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Ann Thorac Surg 1997;63:669-675
© 1997 The Society of Thoracic Surgeons
Division of Cardiovascular Surgery, Department of Surgery, and Division of Cardiology, Department of Pediatrics, The Hospital for Sick Children and University of Toronto Faculty of Medicine, Toronto, Ontario, Canada
Accepted for publication October 1, 1996.
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Abstract |
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Methods. Between May 1980 and December 1994, 22 children underwent a Fontan operation for the treatment of pulmonary atresia with an intact ventricular septum at The Hospital for Sick Children, Toronto. The mean age was 5.8 years (median, 4.9 years). All children had had at least one pre-Fontan palliative procedure; 19 had two, and 7 of these had three or more. Right ventricle-to-coronary artery connections were present in 15 children, including 5 with right ventricle–dependent coronary artery blood flow. Thromboexclusion of the right ventricle was done in 10 children, with 7 undergoing it before and 3 at the time of the Fontan procedure.
Results. There were three early deaths (13.6%) and one late death. The actuarial survival at 10 years after the Fontan operation was 80%. Early postoperative complications occurred in 4 children. Follow-up was completed in all children at a mean of 4 years (range, 1 to 12.5 years) after the Fontan operation. Atrial arrhythmia occurred in 3 children, and permanent pacemakers were required in 4.
Conclusions. Results of the Fontan operation for the treatment of pulmonary atresia with an intact ventricular septum are satisfactory. Thromboexclusion of the right ventricle is indicated in the presence of right ventricle-to-coronary artery connections without right ventricle–dependent coronary artery blood flow. The right ventricle should not be decompressed or thromboexcluded in children with right ventricle–dependent coronary artery blood flow, and at the Fontan operation, saturated blood must enter the right ventricle.
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Introduction |
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Another factor affecting outcome is the presence of connections between the RV and the coronary arteries (RV-CACs) [4, 5]. These fistulous connections may be associated with coronary artery obstruction in some infants, resulting in the absence of any connection between the aorta and the coronary artery. In these cases the distal coronary artery blood flow depends on flow through the connections from the RV (RV-dependent CBF).
A single-ventricle repair, the Fontan procedure, is recommended for children with a small RV incapable of conveying the systemic venous return. (Occasionally a one-and-a-half ventricle repair is considered in such children.) Children at this end of the clinical spectrum many undergo several procedures preparatory to a Fontan operation.
Because of the rarity of PA/IVS, which constitutes 1% to 3% of congenital heart lesions [6], and the high mortality associated with palliation in children with PA/IVS destined for a one-ventricle repair, few children reach the stage of a Fontan procedure [1, 4, 7]. In a Mayo clinic report [8], only 39 children had PA/IVS, constituting approximately 4.5% of a large series of patients who had undergone the Fontan operation. Hanley and co-workers [5] reported on a multiinstitutional study conducted by the Congenital Heart Surgeons' Society. They reported that, of 171 neonates with PA/IVS, 62 had died, 32% of the patients alive at 3 years after entry into the study had undergone a biventricular repair, and only 18% had undergone a one-ventricle repair.
A previous report from our hospital focused on a subgroup of children treated with thromboexclusion of the right ventricle (TERV) [9]. The present study was undertaken to evaluate the results of the Fontan procedure in children with PA/IVS.
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Materials and Methods |
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TopFootnotesAbstractIntroductionMaterials and MethodsResultsCommentReferences |
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All children were considered suitable candidates for a one-ventricle repair (Fontan procedure) as the result of a hypoplastic right ventricle or tricuspid valve; the median Z value was -4.6.
Cardiac catheterization was performed in all children before the operation. Right ventricular angiography and ascending aortography using the balloon occlusion technique were performed to delineate the size and morphology of the RV, evaluate the coronary circulation, clarify whether there was an RV-CAC, and estimate the degree of dependency of the distal coronary artery circulation.
Management
Our algorithm for the initial management of children with PA/IVS included the establishment of a source of pulmonary artery blood flow, decompression of the RV if appropriate, and consideration of balloon atrial septostomy.
ADEQUATE PULMONARY ARTERY BLOOD FLOW.
Initially, adequate pulmonary artery blood flow was established by infusing prostaglandin E1; later this was done by creating a systemic–pulmonary shunt. Our preferred method became a modified right Blalock-Taussig shunt. We created a central shunt if branch pulmonary arteries were less than 3 mm in diameter.
DECOMPRESSION OF THE RIGHT VENTRICLE.
To aid in establishing adequate blood flow, a pulmonary valvotomy or RV outflow patch procedure was performed. Currently, radiofrequency ablation with balloon dilation of the RV outflow track is done in the catheterization laboratory in infants who have an infundibular chamber. Most of these infants require a modified Blalock-Taussig shunt. Children with a very small RV may have RV-dependent CBF; decompression of the RV is contraindicated in these infants. Children with very small RVs and RV-CACs without dependency, or those who have sufficiently connections to contribute to a coronary artery steal and are not RV dependent (ie, their myocardium is supplied by normal coronary arteries), were managed by occluding the tricuspid valve orifice and the RV cavity (TERV), in the belief (as yet unsubstantiated) that closure of RV-CACs may prevent progressive occlusive changes in the coronary arteries.
ATRIAL SEPTOSTOMY.
If the RV could be decompressed and appeared capable of growth, we did not enlarge the atrial septal defect. Otherwise a balloon septostomy (or septectomy) was done to decompress the systemic venous return into the left atrium.
DEFINITIVE REPAIR.
Children judged to have an "adequate RV" proceeded to undergo biventricular repair. Patients with PA/IVS are considered for biventricular repair if their coronary artery circulation is not RV dependent and the tricuspid valve Z value is more than -3. If the child has a small infundibulum and the tricuspid valve Z value is -3 to -4 or less, we give the patient the benefit of the doubt and perform RV outflow track decompression and biventricular or one-and-a-half ventricle repair. A one-ventricle repair (Fontan operation) is indicated if (1) the coronary circulation is clearly considered RV dependent; (2) if there is no infundibulum and the tricuspid valve Z value is -3 to -4 or less; or (3) there are very large ventricle-to-coronary artery connections, but without coronary artery stenosis or interruption. In the later case, biventricular repair is not indicated because decompression of the RV could lead to myocardial ischemia.
Children with a hypoplastic RV required the Fontan operation and underwent a bidirectional cavopulmonary shunt procedure in preparation for it. When RV-CACs were present without RV-dependent CBF, the child underwent TERV then a Fontan procedure. If RV-dependent CBF was present, we carried out a Fontan procedure and included the RV in the pulmonary venous atrium to preserve coronary artery blood flow. It is this combined group of children who proceeded to undergo a Fontan operation whom we focused on in this study.
Patient Characteristics
The mean age of the 22 children at the time of the Fontan operation was 5.8 years (median, 4.9 years; range, 2 to 17 years) (Fig 1
). There were 10 boys and 12 girls. All of the children had well-developed pulmonary arteries, except for 3 who had been documented as having a congenitally stenosed branch pulmonary artery and 1 who had aortopulmonary collaterals.
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Ventricle-to-Coronary Artery Connections
Important RV-CACs were present in 15 children. In 5 of these the coronary artery blood flow was RV dependent and there was coronary artery stenosis or interruption proximal to the connection (Table 1). Of the 10 children without RV-dependent CBF, 7 were managed by TERV either before (n = 5) or at the time of (n = 2) the Fontan procedure.
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); other children had combinations of other procedures (see Table 2).
Surgical Procedure
All patients underwent the Fontan procedure using standard cardiopulmonary bypass with aortic and bicaval cannulation and moderate hypothermia. Warm blood cardioplegia was used for induction, followed by cold blood cardioplegia. The total pump time averaged 145 minutes, and the myocardial ischemia time averaged 42 minutes.
During the first 10 years of the series (from 1980 to 1990), we did right atrial-to-pulmonary artery anastomosis in combination with closure of the atrial septal defect (n = 10). This did not include fenestration. Since 1990, we have done a lateral tunnel Fontan procedure with fenestration (n = 10) or an extracardiac conduit procedure with fenestration (n = 2).
Surgical closure of the tricuspid valve [7, 9] was performed using a patch of dacron or polytetrafluoroethylene (Gore-Tex; W. L. Gore & Assoc, Flagstaff, AZ), which we sized appropriately and sewed to the annulus of the tricuspid valve, taking care to avoid the conduction system. Before completing the suture line, coils and Gelfoam (absorbable gelatin sponge) were injected into the RV to achieve thrombosis and obliterate the cavity.
Ten children underwent TERV, 3 at the time of the Fontan procedure; 7 of these 10 patients had RV-CACs, but none had RV-dependent CBF. The mean age of patients at the time of TERV was 3.1 years (median, 1.7 years; range, 3 months to 8.8 years) (see Fig 1).
Follow-up
Patients were followed up in the outpatient facility of The Hospital for Sick Children for a mean of 48 months (range, 10 to 150 months) after the Fontan procedure. Cardiac catheterization was performed in 7 patients. Kaplan-Meier survival curves of the results were constructed.
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Results |
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TopFootnotesAbstractIntroductionMaterials and MethodsResultsCommentReferences |
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One child died 1 year after a fenestrated Fontan procedure. He had a small RV with a Z value of -4.5 and RV-CACs without RV-dependent CBF. At birth he underwent a balloon atrial septostomy and a right Blalock-Taussig shunt procedure, followed at 1 year of age by a central shunt procedure, atrial septectomy, and TERV; at 18 months of age he underwent a left Blalock-Taussig shunt procedure. He suffered a cardiac arrest during the latter operation and was left with some seizure activity. He then underwent a Glenn anastomosis at 3 years of age and a fenestrated Fontan procedure with bilateral pulmonary arterioplasty at 6 years of age. During the year after the Fontan procedure, the child experienced acute episodes of cyanosis. The fenestration was closed with a clamshell device (Bard, Billerica, MA), but his condition was complicated by pneumonia and empyema. The child died at home 3 months later. An autopsy was not performed.
Complications
Early complications occurred in 4 children: 2 required resternotomy for postoperative bleeding, 1 had a chylothorax, and sternal dehiscence and left hemidiaphragmatic paralysis developed in 1.
Four patients required implantation of a permanent pacemaker. All underwent TERV in accordance with the management algorithm; 1 required pacing early after this procedure, and 3 required late pacing 2, 4.5, and 6.5 years after TERV, respectively. Two children required implantation of the pacemaker before the Fontan procedure, 1 because of atrioventricular complete block after TERV and the other because of atrial fibrillation; these were implanted at 1 week and 2 years after TERV, respectively.
Follow-up
The mean age of patients at the end of follow-up has been 10 years (median, 9.1 years) (see Fig 1). The actuarial survival 10 years after the Fontan procedure has been 80% (Fig 2); Table 1 includes the distribution of deaths. There was no statistically significant difference in survival between children who had TERV and those who did not (Fig 3).
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Comment |
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TopFootnotesAbstractIntroductionMaterials and MethodsResultsCommentReferences |
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There has been a considerable increase in our understanding of coronary artery circulation in patients with PA/IVS, in whom disordered coronary artery circulation promotes myocardial ischemia.
The most disordered coronary artery circulation and RV-dependent CBF occurs most frequently in patients with the smallest RVs, although there are exceptions to this [8]. Indeed, it is our and others' experience [10, 11] that surgical algorithms can be constructed on the basis of one's understanding of coronary artery circulation. A one-ventricle repair is planned for patients whose coronary artery circulation is wholly or largely dependent on the RV, and we make no attempt either to decompress (surgically or in the catheterization laboratory) or to thromboexclude the RV. For those patients in whom a relatively small and distal portion of the coronary artery circulation is RV dependent, one can consider a biventricular repair, depending on the status of the infundibulum or the Z value of the tricuspid valve.
The concept of RV-dependent CBF embraces a spectrum of conditions, including an absent proximal aortocoronary connection between one or both coronary arteries; varying levels of coronary artery interruption; and varying levels of severe coronary artery stenosis. Such patients may also have very large fistulous connections with bidirectional flow promoting a coronary–cameral steal.
In all of these conditions, systemic or suprasystemic RV pressures are necessary to perfuse the coronary circulation in a retrograde fashion during systole. The Boston group [10, 11] has published two reports on the characteristics and degrees of RV dependence and has indicated that RV decompression can be tolerated in some selected cases in which there is a lesser degree of RV dependency involving one coronary artery.
The ability to define a coronary circulation as being wholly or partly RV dependent requires imaging of the coronary circulation. In the newborn such imaging consists of RV angiocardiography and aortography [12].
As reported by Hanley and associates [5], 90% of children selected for the Fontan procedure usually have a small, hypertensive RV. Large, dilated RVs are usually associated with an Ebstein malformation of the tricuspid valve; this anomaly has been reported to be present in 5% [5] of patients with PA/IVS. (It was 9% in our series.) The branch pulmonary arteries are mostly normal; in our series, however, 3 children had congenital stenosis. The tricuspid valve is small and correlates with the size of the RV [2, 3]. The Z value of the tricuspid valve, computed from preoperative two-dimensional echocardiograms, as reported previously [5], correlates with the size of the RV and the presence of an RV-CAC and RV-dependent CBF [8]. The Z value for the tricuspid valve is frequently used to decide the proper approach to management in neonates [5, 8].
The natural history of these RV-CACs is unknown [7]. These connections may progress, persist, or regress. If these channels progress or persist, the RV will continue to supply deoxygenated blood into the coronary artery circulation, resulting in ischemia and subsequent decompensation of the ventricles. We hypothesize that the presence of these connections may lead to the development of coronary artery stenosis or occlusion resulting from turbulent flow (Fig 4). This concept has been supported by the usual finding of coronary artery stenoses close to the connection [13]. Oppenheimer and Esterly [14] have shown the histopathologic abnormalities to consist of intimal and adventitial fibrosis and medial muscular hypertrophy. A coronary artery abnormality may also arise in fetal life [15]. This finding does not contradict our theory, however, in that it is only a matter of time before a secondary coronary artery abnormality develops.
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For these reasons, we recommend TERV in the presence of RV-CACs with no evidence of coronary abnormality. Waldman and associates [7] reported their experience with TERV and recommended that it be performed in the first year of life. (In our series, the median age was 1.7 years.) At our institution, TERV is done in conjunction with other surgical interventions and has been associated with minimal morbidity. It remains to be seen, however, whether the late survival of this subgroup of patients who undergo a Fontan procedure differs from that in patients whose RV is left open to the pulmonary venous atrium.
In children with RV-dependent CBF, decompression of the RV leads to a decrease in the intracavitary RV pressure, which subsequently leads to a decrease in the blood supply to the dependent myocardium. The critical myocardial ischemia is compounded by the fact that this blood is itself venous blood from the RV. For this reason, decompression of the RV is contraindicated in children with RV-dependent CBF. At the time of the Fontan procedure, the RV should instead be incorporated into the repair to receive oxygenated blood from the left (pulmonary venous) atrium.
The overall survival rate in the patients with PA/IVS at our institution has been reported previously to be 48% at 2 years and 24% at 13 years after surgical intervention [4]. Risk factors that were identified included RV-CACs, lower birth weight, and a decreased ratio between the right and left ventricles at initial cardiac catheterization. More recently, Hanley and co-workers [5] reported data from the Congenital Heart Surgeons' Society study. In that study the survival rate was found to be 81% at 1 month and 64% at 4 years and the risk factors that were identified consisted of a small-diameter tricuspid valve, severe RV dependency, low birth weight, and the date and type of the initial procedure.
Fontan Procedure
Cavopulmonary anastomosis was performed in 12 children (55%). In accordance with Jacobs and Norwood [19] and Giannico and associates [20], we believe that performing cavopulmonary anastomosis before the Fontan procedure prepares the systemic ventricle and brings about a decrease in the early mortality associated with the Fontan procedure. The age at which we advocate performing cavopulmonary anastomosis is changing continuously, especially now during this era in which pulmonary vascular resistance and its management are becoming better understood. Reddy and associates [21] reported good results from cavopulmonary anastomosis performed at 1 to 4 months of age. The median age of our patients was 1.9 years, although the trend is toward younger ages (see Fig 1). The same trend is seen for patients undergoing the Fontan procedure, with the age at operation being lower in the recent years (see Fig 1). This trend is also seen for patients undergoing a Fontan procedure for other congenital anomalies.
The overall operative mortality in our study was 13.6% (3 children). All early deaths (n = 10) in our series occurred in the first 10 years (1965 to 1975); these 10 patients had undergone direct atriopulmonary anastomosis without fenestration. Right ventricle–coronary artery connections were present in 2 of the 4 patients who died (3 early, 1 late) in the series reported on here. No early mortality has occurred in the last 12 patients to undergo a Fontan procedure (p = 0.08). We and others [22] attribute this improvement to the performance of a preliminary cavopulmonary shunt procedure and to the addition of a fenestration in the cavopulmonary lateral tunnel. Improved myocardial protection and postoperative care are also recognized to have produced benefits. In 1 patient, evidence of left ventricular outflow-tract obstruction was found at autopsy. This finding was also noted by Razzouk and associates [23] in a detailed study of 12 children who had undergone a Fontan procedure.
The Mayo Clinic's experience with the Fontan procedure for the treatment of PA/IVS [8] included only 4 children with RV-CACs (10%); 1 (2.5%) of them had RV-dependent CBF. This contrasts with our experience, in which RV-CACs were present in 68% and RV-dependent CBF in 22% of the patients. The early mortality in the Mayo Clinic series was 7.7%, compared with 13.6% in our series, which may reflect the higher risk for children with RV-CACs, who were more prevalent in our series.
We conclude that children with PA/IVS still pose a management challenge. Most of the mortality depends on the anatomic substrate. Children with hypoplastic RV or RV-CACs are at high risk but can be treated with the Fontan procedure with a low mortality. Thromboexclusion of the RV is indicated in children with a small RV or with RV-CACs and in those without RV-dependent CBF.
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TopFootnotesAbstractIntroductionMaterials and MethodsResultsCommentReferences |
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