Fontan operation for patients with severe distal pulmonary artery stenosis, atresia, or a single lung

Fontan Operation for Patients With Severe Distal Pulmonary Artery Stenosis, Atresia, or a Single Lung Christo I. Tchervenkov, Edgar G. Chedrawy, and Stephen J. Korkola In the absence of a ventricular pump, the status of the pulmonary circulation is crucial to the success of the Fontan operation. In an updated version (1999) of the optimal criteria for the Fontan operation, several of these criteria address the pulmonary circulation: pulmonary artery pressure, pulmonary vascular resistance, pulmonary artery size, and absence of significant pulmonary artery branch stenosis. This chapter reviews the role of the pulmonary circulation in a successful Fontan operation, with a particular emphasis on surgical techniques to repair severe distal or hilar pulmonary artery stenosis or atresia. The special situation of the patient with a single pulmonary artery is also addressed. Severe hilar pulmonary artery stenosis or atresia can be repaired by the technique of intrapulmonary pulmonary artery reconstruction with pericardial patch or tube and allow the successful completion of the Fontan operation. In the selected patient with a single pulmonary artery and optimal hemodynamics, the Fontan operation is possible with good outcome. However, further experience is needed in a larger number of patients to assess the long-term outcome of these treatment strategies. Copyright © 2002 by W.B. Saunders Company Key words: Fontan, pulmonary artery stenosis, single lung.

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HE FONTAN operation,1 initially described in 1971 as a surgical treatment for tricuspid atresia, has become the operation of choice for a wide range of complex cyanotic congenital heart defects with a functionally single ventricle.2-10 Since then, it also has undergone numerous technical modifications, all achieving total separation of the pulmonary and systemic circulations. These modifications have been brought about in an effort to achieve better hemodynamics and to address complexities of the systemic and pulmonary venous returns. Since the initial description by Choussat et al11 in 1977, many of the classical criteria have been challenged. Several of the original risk factors have been shown not to have a negative

From the Division of Cardiovascular Surgery, Montreal Children’s Hospital, Quebec; and the Department of Surgery, McGill University Health Center, Montreal, Quebec, Canada. Address reprint requests to Christo I. Tchervenkov, MD, Cardiovascular Surgery, Room C-829, The Montreal Children’s Hospital, McGill University Health Center, 2300 Tupper St, Montre´al, Que´bec, Canada H3H-1P3. Copyright © 2002 by W.B. Saunders Company 1092-9126/02/0501-0022$35.00/0 doi: 10.1053/pcsu.2002.31505

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impact, while others have been nullified by technical modifications. Some, such as elevated pulmonary vascular resistance (PVR), remain not only a risk factor, but in fact a contraindication to the Fontan operation. At the same time, other factors not initially appreciated, such as unobstructed systemic circulation, have emerged as increasing the risk of the Fontan operation. In 1999, Tchervenkov and Tsang12 published an updated version of the optimal criteria for the Fontan operation, which are summarized in Table 1. Not surprisingly, several of these criteria deal with the status of the pulmonary circulation: pulmonary artery pressure (PAP), PVR, pulmonary artery size, and absence of significant pulmonary artery branch stenosis. In the absence of a ventricular pump, the status of the pulmonary circulation is therefore crucial to the short- and long-term success of the Fontan operation. This chapter reviews the role of pulmonary circulation in a successful Fontan operation, with a particular emphasis on surgical techniques to repair severe distal or hilar pulmonary artery stenosis or atresia. The special situation of the patient with a single pulmonary artery is also addressed.

Pediatric Cardiac Surgery Annual of the Seminars in Thoracic and Cardiovascular Surgery, Vol 5, 2002: pp 68-75

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Table 1. Optimal Criteria for the Fontan Operation Normal sinus rhythm Normal caval and pulmonary venous connections Normal pulmonary vascular resistance, with a mean pulmonary arterial pressure ⬍15 to 20 mm Hg No significant pulmonary artery branch stenosis that would preclude surgical repair Pulmonary artery-aortic ratio ⬎ 0.75 “Normal” ventricular function No regurgitation of the systemic atrioventricular valve Normal diastolic ventricular function Optimal minimal age: uncertain, but when anatomy and hemodynamics ideal, probably 2 to 4 years Unobstructed systemic circulation (no aortic arch obstruction or subaortic stenosis) Reprinted with permission.12

Pulmonary Circulation in the Fontan Patient Palliative Procedures in Early Life There are many challenges for the patient with a functionally single ventricle. Although the ultimate surgical treatment is the Fontan operation, the systemic and pulmonary circulations cannot be separated in early life because of the naturally elevated PVR. Therefore, staging palliative procedures are necessary in most patients. These procedures are not only necessary to ensure survival, but also should prepare the patient to become and remain an optimal candidate for the Fontan operation. Specifically, palliative procedures should preserve systemic ventricular function (both systolic and diastolic), systemic atrioventricular and semilunar valve function and, most importantly, the integrity of the pulmonary circulation. In the neonate with decreased pulmonary blood flow, a systemic-to-pulmonary artery shunt will be necessary. On the other hand, for the patient with increased pulmonary blood flow, pulmonary artery banding may be needed to control congestive heart failure and protect the pulmonary vascular bed from developing pulmonary vascular obstructive disease. In the patient with hypoplastic left heart syndrome, extensive reconstructive surgery in the form of the Norwood operation is necessary to achieve survival. One of the many treatment controversies centers

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around the patient with functionally single ventricle who has systemic obstruction, either subaortic stenosis or aortic arch obstruction or both. Although traditionally treated with pulmonary artery banding with or without associated coarctation repair, the persistence or development of subaortic stenosis resulting in severe ventricular hypertrophy has led many to advocate the Norwood or the Damus-Kaye-Stansel operation for these patients. These initial palliative procedures have been associated with numerous complications, some of which make the eventual Fontan operation not only higher risk but may actually preclude it. With respect to the pulmonary circulation, these complications are: elevated PVR, elevated PAP and the development of pulmonary vascular obstructive disease, inadequate pulmonary vascular bed from general underdevelopment, and pulmonary artery branch stenosis or atresia. In the rare patient there may be a complete loss of one pulmonary artery, representing a unique surgical challenge.

Pulmonary Artery Size In an attempt to use preoperative pulmonary artery size as a predictor of outcomes for procedures applied to anomalies with reduced pulmonary blood flow, Nakata et al13 introduced the pulmonary artery index (PAI) as a quantitative measure of pulmonary artery size. The crosssectional area of both pulmonary arteries is calculated by measuring the diameter of the bilateral pulmonary arteries immediately proximal to the origin of the upper lobe branches. The PAI is the sum of the cross-sectional area of the right and the left pulmonary arteries divided by the body surface area. The PAI is calculated in square millimeters per square meter of body surface area (mm2/m2). Senzaki et al14 reported that PAI significantly correlated with pulmonary vascular compliance ( r ⫽ 0.71, P ⫽ .01) in postoperative Fontan patients. A PAI less than 100 mm2/m2 indicated higher central venous pressures and increased afterload to the single ventricle. Knott-Craig et al15 showed that patients with unfavorable outcomes (early failure or persistent effusions) had a lower PAI than those with good outcomes (185 ⫾ 47 v 276 ⫾ 83 mm2/m2) after a modified Fontan for tricuspid atresia. Another attempt to standardize pulmonary artery size is the McGoon ratio.16 The sum of the diam-

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eters of both pulmonary arteries is divided by the diameter of the descending aorta just above the diaphragm. In a series of 334 patients, Fontan et al17 showed that the risk of early death or Fontan takedown increased sharply when the McGoon ratio was less than 1.8. Some controversy still exists whether these measurements predict postoperative results. Bridges et al18 retrospectively reviewed 29 patients undergoing Fontan procedures and showed no statistically significant difference in PAI between survivors and nonsurvivors. Also, Mosca et al10 showed no difference in McGoon ratios between survivors and nonsurvivors in patients with hypoplastic left heart syndrome who underwent the Fontan procedure.

Pulmonary Artery Pressure and Pulmonary Vascular Resistance Increased PAP and resistance are well-recognized risk factors. Knott-Craig et al6 retrospectively reviewed 702 patients at the Mayo Clinic and showed that high mean preoperative PAP was significantly associated with early postoperative death and Fontan takedown. Also, Mayer et al7 showed that increasing PAP was associated with increasing risk of failure in a review of 225 patients. Increasing pulmonary artery resistance index, calculated in Wood units 䡠 m2, is associated with decreasing survival in another study by Mayer et al.4 The Fontan success rate of 95% for pulmonary artery resistance index less than 1 U 䡠 m2 declined progressively to 54% for a pulmonary artery resistance index of 2 U 䡠 m2.

Branch Pulmonary Artery Distortion, Stenosis, or Atresia Pulmonary artery distortion is also a recognized risk factor for the Fontan procedure. Most frequently, pulmonary artery distortion is the result of palliative procedures, such as systemic-to-pulmonary artery shunts, pulmonary artery band placement, or the Norwood operation. Although such distortion may cause no obstruction to flow, most commonly there is associated stenosis with impairment of pulmonary artery growth. This results in increased operative risk4 and an ominous prognosis (odds ratio, 1.9 for death or early takedown).5,7,8 In fact, Mayer et al7 showed that pulmonary artery distortion necessitating reconstruction significantly increased risk of Fontan failure (8.3% v 34.1%), most likely because of the increased complexity and time required for the

operation. Occasionally, despite repair such peripheral stenosis may progress to hilar atresia with complete loss of one pulmonary artery. The surgeon is then faced with complex pulmonary artery reconstruction, and if it fails, the prospect of a Fontan operation into a single lung. Reconstruction of stenotic or atretic pulmonary arteries represents a challenging task. Intrapericardial pulmonary artery reconstruction may be performed using several techniques.19,20 Barbero-Marcial et al19 suggested patch augmentation, homograft interposition, and resection with end-to-end anastomosis. Perryman and Jacquiss20 described an atrially based pericardial tunnel for central pulmonary artery reconstruction. Almost one third of the tunnel was constructed from native atrial wall, thus preserving growth potential of the tunnel. Although good results can be anticipated following repair of intrapericardial branch pulmonary artery stenosis, residual or recurrent stenosis may develop. More distal hilar pulmonary artery stenosis represents a particular challenge, and surgical repair often results in simply translocating the stenosis to a more distal and inaccessible location. Percutaneous transluminal angioplasty has been attempted for peripheral stenoses with limited success.21,22 In 1995, Uemura et al23 have described a technique for reconstruction of the intrapulmonary segment of the branch pulmonary arteries using a heterologous pericardial roll. These investigators reported that 11 patients with twoventricle hearts subsequently underwent intracardiac repair. However, none of the three patients with single-ventricle physiology undergoing such reconstruction have undergone the Fontan operation.

Intrapulmonary Pulmonary Artery Reconstruction At Montreal Children’s Hospital (Quebec, Canada), we have performed intrapulmonary pulmonary artery reconstruction using Uemura’s technique in two patients with functionally single ventricle. One patient had developed severe hilar left pulmonary artery stenosis following a modified left Blalock-Taussig shunt and the other had left pulmonary artery atresia at the ductal insertion. Following intrapulmonary pulmonary artery reconstruction, the Fontan operation was suc-

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cessfully completed during the same admission in the first patient and at the same operation in the second. The surgical techniques we have used for intrapulmonary pulmonary artery reconstruction are illustrated in Figs 1 and 2. A left posterolateral thoracotomy is performed and the pleural space is entered through the fifth interspace. Adhesions between the lung and the chest wall are carefully dissected and the lung is retracted downward. The left Blalock-Taussig shunt is located and mobilized leading to the left pulmonary artery. Great care is taken to identify and preserve the phrenic nerve. Dissection is then carried out along the left pulmonary artery proximally and distally until it disappears in the lung. The greater fissure is then carefully opened and the left upper and the left lower lobes are retracted. Dissection is then continued until the intraparenchymal left pulmonary artery is exposed. Distally, the intraparenchymal left pulmonary artery with its lobar and segmental branches are dissected. The segmental pulmonary artery branches are then looped and low-dose heparin is given. The previously mobilized left BlalockTaussig shunt is test clamped and the branch pulmonary artery vessel loops are tightened to ensure that the oxygen saturation will remain adequate. Then the left Blalock-Taussig shunt is divided, the proximal end oversewn, and the distal end is excised from the stenotic left pulmonary artery. A longitudinal incision is made in the left pulmonary artery through the stenotic segment proximally and extended distally into the intrapulmonary portion of the pulmonary artery to the takeoff of the lower lobe branches (Fig 1A). A bovine pericardial patch is then used to enlarge the intrapulmonary left pulmonary artery, starting from the distal end of the incision, carrying it proximally through the hilar stenosis, and ending in the very proximal left pulmonary artery near its origin (Fig 1B). The vessel loops are then removed and the lung is re-expanded. It is impressive to see most of the reconstructed left pulmonary artery disappear inside the lung, showing how distal the reconstruction really is. In the presence of left pulmonary artery atresia, there may be no proximal pulmonary artery that can be enlarged. This situation requires the creation of a complete pericardial tube, with the beveled distal end sutured to a long incision in the intrapulmonary left pulmonary artery and

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the proximal end brought inside the pericardium. If the decision has been made to perform the Fontan operation at a later date, a systemic-topulmonary artery shunt is constructed between the ascending aorta and the proximal pericardial tube. On the other hand, if the decision is to proceed with the Fontan operation, the thoracotomy incision is closed and the patient is turned in supine position. Via a sternotomy incision, a confluence between the pericardial tube and the contralateral pulmonary artery is created and the Fontan operation is performed. Intrapulmonary pulmonary artery reconstruction on the right side may be performed either via a right thoracotomy incision or via a sternotomy in the patient with levocardia. The operation proceeds in a similar fashion, as described above for the left side (Fig 2). The greater fissure is opened fully to expose the intrapulmonary portion of the right pulmonary artery. A significant difference from the left side is the position of the right upper pulmonary vein, which crosses in front of the right pulmonary artery (Fig 2B). This precludes the use of a simple augmentation patch for right-sided reconstructions. The use of a pericardial tube is necessary, even in the presence of only pulmonary artery stenosis, to avoid a compromise to the right upper pulmonary vein. The beveled distal end of the tube is anastomosed to the incision in the right pulmonary artery and the closed proximal end is brought intrapericardially behind the superior vena cava (Fig 2C). The operation is completed with a systemic-to-pulmonary artery shunt into the proximal end of the pericardial tube or a completion Fontan operation is undertaken following creation of a pulmonary artery confluence. The decision to proceed with the Fontan operation or to defer it to a later date may be a difficult one. It is influenced by the size of the pulmonary artery recruited following the intrapulmonary reconstruction and by the pulmonary artery size, PVR, and PAP in the contralateral lung.

Single Lung Fontan Operation The loss of one pulmonary artery is a serious event, resulting in the entire cardiac output going through half the normal pulmonary arterial tree. Not only is a two-ventricle repair in a single pulmonary artery a formidable challenge, a Fontan operation into a single pulmonary artery in

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Figure 1. Intrapulmonary reconstruction of left pulmonary artery. (A) Proposed incision across the stenosis extending distally onto the intrapulmonary portion of the left pulmonary artery. (B) Greater fissure opened with left upper and lower lobes retracted exposing the intrapulmonary segment of the left pulmonary artery. Segmental branches are occluded with vessel loops to control backbleeding. Bovine pericardial patch being sewn in place augments the left pulmonary artery diameter and repairs the hilar stenosis. (C) Reconstructed left pulmonary artery.

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Figure 2. Intrapulmonary reconstruction of right pulmonary artery. (A) Severe stenosis of intrapericardial right pulmonary artery. (B) Greater fissure opened with right upper, middle, and lower lobes retracted exposing the intrapulmonary segment of the right pulmonary artery. Note the location of the right upper pulmonary vein crossing anterior to the right pulmonary artery. Incision is made in the intrapulmonary segment of the right pulmonary artery distal to the right upper pulmonary vein. Segmental branches are occluded with vessel loops to control backbleeding. (C) Bovine pericardial tube shown with a beveled distal end anastomosed to intrapulmonary right pulmonary artery and a closed proximal end brought intrapericardially behind the superior vena cava. A systemic-to-pulmonary artery shunt is constructed to the proximal end of the pericardial tube to provide blood flow to the right lung. the absence of a pulmonary ventricle appears prohibitive, almost a contraindication. Complete loss of one pulmonary artery represents an extreme with an almost 50% reduction in crosssectional area of pulmonary vasculature (the other lung may compensate somewhat), leading to a serious physiologic deficit. Because reduced

pulmonary artery size and increased pulmonary artery resistance are both associated with increased risk of Fontan failure,4,6,7,15,17 it is appropriate to question whether a successful Fontan operation is possible into a single lung. Several years ago, at The Montreal Children’s Hospital we were faced with that dilemma in a

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19-year-old patient with a single ventricle who had lost the right pulmonary artery as a complication of a right Blalock-Taussig shunt. Investigations, including magnetic resonance imaging and cardiac catheterization, showed a complete absence of the right intrapulmonary pulmonary artery. This finding precluded any hope for the previously described type of intrapulmonary pulmonary artery reconstruction. Because of favorable hemodynamics, we performed a modified Fontan operation into the left pulmonary artery. Four years later, the patient is alive and doing well. A review of the literature has found only eight additional cases of a Fontan operation performed into a single pulmonary artery. Sade and Gillette24 reported a patient with a double-inlet left ventricle with subpulmonic stenosis, levo-transposition of the great arteries, and a severely hypoplastic left pulmonary artery who underwent a Fontan at 10 years of age with a Dacron right ventricle-to-pulmonary artery conduit. Follow-up 9 years postoperatively showed the patient was doing well clinically and hemodynamically. Zachary et al25 reported a recent series of seven patients with a single right lung undergoing the Fontan operation. Six of these patients had lost their left pulmonary artery following a Norwood operation. Although in three of these patients recruitment of the left pulmonary artery was attempted at the time of the Fontan operation, subsequent follow-up showed loss of the left pulmonary artery. The authors compared the early postoperative hemodynamics to a contemporary series of patients with two pulmonary arteries undergoing the Fontan operation. There was no difference in early postoperative mortality, length of hospitalization, or effusions. The only significant difference noted was in the postoperative arterial oxygen saturation (87% v 91%). Although there was no operative mortality, two patients died late.

Conclusions The status of the pulmonary circulation is of utmost importance to the success of the Fontan operation. Severe hilar pulmonary artery stenosis or atresia can be repaired by the technique of intrapulmonary pulmonary artery reconstruction with pericardial patch or tube and allow the successful completion of the Fontan operation. In

the selected patient with a single pulmonary artery and optimal hemodynamics, the Fontan operation is possible with good outcome. However, further experience is needed in a larger number of patients to assess the long-term outcome of these treatment strategies.

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tunnel for central pulmonary artery construction. Ann Thorac Surg 64:228-230, 1997 Gentles TL, Lock JE, Perry SB: High pressure balloon angioplasty for branch pulmonary artery stenosis: Early experience. J Am Coll Cardiol 22:867-872, 1993 Hosking MCK, Thomaidis C, Hamilton R, et al: Clinical impact of balloon angioplasty for branch pulmonary artery stenosis. Am J Cardiol 69:1467-1470, 1992 Uemura H, Yagihara T, Kawashima Y, et al: Intrapulmonary reconstruction of pulmonary arteries using a heterologous pericardial roll. Ann Thorac Surg 59:1464-1469, 1995 Sade RM, Gillette PC: Fontan operation in a case of single functional pulmonary artery. J Thorac Cardiovasc Surg 98:153-154, 1989 Zachary CH, Jacobs ML, Apostolopoulou S, et al: Onelung Fontan operation: Hemodynamics and surgical outcome. Ann Thorac Surg 65:171-175, 1998