PA/IVS is a congenital defect characterized by lack of communication between the RV and pulmonary arteries (PAs), resulting in no antegrade blood flow from the RVOT to the pulmonary arteries. A PDA is essential for maintaining adequate pulmonary blood flow and for early survival. Unlike PA with VSD, aortopulmonary collateral arteries are rarely found in patients with PA/IVS. The defect presents with varying degrees of hypoplasia of the RV and tricuspid valve and often involves fistulas from the RV cavity to the coronary arteries. Morphologically and functionally, the hypoplastic tricuspid valve usually varies in direct correlation with the size of the RV chamber. Coronary artery fistulas are present in up to 45 percent of cases and are more common in patients with severely hypoplastic RVs and small but competent tricuspid valves.7 In addition, it should be noted that an Ebstein’s malformation of the tricuspid valve might be present in 10 percent of cases.8 These patients may present with marked cardiomegaly due to right atrial (RA) enlargement, severe tricuspid regurgitation, and a relatively large RV size.
Surgical treatment of this PA/IVS was historically associated with very high morbidity and mortality. The low incidence of this defect combined with its extreme morphologic variability delayed the development of a standardized approach to surgical therapy.
The original Greenwold classification9 of PA/IVS described this defect by two types of RVs: Type I with a hypoplastic RV and Type II with a normal or dilated RV. A further refinement of this classification was offered by Goor and Lillihei who described the tripartite morphology of the RV (a sinus inlet part, a trabecular part, and a conus or outlet portion) and used this as a basis for surgical therapy.10 Bull and associates introduced as part of the pre- and intraoperative decision-making process the actual annular diameter of the tricuspid valve.11 More recently, the surgical approach to PA/IVS has been based on a quantitative Z-score assessment of the tricuspid valve diameter.12 The Z-score is determined by comparing the estimated diameter of the tricuspid valve (as measured by echocardiography) to the expected “normal” size and calculating the difference of the two values in standard deviations. In 1989, Billingsley and associates from UCLA introduced a surgically oriented classification of mild, moderate, and severe hypoplasia of the RV that is used today by many centers.13
Current surgical approaches to patients with PA/IVS are primarily based on the degree of RV hypoplasia and the degree of TV hypoplasia. In most patients, the degree of hypoplasia of these two structures correlate quite well and this facilitates the classification of these patients for purposes of surgical management. With a more systematic approach to this defect, increasing surgical experience, and improved diagnostic modalities, long-term outcomes have steadily improved.14,7,15
In contrast to other forms of RVOT obstruction, PA/IVS is an uncommon congenital cardiac malformation, representing between 1 and 3 percent of all congenital heart defects.16 Without early surgical intervention, children with PA/IVS have an extremely high mortality rate. The natural history in untreated patients is a 50 percent mortality rate at 2 weeks of life and a mortality of approximately 85 percent at 6 months.17 Death occurs as a consequence of severe hypoxemia and progressive metabolic acidosis secondary to closure of the ductus arteriosus and subsequent loss of pulmonary blood flow. In general, most children with PA/IVS will require multiple surgical interventions beginning in the neonatal period and continuing to one or more interventions later in life.
Etiology and Pathogenesis
The etiology of this defect remains unknown. A failure of formation of a patent pulmonary valve during embryonic development results in a completely obstructed RVOT. The obstruction varies in form and may be a relatively thin tissue membrane at the end of a well-formed infundibulum or a thick muscular wall with a poorly formed, or absent outflow tract. Since the ventricular septum remains intact, forward blood flow through the RV is precluded. The growth and development of the RV and tricuspid valve (TV) in utero are severely compromised by this lack of forward flow. Both structures tend to follow a similar pattern of hypoplasia, which is reflected by the TV annular size and the reduced size and volume of the RV chamber. RV-to-coronary artery fistulas are present in 45 percent of cases and are more common in those patients with a severely hypoplastic RV and a small competent TV.13 In 10 percent of patients, the coronary circulation may be dependent on RV pressure for perfusion by way of fistulous communications associated with severe proximal coronary artery stenosis. Pulmonary blood flow in the neonate is dependent almost entirely on a PDA, as aortopulmonary collaterals are uncommon with this defect. Ebstein’s malformation of the TV is seen in 10 percent of patients, adding significantly to the severity of the defect. Although no specific genetic pattern of inheritance has been identified, PA/IVS has been reported in siblings and associated with trisomy 18 or 21.8
Although prenatal diagnosis is increasing for this defect, most neonates with PA/IVS are still diagnosed shortly after birth. The diagnosis is often prompted by varying degrees of hypoxia and cyanosis within the first week of life. Physical examination is often remarkable for prominent venous pulsations. A significant systolic murmur may be indicative of tricuspid regurgitation. This must be differentiated from the continuous machinery murmur of a PDA. Prostaglandin E1 (PGE1) therapy should be initiated as early as possible to maintain ductal patency. Neonates with hypoxia and poor perfusion in spite of medical management should be evaluated for the presence of a restrictive ASD. In this case, balloon septostomy should be performed urgently to relieve the obstruction at the atrial level. Neonates with severely hypoplastic RVs may also require open atrial septostomy. Classification of the defect is determined by echocardiography. Cardiac catheterization and an appropriate operative procedure are selected based on assessment of RV morphology, TV size, the development of the RVOT, and the coronary circulation.
Laboratory and Diagnostic Features
In neonates with PA/IVS, an electrocardiogram usually shows progressive evidence of RA enlargement with prominent P waves. The pattern of RV hypertrophy that is present in most neonates is absent. A chest radiograph is usually unremarkable at birth but may later reveal an increased heart shadow secondary to RA and left ventricular (LV) enlargement. The lung fields are usually clear with normal to diminished vascular markings. Echocardiography remains the initial diagnostic study to identify the anatomic abnormalities and assess RV morphology. The size of the ventricular cavity, valve dimensions and function, and the nature of the RVOT obstruction are also evaluated. Because of the complexity and morphologic variability of PA/IVS, the anomaly must be defined by both echocardiography and right/left heart catheterization. Catheterization should determine the size and competency of the TV, the degree of RV hypoplasia, the size of the pulmonary arteries, the coronary anatomy and presence of coronary sinusoids and fistulas, and ventricular function. Selective coronary injections and an injection into the RV are also required for a complete evaluation. RV-to-coronary artery fistulas are frequently accompanied by the development of fibrous intimal hyperplasia, resulting in stenosis or complete obstruction of the native coronary circulation. The presence of obstructive lesions in the proximal coronaries may produce a RVDCC. Such patients are at high risk for myocardial ischemia as desaturated blood from the RV perfuses a significant portion of the myocardium. An even greater risk of myocardial ischemia is incurred by the reduction of diastolic aortic pressure resulting from the creation of a systemic-to-PA shunt. In such patients, decompression of the RV by either an outflow tract patch or a pulmonary or tricuspid valvotomy is poorly tolerated and may lead to acute myocardial infarction and intraoperative demise. The presence or absence of a RVDCC by catheterization must be established in a neonate prior to determining the operative strategy.
The differential diagnosis encompasses all congenital heart defects with PA. This includes such defects as PA with VSD and single-ventricle defects associated with PA. Echocardiography can easily delineate these defects in most patients and correctly identify those with isolated PA/IVS. Cardiac catheterization is performed in almost all neonates with PA/IVS to confirm the diagnosis and to define and evaluate the anatomy.
Previous surgical experience has indicated that the surgical management of patients with PA/IVS should be based primarily on an anatomic classification system that specifically defines the degree of RV hypoplasia and the TV annular size. A variety of surgical strategies has been proposed in the past for the treatment of these infants.18–23 We and others have found classification of the RV hypoplasia to be an accurate and consistent approach to surgical therapy.24,7,25–27 Using this approach, neonates with PA/IVS are initially separated into three groups of mild, moderate, and severe RV hypoplasia.
In patients with mild RV hypoplasia, the TV and RV cavity are approximately two-thirds or greater of the calculated normal size and the RVOT is well developed. This usually correlates with a Z-score for the TV between 0 and −2. In patients with moderate RV hypoplasia, the TV and the RV cavity are approximately one-half of calculated normal size (with a range of one-third to two-thirds of normal) and the pulmonary outflow tract is usually developed enough to perform an effective pulmonary valvotomy. This usually correlates with a Z-score for the TV of −2 to −4. In patients with severe RV hypoplasia, the TV and RV cavity are one-third or less of calculated normal size and the pulmonary outflow tract is not amenable to an effective pulmonary valvotomy. This usually correlates with a Z-score for the TV of −4 to −6. This approach is not based on any single anatomic component such as RV volumes or the size of the tricuspid annulus but instead assesses the overall RV morphology and the degree of both TV and RV hypoplasia.
During the initial evaluation of patients with PA/IVS, special attention must be paid to the anatomy of the coronary circulation. Abnormalities of the coronary circulation are often found in the severely hypoplastic group and dictate which surgical management options are indicated.28,14 During fetal development, RV hypertension may cause intramyocardial sinusoids to develop. These sinusoids may branch extensively into blind channels or communicate by fistulas with the coronary artery circulation. The morphology of these sinusoids and their specific communications are extremely variable and can change over time. Proximal coronary artery stenoses or obstructions may develop in a coronary artery supplied by these intramyocardial sinusoids. If the distal coronary artery flow is dependent on these sinusoids for adequate myocardial perfusion, they are termed RVDCC.29 Decompression of the RV in these patients is contraindicated and may lead to acute myocardial ischemia and death. The preferred management strategy for these patients is single-ventricle palliation to a Fontan procedure.30
Surgical Management of Neonates
Almost all neonates with PA/IVS will require surgical intervention early in life in order to survive. Treatment with PGE1 maintains pulmonary flow through the PDA and allows time for medical stabilization, diagnostic evaluation, and surgical decision-making. Once the anatomy and morphology of the defect is defined by echocardiography and right/left cardiac catheterization, classification is determined and an appropriate operative strategy initiated. Delay in surgical treatment is hazardous and will reduce early survival.
The surgical approach to most patients is based on the degree of RV hypoplasia and TV measurements (Table 70-1). Initial surgical management of most neonates with PA/IVS involves the establishment of a reliable and adequate source of pulmonary blood flow while optimizing the potential for growth and development of the RV and TV in order to achieve a biventricular repair later in life.
Table 70-1:Surgical Management of Pulmonary Atresia with Intact Ventricular Septum in Neonates |Favorite Table|Download (.pdf) Table 70-1: Surgical Management of Pulmonary Atresia with Intact Ventricular Septum in Neonates
|Classification of RV Hypoplasia ||RV Morphology ||Treatment |
|Mild || || |
|Moderate || || |
|Severe || || |
Neonates with Mild Right Ventricular Hypoplasia.
Neonates with PA/IVS and mild RV hypoplasia with a TV Z-score of 0 to −2 are best treated with a pulmonary valvotomy, insertion of an aorta-to-PA shunt, and ligation of the ductus arteriosus. Occasionally, there are patients in whom a pulmonary valvotomy alone will restore adequate pulmonary blood flow. Experience has shown that initial valvotomy alone often fails to produce effective palliation despite favorable anatomy. In most instances, it is preferable to perform a small shunt to ensure adequate pulmonary blood flow and promote subsequent growth of the branch PAs.
Neonates with Moderate Right Ventricular Hypoplasia.
Neonates with PA/IVS and moderate RV hypoplasia with a TV Z-score of −2 to −4 are best treated with a pulmonary valvotomy, patch augmentation of the pulmonary outflow tract, insertion of an aorta-to-PA shunt, and ligation of the ductus arteriosus. Pulmonary valvotomy and augmentation of the pulmonary outflow tract relieves RV hypertension, reduces tricuspid regurgitation, and potentiates the growth of both the tricuspid annulus and the RV cavity. In many patients with moderate RV hypoplasia, this may allow for a subsequent biventricular repair as the definitive procedure. A transannular pericardial patch (native or bovine) or GoreTex patch may be used to augment the RVOT.
Neonates with Severe Right Ventricular Hypoplasia.
Neonates with PA/IVS and severe RV hypoplasia with a TV Z-score less than −4 are more difficult to manage surgically. Balloon atrial septostomy is recommended at the time of cardiac catheterization, and stenting of the ductus arteriosus may be considered. Pulmonary valvotomy is usually not effective in relieving RV hypertension and augmenting pulmonary blood flow. If stenting of the ductus is not an option, these neonates are best treated with an aorta-to-PA shunt or a subclavian artery-to-PA (modified Blalock–Taussig) shunt. If there are no RV sinusoids or there are tortuous, narrow sinusoids without broad coronary artery fistulas, RV decompression by tricuspid valvotomy may be considered. This can be performed using a closed technique or with an open technique using cardiopulmonary bypass. In most cases, decompression of the RV results in regression of the narrow, tortuous type of sinusoid and does not result in myocardial ischemia (if the native proximal coronary circulation is intact). If broad fistulas from the coronary arteries to the RV can be identified on the epicardial surface of the heart they can be directly ligated at the time of the shunt procedure.
Specific Operative Procedures for Neonates
Below are described some specific surgical techniques utilized in patients with PA/IVS. Details on systemic-to-pulmonary shunts are presented in Chapter 68.
Insertion of a Transannular Right Ventricular Outflow Tract Patch via Sternotomy.
A transannular patch can be placed with relative ease on cardiopulmonary bypass, with aortic and RA cannulation and ligation of the ductus arteriosus. Advantages of performing a transannular patch with the use of cardiopulmonary bypass include better visualization of the annular area, more accurate placement of the edges of the patch, and little blood loss during opening of the RVOT with the RV decompressed.
In some cases with moderate RV hypoplasia, the infundibulum is long and narrow but reaches the pulmonary valve membrane. In these cases, a pericardial transannular patch may be inserted “off pump” without cardiopulmonary bypass (Fig. 70-2A–C). A median sternotomy incision is used. A pediatric cross clamp is placed immediately beneath the bifurcation of the PA. The ductus is kept open to provide pulmonary blood flow. A vertical incision is made in the main PA down to the RV junction. A partial-thickness incision is made over the RV for a distance to bring the incision over the RV cavity. Part of the muscle is resected to a depth of 2 to 3 mm to thin out the RV. A pericardial patch is then sutured to the pulmonary arteriotomy with running polypropylene down to the RV junction. The suture line is continued to the edges of the RV incision leaving the sutures loose inferiorly. A scalpel is then used to incise the valve membrane and to cut into the RV cavity under the pericardial patch. The sutures are pulled up to control bleeding, and the cross-clamp is removed. If the RV pressure is not adequately reduced, a rhizotomy knife is introduced through a purse-string suture in the pericardial patch, and the RV muscle is further incised until an adequate outflow tract has been created to reduce the RV pressure to an acceptable level. Advantages of this technique are the avoidance of cardiopulmonary bypass and also of systemic anticoagulation, although hemodynamic instability can limit the applicability of this technique to only very selected patients.
Off-pump transannular pulmonary outflow tract pericardial patch. A. A cross clamp is placed on the main pulmonary artery as shown. The main pulmonary artery is incised and extended with a partial-thickness incision of the myocardium. B. The pericardial patch suture is left loose along the inferior edge until the annulus is divided and the right ventricular myocardium is completely incised into the outflow tract. C. Additional opening of the right ventricular outflow tract can be achieved with a No. 11 scalpel through a purse-string suture in the patch.
Off-Pump Pulmonary Valvotomy via Left Thoracotomy.
A pulmonary valvotomy may also be performed using a closed technique through a left thoracotomy. The approach is through the fourth intercostal space, with the lung retracted to expose the hilar region. The overlying pericardium is incised and the left PA identified. The main PA and PDA are then identified and the main PA is dissected from the surrounding tissue. Care is taken to avoid dissection of the PDA to maintain its patency during the procedure. The main PA is cross-clamped immediately below the bifurcation, allowing pulmonary perfusion to continue via the ductus arteriosus. The artery is then incised longitudinally and retracted to expose the valve. The fused commissures are identified and incised sharply with a No. 11 scalpel. A thin-bladed vascular C clamp is applied to the incision in the PA, and the cross clamp is removed. A Gore-Tex shunt can then be sutured to the main PA and to the subclavian artery using techniques similar to those used for a modified Blalock–Taussig shunt. The ductus arteriosus is ligated prior to releasing flow into the shunt. Pressure measurements can be obtained to assess the adequacy of the valvotomy and the potential need for further intervention to relieve the RV pressure.
Tricuspid valvotomy is considered in patients with severe RV hypoplasia where the possibility of a subsequent biventricular repair is minimal. As mentioned above, preoperative catheterization must determine the absence of sinusoids or RVDCC prior to decompression of the RV. A tricuspid valvotomy can be performed through a median sternotomy using cardiopulmonary bypass and cardoplegic myocardial arrest. Under direct visualization, the TV can be incised sharply at the commissural sites to allow decompression of the RV with resultant tricuspid valve regurgitation. An enlargement of the ASD can be performed if necessary to improve decompression of the right heart.
A closed technique of TV valvotomy has been described and may be indicated in cases where cardiopulmonary bypass should be avoided.25 In many patients, decompression of the RV results in regression of the narrow, tortuous type of sinusoid and does not result in myocardial ischemia if the native circulation is intact.
Surgical Management of Older Children
Infants with PA/IVS are followed closely after their initial palliative procedures. With improving results, an increasing number of patients are presenting for later interventions. A cardiac catheterization is performed at 3 to 6 months of age, depending on the infant’s initial morphology and subsequent echocardiographic findings. In patients with severe RV hypoplasia, repeat catheterization at 2 to 3 months is recommended as there may be a high mortality in this group while awaiting repair. The selection of operative procedures is based primarily on RV morphology and on assessment of the TV and RV growth since the previous intervention. In many patients, continued growth of the TV and RV will be comparable and relatively similar, making decisions about definitive repair easier. Disparity of growth between the TV and the RV cavity can lead to difficult decisions about subsequent procedures. Whereas in neonates the size of the TV and the RV usually correlate quite well, in older children there can be a significant discrepancy between these two measurements. Definitive procedures will be determined based on the anatomic findings at catheterization. These patients are again divided into those with mild, moderate, or severe RV hypoplasia (Table 70-2).
Table 70-2:Surgical Management for Definitive Repair of Patients with Pulmonary Atresia with Intact Ventricular Septum |Favorite Table|Download (.pdf) Table 70-2: Surgical Management for Definitive Repair of Patients with Pulmonary Atresia with Intact Ventricular Septum
|Classification of RV Hypoplasia ||Treatment Options |
|Mild ||Closure of ASD (adjustable snare), enlargement of RV and RVOT, and transannular patch with monocusp valve. Ligation of previous shunt. |
| ||Closure of ASD (adjustable snare), enlargement of RV and RVOT, and valved pulmonary homograft. Ligation of previous shunt. |
|Moderate ||Closure of ASD (adjustable snare), bidirectional Glenn shunt, enlargement of RV and RVOT, and transannular patch with oversized bioprosthetic valve. Ligation of previous shunt. |
| ||Closure of ASD (adjustable snare), bidirectional Glenn shunt, enlargement of RV and RVOT, and valved pulmonary homograft. Ligation of previous shunt. |
|Severe ||Staged bidirectional Glenn shunt for later Fontan procedure. |
| ||Adjustable ASD. Partial ligation of previous shunt. |
| ||Fontan with adjustable ASD. Ligation of previous shunt. |
The use of an adjustable snare to close the ASD permits control of right-to-left shunting at the atrial level in children where RV volume and compliance may limit forward RV outflow to the pulmonary arteries. The ability to adjust the size of the ASD allows for postoperative control of right-to-left shunting and for the adjustment of forward flow through the RV.31,32 This can be very helpful in optimizing RV output and avoiding excessive cyanosis.
Biventricular Repair for Patients with Mild Right Ventricular Hypoplasia.
In patients with mild RV hypoplasia, later surgical intervention often includes closure of the ASD with an adjustable snare, enlargement of the RV cavity and outflow tract by myocardial resection, and patch augmentation of the RVOT. In order to achieve a competent pulmonary valve, either a pericardial monocusp valve or a bioprosthetic tissue valve is inserted in the RVOT. Use of a homograph pulmonary valved conduit or a Contegra bovine jugular vein valved conduit may also be considered. A successful biventricular repair is achieved in the majority of these patients. Some patients with mild hypoplasia treated by valvotomy may not require subsequent surgery unless the obstruction to the outflow tract has recurred.
Biventricular and Partial Biventricular Repair for Patients with Moderate Right Ventricular Hypoplasia.
In the patient with moderate RV and TV hypoplasia, definitive repair is dictated by the previous growth and development of the RV and the TV. If the TV diameter is one-half to two-thirds normal size, repair will then consist of partial closure of the ASD with an adjustable snare, enlargement of the RV cavity by myocardial resection, and insertion of a valved conduit between the RV and the PA. If the TV diameter is one-third to one-half of normal, then repair will consist of partial closure of the ASD with an adjustable snare, enlargement of the RV cavity, creation of a bidirectional Glenn cavopulmonary shunt, and insertion of a valved conduit between the RV and PA. The bidirectional Glenn cavopulmonary shunt reduces the volume load on the small RV and provides an obligatory source of pulmonary blood flow. This allows the channeling of approximately one-third of the systemic venous return from the superior vena cava (SVC) directly to the pulmonary arteries while the inferior vena cava (IVC) (two-thirds of the systemic venous return in small children) continues to pass through the TV and RV. This has been termed the “one-and-one-half ventricle” or “partial biventricular” repair. The ASD is adjustable to create a gradient between RA and left atrium to encourage forward flow through the RV. This will in turn enhance its development (as well as that of the TV) and increase the likelihood of a subsequent two-ventricle repair. Based on the growth of the RV and the TV, either a two-ventricle repair can be achieved (with takedown of the Glenn shunt) or a single ventricle repair with Fontan completion.
Staged Fontan Procedure for Patients with Severe Right Ventricular Hypoplasia.
In patients with PA/IVS and severe RV and TV hypoplasia, a biventricular repair is usually not possible. Most of these patients will have undergone placement of a systemic-to-PA shunt in the neonatal period with or without tricuspid valvotomy, depending on the presence or absence of RVDCC. The bidirectional Glenn cavopulmonary anastomosis is performed in the first 3 to 6 months of life with a plan for a total cavopulmonary connection within the first 3 to 4 years of life. Fenestration of the Fontan circuit may be used as an ASD with an adjustable snare when a lateral tunnel technique is utilized (see Chapter 77). The Fontan may be performed either as a lateral tunnel or as an extracardiac conduit. Both types of Fontan procedures can be constructed with an effective adjustable fenestration to the atrial chamber.
Surgical Management of Children with PA/IVS with Ebstein’s Malformation.
Ebstein’s malformation of the TV is present in 10 percent of patients with PA/IVS. This group of neonates should be considered separately. Most of these patients will have severe TV insufficiency and a normal-sized or enlarged RV. There is also massive dilatation of the RA. The LV function is often compromised in these infants because of the dilated dysfunctional RV and septal shift into the LV cavity. Although an aorta-to-PA shunt may establish adequate pulmonary blood flow, LV output often remains compromised by the dilated RV. Surgical intervention in these patients is associated with greater than 50 percent mortality.33 Orthotopic heart transplantation should be considered as an initial therapeutic option in these patients.
Surgical Management of Children with Right Ventricle-Dependent Coronary Circulation.
A RVDCC is one in which there are sinusoidal connections between the cavity of the RV and the coronary circulation, either with obstruction in the native coronary circulation or with broad sinusoidal connections that would result in runoff from the coronary circulation into the low-pressure RV. Tortuous sinusoidal connections without coronary stenoses do not usually denote a RVDCC. Decompression of the RV at the time of the bidirectional Glenn anastomosis will usually result in closure of these sinusoids as opposed to the broad-based fistulous connections. In some cases, the large fistulous connections can be identified on the surface of the heart and be suture ligated at the time of the bidirectional Glenn shunt, allowing RV decompression at that time.
In infants with RVDCC, systemic RV pressure must be maintained to ensure adequate coronary perfusion to the myocardium.34 Even in older children, decompression of the RV by augmentation of the outflow tract or tricuspid valvotomy may lead to severe myocardial ischemia and acute cardiac failure. If a RVDCC is identified, a single-ventricle surgical strategy is pursued and a bidirectional Glenn anastomosis performed at 3 to 6 months of age without RV decompression. Any additional source of pulmonary blood flow, such as a previously placed shunt, may be reduced or ligated at the time of the Glenn procedure. At 2 to 4 years of age, the Fontan completion is carried out. In order to bring oxygenated blood to the TV, the atrial septum is excised and the coronary sinus unroofed at the time of Fontan completion.
If there are signs of myocardial ischemia either preoperatively or intraoperatively, the RVDCC may be improved by creating an aortic-to-RV shunt.35 This shunt theoretically changes the RV systolic pressure to equal the systemic pressure, elevating the diastolic pressure and maintaining coronary perfusion. Flow through such a shunt appears to be bidirectional and biphasic. Experience to date has been limited with this technique, and long-term follow-up is not yet available. If myocardial ischemia results from decompression of an undiagnosed RVDCC, coronary artery bypass grafting using the internal mammary artery may be attempted. Unfortunately, the use of coronary artery bypass grafting in these patients is limited by technical difficulties, conduit options, and limited long-term graft patency.
Finally, in patients with RVDCC and severe RV dysfunction, early shunt placement may be followed by consideration of orthotopic heart transplantation.
Specific Operative Procedures in Older Children
Enlargement of the Right Ventricular Cavity and Right Ventricular Outflow Tract.
The RV cavity is enlarged by using cardiopulmonary bypass with bicaval cannulation and cardioplegic arrest to sharply resect trabecular muscle. The RA is opened longitudinally and the TV inspected; the annulus is measured and compared to normal values and its competence tested with cold saline. An incision is made longitudinally from the main PA through the annulus and across the infundibulum to the main RV cavity. The cavity is enlarged by resection of trabecular muscle under direct vision. Care is taken to work between the papillary muscles, which should be avoided. A glutaraldehyde-treated pericardial outflow patch is then placed on the RV incision. In infants, we generally prefer a pericardial patch with a monocusp valve. In older children, we have used a porcine valve within the RVOT or an RV to PA conduit.
Adjustable Atrial Septal Defect.
If the ASD is large, it is closed with a Gore-Tex vascular patch. If the defect is small with firm edges, it may be closed with the purse-string suture of the “adjustable ASD.” The adjustable ASD is created by placing a No. 1 polypropylene suture as a purse string around the tissue edges of the existing septal defect, with a pericardial pledget used as a reinforcement. Both ends of the suture are then brought out through the interatrial groove. An 8F polyethylene tube is cut to length to reach the linea alba and passed over the ends of the polypropylene suture to construct the snare. The tubing is sutured to the atrial wall with a single chromic suture (Fig. 70-3A). The snare is adjusted by tightening or loosening the polypropylene suture at the end of the tubing and securing the length with medium clips. The end of the snare is left under the subxiphoid linea alba, where it can be retrieved under local anesthesia postoperatively for subsequent adjustment. The same technique can be used to create an adjustable defect in a Gore-Tex (expanded polytetrafluoroethylene or ePTFE) patch. The defect in the suture line is left on the right side where it is surrounded by a polypropylene suture as described above (Fig. 70-3B). The ASD is left open until the patient is weaned from bypass. The ASD is then slowly closed, using the snare while monitoring the RA pressure and arterial oxygen saturations. A target RA pressure of about 12 to 14 mm Hg with an oxygen saturation of 88 percent or above on 100 percent inspired oxygen is considered optimal.
Adjustable atrial septal defect with and without patch closure of the native atrial septal defect. A. A No. 1 polypropylene purse-string suture is secured around the border of the atrial septal defect using pericardial or felt pledgets. The snare is constructed using 8F polyethylene tubing placed over the No. 1 polypropylene suture and measured to reach the linea alba. B. If a large secundum atrial septal defect is present, it is closed with a Gore-Tex or pericardial patch, and a defect is left in the lateral wall. A No. 1 polypropylene suture is brought in through the interatrial groove and placed as a horizontal mattress stitch through the edge of the patch. The No. 1 polypropylene suture is then anchored to the edge of the patch with a 5-0 polypropylene suture.
Bioprosthetic Valve Insertion with Transannular Patch.
A transannular incision is made vertically across the pulmonary outflow tract and extended onto the left PA and down into the RV. Any residual membrane in the region of the annulus is resected. The distance between the RVOT and the PA bifurcation is assessed. If it is short, use of a homograft may not be possible, as the proximity of the proximal and distal suture lines will result in bulging of the homograft. For this situation, a larger porcine valve can be placed under a pericardial (autologous or bovine) patch within the RVOT. The porcine valve may be implanted at the level of the native valve annulus (Fig. 70-4A) or in the subvalvular region below the level of the true pulmonary annulus (Fig. 70-4B) to accommodate a larger valve and reduce the amount of compression that may result from closure of the sternum. A running polypropylene suture is used to insert the valve, which is also sutured to the patch anteriorly (Fig. 70-4C).
Insertion of bioprosthetic valve under a transannular patch. An oversized bioprosthetic valve is chosen and is sutured to the native annulus (A). A patch of native pericardium is treated with glutaraldehyde and used to enlarge the right ventricular outflow tract. An alternate technique is to suture the bioprosthetic valve to the outflow tract wall just below the native annulus (B). The anterior sewing ring of the valve is anchored to the patch at the completion of the reconstruction (C).
Homograft Valve Insertion.
If the distance between the RVOT and the PA bifurcation is adequate, an appropriate aortic or pulmonary homograft is chosen. A running polypropylene suture is used distally just below the PA bifurcation. Proximally, the homograft is sutured to the RVOT just below the pulmonary valve with a running suture. The proximal anastomosis of the homograft and the RVOT are augmented with a pericardial or synthetic (ePTFE or Dacron) patch.
Transannular Patch with Pericardial Monocusp Valve.
This technique is used for neonates and infants but can also be used for small children. It should be used for patients with mild or moderate RV hypoplasia and with acceptable PA size as the valve will remain competent for a shorter period of time than a complete tissue valve. It has the advantage, however, of rarely causing obstruction even when the valve has become incompetent.
Bidirectional Glenn Cavopulmonary Shunt.
A median sternotomy incision is used for a Glenn cavopulmonary anastomosis. The right PA and SVC are dissected free from surrounding tissues and the azygos vein is divided between ligatures. Excessive dissection in this region may disrupt lymphatic tissue and result in postoperative chylothorax. The PA pressure is measured on both sides. A left SVC may be identified anterior to the left PA. The SVC is clamped just above the RA and the proximal pressure is monitored. If the pressure does not rise above a mean of 30 mm Hg, a left SVC should be suspected (as it would be in case of absence of the left innominate vein). If both right and left SVCs are present, cardiopulmonary bypass or a temporary shunt may not be necessary. If the proximal pressure in the clamped SVC is 30 mm Hg or greater, a temporary shunt should be used. A vertical purse-string suture is placed on the SVC at its junction with the innominate vein. A second purse-string suture is placed in the RA appendage. The patient is heparinized and a temporary bypass shunt is created using two venous cannulae and a Y connector with a chapeau attachment. The SVC is cannulated with the bevel of the cannula placed toward the right internal jugular vein. The second cannula is placed in the RA appendage. The circuit is connected after air is completely evacuated from the cannulae and the clamps are removed, with visualization of flow. The SVC is then clamped at its junctions with the RA and the innominate vein. The anterior aspect of the SVC and the superior margin of the right PA are marked to ensure proper alignment of the cavopulmonary anastomosis. The SVC is divided at the atrial junction and the open end of the SVC is enlarged by an incision in the posterior wall of the vessel. The anastomosis is performed with a running 6-0 or 7-0 polypropylene suture (Fig. 70-5).
Bidirectional Glenn shunt. The Glenn shunt operation is performed using a superior vena cava–to–pulmonary artery shunt. The cannulae are placed in the superior vena cava and the right atrium, allowing continuous flow of venous return to the right atrium during the reconstruction. To avoid stenosis, the anastomosis is tailored as shown in the insert.
Any previously placed systemic-to-PA shunt is now reduced in size or eliminated to give an estimated QP:QS of 1.3:1 or less. The SVC and PA pressures are measured, as well as the arterial oxygen saturations on 100 percent oxygen.
Lateral Tunnel Fontan with Adjustable Atrial Septal Defect.
A Fontan procedure is usually performed as a second- or third-stage operation. A median sternotomy is performed and bicaval venous cannulation between the SVC and IVC is carried out. Systemic hypothermia to 32°C is used in addition to cold blood cardioplegic arrest.
A right atriotomy is performed just anterior to the linea terminalis and the edges are retracted with stay sutures. The coronary sinus is identified and cannulated with a retrograde cardioplegia catheter. Cold blood cardioplegia is delivered intermittently both antegrade and retrograde.
The atrial septum is excised. The SVC orifice is identified from within the RA. It is important that this orifice be widely open and not restrictive. The right PA is incised adjacent to the opening in the SVC stump. The posterior wall of the anastomosis is created by suturing the adjacent PA and RA together with polypropylene suture. Anteriorly, the connection is bridged with a pericardial patch to assure patency without obstruction.
After the RA-to-PA anastomosis has been completed, the lateral tunnel is constructed. A rectangular Gore-Tex patch is cut from 0.8-mm-thick Gore-Tex vascular patch material. The length is carefully measured from the orifice of the IVC to that of the SVC. The width is left about two-thirds of the length to be trimmed after completion of the posterior suture line. A running polypropylene suture is used for the posterior suture line, which is begun at the IVC orifice (Fig. 70-6A). The suture line is carried superiorly to the site of the orifice of the adjustable ASD where it ends. This site is chosen because it comprises a natural recess close to the right superior pulmonary vein at the superior and lateral end of the fossa ovalis. A second polypropylene suture line is begun at the superior end of the ASD defect and carried superiorly around the SVC orifice. The ASD is sized according to the patient’s age and made large in diameter so that it may be reduced in size if necessary after the patient comes off bypass. As a rule of thumb, the defect’s size is 4 mm for 2-year olds, 6 mm for 4-year olds, and 8 mm for children 6 years old and older. The patch is trimmed appropriately as the suture line advances. Before the anterior suture line is completed, the snare control is placed for the adjustable ASD. A No. 1 polypropylene suture is brought through a pericardial pledget, through the interatrial septum at the lower border of the ASD, and through the edge of the Gore-Tex patch. It is then brought back through the upper edge of the Gore-Tex patch and out through the interatrial septum and through the pericardial pledget. An 8F polyethylene tube is cut to the appropriate length to reach the linea alba and the polypropylene sutures are brought through this snare. The No. 1 polypropylene is sutured to the edge of the Gore-Tex patch with a 5-0 polypropylene suture, the polyethylene tubing is sutured to the lateral wall with 2-0 chromic catgut, and the polypropylene is fixed to the heavy polypropylene with a medium-size clip. These three points of fixation prevent inadvertent closure of the ASD by tugging on the polypropylene. The patch is now trimmed to create a wide-open connection and to reach just anterior to the linea terminalis. The anterior part of the suture line is completed using full thickness sutures to avoid a suture-line leak. The RA incision is then closed with a polypropylene suture (Fig. 70-6B).
Lateral tunnel Fontan with an adjustable atrial septal defect. A tunnel of uniform caliber is constructed by suturing a Gore-Tex vascular patch to the orifice of the inferior vena cava and the superior vena cava and to the lateral atrial wall (A). A defect is left in the tunnel and an adjustable atrial septal defect is achieved by passing a No. 1 polypropylene suture through the lateral portion of the interatrial septum and through the edge of the Gore-Tex tunnel. The No. 1 polypropylene suture is then secured to the edge of the Gore-Tex with a 5-0 polypropylene suture. The suture is brought back out the interatrial septum and through a pericardial pledget. The snare is constructed with a No. 8F polyethylene tubing and anchored to the heart through a pledget as shown (B). The completed lateral tunnel Fontan reconstruction is shown with the adjustable atrial septal defect left open.
Transthoracic lines are generally placed in the left and right atria. If an internal jugular line is not inserted, the RA line can be inserted to measure the pressure in the pulmonary system via the Fontan tunnel or the Glenn anastomosis. The patient is weaned from cardiopulmonary bypass and the ASD snare is adjusted to achieve arterial saturations of 80 to 85 percent with an Fio2 of 50 percent while attempting to maintain pressure in the Fontan circuit at or below 16 mm Hg.
Extracardiac Fontan with Adjustable Atrial Septal Defect.
The extracardiac Fontan is performed through a median sternotomy using cardiopulmonary bypass and bicaval cannulation. The procedure can be completed in most patients without the need for cardioplegic arrest of the heart. A clamp is placed on the IVC near its junction to the RA. The IVC is then divided between the snared venous cannula and the clamp. The atrium is repaired and the clamp is removed.
The open end of the IVC is anastomosed end-to-end to a Gore-Tex conduit (16–20 mm in diameter) using a running Gore-Tex suture. The proximal anastomosis is performed end-to-side between the Gore-Tex conduit and the inferior aspect of the right PA. The clamps are released and flow is established between the IVC and the pulmonary arteries.
To create the adjustable fenestration, a partially occluding vascular C clamp is placed on the Gore-Tex graft. A direct anastomosis is performed between the extracardiac conduit and the RA. A snare is inserted to control the opening and closing of this “ASD” (Fig. 70-7A). An alternate method uses a conduit for the defect. With this technique an 8 mm Gore-Tex graft is anastomosed end-to-side to the middle of the larger conduit. A similar technique is used to create an opening in the RA and the other end of the 8 mm graft is anastomosed to this site. A snare is inserted around the smaller conduit (Fig. 70-7B). A distinct drawback to the extracardiac Fontan is the need for anticoagulation with warfarin postoperatively for up to a year, with subsequent conversion to aspirin therapy.
Extracardiac Fontan with an adjustable fenestration. The extracardiac conduit is implanted and a direct anastomosis is made between the conduit and the atrial wall. The defect is controlled with an adjustable snare (A). The extracardiac conduit is implanted and a communication is established between the conduit and the atrium using an 8 mm Gore-Tex graft. The graft diameter is then controlled by an adjustable snare (B).