MMCTS
(October 18, 2007). doi:10.1510/mmcts.2006.002394
Copyright © 2007 European Association for Cardio-thoracic Surgery
Procedure
Surgical approaches for single ventricle palliation
Mahesh S. Sharma,
Martin Kostolny,
Marc R. de Leval and
Victor T. Tsang*
Cardiothoracic Unit, Great Ormond Street Hospital for Children, London WC1N 3JH, UK
* Corresponding author: * Tel.: +44-20-7813 8159; fax: +44-20-7430 1281 tsangv{at}gosh.nhs.uk
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Summary
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In this document, we include under the heading of univentricular heart, complex cardiac malformations which have in common the presence of a functionally single ventricle. The evolution of the surgical management of univentricular hearts is discussed along with the indications, selection criteria, and operative approaches for staged palliation. Herein, we describe our technique for bidirectional cavopulmonary anastomosis and total cavopulmonary connection using an extracardiac conduit.
Key Words: Anastomosis • Bidirectional cavopulmonary • Palliation • Total cavopulmonary connection • Univentricular heart
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Introduction
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‘Univentricular’ heart is a term used to describe a heterogeneous group of complex cardiac malformations characterized by the existence of only one functional pumping chamber. This heart has to maintain both the systemic and the pulmonary blood circulation, which are not connected in series but in parallel. The Fontan principle has been applied in the definitive management for single ventricle circulations. This strategy relies on separating the systemic and pulmonary circulations in a staged approach ultimately leading to systemic venous return being routed to the pulmonary arteries without the interposition of an adequate ventricle.
Historical time line
1943 – Starr et al. reported no significant rise in the venous pressure following the destruction of a large portion of the right ventricle by cautery [1].
1949 – Rodbard and Wagner achieved successful right ventricular exclusion by ligating the main pulmonary artery and anastomosing the right atrial appendage to the pulmonary artery [2].
1956 – Galankin and Darbinian performed independent experimental and clinical work using the cavopulmonary anastomosis [3].
1966 – Haller et al. performed, as a first stage, a side-to-side anastomosis of the superior vena cava to the right pulmonary artery and, as a second stage, closed the tricuspid valve so as to achieve a complete bypass of the right ventricle [4].
1968 – Fontan and Baudet performed their first atrial pulmonary connection in a case of tricuspid atresia [5].
1972 – Azzolina et al. applied the bidirectional cavopulmonary connection clinically as a definitive palliation or in preparation for a Fontan type of operation [6].
1988 – de Leval et al. studied the flow characteristics through the reconstructed circulation to achieve the more energy efficient total cavopulmonary connection which initially involved the creation of an intra-atrial baffle between the inferior vena cava and pulmonary artery (lateral tunnel technique) [7].
1990 – Marcelletti et al. used an extracardiac interposition graft between the transected inferior vena cava and the pulmonary artery (extracardiac technique) [8].
1998 – Uemura et al. performed total cavopulmonary connection in selected patients without the use of cardiopulmonary bypass [9].
Indications for the Fontan operation
The Fontan procedure, initially described for the treatment of absent right atrioventricular connection, has been extended to many complex cardiac malformations with only one well-developed ventricle. These include:
- Absence of left atrioventricular valve connection
- Double-inlet left or right ventricle
- Pulmonary atresia with intact ventricular septum
- Biventricular hearts with hypoplastic right or left ventricle with ventricular septal defects, with or without straddling atrioventricular valve
- Hypoplastic left heart syndrome
Selection criteria for Fontan operation
Fontan and colleagues established criteria for selection of patients, known as the ‘ten commandments’ (Table 1). Time, growing experience, and extension of the Fontan procedure to numerous other cardiac malformations have established that these criteria are not as rigid as first estimated.
Key points
- Avoid performing prior to child walking/crawling (beneficial effect of muscular contraction on the venous return).
- Preoperative sinus rhythm does not appear to be indispensable for a successful outcome.
- Abnormal systemic venous drainage is compatible with a Fontan type of operation.
- Pulmonary arteriolar resistance is probably the most important preoperative criterion and should be <4 U/m2.
- Preservation of ventricular function is crucial and severe or long-standing volume overloading prior to the Fontan circulation should be avoided.
- Increased systemic ventricular afterload (subaortic stenosis or coarctation) should be aggressively managed.
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Surgical preparation for the Fontan circulation
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In patients with a single ventricle, the systemic and pulmonary circulations are in parallel with mixing of the circulations within the heart. In most patients, blood flow is preferentially to the systemic circulation, but in some cases there may be pulmonary overcirculation. On rare occasions, the systemic and pulmonary circulations are balanced. In the Fontan circulation, the systemic and pulmonary circulations are separated and placed in series, with the single ventricle connected to the systemic circulation. Therefore, to reach the Fontan state, many patients will need preliminary operations to balance the pulmonary and systemic circulations and to provide the anatomical set-up for the Fontan circuit. Furthermore, other significant hemodynamic abnormalities (such as pulmonary venous obstruction or systemic ventricular outflow obstruction) may have to be addressed. The choice of procedure is guided by the underlying anatomy and pulmonary vascular resistance, both of which are subject to changes over time. It is important to remember that inappropriate or poorly performed preliminary procedures can result in loss of Fontan suitability. Many centers will now not wait until the patient becomes symptomatic, but perform early evaluation for suitability for a Fontan circulation once the pulmonary vasculature has matured. Occasionally, in patients with good Fontan characteristics, the Fontan circulation may be completed in a single stage. However, in most cases, the Fontan circulation is achieved via a staged procedure. This initially involves a cavopulmonary anastomosis, followed at a later stage by completion of the total cavopulmonary connection.
Cavopulmonary anastomosis
The classic cavopulmonary anastomosis, diverting the superior vena caval blood to the right lung, is performed rarely because it results in right-to-left pulmonary artery discontinuity. If a Fontan type of procedure is to be carried out later, major reconstructive surgery is required to establish continuity between the two pulmonary arteries, or the inferior vena caval blood (two-thirds of the systemic venous return) has to be diverted to the smaller left lung. We prefer the use of the bidirectional cavopulmonary anastomosis, in which the superior vena cava is connected end-to-side to the (undivided) right pulmonary artery, thus supplying blood to both the right and the left lung. An alternative to the bidirectional cavopulmonary anastomosis is the hemi-Fontan modification, which involves a connection between the right atrial–superior vena caval junction and the pulmonary arteries and patch augmentation of the central pulmonary arteries. This operation has particularly gained popularity in patients with hypoplastic left heart syndrome, where, after the first stage Norwood operation, pulmonary artery hypoplasia and distortion are common.
The criteria for successful bidirectional cavopulmonary anastomosis are not uniformly agreed upon, but it is generally accepted that they are less rigid than for a Fontan type of procedure. If indicated, concomitant repair of the pulmonary arteries and atrioventricular valves can also reduce the risks at subsequent Fontan completion. Patients with interrupted inferior vena cava and azygos continuation (usually left isomerism) are particularly good candidates for a bidirectional Glenn procedure, as the superior vena cava carries all the systemic venous blood except the hepatic and coronary venous return [9].
Case summary
A nine-month old male infant (8 kg) with a diagnosis of double outlet right ventricle (DORV), double conus, dysplastic pulmonary valve, subpulmonary VSD, ASD, and abnormal coronary anatomy (left anterior descending from pulmonary artery) underwent initial balloon atrial septostomy. Due to the dysplastic pulmonary valve, the child was not suitable for an arterial switch operation. Moreover, intraventricular repair was not possible without creating right ventricular inflow and outflow tract obstruction. Thus, a univentricular strategy was undertaken with Damus-Kaye Stansel connection and a right modified Blalock-Taussig shunt (3.5 mm PTFE graft) was placed. The child presented for second-staged palliation of his complex congenital heart disease.
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Surgical techniques
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Bidirectional cavopulmonary anastomosis and central pulmonary artery reconstruction
We prefer to do the bidirectional Glenn procedure under normothermic cardiopulmonary bypass (CPB) from a midline sternotomy. The dissection is performed and the aortic cannulation purse-string suture is placed as usual. A purse-string suture is placed on the right atrial appendage (Schematic 1, Video 1).
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Schematic 1 Venous cannulation scheme showing vertically oriented purse-string in superior vena cava using fine suture material (6-0 polypropylene) and right atrial appendage. (Reproduced with permission from: Stark JF, de Leval MR, Tsang VT. Surgery for congenital heart defects, John Wiley & Sons Ltd, Chichester, UK, 2006.)
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Video 1 Initial cannulation scheme.
Thymus gland has been removed to expose the innominate vein with full mobilization of superior vena cava. Attention must be paid to the phrenic nerve during dissection. The prior shunt has been dissected. The aorta has been cannulated after full heparinization. A cannula is introduced into the right atrium through the right atrial appendage. CPB is initiated to assist with further dissection.
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After CPB has been established, the prior shunt, in this case, was ligated and divided (Video 2). Subsequently, the superior vena cava (SVC) is cannulated using a small metal-tipped right angle cannula (Photo 1, Video 3).
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Video 2 Occlusion of prior shunt.
The previous right modified Blalock-Taussig shunt is doubly ligated using silk ligatures.
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Photo 1 (A) Rounded tip modified Pacifico cannulae (Great Ormond Street Hospital, London, UK); (B) angled DLP venous cannula for comparison.
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Video 3 Cannulation of the SVC.
A vertically oriented purse-string is placed high on the superior vena cava (SVC) using fine suture material (6-0) and the SVC is cannulated with a small rounded metal-tip cannula to minimize vascular trauma.
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The azygos vein is ligated or divided between ligatures (Video 4). A snare is passed around the SVC and snugged down onto the venous cannula (Schematic 2). Alternatively, the SVC is occluded with a vascular clamp just proximal to the cannula. Care must be taken to avoid injury to the phrenic nerve recognizing its close proximity to the caval veins. After proximal and distal control is achieved, the SVC/right atrial junction is divided and prepared (Video 5). Dissection of the pulmonary artery is performed in preparation for the Glenn anastomosis (Video 6).
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Video 4 Division of the azygos vein.
Circumferential dissection around the SVC is completed and the azygos vein is ligated. This is done to prevent a run-off from the higher pressure SVC to the lower-pressure IVC after cavopulmonary anastomosis. If there is interruption of the IVC with azygos continuation, the azygos vein must be kept patent.
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Schematic 2 The SVC may be snared distal to the cannula as shown here. If there is azygos continuation of the IVC, the site of occlusion of the SVC must be proximal to the azygos connection. This may significantly reduce the length of the vein available for the anastomosis, and there may be a risk of obstructing the azygos return during the operation. The proximal ‘cardiac’ end of the SVC has been occluded with a vascular clamp and divided. (Reproduced with permission from: Stark JF, de Leval MR, Tsang VT. Surgery for congenital heart defects, John Wiley & Sons Ltd, Chichester, UK, 2006.)
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Video 5 Division and over-sewing of ‘cardiac’ end of SVC.
The SVC is occluded with a vascular clamp just proximal to the cannula and a vascular clamp is then applied immediately above the cavoatrial junction. Care must be taken not to damage the sinus node. The SVC is divided immediately above the clamp and the cardiac end of the SVC is over-sewn with a continuous 6-0 polypropylene suture. The proximal clamp is released. The adventitia of the SVC is trimmed in preparation for cavopulmonary anastomosis.
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Video 6 Pulmonary artery dissection and vascular isolation.
The pulmonary artery is dissected away from prior homograft patch material used on the vessel during the child's first operation as well as the PTFE shunt remnant. A large side-biting clamp is applied over the superior aspect of the right pulmonary artery. The right shunt is disconnected from the pulmonary artery.
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Vascular control is achieved with a partial occluding clamp and the right pulmonary artery is opened (Schematic 3, Video 7). If the shunt has been placed near the right upper lobe artery, it is sometimes necessary to perform a pericardial patch angioplasty of the right pulmonary artery before the cavopulmonary anastomosis. Central pulmonary artery reconstruction may be necessary to optimize the cavopulmonary connection.
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Schematic 3 Placement of partial occluding vascular clamp on right pulmonary artery with proposed line of arteriotomy. (Reproduced with permission from: Stark JF, de Leval MR, Tsang VT. Surgery for congenital heart defects, John Wiley & Sons Ltd, Chichester, UK, 2006.)
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Video 7 Pulmonary arteriotomy.
The pulmonary arteriotomy is performed with a blade and extended from its origin to its branching. We use modified Pacifico (Great Ormond Street Hospital, London, UK) cannulae tips to size the pulmonary artery. If judged to be inadequate, the pulmonary artery should be reconstructed.
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The cavopulmonary anastomosis is then carried out with a running suture of 6-0 Prolene (Videos 8 and 9). The completed bidirectional Glenn is depicted (Schematic 4).
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Video 8 Cavopulmonary (Glenn) anastomosis.
Two stay sutures (7-0 polypropylene) have been placed on the lateral aspects of SVC to ensure proper alignment of the connection. Fine suture material (6-0 polypropylene) is used in a running fashion to construct the bidirectional Glenn anastomosis. The suture line is locked in several areas to avoid a purse-string effect and to maintain a wide anastomosis.
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Video 9 Cavopulmonary (Glenn) anastomosis (Continued).
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Schematic 4 Completed bi-directional cavopulmonary anastomosis (Glenn) shown with over-sewn cardiac end. (Reproduced with permission from: Stark JF, de Leval MR, Tsang VT. Surgery for congenital heart defects, John Wiley & Sons Ltd, Chichester, UK, 2006.)
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The patient is rewarmed and CPB is discontinued. In the case of bilateral superior vena cavae, it is necessary to do a bilateral bidirectional cavopulmonary anastomosis, unless there is a large bridging vein and one of the two cavae is small. We do not routinely cannulate the caval veins in this case and CPB is instituted via aortic inflow and right-atrial drainage. The hemi-azygos vein is ligated unless there is hemi-azygos continuation of the IVC, and the left cavopulmonary anastomosis is constructed as described above for the right side.
Total cavopulmonary connection (TCPC)
Total cavopulmonary connection consists of driving the superior vena caval blood directly into the pulmonary arteries (bidirectional cavopulmonary anastomosis or hemi-Fontan) combined with channeling the inferior vena caval blood to the pulmonary artery (lateral tunnel, intra-atrial tunnel, or extracardiac conduit). The theoretical advantages of the total cavopulmonary connection are better flow dynamics and reduction of the risk of thrombosis and arrhythmias due to less atrial distension.
Case summary
A nine-year-old boy with DORV, counter-clockwise rotation of the heart, non apex-forming left ventricle, and large confluent muscular outlet VSD. Prior surgical palliation included a pulmonary artery banding in infancy and subsequent bidirectional cavopulmonary anastomosis with atrial septectomy at the age of 2 years. There was residual flow across the pulmonary outflow tract through the band, which was left in place. He became symptomatic seven years later. Workup included exercise testing which revealed desaturation to 45% from 80% at rest with a VO2 max of 25.6 (58% predicted). Cardiac catheterization revealed patent Glenn with adequate sized branch pulmonary arteries and mean pulmonary artery pressure of 11 mmHg. Ventriculogram revealed a RV EDP of 4 mmHg with good function and minimal AV valve regurgitation. He was scheduled for elective TCPC.
Completion of TCPC with an extracardiac connection and disconnection of the banded main pulmonary trunk
The re-sternotomy and dissection is performed. Cardiopulmonary bypass is established via aorto-bicaval cannulation (high SVC and low IVC venous return) at 34 °C (Video 10). The main pulmonary artery and its bifurcation, the right and left branches, are circumferentially dissected and mobilized. In this case, an aortic root vent is placed and the heart subjected to a short duration of fibrillatory arrest. The main pulmonary artery is transected above a vascular clamp and closed (Video 11). To prevent bleeding, thrombus, and aneurysm formation, the proximal stump is closed with a double row of continuous 5-0 polypropylene sutures, reinforced with two small Teflon felt strips, and the pulmonary valve leaflets incorporated in the suture line.
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Video 10 Re-operative dissection and cannulation.
Careful re-operative dissection is performed freeing areas around the aorta, superior cavopulmonary anastomosis, and inferior vena cava. The SVC is fully mobilized, taking care not to damage the left phrenic nerve. The aorta is cannulated using a DLP cannula (DLP Medtronic, Grand Rapids, MI – MMCTSLink 116). Next, the cavae are cannulated with right-angled cannulae superiorly near the innominate vein and inferiorly at the cavoatrial junction. It is particularly important that the IVC is cannulated low down for the subsequent conduit connection.
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Video 11 Division of the main pulmonary artery.
A root vent is inserted to aid in de-airing the heart. The heart is fibrillated and the main pulmonary artery transected. The proximal main PA stump is closed with a double row of continuous 5-0 poly-propylene sutures, reinforced with two small Teflon felt strips. The heart is defibrillated.
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Ideally, the pulmonary valve should be closed. If control of the proximal pulmonary artery is difficult and the risk of introducing air into the single ventricle is judged to be high, the procedure should be carried out during a short period of cardioplegic arrest. The heart is defibrillated and the remainder of the procedure is performed on a beating heart under normothermic (35 °C) cardiopulmonary bypass. The distal main pulmonary artery is closed in two layers using a 5-0 polypropylene suture (Video 12).
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Video 12 Closure of distal main pulmonary artery.
The distal main PA is closed using a running 5-0 polypropylene suture.
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The space between the lower pulmonary vein and the IVC is dissected and adhesions between the right side of the heart and pericardium are taken down to create space for the conduit. Care is taken to avoid injury to the phrenic nerve. A Gore-TexTM conduit (W.L. Gore and Associates Ltd., Livingston, UK – MMCTSLink 154) of at least 18 mm diameter is used for creation of the extracardiac TCPC. The size of the conduit may vary according to the patient weight (18–22 mm). The top end of the 20 mm Gore-Tex conduit is anastomosed end-to-side to the undersurface of the right pulmonary artery after being appropriately tailored with continuous 5-0 polypropylene (Schematic 5, Videos 13 and 14).
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Schematic 5 Fenestrated TCPC showing extracardiac conduit anastomosis. Inset – creation of fenestration. (Reproduced with permission from: Stark JF, de Leval MR, Tsang VT. Surgery for congenital heart defects, John Wiley & Sons Ltd, Chichester, UK, 2006.)
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Video 13 Preparation of right pulmonary artery.
An arteriotomy is made in the right pulmonary artery and extended in preparation for the future anastomosis. A 20 mm PTFE (Gore-Tex) tube is fashioned to match the arteriotomy.
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Video 14 Proximal conduit to pulmonary artery anastomosis.
A 20 mm PTFE (Gore-Tex) pre-tailored tube graft is anastomosed end-to-side to the right pulmonary artery using a continuous technique.
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The conduit is brought in a gentle curve to the IVC. The conduit is trimmed obliquely with the medial aspect slightly longer, so that it lies flush (Video 15). A conduit of excess length can produce distortion of the pulmonary artery and using a graft, which is too short, may cause pulmonary venous compression. A vascular clamp is placed across the cavoatrial junction and the cavoatrial junction divided with the cardiac end over-sewn using a 4-0 polypropylene suture in two layers (Video 16). The graft to IVC anastomosis is carried out using a running 5-0 polypropylene suture technique (Video 17).
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Video 15 Division and over-sewing of the ‘Cardiac’ end of IVC.
The IVC in encircled with an umbilical tape and snared. A vascular clamp is placed across the cavoatrial junction taking care to avoid obstruction of coronary sinus flow to the atrium. The cavoatrial junction is transected on the clamp and the cardiac end over-sewn with continuous 4-0 polypropylene. The clamp is released and the second running layer of 4-0 polypropylene is completed.
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Video 16 Preparation of conduit.
The PTFE tube graft is positioned so as to lie in a gentle curve to the undersurface of the pulmonary artery. The graft is trimmed in a curvilinear manner using a #11 blade and fashioned to match the inferior caval vein.
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Video 17 Distal conduit to IVC anastomosis.
The conduit is anastomosed end-to-end to the transected IVC using continuous 5-0 polypropylene.
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Fenestration of the Fontan circuit
Systemic venous hypertension post Fontan causes capillary leakage [10]. A simple method to minimize this complication was developed by groups from Boston and Los Angeles [11, 12]. The technique consists of fenestrating the atrial baffle or conduit or making an adjustable atrial septal defect. Right-to-left shunting through this defect allows the cardiac output to be maintained at the expense of some arterial desaturation and prevents undue elevation of the systemic venous pressure. In this case, a fenestration can be created in the extracardiac conduit by fashioning a 4 mm hole (Schematic 6, inset) in the Gore-Tex tube and a slightly larger hole in the opposite free atrial wall (Video 18). Of note, the suture technique involves anastomosing the free edge of the atrial opening to the conduit a few millimeters away from the margin of hole. This would minimize the risk of premature closure of the fenestration.
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Schematic 6 Intracardiac TCPC. A sump sucker is placed into the IVC through the purse-string suture of the cannulation site allowing good visualization of the IVC orifice from within the right atrium. (Reproduced with permission from: Stark JF, de Leval MR, Tsang VT. Surgery for congenital heart defects, John Wiley & Sons Ltd, Chichester, UK, 2006.)
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Video 18 Creation of fenestrated Fontan circuit.
A side-biting clamp is placed on the atrium and the PTFE graft. The atrium is incised. A large atriotomy is created and trabeculations are removed. A channel is created in the PTFE conduit using a 4 mm punch device (Actamed Limited, West Yorkshire, UK). To avoid obstruction of the fenestration by atrial tissue, the free edge of the atrial opening is anastomosed to the Gore-Tex tube a few milli-meters away from the margin of the hole in the prosthesis with 6-0 running polypropylene suture technique. Atrial and ventricular pacing wires are placed and drains in the mediastinum and both pleural spaces are inserted.
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Intracardiac connection
Introduced in the mid-1980s, the lateral tunnel provides a tubular path between the inferior caval vein and the pulmonary artery, consisting of a native or prosthetic baffle and a portion of the lateral atrial wall. Advantages of this circuit include application in cases of anomalous drainage of the hepatic veins and growth potential allowing TCPC. It leaves a minimal amount of atrial tissue exposed to elevated pressure, which in time may cause atrial arrhythmia. However, the placement of an intracardiac prosthetic baffle to construct a lateral tunnel carries a potential risk of interatrial obstruction and thromboembolic complications in the systemic circulation. Using an extra-cardiac conduit for TCPC is beneficial for anatomic considerations such as pulmonary veins at risk for obstruction by a lateral tunnel configuration or systemic veins positioned posterior to an ipsilateral ventricular apex make this circuit an appealing option. The extracardiac conduit creates a circuit which leaves the entire atrium at low pressure, has none to minimal atrial suture lines, and can be performed without aortic cross-clamping or even cardiopulmonary bypass. However, it has no growth potential and should be offered to patients large enough to accept a graft adequate for the inferior caval vein flow.
Intra-atrial conduit
Arterial cannulation of the ascending aorta and bicaval venous cannulation is performed using right-angled cannulae (superiorly near the innominate vein and inferiorly at the cavoatrial junction). Cardiopulmonary bypass is initiated, and the patient is cooled to 32 °C. The aorta is cross-clamped, and cold blood cardio-plegic solution is infused. A needle vent is placed in the ascending aorta. The main pulmonary artery is transected. If the distal main pulmonary artery is not used for the cavopulmonary connection, it is closed with a patch, so as not to narrow or distort the branch pulmonary arteries. The right atrium is then opened. The atrial septal defect is left open or is sometimes enlarged when the left atrioventricular valve is atretic or stenotic, to allow the pulmonary venous return to reach the right atrioventricular valve in an unobstructed fashion. The bypass flow is reduced to quarter flow. The IVC cannula is clamped and removed and the IVC snare released. A sump sucker is placed into the IVC through the purse-string suture of the cannulation site (Schematic 6). This allows good visualization of the IVC orifice from within the right atrium. The length of the atrial conduit is measured between the Eustachian valve and the crista terminalis. The conduit should be as short as possible.
A Gore-Tex prosthesis of at least 18 mm (MMCTSLink 155) is then sewn in the IVC at its junction with the right atrium, with a running suture of 4-0 or 5-0 poly-propylene (Schematic 7A). The conduit is trimmed obliquely, shortened, and subsequently sewn to the prominent ridge made by the crista terminalis in front of the SVC (Schematic 7B). The right atriotomy is then closed with a running 5-0 Prolene suture.
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Schematic 7 (A) Intracardiac conduit. A Gore-Tex prosthesis of at least 18 mm is then sewn in the IVC at its junction with the right atrium, with a running suture of 4-0 or 5-0 polypropylene. (B) Gore-Tex prosthesis trimmed obliquely and shortened, to be sewn on the prominent ridge made by the crista terminalis in front of the SVC. (Reproduced with permission from: Stark JF, de Leval MR, Tsang VT. Surgery for congenital heart defects, John Wiley & Sons Ltd, Chichester, UK, 2006.)
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Lateral tunnel
Using cardiopulmonary bypass and a brief period of cardioplegic arrest, a right atriotomy is made parallel and anterior to the sulcus terminalis. To connect the inferior vena cava to the pulmonary arteries, a piece of PTFE tubing 7–10 mm in diameter is cut in half lengthwise and used as a baffle for channelling inferior vena cava flow along the lateral aspect of the right atrial wall to the dam created to close the superior vena cava entrance into the right atrium (Schematic 8A). The baffle is sewn with a running 5–0 monofilament suture around the orifice of the inferior vena cava, along the floor of the right atrium, immediately anterior to the edge of the atrial septal defect, and around the patulous orifice in the superior vena cava entrance, created by merely excising the homograft dam placed 6 months earlier. The superior aspect of this lateral tunnel is then completed by incorporating the upper edge of the PTFE baffle in the suture line closing the atriotomy (Schematic 8B). In order to lower the systemic venous pressure, a deliberate right-to-left shunt could be created by placing a fenestration in the midportion of the PTFE baffle.
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Schematic 8 Lateral tunnel technique. (A) PTFE baffle for channelling inferior vena cava flow along the lateral aspect of the right atrial wall. (B) The baffle is sewn with a running 5-0 monofilament suture around the orifice of the inferior vena cava, along the floor of the right atrium, and around the superior vena cava entrance. (Reproduced with permission from: Stark JF, de Leval MR, Tsang VT. Surgery for congenital heart defects, John Wiley & Sons Ltd, Chichester, UK, 2006.)
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The rest of the operation is identical in all cases. The IVC cannula is replaced, and the perfusion flow is increased. The distal opening of the main pulmonary artery is enlarged, making an incision toward the right pulmonary artery. Alternatively, the anastomosis can be made on the undersurface of the right pulmonary artery only. At the beginning of our experience, we used to make an incision on the medial aspect of the SVC to enlarge it to the diameter of the IVC. This does not deal with the restriction produced by the crista terminalis within the right atrium. If this incision was carried out into the right atrial chamber, there would be a risk of damaging the sinus node artery in a significant proportion of patients.
We do not enlarge the cardiac end of the SVC. The anastomosis between the cardiac end of the SVC and the pulmonary artery is done with a running suture of 5-0 or 6-0 polypropylene. The suturing starts with the right pulmonary artery, taking wider bites on the pulmonary artery than on the SVC, so as to make up for the discrepancy in the diameter of the two structures (Schematic 9A). Usually, this anastomosis can be made without a patch. However, it is sometimes necessary to use a small pericardial patch medially (Schematic 9B). It is a mistake to simply anastomose the transected main pulmonary artery and the transected SVC, as this distorts the pulmonary trunk, which has to be brought right-ward and anteriorly (inset, Schematic 9). The patient is fully rewarmed, and air is evacuated from the heart. It is particularly important to aspirate the air from that portion of the right atrium that is now part of the systemic circulation. A left atrial line is inserted into the right upper pulmonary vein or directly into the left atrium before cardiopulmonary bypass is discontinued. In patients who have had a prior hemi-Fontan operation, the beginning of the operation proceeds in the same way. Following opening of the right atrium the previously patched SVC orifice is opened. Placement of the intra-atrial tunnel to complete the total cavopulmonary connection then proceeds as described above.
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Schematic 9 (A) Completion of intracardiac TCPC with anastomosis between the cardiac end of the SVC and the pulmonary artery. (B) Use of a small pericardial patch medially. (Inset) Distortion of the pulmonary artery created by anastomosing the transected main pulmonary artery to the transected SVC. (Reproduced with permission from: Stark JF, de Leval MR, Tsang VT. Surgery for congenital heart defects, John Wiley & Sons Ltd, Chichester, UK, 2006.)
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Results and discussion
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Early mortality and morbidity
Over the three decades since the introduction of the Fontan operation, the operative mortality has decreased from around 20% to around 5%. These improved results apply both to the intracardiac tunnel techniques and extracardiac conduit Fontans and have occurred in spite of liberalizing the original Fontan selection criteria and extending the procedure to many forms of complex single ventricle [13,14,15]. Factors thought to have contributed to the improved outcome are the more energy-efficient circuit design with the use of a lateral tunnel or extracardiac conduit and the reduction of cross-clamp time and bypass time, both of which can sometimes be avoided in the extracardiac Fontan [6, 7, 16]. Patients with heterotaxy syndrome remain a high risk population for the Fontan circulation because of their multiple associated cardiovascular abnormalities. A recent paper from Toronto reported that surgical mortality had been reduced to 13% in this group of patients, and the authors indicated that further improvements could be achieved by early detection and repair of obstructed pulmonary venous return and correction of atrioventricular valve regurgitation [14].
The Fontan patient is particularly sensitive to a loss of sinus rhythm and also has impaired ability to increase the heart rate. In our experience, arrhythmias such as His bundle tachycardia, have a very poor prognosis in the Fontan patient. Pleural and pericardial effusions and ascites are relatively common. Effusions are usually serous but occasionally chylous. The chyle probably escapes from the lymphatic system at multiple points, rather than through an area of trauma of the thoracic duct as a result of systemic venous hypertension [17].
Late outcome after the Fontan circulation
Twenty years after the introduction of the procedure, Fontan and his colleagues reported that the ‘Fontan state’ was associated with a premature decline in functional status and survival [18]. Even when the operation had been performed under perfect conditions, the predicted survival was only 86%, 81% and 73% at 5, 10 and 15 years, respectively. The reasons for the ongoing late attrition are not known, but they are likely to be complex and multifactorial. A significant proportion of the late complications may be related to the surgical pathways used in the earlier Fontan operations. For the more recently introduced lateral tunnel modification of the Fontan operation, survival has been reported as 93% and 91% at 5 and 10 years, respectively [13]. Chronic elevation of the systemic venous pressures is likely to play an important role in the late morbidity.
Atrial arrhythmias are a frequent problem at long-term follow-up. The incidence has been reduced with the introduction of the lateral tunnel and extracardiac Fontan modifications [13]. Problems related to the surgical pathways such as baffle leaks and localized stenoses are common and increase with time. The recent introduction of the extracardiac conduit is potentially a problem for small children, in whom the prosthesis may become too small with somatic growth, with resultant systemic venous pathway obstruction.
Pulmonary arteriovenous fistulae have been reported following cavopulmonary anastomosis and the Fontan operation. Their aetiology remains unclear, but lack of a hepatic factor in the pulmonary circuit may be important and resolution of the malformations has been observed after including hepatic venous return in the Fontan circulation. Peculiar venous communications in many different organ systems have been reported in patients with atrial isomerism. All of the above collateral channels can result in significant right-to-left shunting, with resultant hypoxaemia and cyanosis. Systemic-to-pulmonary artery collaterals are also common and can create a significant left-to-right shunt, imposing a volume load on the single ventricle. In patients with progressive cyanosis or heart failure, an aggressive search for collateral vessels should be made and, if possible, followed by occlusion of the channels.
Thromboembolic complications occur both early and late after the Fontan operation, and involve pathway thrombosis, pulmonary artery thrombosis and cerebral emboli or stroke. The reported clinical incidence varies widely, but has been reported up to 16% for venous thrombosis and 19% for stroke [14]. At our institution we currently use heparin following by coumadin for the first 6 weeks and then convert to aspirin unless there are clinical reasons to modify this regimen. Protein-losing enteropathy has a reported incidence of up to 15%, with 50% mortality at 5 years following diagnosis [20]. An elevated  1-antitrypsin level in the stools is diagnostic. Non-selective protein loss may result in peripheral edema, ascites and effusions, immunodeficiency and coagulopathy.
In conclusion, this article has highlighted some of the surgical principles for univentricular heart palliation. The outcome of these complex patients can also be Influenced by more subtle but haemodynamically important anatomic variations, which would require intraoperative interventions.
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Acknowledgements
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The authors would like to thank Nicholas Geddes for his video editorial assistance.
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References
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Summary
Introduction