Fontan, 1½ Ventricular Repair, and Fontan Conversion Operations in Adults
11.1.2 Primary Extracardiac Fontan Operation with Fenestration
Constructing a fenestration with an extracardiac conduit requires strategies to avoid air entry to the left side. One method is to use aortic cross-clamping and cardioplegic arrest that requires a more extensive aortic dissection, increases the chances for complications, and requires a period of myocardial ischemia that was not necessary for the extracardiac conduit placement. Nevertheless, this is probably the best way to accomplish the fenestration without the possibility of introducing air into the left side. Alternatively, aortic cross-clamping can be avoided if side-biting clamps are used on the atrium with careful anastomotic techniques. This method is decidedly more difficult and increases the chances of unwanted air entry into the left side. Figure 11.7 shows the method of side-to-side anastomosis to the atrium at the mid-portion of the extracardiac conduit. This anastomosis is difficult to construct and predict, owing to the varying thickness of the atrial wall. The thicker the wall, the more difficult it is to assess the actual size of the anastomosis. Another method is to make a hole in the conduit and suture the wall of the incised atrium around the orifice of the fenestration without placing the sutures into the orifice. This way the actual fenestration is ensured. An easier anastomosis is to construct an interposed, sized PTFE graft between the extracardiac conduit and the atrium, as in Fig. 11.8. Another method, which requires aortic cross-clamping and cardioplegic arrest, is to perform a side-to-side anastomosis with the extracardiac conduit and a portion of the ICV, as shown in Fig. 11.9. The most effective reconstruction is the one with which the surgeon is most comfortable and most experienced. We have used the techniques in Figs. 11.7 and 11.8 and mildly favor the side-to-side anastomosis, but there may be indicationsfor any of the methods described.
11.1.3 Primary Lateral Tunnel Fontan Operation with or without Fenestration
The lateral tunnel Fontan operation in adults is performed as a matter of preference by some surgical groups. Some surgeons prefer to use the lateral tunnel for all Fontan completion operations, regardless of the single-ventricle diagnosis, owing to the ease and consistency of performing the atrial fenestration. There have been preliminary reports suggesting that more atrial arrhythmias occur with the lateral tunnel Fontan operation than with the extracardiac Fontan operation, but no prospective studies have confirmed these results, and fewer data are available for adult patients. Whether to use the extracardiac Fontan or lateral tunnel Fontan (with or without fenestrations) depends on the experience of the operating team. Figure 11.10 shows neoaortic cannulation and application of the aortic cross-clamp with antegrade cardioplegia (not shown). Also not shown are the caval drainage catheters. The baffle that was placed to ensure SCV flow to the right and left pulmonary arteries is being resected in preparation for the lateral tunnel placement. Figure 11.11 shows longitudinal incision of a tube PTFE graft and three 2.7-mm fenestrations, which were made with a graded punch apparatus. Some surgeons place one 4- or 5-mm fenestration, depending on the clinical circumstances. The tube graft has fallen out of favor and has been replaced by a flat PTFE patch that can be fashioned more easily to construct the complex internal baffle, as in Fig. 11.12. Figure 11.13 shows the atriorrhaphy in progress, which is accomplished by suturing the lateral atrial wall, the anterior atrial wall, and the PTFE graft into one suture line. Figure 11.14 demonstrates the completed operation. The large arrow indicates the path of the pulmonary venous return from the pulmonary veins through the atrial septal defect (ASD) and into the right ventricle. The smaller arrows signify the flow through the fenestrations into the common atrium.
When a bidirectional Glenn shunt and not hemi-Fontan reconstruction is used en route to orthoterminal correction (Fontan operation), the lateral tunnel and ICV pathway to the right pulmonary artery is quite different (Fig. 11.15). The PTFE lateral tunnel reconstruction is more direct and does not need to be directed to the dome of the right atrium that was reconfigured for the hemi-Fontan reconstruction. The lateral tunnel is therefore more lateral and depends on the cardiac end of the SCV to shunt blood flow to the right pulmonary artery, as noted. Some surgeons note that the orifice of the cardiac end of the SCV is smaller than the orifice of the ICV. This has not proven to be a clinical problem, but there are circumstances in which the cardiac end of the SCV is indeed too small, such as in the condition of bilateral SCV. Under these circumstances, the cardiac end of the SCV must be enlarged, but doing so may threaten the sinoatrial node, a concern for any incision that is performed in this area. In this case, a 4- to 5-mm single fenestration isaccomplished.
In an effort to better standardize the fenestrationsize and maintain the benefits of an extracardiac Fontan operation, Jonas introduced the intracardiac/extracardiac repair, which is illustrated in Fig. 11.16. The operation is performed under aortobicaval cardiopulmonary bypass, aortic cross-clamping, and cardioplegic arrest. A large PTFE graft (20 mm) is sutured to the orifice of the ICV. A fenestration is performed by a measured punch device in a portion of the graft that remains within the atrium. The graft then is fashioned to emerge from the atrium and course in an extracardiac fashion to the inferior portion of the right pulmonary artery, where it is anastomosed to complete the Fontan reconstruction. The large arrow on Fig. 11.16 indicates the blood flow of the pulmonary venous return, and the smaller arrow indicates the shunted right-to-left atrial flow. Some surgeons have expressed concern about this arrangement, citing the possibility of systemic emboli from the intra-atrial portion of the PTFE graft. Anticoagulation is recommended if this procedure is used.
11.2 1½ Ventricular Repair
The 1½ ventricular repair was introduced by Hillel Laks, almost as an afterthought, in one of his papers on pulmonary atresia and intact ventricular septum. He reasoned that he could apply partial right heart bypass by way of a bidirectional cavopulmonary anastomosis to unload the small right ventricle and still provide pulsatile pulmonary artery blood flow. It worked. The concept was expanded and now is an integral part of some congenital heart repairs that segregate into four categories (Figs. 11.17, 11.18, 11.19, and 11.20).
Perhaps the most successful application of this strategy is for Group A patients, who have small but functioning right ventricles with distinct inlet, body, and outlet portions (Fig. 11.17). In general, this operation can be used for patients with pulmonary stenosis/atresia and intact ventricular septum who have a functioning right ventricle that is at least 40% of normal. Some surgeons leave an atrial fenestration, but the right-sided bypass in the form of the bidirectional Glenn shunt obviates the need for this strategy, ensuring 100% (or near 100%) systemic oxygen saturation.
Group B patients (Fig. 11.18) are those with a poorly functional right ventricle, as seen in some patients with advanced Ebstein’s anomaly of the tricuspid valve. Unloading the right ventricle in this situation shifts the Starling curve to the left, which may improve function.
Figure 11.19 shows the 1½ ventricular repair as applied to Group C, patients with a left SCV that drain to the dome of the left atrium, causing cyanosis. Intra-atrial baffles are prone to obstruction and arrhythmias, and this strategy allows left SCV flow without ligation. The hemodynamic result is favorable unless there is a left pulmonary artery stenosis distal to the entry of the anastomosis of the SCV and pulmonary artery, which results in intractable headaches and systemic venous hypertension. Care must be taken with this anastomosis as it tends to be difficult owing to the location that is often well into the left side of the mediastinum.
Perhaps the most interesting application of the 1½ ventricular repair is in Group D, patients with congenitally corrected transposition of the great arteries (ccTGA; Fig. 11.20). This strategy is discussed and illustrated in Chap. 10for those patients with ccTGA and pulmonary stenosis, with or without ventricular septal defect (VSD). The idea is to construct a physiologic repair (right ventricle to aortic continuity) without having to resort to a conduit from the left ventricle to the pulmonary artery, which complicates the repair by coronary artery problems and conduit changes over time. The operation is performed by VSD closure (if present), pulmonary artery valvotomy/subpulmonic resection, and right atrial unloading by a bidirectional Glenn shunt to lower the developed pressure in the left ventricle. This helps by keeping the left ventricular pressure sub-systemic for optimal coronary artery flow and helps to stabilize the interventricular septum. Stabilizing the septum prevents right ventricular distention and help to avoid tricuspid regurgitation on the basis of papillary muscle stretching. This strategy actually works. The second application of the 1½ ventricular repair for patients with ccTGA is in double switch operations when the surgeon feels that the atrial baffle is too complex to include the SCV flow. Under these circumstances, a pericardial baffle is constructed to direct ICV flow to the tricuspid valve and right ventricle, which is to become the pulmonary ventricle after the arterial switch operation. The SCV flow is resolved by a bidirectional Glenn shunt, thereby completing the 1½ ventricular repair.
Sometimes missed diagnoses, right ventricular growth, or misapplied operations can complicate patient physiology. There have been reports of a 1½ ventricular repair in patients with atriopulmonary Fontan operations for tricuspid atresia who experienced right ventricular growth. During maturation, they developed protein-losing enteropathy. These relatively rare cases underwent placement of a conduit from the right atrium to right ventricle and reinstitution of right ventricle to pulmonary artery continuity with a bidirectional Glenn shunt (Fig. 11.21). The result was lower right atrial pressure, pulsatile pulmonary artery blood flow, and resolution of the protein-losing enteropathy.
Another situation, probably unique in character and scope, is noted in Figs. 11.22 and 11.23. Figure 11.22 shows the artist’s coronal view of the resultant anatomy and function in a patient who had an atriopulmonary Fontan operation for presumed dextrocardia, tricuspid atresia, and no VSD. Because of decreasing functional status, the patient underwent reassessment and was found to have dextrocardia, crisscross heart, tricuspid stenosis, VSD, severe pulmonary artery stenosis, normally related great arteries, baffle stenosis, cyanosis, and atrial reentry tachycardia. Figure 11.23 shows the operative repair by VSD closure, baffle augmentation, a modified right-sided maze procedure, right ventricular to pulmonary artery valved conduit, and a bidirectional Glenn shunt, thereby completing the 1½ ventricular repair in this very complex patient.
11.3 Fontan Conversion and Arrhythmia Surgery
Management of patients withfailing Fontan circulation has been the focus of significant scientific and clinical inquiry over the past decade, owing to the realization that the obligatory high venous pressure that characterizes this unique physiology has resulted in protein-losing enteropathy, plastic bronchitis, liver failure, liver cancer, atrial arrhythmias, pathway obstructions, valvar insufficiency, aneurysm formation, ventricular dysfunction, and decreased functional class. This litany of potential complications becomes more significant and more likely as the patient ages. As a result, one could expect that most, if not all, patients with Fontan physiology will have to undergo therapeutic interventions that include intense medical therapy, pacemaker placement, Fontan conversion, and eventually, cardiac transplantation. This chapter centers around good candidates for Fontan conversion, which was introduced in 1994 for select patients with failing Fontan physiology and atrial arrhythmias. The operation comprises conversion to extracardiac connections of vena cava to pulmonary artery, arrhythmia surgery, and pacemaker placement. The benefits of this operation have been confirmed by many clinical groups worldwide.
Patients have done best when there was preservation of ventricular function and absence of protein-losing enteropathy. The long-term effects of this operation are to improve functional status, treat debilitating arrhythmias, repair pathway obstructions, repair valves, and delay cardiac transplantation. For the most part, this operation has been highly effective. Over the years, we have been confronted with many impediments that were resolved intraoperatively. These techniques are noted in this chapter.
11.3.1 General Principles
From the onset of the operation, Fontan conversion is attended by potential complications relating to multiple sternotomies and the realization that an unwanted intracavitary entry can cause hemodynamic compromise and instability that can very quickly result in cardiovascular collapse. The driving force for cardiac output is controlled by venous pressure to the pulmonary artery. Any instability in this regard, even if effectively controlled, can result in renal failure, ventricular dysfunction, and ischemic brain injury. Patients with giant right atria that are adhered to the underside of the sternum may require peripheral cannulation and partial bypass before resternotomy. If femoral cannulation is employed, every effort should be made to convert to aortobicaval cannulation with femoral vessel repair to avoid limb ischemia, swelling, and compartment syndrome.
Once successful mediastinal reentry is performed, strategic and careful dissection is carried out to ensure hemostasis. Both thoracic cavities must be entered, with lysis of pulmonary adhesions to enable effective tube thoracostomy during the closing stages of the operation. The required optimal exposure is usually facilitated by self-retaining mammary retractors for hemostasis. Excessive postoperative bleeding after the Fontan operation is to be avoided. Once comprehensive dissection is achieved, aortobicaval cardiopulmonary bypass is instituted, with slow systemic cooling.
At this point in the operation, the surgeon must implement the preoperative plan to accomplish all the parts of the operation in the proper order. Every patient needs a period of aortic cross-clamping and cardioplegic arrest, if for no other reason than to perform the atrial septectomy. Other considerations include valve repair, pathway revisions, aneurysm resection, pulmonary artery augmentation, and left-sided maze procedures. The following are some of the characteristics of the Fontan conversion operation.
11.3.2 Uncomplicated Fontan Conversion with Modified Right Atrial Maze Procedure and Epicardial Pacemaker Lead Placement
The most straightforward Fontan conversion involves extracardiac connections, a modified right-sided atrial maze procedure, and epicardial pacemaker placement. Figure 11.24 shows the cannulation technique for Fontan conversion using aortobicaval cardiopulmonary bypass with left ventricular venting through the right superior pulmonary vein in a patient with tricuspid atresia and extant atriopulmonary Fontan. Figure 11.25 shows the degree of right atrial wall resection (dotted-dashed lines), which includes a significant part of the right atrial free wall. This resection is an important part of the arrhythmia surgical procedure because it is instrumental in removing scarred myocardial tissue, which could harbor areas of slow conduction and be responsible for atrial reentry circuits. Figure 11.26 shows dissection of the atrioventricular groove to facilitate right atrial wall reduction and provide an unscarred atrial target for atrial pacemaker lead placement. Also demonstrated is the firstintracardiac part of the operation, which involves ICV transection and end-to-end anastomosis with a 24-mm PTFE tube graft. This part of the operation can be performed in a beating heart as long as there is no atrial communication to the left side of the heart, which is usually the case. The aorta can then be cross-clamped, followed by administration of antegrade cardioplegia. The SCV is transected at the cavo-atrial junction. An atriotomy is subsequently accomplished to connect the orifices of the SCV and ICVs (Fig. 11.27). This results in optimal exposure of the right atrium and allows atriopulmonary disconnection and septum primum resection, as noted. Figure 11.28 shows the completion of the modified right atrial maze procedure, comprising cryoablation lesions to connect the coronary sinus with the cut edge of the ICV, the coronary sinus with the ASD, the ASD with the posterior atrial flap across the crista terminalis, and a lesion to connect the base of the resected atrial appendage and the ASD. A large atrial resection is performed to achieve a right atrial wall reduction, and the atrium is closed without regard to the sinoatrial node, using running suture technique (Fig. 11.29). The sinoatrial node in these patients is often dysfunctional because of either previous surgical injury or the influence of long-standing arrhythmias. The intention is to use atrial pacing after the operation to limit the occurrence of premature atrial contractions and therefore limit episodes of atrial reentry tachycardia. After appropriate air maneuvers are performed, the cross-clamp can be removed, and the patient can be rewarmed. During this stage, the superior portion of the extracardiac PTFE conduit is cut to the appropriate size and on a bevel. It is then anastomosed to the inferior portion of the right pulmonary artery to ensure an anatomic offset with the SCV (Fig. 11.30). Next, the superior cavopulmonary anastomosis is performed, using interrupted suture technique. Some surgeons use running suture technique, which is acceptable as long as the anastomosis is not purse-stringed. After the patient is ventilated and separated from cardiopulmonary bypass, protamine is given and all bleeding is controlled. Attention can now be given to the pacemaker system. Bipolar, steroid-eluting, epicardial leads are placed on the surface of the atrium and ventricle and tested for sensing and pacing (Fig. 11.31). The pacemaker is programmed for the atrial pacing and sensing (AAI) function. A good sign for efficacy is if the patient is in nodal rhythm and responds to atrial pacing, yielding a paced sinus rhythm. The operation is concluded by ensuring careful hemostasis, which may take hours to achieve. The importance of this part of the operation cannot be emphasized enough.