Volume 11, Issue 2 , Pages 105-122, Summer 2006
The Lateral Tunnel Fontan
Article Outline
- Surgical Procedure for the Lateral Tunnel Fontan
- Single-Stage Lateral Tunnel Fontan With Gore-Tex Intraatrial Baffle
- Operative Technique
- Gore-Tex Intraatrial Baffle For Completion Of TCPC Following Previous Cavopulmonary Shunt
- Postoperative Care
- Results
- References
- Copyright
The Fontan circulation is the definitive surgical palliation for single-ventricle circulations. Originally described for the treatment of absent right atrioventricular connection, the technique has now been extended to many complex cardiac abnormalities with only one well-developed ventricle.
In the structurally normal heart, the systemic and pulmonary circulations are in series, each supported by a dedicated ventricle. However, in patients born with a functionally single ventricle the systemic and pulmonary circulations are in parallel, with mixing of circulations within the heart. To achieve the Fontan circulation, the systemic and pulmonary blood flow is separated and placed in series, with the single ventricle connected to the systemic circulation. For this to be possible, many patients will need preliminary procedures to balance the systemic and pulmonary circulations and provide the anatomical setup for the Fontan operation.
The initial selection criteria for the Fontan circulation described by Fontan and colleagues were strict and known as the “ten commandments.” The criteria have been relaxed over time, but low pulmonary arteriolar resistance remains mandatory (Table 1). Assessment of the pulmonary vascular bed can be difficult, especially in the presence of accessory sources of pulmonary blood flow (such as aorta-pulmonary collaterals or systemic-to-pulmonary artery shunts) or very low pulmonary blood flow. The size of the pulmonary arterial bed is also important, and this has been expressed as the McGoon ratio1 or the Nakata index.2 However, these indices have to be used with caution, because they do not take into account the compliance of the pulmonary vascular bed and any distortion of pulmonary arteries related to previous shunts. The importance of preservation of ventricular function has been recognized, and in particular, severe or longstanding volume or pressure overload before the Fontan circulation should be avoided. It must also be remembered that inappropriate or poorly performed preliminary procedures can result in loss of candidacy for the Fontan operation.
Table 1. Selection Criteria for the Fontan Operation
| Original 10 Commandments | Revised Criteria | |
|---|---|---|
| 1 | Minimum age 4 years | Minimum age <4 years. Lowest and optimal age for performing Fontan operation unknown |
| 2 | Sinus rhythm | Sinus rhythm desired |
| 3 | Normal caval drainage | Normal caval drainage desired |
| 4 | Right atrium of normal volume | Small size atrium contraindication for lateral tunnel Fontan |
| 5 | Mean pulmonary artery pressure <15 mm Hg | Mean pulmonary artery pressure <15 mm Hg |
| 6 | Pulmonary alveolar resistance <4 U/m2 | Pulmonary alveolar resistance <4 U/m2 |
| 7 | Pulmonary artery to aorta diameter ratio >0.75 | Adequate size of pulmonary vascular bed. Use of McGoon and Nakata index may be helpful |
| 8 | Normal ventricular function (ejection fraction >0.6) | Preserved ventricular systolic and diastolic function |
| 9 | Competent left atrioventricular valve | Competent atrioventricular valve |
| 10 | No impairing effects of previous shunts | No impairing effects of previous shunts |
The surgical techniques for the Fontan operation continue to evolve. The original atriopulmonary connection has been shown to result in atrial distension, which has been implicated in the genesis of atrial arrhythmias and thromboembolic complications seen at long-term follow-up. It has also been shown that in the Fontan circulation the atrium is inefficient as a pulmonary pump. The operation has since evolved to a total cavopulmonary connection (TCPC), in which the superior vena cava is connected directly to the pulmonary artery and the inferior vena caval blood is baffled to the pulmonary artery via either an intracardiac or an extracardiac channel. It has also been recognized that results can be improved by staging the Fontan initially with the superior cavopulmonary anastomosis. Also, a small fenestration in the inferior cavopulmonary baffle may help maintain cardiac output at the time of impaired pulmonary flow, but at the expense of some systemic desaturation.
Various surgical techniques for the TCPC have been described. For the superior cavopulmonary anastomosis we, and many other institutions, prefer the bidirectional Glenn shunt. This involves anastomosis of the transected superior vena cava to the upper margin of the right pulmonary artery, thus providing blood flow to both lungs. For completion of the TCPC, the lateral tunnel technique, whereby an intraatrial baffle is created to direct the inferior vena caval blood to the pulmonary artery, remains the procedure of choice in many centers. The lateral tunnel has potential for growth, but has the disadvantage that there are multiple atrial suture lines and part of the atrium continues to be exposed to high venous pressure. Recently, the extracardiac Fontan has gained popularity for completion of the TCPC. This involves insertion of an extracardiac interposition graft between the transected inferior vena cava (IVC) and the pulmonary artery and is especially useful in patients with a small atrium who may be at risk of systemic or pulmonary venous obstruction. In addition, the procedure may be performed without aortic cross-clamping, and in selected patients also without the use of cardiopulmonary bypass. The lack of growth of the prosthetic conduit remains a concern. In situations whereby the IVC is remote from the pulmonary artery, the shorter intracardiac baffle may be preferable.
The hemi-Fontan operation is an alternative form of superior cavopulmonary anastomosis that has gained particular interest in the Norwood strategy for palliation of hypoplastic left heart syndrome. Briefly, the central pulmonary arteries are opened anteriorly and anastomosed to a counter-incision along the base of the right atrial appendage extending into the superior vena cava (SVC). Patch augmentation is used to enlarge the newly created cavopulmonary confluence and a further patch to close off the SVC/right atrial junction. At the time of completion of the TCPC the latter patch is removed and a lateral tunnel is created. This modification of the bidirectional cavopulmonary anastomosis differs from the bidirectional Glenn in that it requires cross-clamping of the aorta to place the intracardiac patch. Furthermore, the intraatrial suture lines may contribute to arrhythmias.
Surgical Procedure for the Lateral Tunnel Fontan
We used to perform the lateral tunnel TCPC as a single-stage operation consisting of a bidirectional Glenn shunt and intraatrial inferior cavopulmonary baffle. The operation is described in detail below. More recently we have moved to a staged TCPC, with initially a bidirectional Glenn shunt, followed at a later date by completion of the TCPC with an extracardiac conduit. Other institutions, however, prefer completion of the Fontan with an intraatrial baffle. For an example of the surgical technique for the staged lateral tunnel Fontan, we have used the description by Jonas.3
We routinely fenestrate the intraatrial baffle. If additional procedures are required to optimize Fontan candidacy, such as relief of pulmonary artery stenosis, resection of subaortic stenosis, or repair of atrioventricular valve regurgitation, we aim to perform these before surgery for completion of the TCPC.
Single-Stage Lateral Tunnel Fontan With Gore-Tex Intraatrial Baffle
The procedure is performed via median sternotomy, on cardiopulmonary bypass with moderate hypothermia, eg, 28 to 30°C. The technique described is for a patient with single right SVC.
Operative Technique
Figure 1.
The right lobe of the thymus is subtotally removed to facilitate exposure and dissection of the innominate vein and SVC. The pericardium is opened in the midline. The SVC is fully mobilized, taking care not to injure the phrenic nerve. The azygos vein is also dissected and may be temporarily occluded during the anastomosis of the SVC to the pulmonary artery. The main pulmonary artery and its bifurcation, and the left and right branches, are mobilized. The ligamentum arteriosum is doubly ligated and divided. If present, any patent systemic to pulmonary artery shunts are dissected free from the surrounding tissues. Marking sutures are placed on the SVC and right pulmonary artery to facilitate proper alignment of the future anastomosis.
The ascending aorta is cannulated. The cavae are cannulated with a small right-angled cannula near the innominate vein, and a larger cannula inferiorly at the cavo-atrial junction. A tourniquet is placed around the IVC, but not yet tightened. Cardiopulmonary bypass is initiated and the patient cooled to 30°C, and the heart is kept beating. Any patent shunts should now be controlled. Further dissection is completed if necessary. IVC = inferior vena cava; RPA = right pulmonary artery; SVC = superior vena cava; v = vein.
Figure 2.
The SVC is occluded with a vascular clamp just proximal to the cannula. If there is azygos continuity, the clamp is placed proximal to the azygos connection. A further vascular clamp is placed immediately above the cavo-atrial junction, taking care not to injure the sinus node. The SVC is transected immediately above this clamp. SA = sinoatrial; SVC = superior vena cava.
Figure 3.
A large side-biting clamp is placed over the upper margin of the right pulmonary artery, which is incised. If a shunt is present on this site, it is disconnected and any distortion or narrowing is repaired using patch angioplasty.
Figure 4.
An end-to-side anastomosis is then performed between the SVC and right pulmonary artery using a running 6-0 or 7-0 polypropylene. To avoid a purse-string effect and maintain a wide anastomosis, the suture line is locked in several places. In the case of bilateral SVCs, it is necessary to do bilateral cavopulmonary shunts, unless a large bridging vein is present, or one of the cavae is very small, in which case the cardiac end of this SVC can be closed. We would not routinely cannulate bilateral SVCs because of the risk of causing stenosis of the small SVCs. During the construction of the cavopulmonary anastomosis the clamp on the cephaloid end of the SVC can be intermittently released if there is concern about venous hypertension. SVC = superior vena cava.
Figure 5.
The aorta is cross-clamped and diastolic cardiac arrest is achieved using cold blood cardioplegia. The main pulmonary artery is transected. To prevent bleeding or aneurysm formation, the proximal pulmonary artery stump is closed using a double row of running 5-0 polypropylene suture that incorporates the valve leaflets and is reinforced with two Teflon felt strips. The distal main pulmonary is closed with a autologous pericardial or Gore-Tex patch so as not to narrow or distort the branch pulmonary arteries. MPA = main pulmonary artery.
Figure 6.
The tourniquet around the IVC is snared down. The vascular clamp on the SVC–atrial junction is released. The right atrium is opened parallel to the crest of the septum. If necessary, the intraatrial communication is enlarged to allow unobstructed pulmonary venous flow to the systemic ventricle. The length of the baffle is measured between the Eustachian valve and crista terminalis. ASD = atrial septal defect; CT = crista terminalis; EV = Eustachian valve; IVC = inferior vena cava; RA = right atrium; SVC = superior vena cava.
Figure 7.
The intraatrial pathway is a composite tunnel made of the atrial sinus venarum and a Gore-Tex patch (A). A Gore-Tex tube of at least 16 mm diameter is cut to length, split longitudinally, and shaped (B). If required, a 4- to 5-mm fenestration is cut (C). CT = crista terminalis; EV = Eustachian valve.
Figure 8.
The prosthetic baffle is sewn in around the upper half of the junction of the IVC with the right atrium, along the posterior wall of the atrial septum (taking care not to injure the sinus node) (A), and the crista terminalis (the prominent ridge in front of the SVC), and finally the anterior wall of the atrium (B). The coronary sinus remains outside the baffle. The atrial incision is closed with a running 5-0 polypropylene suture. ASD = atrial septal defect; IVC = inferior vena cava; SVC = superior vena cava.
Figure 9.
The undersurface of the right pulmonary artery is incised so that an unobstructed anastomosis can be created between the intraatrial tunnel and the pulmonary artery. It may be necessary to enlarge the anastomosis with a patch plasty (inset) but care has to be taken not to compromise the sinus node or its artery. To optimize Fontan hemodynamics, the anastomosis of the inferior vena cava can be offset from the superior cavopulmonary anastomosis to direct blood preferentially into the right pulmonary artery, but this is not always possible because of the anatomical setup. The SVC stump is then anastomosed to the undersurface of the right pulmonary artery using 5-0 polypropylene. It is a mistake to simply anastomose the SVC stump to the transected pulmonary artery, as this distorts the pulmonary artery, which has to be brought out right and anteriorly.
A needle vent is placed in the ascending aorta. The heart is carefully deaired, and it is particularly important to evacuate air from the right atrium, which is now part of the systemic circulation. The aortic cross-clamp is released and the patient is fully rewarmed. RPA = right pulmonary artery; SVC = superior vena cava.
Figure 10.
A direct pressure monitoring line is placed in the pulmonary venous atrium (pulmonary artery pressure is measured via a percutaneous line in the internal jugular vein). Two atrial and two ventricular pacing wires are placed on the heart. The patient is weaned from cardiopulmonary bypass. Mediastinal and pleural drains are placed and the chest is closed. RA = right atrium; RV = right ventricle.
Gore-Tex Intraatrial Baffle For Completion Of TCPC Following Previous Cavopulmonary Shunt
The description of this operation is based on the technique published by Jonas.3 The procedure is performed via redo-median sternotomy and on cardiopulmonary bypass. The heart, including the cavopulmonary anastomosis, is dissected out.
Figure 11.
Limited dissection is done of the SVC, taking care not to injure the phrenic nerve. The ascending aorta is cannulated; a small right-angled cannula is placed high up in the SVC or the innominate vein, and a further venous cannula is placed at the inferior cavo-atrial junction. On cardiopulmonary bypass with moderate hypothermia, the aorta is cross-clamped and cardioplegia is infused via the aortic root. A vascular clamp is placed across the SVC and the tourniquet around the IVC is snared. Ao = aorta; IVC = inferior vena cava; MPA = main pulmonary artery; RA = right atrium; RV = right ventricle; SA = sinoatrial; SVC = superior vena cava.
Figure 12.
The right atrial free wall is opened parallel to the atrioventricular groove, and the superior end of the incision veers anterior to the sinus node. A longitudinal incision is made on the inferior surface of the right pulmonary artery. The superior end of the atrial incision is sutured to the posterior edge of the right pulmonary artery incision using continuous 5-0 polypropylene (inset). PTFE = polytetrafluoroethylene; RA = right atrium; RPA = right pulmonary artery; SVC = superior vena cava.
Figure 13.
A Gore-Tex baffle is cut to size, fenestrated, and sutured into the right atrium so as to direct IVC blood flow to the right pulmonary artery.
Figure 14.
Finally, to complete the pulmonary venous atrium, the free edge of the original right atrial free wall is sutured obliquely over the anterior surface of the Gore-Tex baffle. ASD = atrial septal defect.
Postoperative Care
Caval and systemic atrial pressures are monitored postoperatively and a modest and temporary increase in transpulmonary gradient is often seen within the first 24 hours. A persistently elevated transpulmonary gradient may be a sign of a failing Fontan circulation and is often associated with low cardiac output and progressive acidosis. In this case, early investigation of the Fontan pathways should be performed. A gradient of 1 to 2 mm Hg over a cavopulmonary anastomosis may indicate a significant stenosis and the anastomosis may have to be redone. If it is not possible to break the hemodynamic downward circle of the failing Fontan circulation, then the only chance for survival may be early return to theater and take down of the Fontan circuit.
Early extubation is generally beneficial, because the negative intrathoracic pressure in the spontaneously breathing patient facilitates blood flow through the pulmonary vascular bed. The Fontan patient is particularly sensitive to loss of sinus rhythm and also has impaired ability to increase the heart rate. Therefore, dysrhythmias should be treated aggressively, including the use of atrioventricular sequential pacing. We routinely anticoagulate our patients once postoperative blood loss is minimal, usually commencing on the first postoperative day. Initially heparin is used (aiming at a prothrombin time of twice baseline), and once the patient is taking oral medication this is converted to warfarin for a period of 6 weeks (aiming at an International Normalized Ratio of around 2). Care has to be taken to prescribe low-dose warfarin in the early postoperative period, because over-anticoagulation occurs easily, probably related to impaired hepatic function. Chest drains stay in at least for 2 to 3 days because of the high incidence of pleural effusions. If there are ongoing drain losses, the Fontan hemodynamics should be carefully evaluated and any pathway obstruction corrected.
A significant proportion of fenestrations will close spontaneously. For those that remain patent, the indications and optimal timing for closure are not known.
Results
The current operative mortality for the intracardiac tunnel Fontan is around 5%.4, 5 However, patients with single-ventricle circulation and heterotaxy syndrome continue to have a much higher mortality because of multiple associated cardiac and noncardiac abnormalities.
It is well known that the Fontan state is associated with an ongoing late attrition. Long-term survival has improved with recent modifications of the Fontan operation, and for the lateral tunnel 93 and 91% survival has been reported at 5 and 10 years,4 respectively. In the same series, freedom from new supraventricular tachyarrhythmias was 96% at 5 years and 91% at 10 years, respectively, and for new bradyarrhythmias this was 88 and 79%. Other common complications include development of collateral circulation, thromboembolism, protein-losing enteropathy, surgical pathway problems, and ventricular failure. Chronic elevation of the systemic venous pressures is likely to play an important role in these problems. Management of the failing Fontan is a difficult problem, and if ventricular dysfunction is the main reason, the patient should be assessed for cardiac transplantation.
References
- The size of the pulmonary arteries and the results of the Fontan operation . J Thorac Cardiovasc Surg . 1989;98:711–719
- Pulmonary artery size and clinical outcome after the modified Fontan operation . Ann Thorac Surg . 1993;55:646–651
- . Single ventricle . In: Jonas RA editors. Comprehensive Surgical Management of Congenital Heart Disease . London: Arnold; 2004;p. 357–385
- . Long-term results of the lateral tunnel Fontan operation . J Thorac Cardiovasc Surg . 2001;121:28–41
- Extracardiac conduit versus lateral tunnel cavopulmonary connections at a single institution (impact on outcomes) . J Thorac Cardiovasc Surg . 2001;122:1219–1228
PII: S1522-2942(06)00054-7
doi:10.1053/j.optechstcvs.2006.05.001
© 2006 Elsevier Inc. All rights reserved.
Volume 11, Issue 2 , Pages 105-122, Summer 2006
