that the subaortic area and the aortic arch are incorporated into different parts of the circulation after the repair. While the aortic arch remains part of the systemic circulation, the subaortic area becomes the subpulmonary area. This means that residual AAO is a problem
faced by the left heart, with resultant left heart failure and inadequate systemic perfusion. On the other hand, inadequate relief SAO results in residual obstruction in the right heart and the pulmonary circulation after the ASO. There are few published reports dealing specifically with AAO in patients with TGA complexes. In a multi-institutional study by the Congenital Heart Surgeons Society on neonatal coarctation, the overall mortality was 19% for patients with TGA-NS and TGA-VSD and 50% for those ''''ith the TBH.20 Although, the surgical approach used is unclear, it is likely that most patients underwent a staged repair.
Staged Approach Versus Single-Stage Anatomic Repair The association of AAO with complex congenital heart disease presents a formidable surgical challenge and has been associated with a high mortality. Traditionally, these patients were repaired in two stages. At the first stage the AAO is repaired through a left thoracotomy with the intracardiac malformation palliated with a pulmonary artery band. The intracardiac repair was delayed by several months or years. In published reports, total mortality with the two-stage approach has ranged between 31 % and 64%.19,20,22,33 Several factors may have contributed to these discouraging results. The frequent association of tubular hypoplasia of the aortic arch in patients with coarctation and complex congenital heart disease has only been recognized recently.33 Furthermore, the deleterious effects of pulmonary artery band have become increasingly apparent. 19 Finally, outcome assessment of the two-stage approach must take into account not only the mortality of the initial palliation, but also the interval mortality and the mortality of intracardiac repair. There is increasing evidence that a single-stage anatomic repair may be the preferred treatment modality in patients with TGA complexes and AAO.19,23,24 Despite the increased com-
Transposition Complexes
plexity of the procedure and the smaller size of the baby at the time of repair, there appears to be a lower associated operative mortality in the group undergoing single-stage anatomic repair. 19,23,24,30,33 The single-stage repair for TGA and AAO was first reported by Pigott et al 26 in five patients. Four of the five patients were corrected in a single stage as neonates. They reported one early death from coagulopathy and one reoperation for distal AAO. In 1993, Planche et al 19 from Marie-Lannelongue Hospital in Paris, showed that the singlestage approach was superior when compared with a staged approach. They compared 40 patients with TGA-VSD and AAO having either single-stage (I4 patients) or two-stage repair (26 patients). Of the 14 patients in the single-stage group, there were two early deaths (14.2%) and one late death. Actuarial survival rate and rate of freedom from reoperation at 3 years were 78.5% and 81.5%, respectively. Conversely, in the 26 patients undergoing two-stage repair, there were eight early deaths (three after aortic arch repair and five after VSD closure and arterial switch) for an early mortality of 30.7%. Actuarial survival rate and rate of freedom from reoperation at 5 years were 57.5% and 49.9%, respectively. They noted how the placement of a pulmonary artery band may worsen the malalignment of the infundibular septum that is often present, leading to worsening or unmasking of SAO. Conte et aP3 updated this report with additional patients in 1995 with similar conclusions. From the same institution, Serraf et aF reported on a large series of 432 patients with TGA undergoing ASO. Twenty-three of their patients had associated coarctation of the aorta. Eighteen of these patients were repaired using a single-stage approach with a mortality of 13.3%, which was higher than the mortality of 7.6% in TGA-IVS patients and 8.5% in TGA-VSD patients undergoing ASO without associated AAO. By contrast, Tchervenkov et al 24 have not experienced an increased risk in a single-stage ASO with
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concomitant aortic arch repair with no operative mortality in 18 consecutive patients with TGA complexes and AAO. More recently, other investigators have reported good results with the single-stage approach as well. 3o ,33,39,4o In the most recent report from Marie-Lannelongue Hospital published in 1997, Lacour-Gayet et apo described their results with biventricular repair of 103 patients with conotruncal anomalies associated with aortic arch obstruction. Ninety-one of 103 patients in their series had a transposition complex (TGA-NS in 15, TGA-VSD in 44, and TBH in 32) as the conotruncal anomaly. The AAO was in the form of coarctation of the aorta in 88 cases and interrupted aortic arch in 15 patients. In the patients with coarctation, 64 of 88 had associated hypoplasia of the aortic arch. They performed biventricular repair and aortic arch reconstruction using either a two-stage or single-stage approach. The hospital mortality for the singlestage group was 12% (7 of 58), while it was 20% (9 of 45) for the group having two-stage repair. The investigators now reserve the two-stage approach for the patient with multiple VSDs, neurologic disorders, and multiorgan failure.
Surgical Techniques Subaortic Obstruction The ASO is currently the procedure of choice for TGA and double-outlet right ventricle with subpulmonary VSD.l The presence of SAO makes the surgical repair more challenging. The subaortic stenosis common in TGA-VSD and TBH is usually secondary to malalignment of the infundibular septum with hypertrophy of the subaortic conus. When repair is performed by ASO, this subaortic area becomes the subpulmonic area. The obstruction can usually be dealt with by division and resection of the obstructing bands of muscle,3o followed by primary closure of the right ventricular outflow tract. In some cases, it may be necessary to augment the right ventricular outflow tract with a
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patch of autologous pericardium 26 ,3o or to bypass the obstruction with a valved homograft conduit. 26 These techniques are applicable in the majority of cases, but there are instances in which the subaortic area is extremely hypoplastic and/or when anomalous coronaries cross the right ventricular outflow tract. In these cases, we have performed an anatomic repair by combining the salient features of the Rastelli and Norwood operations. 23 The left ventricle is tunneled through the VSD into the proximal pulmonary artery, which is then transected and incorporated into the systemic circulation. The ascending aorta is anastomosed to the proximal main pulmonary artery and the entire ascending aorta and arch is reconstructed using a pulmonary artery homograft patch. The right ventricular outflow tract is then reconstructed using a valved pulmonary artery homograft after oversewing the subaortic conus to render the aortic valve atretic.
Aortic Arch Obstruction Aortic arch obstruction manifesting as interrupted aortic arch, tubular hypoplasia, or coarctation may occur in isolation or in combination with subaortic stenosis. Traditional techniques to deal with coarctation with or without tubular hypoplasia of the aortic arch include resection and primary end-ta-end anastomosis, extended end-ta-end anastomosis, subclavian flap angioplasty, and patch (synthetic or homograft) aortoplasty. Coarctation of the aorta in association with transposition complexes is most commonly addressed with resection of the coarctation and primary end-to-end anastomosis. 3o ,37,39,4o Hypoplasia of the aortic arch is a frequently associated lesion and can be managed by extended end-to-end anastomoses of the descending aorta to the undersurface of the aortic arch as necessary. Advantages of this option are that it can be performed through a thoracotomy (staged approach) or median sternotomy (single-stage repair). This involves resection of the coarctation
and periductal tissue and does not involve the use of patch material. However, there may be significant tension on the suture line and proximal obstructions in the proximal arch and ascending aorta may be left unattended. Subclavian flap aortoplasty has been advocated by some for its relative ease to perform, requiring limited dissection with a p0tential for growth,4J \Vhile this simplifies the operation, this approach does not address the aortic arch hypoplasia that is often present, with the potential for leaving systemic obstruction. This technique is not applicable during single-stage repairs through a sternotomy. Synthetic patch aortoplasty has fallen out of favor because of the risk of sudden rupture and aneurysm formation.-t246 Replacement of the aorta with a tube graft is not practical in the neonate because of the obvious lack of growth potential. At the Montreal Children' Hospital we advocate the almost exclusive use of pulmanary homograft patch aortoplasty (Fig I) for our combined neonatal aortic arch reconstructions and intracardiac repair for a number of reasons. This technique is relatively straightforward and reproducible. It achieves three important objectives for adequate repair: (I) the arch repair can be extended proximally and distally as needed to make the aorta an adequate size throughout, regardless of the initial dimensions, (2) it corrects the often marked size discrepancy between the proximal neoaorta and the distal aorta, which is often present in patients with TGA, VSD, or the TBH; and (3) it results in a single tension-free anastomosis between the proximal neoaorta and the enlarged distal aorta. While the extended end-ta-end anastomosis results in excision of the coarctation shelf and avoids the use of foreign material, it accomplishes none of the three previously mentioned objectives. Some have expressed concern over the use of nonviable material crossing ductal tissue leading to recoarctation in the future. u Since 1988, we
Transposition Complexes
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Figure 1. Technique of pulmonary homograft patch aortoplasty. Note the flexible arterial cannula advanced and snared in the innominate artery allowing continuous low-flow cerebral perfusion during reconstruction of the aortic arch. have performed single-stage anatomic repair of 22 patients with transposition complexes and aortic outflow tract obstruction using pulmonary homograft patch aortoplasty. In this group, we have observed one recoarctation (4.5%) requiring balloon dilatation and no aneurysm formation. Interrupted aortic arch in patients with TGA complexes can be repaired by direct anastomosis, as in patients with isolated interrupted aortic arch. Recently, Liddicoat et al described a new technique of repairing interrupted aortic arch associated with TGA complexes. 36 Anatomic single-stage repair was performed in two patients combining an ASO with bypass of the hypoplastic aortic arch by anastomosing the ascending aorta directly to the descending aorta and sewing
the neoaorta to the undersurface of the new aortic arch. Mavroudis et al used a similar technique to perform a single-stage repair of a TBH with SAO, a small ascending aorta, and coarctation. Great artery transection and coronary transfer were performed followed by coarctation resection. The ascending and descending aorta were then joined together in a manner similar to that described previously. A valved homograft was used to reconstruct the right ventricular outflow tract after subvalvar resectionY
Aortic Arch Reconstruction Without Circulatory Arrest Traditionally, reconstruction of the aortic arch in the neonate has required the use of deep hypothermic circulatory arrest. It has
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increasingly rccognized in recent yc~ars that deep hypotlwrmic circulatory arrest may be associatt'{l with significant neuI'Ologk morbidity:i7 As a consc'qlwnce, we and (It hers ha\'(' devised techniques to avoid or limit tl\(' Us(' of circulatory '\I·rt~styl-j:1 I;'or pati('nts with transposition complexes and AAO undt'rgoing simultaneous arch reconstruction and biventriculur repair, we have usc'd two main techniqu('s to avoid circulatory arn'st. The first technique involves Cllntinuoll!! low-flow c(~ rc'bral perfusion via the innominate artc'ry during arch reconstruction with tile' ardl vCl'lS(·ls snared and dcsl'C~nding aorta dump(~d (Fig I). The aorta is then augml'ntc'd with a patch of' pulmonary homograft as previously described.:'?:1 Arterial switch is pl'rrorm(~d in the usual manner with tilt' augm(~nt(·d ascending aorta being s('wn to the Iwoaorta. The other techniqUt: we have used to avoid circulatory arrcst is the applkation of the aortic cross clamp bctw('c'n the innominate artery and the left ('arotid artery. This allows continuous perfusion of the myocardium and cerebral circulation via the innominate artery. Single-stage reconstruction of the aortic arch with biventricular repair or complex intracardiac defects can be accomplished consisll'ntly without the use of circulatory arrest or direct cannulation ofthc arch vessels. Further expaiem'(~ with long-term follow-up is required to assess impact on neurologic outcomes.
bt~com(~
Experience At The Montreal Children's Hospital At the Montreal Children's lIospital, we adopted in 19HH an aggressive approach of thc single-stage anatomic repair uf congenital cardiac defects associated with AAO, consistent with our surgical philosophy of carly primary intracardiac repair. Since then we haw performed single-stage anatomic repairl'l in 4!) out or 50 eonseclitive patients with ('ardial' defrets associated with AAO with a ,~% m()rtality.2'~ A single-stage ASO
with or without VSD closure and concomitant aortic arch reconstruction was performed in 22 patients with TGA complexes and AAO.23,24 When present, subaortic stenosis was relieved by an outflow pericardial patch, except in one patient with the TBll. In this patient, severe tubular SAO and the presence of a major coronary artery across the outflow tract precluded the use of a transannular patch. This patient underwent a single-stage biventricular anatomic repair applying features of the Rastelli and Norwood operations using a right ventricle-topulmonary artery conduit. In this series of patients, we have had no early deaths and only one late death from a hepatoblastoma at 39 months. The only patient in this series nut having a single-stage repair was the first patient, a neonate with the TBll that became unstable after the induction of anesthesia. He underwent coarctation resection and extended end-to-end anastomosis through a left thoracotomy and a pulmonary artery banding. Because of persisting severe congestive heart failure, 12 days later he underwent an ASO, VSD closure, and debanding. As previously mentioned, in our experience, the presence of MO in patients with TGA complexes has not been associated with increased mortality following the ASO. Similar to our own experience, Comas et al found that AAO in association with TBII did not adversely affect outcome. 34 We believe that the appreciation for the presence of tubular hypoplasia of the aortic arch has led us to have a low threshold for enlarging the aortic arch at the time of ASO. We use criteria suggested by Karl et altO to define aortic arch hypoplasia requiring intervention. If the transverse aortic arch diameter by echocardiography is less than the patient's weight in kilograms plus one, it is considered hypoplastic. For example, in a 3-kg baby, if the aortic arch is less than 4 mm (ie, 3 + I), we consider it hypoplastic and would enlarge it surgically. We believe that a degree of hypoplasia of the aortic arch that
Transposition Complexes
may be well tolerated fonowing coarctation repair in an otherwise normal heart will not be tolerated by a heart that has been subjected to a complex intracardiac repair with a significant duration of myocardial ischemia and cardiopulmonary bypass. The decision to enlarge or not what appears to be a hypoplastic aortic arch is not always an easy and straightforward one. Therefore, a word of caution is advised. We have experience with a 5-week-old baby (3.96 kg) with TGA-VSD and tubular hypoplasia of the aortic arch measuring 5 mm on preoperative echocardiogram, just over the cutoff we use to consider augmentation (weight in kg + I = 4.96 mm). After ASO and VSD closure, the patient was weaned twice from cardiopulmonary bypass. Each time, about 45 minutes later, there was a rapidly progressive hypotension, necessitating reinstitution of cardiopulmonary bypass. In the face of well-perfused and clearly distended coronary arteries, the etiology of the patient's deterioration was thought to be secondary to a borderline aortic arch. The pulmonary and aortic anastomoses were taken down and the aortic arch was enlarged with a pulmonary homograft patch aortoplasty. Despite a total myocardial ischemia time of more than 3 hours and cardiopulmonary bypass time of more than 10 hours, the patient was then weaned successfully from cardiopulmonary bypass with relative ease and went on to recover without further problem. Conversely, in three patients, despite the aortic arch being suspected as being hypoplastic on preoperative echocardiogram, intraoperative probing of the internal diameter showed an adequate size, precluding surgical enlargement. A very large patent ductus arteriosus compressing the aortic arch was thought to have given the appearance of hypoplasia on the preoperative echocardiograms. However, one of these patients has returned 5 months after the neonatal ASO for TGA-IVS with discrete coarctation of the aorta. On routine follow-up, the patient was found to have absent femoral pulses secondary to a discrete
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coarctation confirmed by echocardiogram and magnetic resonance imaging. He underwent uneventful coarctation resection and primary end-to-end anastomosis through a left thoracotomy. The other two patients have no evidence of aortic arch obstruction on follow-up.
Conclusions The importance of systemic obstruction in association with transposition complexes has become apparent in recent years. Aortic arch obstruction and subaortic stenosis occur frequently in association with the TBH and TGA-VSD with anterior malalignment VSD and, rarely, in TGA-IVS. Since 1989 we have adopted a single-stage intracardiac repair with concomitant aortic arch reconstruction with excellent outcomes. The technique of pulmonary homograft patch aortoplasty has achieved an unobstructed systemic circulation, has allowed for correction of the frequently observed great vessel discrepancy with a tension-free anastomosis, and has been associated with a low recoarctation rate. Recently, the use of low-flow cerebral perfusion techniques has allowed the performance of all our aortic arch reconstructions to avoid the use of deep hypothermic circulatory arrest. The implications of these techniques will be become apparent in the next few years as the survival and functional status of these patients continues to improve.
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