Pulmonary atresia (PA) with ventricular septal defect

Transcription

1 One-Stage Repair and Unifocalization for Pulmonary Atresia with Ventricular Septal Defect and Major Aortopulmonary Collateral Arteries in Early Infancy Gary K. Lofland, MD UMKC School of Medicine, Section of Thoracic and Cardiovascular Surgery, Children s Mercy Hospitals and Clinics, Kansas City, Missouri. Address reprint requests to Gary K. Lofland, MD, Children s Mercy Hospitals and Clinics, Section of Thoracic and Cardiac Surgery, 2401 Gillham Road, Kansas City, Missouri glofland@cmh.edu Pulmonary atresia (PA) with ventricular septal defect (VSD) and major aortopulmonary collaterals (MAPCAs) is a complex and rare lesion in which considerable morphologic variability exists regarding the sources of pulmonary blood flow. The true central pulmonary arteries range from a size approaching normal to complete absence. Major aortopulmonary collaterals, probably derived embryologically from the splanchnic vascular plexis, 1 are also highly variable in their size, number, course, origin, arborization, and histopathologic makeup. 2-5 A segment of lung may be supplied solely from the true pulmonary arteries, solely from the aortopulmonary collaterals, or from both with connections between the two sources occurring at central or peripheral points and at single or multiple sights. 4 By contrast, the intracardiac component of this defect is usually relatively straightforward, with a large anteriorly malaligned ventricular septal defect, well-developed right and left ventricles with appropriate atrioventricular valves, and concordant atrioventricular and ventriculoarterial connections. More complex intracardiac arrangements may occur but are rare with MAPCAs. More complex intracardiac arrangements occur more frequently with ductal-dependent forms of pulmonary atresia. The ultimate goal of surgical therapy is a biventricular correction. Definitive correction should include closure of the ventricular septal defect, closure of any interatrial communications, and establishment of continuity between a constructed or reconstructed pulmonary artery confluence and the right ventricle. 6-9 This may require a series of staged unifocalizations in an attempt to build pulmonary arteries, followed by the establishment of right ventricular to pulmonary arterial continuity, with or without closure of the ventricular septal defect. This approach requires, on average, three separate operations. 6-8 Other individuals have taken a more aggressive approach in an attempt to achieve a single-stage correction. 10,11 An important physiologic indicator of a favorable outcome is the postrepair peak right ventricular pressure. 6,10-12 Although obviously this should be low, it may depend greatly on the pulmonary arterial and MAPCA morphology. The natural history of major aortopulmonary collaterals includes progressive stenosis and occlusion, sometimes making pulmonary segments supplied by these collaterals inaccessible, or unusable, if incorporated into definitive correction. Manipulation of these aortopulmonary collaterals in attempts at unifocalization can produce iatrogenic occlusion in the form of scarring or anastomotic stenoses. Major aortopulmonary collaterals without obstruction can lead to pulmonary vascular obstructive disease in the segments supplied by these collaterals. A single-stage correction in early infancy, before stenosis can occur, and before irreversible pulmonary vascular obstructive disease can occur, would logically be an ideal strategy for managing this otherwise frustrating condition. The earlier in life that the greatest number of healthy lung segments can be incorporated into the unifocalized pulmonary circulation, the more likely one is to capitalize on the tremendous potential for additional growth and development of the pulmonary circulation and parenchyma that exist in early infancy. Clinical Presentation and Initial Management These patients usually present at birth or early in the neonatal period with variable degrees of cyanosis and a murmur. The occasional patient may be missed until later in infancy. The oldest patient presenting de novo in our series was 6 months of age. Echocardiography suggests pulmonary atresia and ventricular septal defect but is inadequate at defining collaterals. Consequently, prostaglandin E 1 (PGE 1 ) is usually started until lack of ductal dependency is determined by a cardiac catheterization. Once the presence of collaterals has been established, PGE 1 is discontinued and the patient is ultimately discharged. An occasional patient may require supplemental oxygen. No intervention for cyanosis should be needed in the neonatal period, and the rare patient may have large collaterals resulting in pulmonary overcirculation and congestive heart failure amenable to early definitive correction /07/$-see front matter 2007 Elsevier Inc. All rights reserved. doi: /j.optechstcvs

2 96 G.K. Lofland Subsequent management consists of achieving all goals outlined for the neonatal period. A repeat cardiac catheterization is done at 3 months of age to further assess the progression of collaterals. In recent years we have also included a rapid computed tomography with digital three-dimensional reconstruction of the heart, great vessels, and MAPCAs to better define the course of the MAPCAs through the mediastinum. Following the 3-month evaluation, our subsequent management strategy is illustrated in Figure 1. The illustrations in the following section define the operative technique used if, at the 3-month evaluation, the patient is considered to have suitable anatomy for a complete unifocalization and establishment of right ventricular to pulmonary arterial continuity, with or without closure of the ventricular septal defect. Operative Technique 3 months Cardiac Cath 3-DCT Adequate PA s Good collaterals Small PA s Adequate collaterals Diminutive PA s Small collaterals No native PA s Good collaterals No native PA s Inadequate collaterals Single stage Unifocalization RV/PA Conduit VSD Closure Unifocalization RV/PA Conduit ±VSD Closure Central Shunt Unifocalization RV/PA Conduit? Re-Cath 6 mos 1 yr Intervention Re-Cath 6 mos 1 yr Re-Cath 6 mos - 1 yr Intervention VSD Closure RV-PA Conduit Unifocalization ±VSD Closure ±VSD Closure Figure 1 The decision algorithm begins at approximately 3 months of age and is depicted by this decision tree. 3-DCT three dimensional computed tomography; PA pulmonary artery; RV right ventricle; VSD ventricular septal defect.

3 Repair and unifocalization for pulmonary atresia 97 Figure 2 Through a standard midline incision, a median sternotomy and a subtotal thymectomy are performed. Both pleural spaces are opened widely just beneath the sternum and well anterior to the phrenic nerve. The bottom illustration depicts the anatomy in a patient with a right-sided aortic arch and a single collateral emerging from the proximal descending aorta, which bifurcates to supply both the right and the left lungs. This patient also had diminutive but present native central pulmonary arteries. Ao aorta; LCA left coronary artery; MPA main pulmonary artery; R right; RCA right coronary artery; RPA right pulmonary artery.

4 98 G.K. Lofland Figure 3 Early in our experience, we evolved the strategy of establishing normothermic cardiopulmonary bypass with dual caval cannulation to allow for complete cardiopulmonary decompression. This simple maneuver allows for much easier identification and dissection of collaterals, as both the heart and the lungs can be manipulated to achieve better exposure of the posterior mediastinum. Ao aorta; IVC inferior vena cava; MPA main pulmonary artery; RA right atrium; RV right ventricle; SVC superior vena cava.

5 Repair and unifocalization for pulmonary atresia 99 Figure 4 The native central pulmonary arteries are then gently dissected, and the posterior pericardium is incised between the superior vena cava and the aorta. The floor of the pericardial reflection and the transverse sinus are opened, and the posterior mediastinal soft tissues are dissected to expose the aortic segments and the collaterals in this region. The presence of a nasogastric tube or a transesophageal echocardiographic probe facilitates identification of posterior mediastinal structures. Opening the posterior mediastinal space also allows for an avenue for rerouting collaterals so that the collaterals can be dissected along their entire length and all anastomoses are accomplished under no tension. The insert depicts dissection along the course of the proximal right pulmonary artery using electrocautery. The collateral has been gently ensnared with a silastic tape to allow for retraction. Ao aorta; AP aortopulmonary; MPA main pulmonary artery; RA right atrium; RPA right pulmonary artery.

6 100 G.K. Lofland Figure 5 Once dissected, the collaterals are then permanently ligated at their origin from the aorta, using either vascular clips, ligatures, or both. Because all collaterals are ligated while on cardiopulmonary bypass, oxygenation is never in question. The silastic tape is gently retracting the diminutive native pulmonary artery to better expose the collateral. Following ligation, all collaterals are transected as depicted in the insert and unifocalization is ultimately accomplished with tissue-to-tissue anastomoses. AP aortopulmonary; Desc. Ao descending aorta.

7 Repair and unifocalization for pulmonary atresia 101 Figure 6 Throughout the unifocalization process, emphasis is placed on avoiding any synthetic or allograft materials in the periphery, and none have been used in our patients. All anastomoses are accomplished using 7.0 polypropylene suture on fine needles. Collaterals may be anastomosed in the following manner: 1. Side-to-side anastomosis of the collateral to the central pulmonary arteries, thereby augmenting the hypoplastic pulmonary arteries 2. Side-to-side anastomosis of collateral to peripheral native pulmonary artery 3. End-to-side anastomosis of collateral-to-collateral or collateral-to-native pulmonary artery. In this case, the large collateral supplying both lungs is being anatomosed to the native proximal right pulmonary artery in an end-to-side manner. The native right pulmonary artery measured approximately 1.5 to 2 mm in diameter. AP aortopulmonary; RPA right pulmonary artery.

8 102 G.K. Lofland Figure 7 Following complete unifocalization, the diminutive small main pulmonary artery, if present, is ligated and divided. Although by definition these patients have no flow between the right ventricle and the proximal main pulmonary artery, oozing can occur from very small vessels located within the adventitia of the native main pulmonary artery. The arteriotomy then needs to be extended onto the right and left pulmonary arteries to allow for adequate anastomotic length to accommodate the valved conduit. During this time, the patient is being cooled to 22 C and the decision is being made as to whether to close the ventricular septal defect or leave it open. This is largely a decision based on the size of the native central pulmonary arteries and the size of collaterals. If the ventricular septal defect is going to be closed, cardioplegic solution is administered into the aortic root and the aorta is cross-clamped. If the ventricular septal defect is going to remain open, cooling the patient to 22 C prevents ejection from the ventricle due to the relative mechanical quiescence induced by cooling. MPA main pulmonary artery.

9 Repair and unifocalization for pulmonary atresia 103 Figure 8 The proximal main pulmonary artery has been ligated and divided, and the arteriotomy is extended out onto the diminutive right and left pulmonary artery. Polypropylene stay sutures (6.0) have been placed in the pulmonary artery to allow for better visualization of the pulmonary arterial confluence. Stay sutures have also been placed on the right ventricular free wall using 5.0 braided polyester suture to facilitate retraction of the ventricle and to allow for a much more precise ventriculotomy. MPA main pulmonary artery; R right.

10 104 G.K. Lofland Figure 9 A cryopreserved pulmonary allograft of appropriate size is then tailored and the distal anastomosis is accomplished into the pulmonary artery confluence. In this case, an 11-mm cyropreserved pulmonary allograft was chosen. Because of the delicacy of the tissues, 7.0 polypropylene is utilized for these anastomoses.

11 Repair and unifocalization for pulmonary atresia 105 Figure 10 We then prefer to preserve the geometry of the right ventricular outflow tract by one of two methods. The allograft may be anastomosed to the posterior portion of the right ventriculotomy for approximately a third of its length, as depicted here, followed by a Gore-Tex proximal extension as a hood.

12 106 G.K. Lofland Figure 11 An alternative method involves performing an end-to-end anastomosis between a beveled Gore-Tex graft and the right ventriculotomy, followed by an end-to-end anastomosis between the distal end of the Gore-Tex graft and the cryopreserved pulmonary allograft. We avoid using pericardium for the proximal extension of the right ventricular to pulmonary arterial conduit, because it can dilate and become aneurysmal in the presence of high downstream resistance. This is usually the case with diminutive central pulmonary arteries.

13 Repair and unifocalization for pulmonary atresia 107 Figure 12 As a third alternative, one can perform a direct anastomosis between the proximal portion of the allograft and the right ventriculotomy if the graft is of sufficient length and the ventriculotomy is in a location that geometrically lends itself to this kind of anastomosis. Although this is our standard method of right ventricular outflow tract reconstruction or pulmonary valve replacement in patients undergoing Ross procedures, the markedly anterior location of what should be the infundibulum in these patients usually does not lend itself to this type of direct anastomosis. SVC superior vena cava.

14 108 G.K. Lofland Discussion Pulmonary atresia with ventricular septal defect represents an extreme form of tetralogy of Fallot. 13 It may occur as an isolated lesion or as part of a genetic syndrome. 14 Recent studies have documented that tetralogy of Fallot with pulmonary atresia belongs to a spectrum of conotruncal cardiac malformations that are often associated with monosomy 22q The clinical presentation of monosomy 22q11 includes patients with conotruncal anomaly face syndrome, velo-cardio-facial syndrome, and DiGeorge syndrome. 16,17 More recently, these syndromes have been incorporated as a group under the acronym CATCH 22 (cardiac defect, abnormal face, thymic hypoplasia, cleft palate, hypocalcemia, and micro deletion 22q11). 18 Two groups have recently demonstrated an association between patients with pulmonary atresia, ventricular septal defect, and major aortopulmonary collateral arteries and monosomy 22q11. 13,19 In both studies, anywhere from 40 to 48% of patients with pulmonary atresia, ventricular septal defect, and major aortopulmonary collaterals were shown to have a microdeletion in 22q11. 13,19 Pulmonary atresia with ventricular septal defect and major aortopulmonary collaterals is uncommon, comprising only about 25% of all cases of pulmonary atresia and ventricular septal defect. 6 In this defect, there is an absolute deficiency of the central pulmonary arteries, with most of the pulmonary parenchyma being supplied by major aortopulmonary collaterals. The systemic hemodynamic and morphologic studies of the collateral supply in this lesion have been accomplished by Macartney and associates, 20 Haworth, 21 Haworth and colleagues, 22 Thiene and coworkers, 23 and Rabinovitch and associates. 5 The concept of unifocalization of multiple sources of vascular supply to the lungs in an attempt to establish a pulmonary arterial confluence was suggested by Haworth and McCartney. 4 The idea of promoting growth of central pulmonary arteries with a shunt, either central or direct aorto-pulmonary arterial anastomosis, and subsequent staged unifocalization with a right ventricular to pulmonary arterial conduit was proposed by Iyer and Mee 7 and subsequently revisited by Duncan and coworkers. 24 However, this approach is only applicable if central pulmonary arteries are actually present, and these authors began the process of building pulmonary arteries at approximately 6 months of age. The results with the staged approach of unifocalization have been extremely variable. 6-9,25 In all series reviewed, total repair was accomplished in 12 to 60% of patients. These series also do not take into account attrition occurring before surgical intervention, or exclusion of patients who are deemed unsuitable for any intervention. It is felt that only 20 to 30% of a cohort of newborn infants with this combination of anomalies will have complete repair with acceptable right ventricular hemodynamics if a delayed, staged approach is taken. 10 In 1995, Reddy and coworkers demonstrated that by using a one-stage approach through a midline sternal incision, it was possible to achieve a complete correction. 10 In their series of 10 patients ranging in age from 1.4 months to 37 years, complete correction was achieved in all patients. The median age of correction was 2.1 years and the mean age at correction was 6.0 years. These investigators speculated that ideally correction should be accomplished between 3 and 6 months of age. Early definitive correction was accomplished by Lofland 11 at a mean and median age of 3 months. This was a consecutive series of 11 patients, with one patient in the series experiencing no growth whatsoever of his aortopulmonary collaterals between birth and the time of operation, and no central pulmonary arteries demonstrable anatomically. The importance of pulmonary artery morphology was nicely demonstrated in a series by Griselli and colleagues. 26 In their series of 164 patients, the best prognosis was in patients having intrapericardial pulmonary arteries 75% of predicted size, and the worst prognosis was in patients with no native pulmonary arteries and collaterals only. These authors also showed that nonclosure of a ventricular septal defect at the time of unifocalization and establishment of continuity between the right ventricle and the pulmonary arteries had no effect on outcome. The importance of native pulmonary arteries was further demonstrated in a series by d Udekem and associates. 27 In their series of 82 consecutive patients undergoing a multistage approach, late survival depended exclusively on the growth of the native pulmonary circulation. In a final series by Hanley and colleagues 28 of 300 consecutive patients, excellent results were achieved at a median age at first surgery of 8 months. Conclusions In conclusion, complete unifocalization of all sources of pulmonary blood supply, and repair of pulmonary atresia with ventricular septal defect and major aortopulmonary collaterals, can be accomplished in a single stage through a standard median sternotomy incision. The repair can be accomplished with acceptable morbidity and mortality in patients with appropriate anatomy. We do, however, feel that patient selection will ultimately prove to be very important. We also feel that a genetic component to this will be found to exist. 29 It may be that there are subgroups of patients who are genetically programmed to not grow central pulmonary arteries. However, we also feel that early definitive correction with incorporation of these clearly abnormal segments into whatever pulmonary vascular bed is present provides the best opportunity for pulmonary arterial and pulmonary parenchymal growth. References 1. DeRuiter MC, Gittenberger-de Groot AC, Poelmann RE, et al: Development of the pharyngeal arch system related to the pulmonary and bronchial vessels in the avian embryo: with a concept on systemicpulmonary collateral artery formation. 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