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Ann Thorac Surg 1999;68:2293-2297
© 1999 The Society of Thoracic Surgeons

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Original Articles

Surgical treatment of aortic arch hypoplasia in infants and children with biventricular hearts

^a Division of Cardiovascular Surgery, The Hospital For Sick Children, Toronto, Ontario, Canada
^b Division of Pediatric Cardiology, The Hospital For Sick Children, Toronto, Ontario, Canada

Address reprint requests to Dr Van Arsdell, Division of Cardiovascular Surgery, The Hospital For Sick Children, 555 University Ave, Suite 1525, Toronto, ON, Canada M5G 1X8
e-mail: glen.vanarsdell{at}sickkids.on.ca

Presented at the Thirty-fifth Annual Meeting of The Society of Thoracic Surgeons, San Antonio, TX, Jan 25–27, 1999.

	Abstract

Top Abstract Introduction Patients and methods Results Comment References

 
Background. Results of aortic arch reconstruction in the setting of biventricular physiology are well documented in the adult population, however, in children, surgical outcome of this subgroup of patients is less clear.

Methods. We studied the clinical outcomes of 37 children aged 8 days to 15 years (median 26 months), who underwent aortic arch reconstruction for arch hypoplasia from 1982 to 1997. The children were divided into three groups: Group 1 (20 patients) had isolated aortic arch lesions, Group 2 (13 patients) had associated intra-cardiac pathology yet conserving a biventricular physiology, Group 3 (4 patients) had Williams Syndrome. Previous interventions for coarctation had been performed in 30 patients (81%). Arch repair consisted of a patch aortoplasty in the majority of patients (35 of 37 children).

Results. Operative mortality occurred in 5 children, 4 in Group 2 (31%), 1 in Group 3 (25%) and none in Group 1. Permanent neurological complications occurred in 2 children (5 %). During the follow-up, which ranged from 1 month to 8 years, balloon angioplasty for arch obstruction was required in 1 child. There was one late death, associated with a subsequent intra-cardiac repair.

Conclusions. Aortic arch surgery in children with isolated arch hypoplasia, is associated with excellent early and late survival in addition to a low reintervention rate. Alternative perfusion and operative strategies must be implemented in infants with associated intra-cardiac anomalies to improve results.

	Introduction

Top Abstract Introduction Patients and methods Results Comment References

 
Transverse aortic arch hypoplasia involving all segments of the arch, or tubular hypoplasia, usually occurs in association with intra-cardiac anomalies of varying severity ranging from a simple ventricular septal defect to hypoplastic left heart syndrome. Uniform narrowing of the whole arch can also coexist with isolated coarctation or occur independently, in both neonates and older patients [1–3]. Although operative results of extensive arch reconstruction in the presence of univentricular circulation (ie. Norwood procedure) have been the subject of numerous publications, only a few small case series have reported outcomes of arch repair in children with tubular hypoplasia with biventricular hearts [3, 4]. Results of arch reconstruction in the setting of biventricular physiology are well documented in the adult population for acquired lesions, with mortality rates of 15% and major permanent neurologic deficits in 7 to 10% of patients [5]. Extrapolation from this data of operative outcomes for the pediatric population is, however, inappropriate due the difference in disease process, comorbid states and the presence of the atherosclerosis. We therefore studied 37 patients who underwent arch reconstruction for tubular hypoplasia to determine short and long term operative results.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment References

 
All children with biventricular physiology who underwent aortic arch reconstruction for arch hypoplasia between July 1982 and October 1997 at the Hospital for Sick Children, Toronto, were included in the study. Aortic arch hypoplasia was defined as an aortic arch diameter less than 50% of the ascending and/or descending aorta involving all segments of the arch from the origin of the innominate artery to the descending thoracic aorta (Fig 1). Arch hypoplasia was identified preoperatively by echocardiography and /or angiography. Surgical indication included arch hypoplasia, accompanied by symptoms, a systolic arm-leg gradient more than or equal to 20 mm Hg, or proximal systemic hypertension. Patients with univentricular physiology who underwent Norwood procedures were excluded from the study. Children with isolated coarctation or recoarctation involving solely the isthmus with or without distal arch narrowing were also excluded. Our results of surgical repair of recoarctation are outlined in a previous publication [6].

View larger version (141K): [in this window] [in a new window]   Fig 1. Example of tubular arch hypoplasia.

Clinical data
Thirty-seven (37) patients (14 females, 23 males) underwent arch reconstruction for aortic arch hypoplasia as defined above. Ages ranged from 8 days to 15 years (median = 26 months). Three distinct subgroups of patients were identified based on great vessel and cardiac morphology: Group 1 (20 patients) had isolated aortic arch hypoplasia; Group 2 (13 patients) presented associated intra-cardiac amenable to a biventricular repair; Group 3 (4 patients) had Williams Syndrome. The clinical data of all 3 groups is summarized in Table 1.

At arch repair, Group 1 children were significantly older than the other 2 groups. Only one patient was symptomatic preoperatively, however, all had gradients greater than 20 mm Hg using one or more modes of measurement. Proximal systemic hypertension was observed in 11 children (55%).

Group 2
Table 2 lists the intracardiac lesions and procedures performed in Group 2 children. There were 6 neonates in the total cohort of patients and all were amongst the infants of this group. A prior repair of coarctation had been performed in 10 (77%) of the children during the neonatal period. An end-to-end technique had been used in 7 patients (70 %) and a subclavian flap in 3 patients (30%). The mean postoperative arm-leg gradient after coarctation repair was 29±25 mm Hg. Two patients underwent unsuccessful balloon dilations of recoarctation sites prior to arch repair. All of the children had signs and symptoms of congestive heart failure prior to arch reconstruction. Four children presented with signs of systemic hypoperfusion. None had proximal hypertension, however, 9 of the 13 (69%) children had preoperative gradients greater than 20 mm Hg using 1 or more modalities of measurement.

Operative procedures
Details of the operative procedures are outlined in Table 3. A patch aortoplasty, from the innominate artery extending distally to the isthmus, was performed to relieve arch hypoplasia in 35 children (95%). In 60% of children (n = 17), a patch of cryopreserved aortic or pulmonary homograft was used. Other patch materials included polytetrafluoroethylene (PTFE) in 9 (26%) patients, Dacron in 2 (6%) and a glutaraldehyde-treated autologous pericardial patch in 3 (9%). In one child, the arch was augmented using the left carotid artery as a patch. In one child from Group 2, a conduit was placed between the ascending and descending thoracic aorta and another child of Group 1 had a radical extended end-to-end repair.

All patients who underwent hypothermic circulatory arrest were managed using an alpha-stat regime, the hematocrit was kept at 20 to 22%, and steroids (Methylprednisolone 20 mg/kg) were administered at the beginning of the procedure. In 1990, the perfusion protocol was modified. Cooling was performed at a slower rate, a minimum of 20 minutes, with the perfusate temperature kept above 15°C rather than 8 °C used prior to 1990. The CPB flows for infants less than 10 kg were calculated according to weight (100 to 120 ml/Kg/min) rather than body surface area (2.4 to 3.2 L/min/m²) maintaining the perfusion pressures between 20 and 30 mm Hg. Twenty-seven (73%) patients were repaired after 1990, with these changes in perfusion management.

	Results

Top Abstract Introduction Patients and methods Results Comment References

 
Operative mortality
There were no deaths in Group 1 with isolated aortic arch hypoplasia. Four of the 13 (31%) patients with associated lesions died following surgery: 2 from inadequate ventricular size, 1 from aspiration, and 1 tamponade related to the removal of an intra-cardiac line. No arch obstruction was observed at autopsy. The death in Group 3 was in a child who could not be weaned from cardio-pulmonary bypass. An autopsy revealed persistent supra-valvar aortic stenosis, which had not been identified intra-operatively. The operative mortality (< 30 days after surgery or during the same hospitalization) for the total cohort of patients was 13.5%.

Operative morbidity
Four children (10.8%) developed postoperative neurological symptoms [seizures (3), cortical blindness (2), choreoathetosis (1)]. The only child from Group 1 with postoperative neurologic complications had preoperative seizures dating to a prior cardiac arrest during the neonatal period. Over 11 years after arch surgery, the seizures are controlled with medication however the child displays motor and cognitive delay. The only neonate to develop neurologic symptoms did so following a ventricular septal defect closure and arch reconstruction (Group 2). Left-sided focal seizures were observed and a middle cerebral artery infarct was diagnosed on a CT Scan. Two years after surgery, the seizures have subsided however the child has signs of motor and speech delay. The 2 other children, one with TGA (Group 2) and the other with Williams syndrome (Group 3) presented transient neurologic complications. The changes in perfusion protocol in 1990 did not influence neurologic morbidity (p = 0.648) or operative mortality (p = 0.4).

Other postoperative events included one immediate reintervention for a residual arm-leg gradient detected upon arrival at the intensive care unit. Vocal cord palsy occurred in one patient and reoperation for bleeding in 4 (11%). Eight children had a postoperative infection (22%), and residual hypertension present in the immediate postoperative period in 7 (19%).

Long term follow-up results
Postoperative follow-up was available in 31 of the 32 survivors (97%). The mean follow-up period was 48.9±37 months, ranging 2 to 140 months (median = 43 months).

Survival
There was one late death associated with a subsequent intracardiac repair in a Group 2 patient. No aortic arch obstruction was noted at autopsy.

Reintervention
Freedom from reintervenion was 97% at 5 and 10 years. One child in Group 1 had a balloon angioplasty for distal arch stenosis. Six years later, a 7 mm Hg arm-leg gradient persists but has not progressed. Two patients had other procedures for intra-cardiac anomalies: a subaortic ridge resection 3 months after the aortic arch repair and a late arterial switch operation 4 months after arch repair.

Clinical status
At last follow-up, noe of the surviving children had cardiac symptoms and all reported a normal functional status. No additional neuro-developmental anomalies have been identified in addition to the 2 patients with residual neurological sequelae identified during the perioperative period. Only one patient remained hypertensive requiring therapy. There were no pressure arm-leg gradients at rest greater than 20 mm Hg. MRI studies were obtained in 11 patients from Group 1 a mean of 42.3±36 months postoperatively. No restenosis or dilation was documented at the site of the arch reconstruction or at the level of the native aorta. There was also no evidence of dilation or obstruction at any level of the aorta in the 22 survivors that underwent echocardiographic evaluation (2-dimensional and Doppler) a mean of 43±25 months after surgery.

	Comment

Top Abstract Introduction Patients and methods Results Comment References

 
The actual incidence of arch hypoplasia is difficult to determine due to the lack of a consensus on its definition. In a classic autopsy series by Moulaert and associates [7], the aortic arch was considered hypoplastic when the ratio between the aortic arch and ascending aorta was less than 0.5. We chose a variation of this definition which also takes into account the size of the arch with respect to the descending aorta. From a purely hemodynamic point of view, the ascending aorta is more likely than the descending to display an abnormal blood flow pattern in the setting of previous coarctation and/or commonly associated intra-cardiac lesions (left-to-right shunting and subvalvar or valvar aortic stenosis). Morrow and associates [8] have shown that the ascending aorta is smaller in the setting of coarctation than in normal patients. The descending aorta, however, is the same in both groups making the arch-descending aorta ratio a more reliable determinate of arch hypoplasia. We also chose to include only children with arch narrowing involving all segments of the arch to not confound these patients with simple coarctation or recoarctation in whom 60 to 70% have some degree of distal arch hypoplasia [1, 9, 10].

Contemporary clinical studies have shown that the spontaneous growth of the hypoplastic arch in children beyond the neonatal period is usually inadequate when only the isthmic obstruction is treated [11, 12]. Histological studies have confirmed these findings by demonstrating that the hypoplastic segment of the arch has a significantly higher than normal ratio of elastin lamellas by the diameter of the vessel, an increase in collagen and a decrease in alpha-actin positive cells that could contribute to a decreased ability of the affected arch to distend [13]. This lack of growth appears to have played a part in the pathophysiology of arch obstruction in our patient population and particularly evident in the subgroup with isolated arch hypoplasia (Group 1). Of the 17 children with isolated arch hypoplasia, all had coarctation repair beyond the neonatal period with immediate postoperative gradients which never resolved. Only 4 children had at least a portion of the arch narrowing addressed using an extended end-to-end repair. These findings once more illustrate the importance of addressing aggressively any obstruction at the level of the arch at coarctation repair with liberal use of end-to-end techniques. Furthermore, with the increasing number of children with coarctation treated primarily by percutaneous balloon angioplasty of the isthmus, which does not relieve arch obstruction, we can speculate that late transverse arch obstruction requiring surgical repair may become more frequent in the near future. For the moment, arch hypoplasia has been identified as a potential cause of early failure of balloon dilation [14].

Operative results of aortic arch reconstruction in the infants and children with isolated arch hypoplasia or Group 1 were excellent. There was no operative mortality, no de novo neurological sequelae despite the use of hypothermic circulatory arrest in 85% of patients and no late deaths or reoperation during a mean follow-up period of 4.6 years. There is little data on congenital complete arch reconstruction in the setting of biventricular physiology. DeLeon and associates [3] recently reported the only other comparable series of 6 patients. A PTFE patch aortoplasty, using hypothermic antegrade cerebral perfusion during circulatory arrest, was practiced without postoperative mortality or gross neurological abnormalities and no evidence of recurrent arch obstruction or dilation at a mean follow-up of 15 months.

Operative mortality occurred only in patients with associated lesions. They were either related to complications of the intra-cardiac repair (2 patients) or due to non-cardiac causes (1 aspiration, 1 related to removal of intra-cardiac line). Similar results of combined arch and intra-cardiac repair have been reported by Karl and associates [4]. They observed a 13% operative mortality rate in a group of 15 infants who underwent a one stage repair, addressing the arch hypoplasia with extended end-to-end repair performed using hypothermic circulatory arrest. We continue to perform one stage repairs of both the arch and intra-cardiac anomalies except in the presence of co-morbid states that render CPB a higher risk (for example cerebral hemorrhage, sepsis). In these instances, a staged approach is used and, initially, the aortic obstruction is corrected off CPB.

The choice of a patch aortoplasty in our patients was dictated by the fact that the majority had either underwent a previous coarctation repair or presented diffuse aortic thickening characteristic of Williams Syndrome patients. Aneurysmal dilation following patch repair of coarctation has been reported. The mechanism of aneurysm formation at the site of these repairs is not completely understood but a number of predisposing factors have been hypothesized. These include excessive resection of the intimal shelf, retention of the abnormal aortic tissue, intensification of the pulse wave at the native tissue opposite the patch and excessive bulging of the patch itself [15]. Although the intermediate follow-up results in our cohort are promising, long-term follow-up is needed to adequately assess the results of this technique since complications of patch aortoplasties occur more frequently 10 years after repair. One promising feature of this repair is the virtual absence of postoperative hypertension which may be beneficial for late outcomes.

Three children had new neurological symptoms following arch repair. In one of these the symptoms are persistent. As in many other reviews, it is difficult to determine culprit neurological insults without prospective pre- and postoperatively neurodevelopmental data. Do children with arch hypoplasia and intra-cardiac anomalies have a higher incidence of structural brain lesions, similar to the more severe forms of hypoplastic left heart syndrome? Is cerebral perfusion critically decreased in the presence of arch obstruction and compounded by preoperative heart failure? Does cerebral reactivity differ in these children rendering them susceptible to hypothermic circulatory arrest and reperfusion injury? Better preoperative evaluation, aggressive treatment of hypoperfusion states and alternative cerebroprotection techniques are needed to improve outcomes of arch reconstruction of higher risk patients. Despite improved perfusion strategies, arch reconstruction using deep hypothermic circulatory arrest has a persistent incidence of postoperative neurological complications. Two interesting alternative cerebroprotection strategies were successfully used in our patient population: hypothermic antegrade hemi-cerebral perfusion through the innominate artery and retrograde cerebral perfusion. More information is needed concerning technique and outcome before these methods are routinely used.

In conclusion, aortic arch reconstruction for tubular arch hypoplasia in infants and children without associated intracardiac lesions can therefore be performed with excellent early and intermediate-term results. At intermediate follow-up after patch aortoplasty, there are few complications related to the site of repair. Alternative perfusion and operative strategies must be implemented in infants with intracardiac anomalies undergoing arch reconstruction to improve outcomes.

	Acknowledgments

 
The authors thank Mr Jay Joseph for his support in preparing and analyzing this data. This work was made possible through a grant from La Fondation de Recherche en Santé du Québec.

	References

Top Abstract Introduction Patients and methods Results Comment References

 

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