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Ann Thorac Surg 2007;83:613-618
© 2007 The Society of Thoracic Surgeons
Bakoulev Scientific Center for Cardiovascular Surgery, Moscow, Russia
Accepted for publication August 19, 2006.
* Address correspondence to Dr Zaets, 1 Wall St, 5B, Fort Lee, NJ 07024 (Email: zaets001{at}yahoo.com).
| Abstract |
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METHODS: From 1983 to 2003, 27 patients with tetralogy of Fallot and unilateral absence of the left (n = 25) or right (n = 2) pulmonary artery underwent different surgical interventions. The age of patients ranged from 40 days to 37 years (median, 5.3 years). Pulmonary arterial Nakata index and Nakata index Z-score were used for the quantitative assessment of the contralateral pulmonary artery. Twenty patients underwent various palliative procedures, namely Blalock-Taussig or Gore-Tex shunt, transluminal balloon pulmonary valvuloplasty, and reconstruction of right ventricular outflow tract without ventricular septal defect closure. At a median interval of 3.6 years after palliation, 13 patients underwent complete repair of tetralogy of Fallot. In the other 7 patients, complete repair was performed as a primary intervention.
RESULTS: Hospital mortality after palliation and after a complete repair was the same and reached 5%. Sixteen patients with the Nakata index greater than 200 mm2/m2 and Z-score greater than 4 survived after a complete repair. One of 4 patients with Nakata index less than 200 mm2/m2 and Z-score less than 4 died after surgery.
CONCLUSIONS: Majority of patients with tetralogy of Fallot and unilateral absence of the pulmonary artery require palliative intervention as a first step of surgical treatment. Nakata index greater than 200 mm2/m2 and Nakata index Z-score greater than 4 are criteria for a successful complete repair.
| Introduction |
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Interpretation of embryologic development of UAPA is contradictory. Several theories have been introduced to explain this lesion. According to the theory of involution of the sixth aortic arch, the absorption of either the right or left arch leads to the absence of one of the main pulmonary branches [5, 6]. The concept, however, does not explain frequent association of agenesis of the left pulmonary artery with tetralogy of Fallot or why the absence of the right pulmonary artery is usually not associated with other congenital heart defects. According to the ontogenetic theory, the absence of one of the pulmonary arteries is caused by abnormal septation of the truncus [7]. Dorsal shift of either the right or left truncal ridges results in agenesis of the right or left pulmonary arteries, correspondingly. The theory successfully explains the fact that agenesis of the right pulmonary artery is most often an isolated anomaly as well as why a frequent association of tetralogy of Fallot with the absence of the left pulmonary artery does occur. However, the concept fails to explain the association of tetralogy of Fallot with agenesis of the right pulmonary artery.
World literature describes fewer than 100 cases of surgical treatment of tetralogy of Fallot associated with UAPA. Palliative surgery encounters approximately 20 operations with a high hospital mortality that reaches 35% [5, 8, 9]. The number of complete repairs of tetralogy of Fallot with UAPA does not exceed 70 operations with hospital mortality of approximately 8% [3, 4, 1012].
The first reports of successful complete repair of tetralogy of Fallot with concomitant absence of the left or right pulmonary artery were published in 1962 and 1975, respectively [13, 14]. However, this type of intervention still represents a surgical challenge and is associated with a relatively high operative risk. A certain percentage of patients require heart or heart-lung transplantation after a complete repair because of biventricular failure [15]. The aim of the present study is to summarize our 22-year experience in surgical correction of tetralogy of Fallot associated with UAPA as well as to present novel approaches to the treatment of this complex disorder.
| Patients and Methods |
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The age of the patients ranged from 40 days to 37 years (median, 5.3 years). Fifteen patients were females and 12 were males. All patients were cyanotic: the levels of arterial oxygen saturation and hemoglobin reached 70.0% ± 14.6% and 175.0 ± 27.6 g/L, respectively. Eight (30%) patients had a history of hypoxic spells.
Preoperative examination included electrocardiogram, chest roentgenogram, transthoracic echocardiography, cardiac catheterization, and angiocardiography as well as computed tomography or magnetic resonance imaging scan. Angiocardiographic examination included right ventriculography (n = 27), pulmonary arteriography (n = 24), and aortography (n = 26). In 26 patients, UAPA was diagnosed before surgery, and only in 1 was it identified intraoperatively. In the last case, severe stenosis of the right ventricular outflow tract made pulmonary arterial catheterization and pulmonary arteriography technically impossible as well as worsened proper visualization of the pulmonary artery during right ventriculography. Concomitant heart defects are presented in Table 1. Twenty-four patients had a subaortic (subcristal) ventricular septal defect (VSD) of malalignment type, and 3 had a subarterial (subpulmonary) VSD. Atrial septal defect was present in 1 patient only. In 2 patients, conus branches of the right coronary artery were crossing the right ventricular outflow tract. Different systemicpulmonary collaterals were revealed in 18 patients. Four of them had aortopulmonary collaterals to the ipsilateral left lung. The diameter of these collaterals did not exceed 3 mm in 3 patients and was bigger than 5 mm in 1 patient only. However, in the last patient, dimensions of these collaterals were underestimated during preoperative examination. The other 14 patients had enlarged intercostal arteries (n = 12) supplying the ipsilateral left lung or big mediastinal arteries (n = 2) providing perfusion of the right or left ipsilateral lungs. None of the patients with systemicpulmonary collaterals had hemoptysis.
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Reconstruction of the right ventricular outflow tract without VSD closure was performed in 13 patients. Their median age at the moment of surgery was 6.1 years (range, 3.5 to 19.5 years). Two patients underwent repeated reconstructions. The procedure was carried out using cardiopulmonary bypass and moderate hypothermia (mean bypass time, 80.1 ± 42.4 minutes; rectal temperature, 26.9° ± 2.8°C). In 11 patients, a pericardial patch was used for the right ventricular outflow reconstruction.
Complete repair of tetralogy of Fallot was performed in 20 patients at the median age of 8.3 years (range, 7 months to 10.3 years). Only for 7 of them was it a primary intervention. A staged approach was used in 13 patients. The median interval between the palliation and complete repair was 3.6 years. The operation was performed using cardiopulmonary bypass, hypothermia, and cardioplegia (mean bypass time, 125.5 ± 40.0 minutes; rectal temperature, 23.1° ± 2.1°C; aortic cross-clamp time, 68.3 ± 28.4 minutes). In 3 patients, complete repair was performed without right ventricular outflow tract enlargement. In 2 patients, a xenopericardial patch was used for the right ventricular outflow tract reconstruction. Fifteen patients required transannular and pulmonary trunk reconstruction using a xenopericardial patch. In the majority of patients (12 of 15), a monocusp patch was used. In 2 patients with proximal stenosis of the right pulmonary artery, a reconstructive procedure was performed after transection of the ascending aorta. In 1 patient who had an atrial septal defect, the defect was sutured during the complete repair of the main lesion.
Statistics
Statistical analysis was performed using BIOSTAT software for Windows. Continuous variables were expressed as mean ± standard deviation or as median with 95% confidence interval (with 25th and 75th percentiles) as appropriate. Categorical variables were expressed as percentages. Comparison between continuous variables was performed using paired Students t test, analysis of variance followed by Newman-Keuls test for post hoc analysis, or nonparametric Mann-Whitney test as appropriate. Differences were considered statistically significant at a probability level of less than 0.05.
| Results |
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In both groups of patients (with a single or multiple palliations), surgical procedures resulted in statistically significant increase in arterial oxygen saturation and systolic pulmonary arterial pressure (Table 4). On the contrary, the levels of hemoglobin significantly decreased. Above-mentioned positive hemodynamic results were demonstrated after all types of palliation, namely Blalock-Taussig or Gore-Tex shunts, transluminal balloon pulmonary valvuloplasty, and right ventricular outflow tract reconstruction without VSD closure. The size of the contralateral pulmonary artery after palliative interventions but before a complete repair is shown in Figure 1. The diameter of the right ventricular outflow tract measured intraoperatively after palliative reconstruction reached 11 ± 2.4 mm. The median pulmonary arterial valve Z-score after this procedure was equal to 1.8 (range, 3.2 to 1.2). The relationship between postoperative Z-score and systolic pulmonary arterial pressure is shown in Figure 2.
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| Comment |
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The "ideal" repair of UAPA is aimed not only at correcting intracardiac defects but also at restoring physiologic blood flow in the ipsilateral lung. However, such operations are rare and are described mostly in neonates with isolated UAPA [2225]. The rationale for this complex staged procedure is that lobar, segmental, and acinar pulmonary arteries of the ipsilateral lung may preserve normal structure and function. Pulmonary artery continuity is achieved by means of a conduit. Adequate size of the pulmonary hilus artery is a main requirement for this operation. In our series, there were only 5 patients during the first year of life. Four of them were 6 to 7 months old. All patients had agenesis of the left pulmonary artery, severe hypoxemia (arterial oxygen saturation less than 60%), and frequent hypoxic spells. Because of their critical condition, we did not make an attempt to identify the pulmonary branch at the lung hilum to establish pulmonary circulation in the ipsilateral lung.
Systemic-to-pulmonary shunt is the most frequent palliative surgical procedure used for tetralogy of Fallot associated with UAPA. Besides classic or modified Blalock-Taussig shunts with the contralateral pulmonary artery, shunts between the left subclavian artery and the pulmonary trunk have been described [1, 26, 27]. The use of a left thoracotomy allows avoiding right lung dysfunction. Partial clamping of the pulmonary trunk provides sufficient blood flow through the right pulmonary artery during construction of a shunt. To reduce the risk of a palliative procedure, cardiopulmonary bypass can be also used [28]. In our opinion, classic or modified Blalock-Taussig shunt with the contralateral pulmonary artery is an effective palliation in infants with severe arterial hypoxemia. Partial clamping of a single pulmonary artery is an important element of this procedure, which maintains an adequate blood flow in the contralateral lung. Complete clamping may result in severe arterial hypoxemia or asystolia [26, 29]. Taking into consideration the fact that systemic-to-pulmonary shunt in patients with tetralogy of Fallot and UAPA is associated with high operative risk and technical difficulties, other authors believe transventricular infundibulectomy and valvotomy (Brock procedure) to be better choices [30, 31].
Transluminal balloon valvuloplasty and right ventricular outflow reconstruction without VSD closure can be considered as alternatives to the Brock procedure. However, we have failed to find any studies describing the use of these techniques for the treatment of tetralogy of Fallot with UAPA. Our experience shows that transluminal balloon valvuloplasty is an effective and safe method for this category of patients.
In our series of patients, we also frequently used right ventricular outflow reconstruction without VSD closure as a palliative intervention. This procedure, performed in patients with right ventricular outflow tract obstruction associated with a severe hypoplasia and a single pulmonary artery, provides for equal growth of pulmonary arterial segments and does not lead to either deformation or local stenosis, which frequently occur after systemic-to-pulmonary shunt. One of the main goals of the reconstruction is to create a right ventricular outflow tract of an adequate size. Our data show that a median pulmonary arterial valve Z-score equal to 1.8 corresponds to a systolic pressure in the contralateral pulmonary artery equal to 33.6 ± 6.9 mm Hg. Precise information about systemic-to-pulmonary collaterals is crucial when planning right ventricular outflow reconstruction without VSD. Underestimation of systemic-to-pulmonary collaterals led to the death of 1 of our patients as a result of inadequate cardiopulmonary bypass. In the other patients, aortopulmonary collaterals were of minor size and therefore did not require any intervention.
In our series, a complete repair was performed in 13 (87%) of 19 patients who survived after palliation. Ten of these patients underwent single palliation, and 3 had multiple palliations. Thus, the frequency of following complete repair did not differ in these groups of patients (67% and 60%, respectively). It should be mentioned that in the majority of these patients (10 of 13, or 77%), the preoperative Nakata index of the contralateral pulmonary artery was normal or moderately decreased (Nakata index Z-score greater than 4).
Before 1994, the world experience in a complete repair of tetralogy of Fallot with concomitant UAPA was represented by case reports or small series of operations [11, 12, 3235]. In 1994, Liu and Wang [3] reported on 23 complete repairs. This publication was followed by the work of Zhang and associates [4], who analyzed the results of 24 operations performed during a 29-year period. In this series of operations, all patients underwent a primary complete repair with hospital mortality of 8.3% and 95% 15-year survival. The only cause of hospital mortality was left ventricular hypoplasia. The authors came to the conclusion that the main requirements for candidates for a complete repair of tetralogy of Fallot with concomitant UAPA are normal left ventricular dimensions (end-diastolic volume greater than 30 mL/m2) and normal size of the contralateral pulmonary artery (pulmonary arterial diameter to descending aorta diameter ratio greater than 1.5). We share the authors opinion. However, they do not provide an estimate of the minimal size of the contralateral pulmonary artery with which they believe a complete repair is possible. We also agree that a monocusp patch used for transannular reconstruction is an optimal method, which allows the avoidance of pulmonary regurgitation. Our previous study has shown that the use of monocusp patches in patients with tetralogy of Fallot but without UAPA significantly improves postoperative hemodynamics, minimizes pulmonary regurgitation, and prevents right ventricular failure [36]. In our series, we did not leave the atrial septal defect open or perform a fenestration of the atrial septum. However, we think that it might be appropriate to use this approach in patients with a moderate hypoplasia of the contralateral pulmonary artery to prevent right ventricular failure. The use of extracardial conduits is appropriate if large branches of coronary arteries abnormally cross the right ventricular outflow tract, making its reconstruction impossible.
We consider the following surgical strategy to be appropriate in tetralogy of Fallot associated with UAPA. Primary complete repair is indicated in patients with a normal size of the contralateral pulmonary artery (Nakata index greater than 200 mm2/m2, and Nakata index Z-score more than 2) or its mild hypoplasia (Nakata index Z-score equal to or less than 2, but more than 4). Absence of contraindications such as left ventricular hypoplasia is also required for a complete repair. Complete repair in patients with a moderate hypoplasia of the contralateral pulmonary artery (Nakata index more than 6 but less than or equal to 4) is associated with a higher risk. These patients will benefit from a staged approach when a palliative operation is performed as the first intervention. The spectrum of palliative procedures includes systemic-to-pulmonary shunts or transluminal balloon pulmonary valvuloplasty. A staged approach is the only choice for patients with severe hypoplasia of the contralateral pulmonary artery (Nakata index Z-score less than 6). Right ventricular outflow reconstruction without VSD closure or a systemic-to-pulmonary shunt can be performed at the first stage of surgical treatment; however, we believe that right ventricular outflow reconstruction ensures better growth of the pulmonary artery and does not cause its iatrogenic stenosis or deformation. Further studies are needed to develop an optimal algorithm of surgical treatment in patients with tetralogy of Fallot associated with UAPA.
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