Toward the end of the decade of the 1980s, several surgical groups,1–3 recognizing the limitations of surgical strategies that left the morphologically right ventricle as the sole systemic pumping chamber, attempted surgical repairs encompassing an atrial baffle procedure, either the Mustard or Senning operation, to address the physiology of discordant atrioventricular connections, together with a Rastelli procedure, involving construction of an interventricular baffle and placement of an extracardiac conduit, to address the problems created by, on the one hand, the discordant ventriculo-arterial connections, and on the other hand, the sub-pulmonary obstruction (Fig. 1). Ilbawi et al.1 were the first to report a successful series of such procedures, which eventually came to be known as double switch operations. As is discussed in the review of nomenclature elsewhere in this supplement,4 this term is more precise and accurate when applied to the combination of an atrial baffle procedure and an arterial switch operation, as has more recently been advocated for congenitally corrected transposition in the absence of important sub-pulmonary obstruction. Procedures of this type, considered technically more ambitious than earlier repairs consisting of anatomic closure of the ventricular septal defect and interposition of a conduit between the morphologically left ventricle and the pulmonary arteries, have been touted as having the advantage of placing the morphologically left ventricle and mitral valve in the systemic circulation. In the majority of instances, the double switch reconstruction for patients with important sub-pulmonary obstruction is performed after initial palliation with a systemic-to-pulmonary shunt, though occasionally it is performed as a primary repair in early infancy.
Figure 1. Cartoon showing the essence of anatomic correction incorporating creation of an atrial baffle combined with the Rastelli procedure.
The problems with the biventricular options for repair
While having the theoretical advantage of restoring circulatory physiology that is intended to be similar to normal, with the systemic and pulmonary circulations in series, and with the morphologically left ventricle as the systemic pump, the combination of an atrial baffle procedure and a Rastelli operation also has the potential to result in a combination of any or all of the complications known to be associated with the two components of the repair. The atrial baffle procedure, be it of the Senning or the Mustard type, is associated with the potential for development of obstruction within either the systemic or the pulmonary venous pathways. The atrial incisions, and extensive suture lines, are known to be associated with time-related risk of sinuatrial nodal dysfunction and atrial tachyarrhythmias. In addition, both types of atrial baffle procedures are technically more challenging in the setting of juxtaposition of the cardiac apex to the inferior caval vein, which is a frequently occurring feature of hearts with discordant atrioventricular connections. In patients with important sub-pulmonary obstruction, the portion of the double switch operation that addresses the discordant ventriculo-arterial connections is the Rastelli operation, in other words creation of the interventricular baffle and placement of the extra-cardiac conduit. While placing the morphologically left ventricle in the systemic circulation, as discussed above, the Rastelli procedure is also associated with a number of well-recognized problems. Frequently there is a need for enlargement of the ventricular septal defect. Failure to do so may result in progressive obstruction of the outflow from the morphologically left ventricle. But even judicious septal resection can have a negative impact on ventricular function. The conduction system, of course, is susceptible to sutures placed to secure the interventricular baffle. Intraventricular conduction delays, or complete heart block, are among the complications of this part of the operation. And of course, there is the need for placement of an extra-cardiac valved conduit which, in the setting of hearts with discordant atrioventricular connections is particularly susceptible to sternal compression, and which is associated with the virtual certainty of reoperations for replacement of the conduit.
When the Rastelli operation is performed in the less complex setting of hearts with physiologically uncorrected transposition, a ventricular septal defect, and sub-pulmonary obstruction, the late results reveal the inherent shortcomings of this operative strategy. In a review of 25 years experience with the procedure at Children's Hospital, Boston, Kreutzer et al.5 reported early mortality of 7 percent, and late mortality of 17 percent. Of their cohort of 101 patients, 44 had undergone reoperations for failure of the conduit, and 11 for obstruction of the morphologically left ventricular outflow tract. An additional 28 patients had undergone catheter interventions for obstruction within the conduit, 9 patients experienced significant late arrhythmias, and 5 had died suddenly. Interestingly, actuarial estimates of survival did not improve with era of surgery. So, we are left with the philosophical challenge common to the management of many complex forms of congenital cardiac disease: “Is a high-risk biventricular repair always preferable to conversion to a single ventricle repair?” This question was addressed in a retrospective study from the Hospital for Sick Children at Great Ormond Street, London.6 They evaluated the outcomes achieved in a group of 34 patients with a variety of transposition complexes with pulmonary stenosis or atresia who had undergone biventricular repair. These were compared to 16 patients with the same diagnoses who had undergone modified Fonatan operations. Freedom from reoperation at 7 years was 45.5 percent in the group undergoing biventricular repair, but was complete in those converted to the Fontan circulation. The actuarial estimate of survival at 7 years was 68.0 percent in those submitted to biventricular repair, and 93.8 percent in the group with the Fontan circulation. So clearly, as they concluded, “there may be circumstances where the short term and intermediate term risks associated with a complex biventricular repair may outweigh the long-term disadvantages of a single ventricle approach”.6 And, in that historical series, the biventricular repair was not associated with the added complexity of construction of an atrial baffle.
What, therefore, about the circumstance where the complex biventricular repair combines the construction of an atrial baffle with the Rastelli operation? Certainly, there have been numerous reports of series of double switch procedures with excellent early results and relatively short periods of follow-up. Imai et al.7 reported on 44 patients, including 35 who had undergone Senning and Rastelli procedures, and 9 who had undergone double switch procedures. Early mortality was 9.1 percent. Reddy et al.8 reported on 11 patients aged 5 months to 8 years, with early mortality of 9 percent. And Acar et al.9 reported on 9 patients undergoing double switch procedures with early mortality of 11 percent. But one must ask: what are the contemporary results of anatomic repair with longer periods of follow-up? In 2003, the group from Birmingham, United Kingdom,10 reported their midterm results after restoration of the morphologically left ventricle to the systemic circulation in patients with congenitally corrected transposition. Their series included 54 patients who had undergone Rastelli and Senning operations, with early mortality of just 5.6 percent. But, there were six new cases of left ventricular dilation or impaired systolic function, one take-down, 3 changes of conduit, and 8 cases of newly created complete heart block requiring pacemakers. Freedom from reoperation was no more than 68 percent at 7 years. In 2006, the group from Children's Hospital, Boston,11 reported on 44 patients with congenitally corrected transposition who had undergone anatomic repair. All had an atrial baffle procedure, and 23 patients had a Rastelli procedure while 21 underwent an arterial switch. Morphologically left ventricular function deteriorated in 8 patients. Patients with a Rastelli procedure were more likely to have worse postoperative ventricular function compared to their preoperative state. And, left ventricular function tended to deteriorate in patients who required a pacemaker. At the 2006 meeting of the American Association for Thoracic Surgery, Shinoka et al.12 from Tokyo, Japan, reported on a series of 195 patients who had undergone repair of congenitally corrected transposition or discordant atrioventricular connections with double outlet right ventricle. The series spanned over several decades, and a variety of reparative strategies were utilized. Of their overall cohort, 38 patients had been converted to the Fontan circulation rather than being submitted to complex biventricular repair. The actuarial survival at 20 years was as high for those with the Fontan circulation as for any of the other operative groups. Furthermore, the actuarial survival free of further events was higher for those with the Fontan circulation than for any of the groups undergoing biventricular repair.
Does conversion to the Fontan circulation have a place?
In our opinion, there is no question but that the problems associated with the combination of construction of an atrial baffle and the Rastelli operation are sufficiently serious to warrant consideration of conversion to the Fontan circulation as definitive therapy for patients with discordant atrioventricular connections and severe sub-pulmonary obstruction, particularly when considered in the light of the excellent results obtained by others using this approach. Our recent experience in Philadelphia at St Christopher's Hospital encompasses 7 patients with this anatomic constellation, born between 1995 and 2005. Their current ages range from 1.8 years to 11 years. Five patients have the usual arrangement of atrial chambers and bodily organs, with segmental anatomy (S,L,L), and two have the mirror-imaged arrangement, with cardiac segmental anatomy (I,D,D). Of the 7, 6 have successfully undergone completion of the Fontan circulation, 4 with fenestrated lateral atrial tunnels, and 2 with extra-cardiac conduits. The other patient has undergone a superior cavopulmonary connection, and is ready for completion of the Fontan circulation. Follow-up after the completion of the Fontan circulation ranges from 1 year to 10 years. There has been no early or late mortality. There have been no take-downs. No patient has required a pacemaker. There have been no thromboembolic events, and no cases of protein losing enteropathy. In all patients, the rhythm remains sinus, or else a non-sinus atrially conducted rhythm. Based upon 24 hour ambulatory monitoring at six monthly intervals, there have been no sustained atrial tachyarrhythmias. Routine diagnostic catheterization has been performed one year after completion of the Fontan circulation in 5 patients, and no other interventions have been indicated. This is a healthy group of young patients. Of course, the long-term outlook for these patients remains uncertain, despite the general improvement in outcomes for patients with functionally univentricular hearts. Whether patients with functionally biventricular hearts treated by conversion to the Fontan circulation may perform better, or be more durable, than those with functionally univentricular arrangements is purely a matter of speculation. But the evidence is compelling that, for this small group of patients, the quality of life after a modified Fontan procedure has been good, and event free. We are optimistic that this satisfactory situation will be durable. Would these patients have been better served in the long run by initial construction of an atrial baffle combined with the Rastelli operation? Only time will tell.
The role of aortic translocation
As already discussed at length in the first part of our review, when contemplating the surgical management of patients with congenitally corrected transposition in the setting of a ventricular septal defect and pulmonary stenosis, there are two main options. The simplest repair is to close the ventricular septal defect and insert a conduit between the morphologically left ventricle and the pulmonary arteries. This leaves the morphologically left ventricle, however, in subpulmonary position. If the morphologically left ventricle is to be restored to its systemic role, then an atrial switch procedure needs to be combined with a Rastelli repair. As discussed at length above, the problems with these options are such that consideration should also be given to conversion to the Fontan procedure. But it must not be forgotten that, in suitable patients, there is a third option, namely aortic translocation. This procedure was first described, as far as we are aware, in 1980, when Bex et al.13 described moving the aortic root, together with the coronary arteries, to the pulmonary position as a way to provide a true anatomical correction for a patient with physiologically uncorrected transposition. The procedure was perfected in anatomical specimens before it was carried out successfully in a three-year-old patient. Then, in 1984, Nikaidoh14 described again, and popularized, the concept of aortic translocation.
Our own experience with aortic translocation for such patients with physiologically uncorrected transposition led us to consider it as a surgical alternative for the management of patients with congenitally corrected transposition. We have now undertaken aortic translocation combined with a Senning procedure in 3 patients. In 2 of them, the ventricular septal defect opened to the inlet of the morphologically right ventricle, while in the third there was straddling and overriding of the morphologically tricuspid valve. In this small series, one of the patients died prior to discharge from hospital due to a massive cerebrovascular accident, despite excellent postoperative cardiac function. On follow-up, both survivors have normal ventricular function, albeit that one has developed atrial flutter.
It is our opinion that aortic translocation, combined with biventricular reconstruction of the outflow tracts results in an anatomic repair, when compared to the Rastelli procedure, that is closer to normality (Fig. 2). It is our hope that this could result in improved cardiac performance and long-term survival. The right and left ventricular outflow tracts are better aligned, avoiding the right angle turns created by the Rastelli repair. Aortic translocation avoids the creation of an intraventricular tunnel, which should result in a much lower incidence of postoperative obstruction of the left ventricular outflow tract. To date, as far as we know, there has been no reported case of such obstruction after aortic translocation, be it performed for physiologically uncorrected or congenitally corrected transposition.
Figure 2. (a) shows a lateral view of the heart with physiologically uncorrected transposition, ventricular septal defect, and pulmonary stenosis. (b) shows the same heart with a classical “Rastelli procedure”. Although a tried and true procedure, this demonstrates that the outflow of each ventricle must make a right angle turn, pass through a muscular tunnel, either the ventricular septal defect (VSD) or a ventriculotomy, and continue in an anterior conduit subject to compression by the sternum. (c) shows the lateral View of the same heart with the aortic valve transferred posteriorly to the outflow tract of the morphologically left ventricle, with reconstruction of the pulmonary arteries directly end-to-end to the right ventricular outflow tract. The ventricular outflow is straight and direct, and unobstructed without risk of sternal compression by the sternum. (Reprinted with permission from Reference #18). Abbreviations: RA, RV right atrium and right ventricle; LA, LV: left atrium and left ventricle; AO: aorta; PA: pulmonary trunk.
The reconstructed outflow tract from the morphologically right ventricle, with or without placement of a conduit, sits more posteriorly in the mediastinum, and is therefore less susceptible to sternal compression (Fig. 2). This may result in improved longevity should a conduit be needed. Our most recent modification of the procedure15 includes a direct anastomosis between the pulmonary arteries and the right ventricle (Fig. 3). As already reported in the literature,16 this should also result in a decreased incidence of reoperations.
Figure 3. After translocation of the aorta, and performing the Lecompte manoeuvre, the pulmonary trunk is sutured directly to the right ventricle using an anterior patch of autologous pericardium to augment the area of anastomosis.
In patients with congenitally corrected transposition, the atrioventricular conduction axis runs anterior and cephalad to the pulmonary valve, and then descends along the anterior margin of the ventricular septal defect before diverging into the bundle branches.17 Division of the muscular outlet septum, therefore, does not result in complete heart block, but care should be taken when suturing the patch around the septal defect so as not to injure the conduction tissue. When using this technique we have noticed that, once the aorta has been harvested from the morphologically right ventricle, and the muscular outlet septum divided, the exposure provides for an excellent visualization of both the defect and the atrioventricular valves. Thus, the closure of the defect is easier and more precise, especially in patients who have a straddling and overriding valve. In our series, nonetheless, one patient did develop postoperative complete heart block requiring a pacemaker.
Aortic translocation, therefore, can be an attractive alternative for patients with intracardiac anatomy that is not conducive to a repair using the Rastelli approach. The abnormal course of a major coronary artery crossing the morphologically right ventricular outflow tract could preclude the performance of a distal right ventriculotomy. The presence of a ventricular septal defect opening to the inlet of the morphologically right ventricle, or one that is restrictive, or association with straddling of an atrioventricular valve, may all prove to be major anatomical obstacles in creating the intraventricular tunnel. Interestingly, the presence of a straddling tricuspid valve has been associated with an increase in early and late mortality after a Rastelli repair.16 Also, the volume within the morphologically right ventricle is partially compromised by the interventricular tunnel, thus, the presence of right ventricular hypoplasia can be considered a contraindication to a Rastelli repair.
Conclusions
Our own small experiences reported here, combined with an extensive review of experience reported elsewhere, indicates that both aortic translocation in combination with an atrial switch procedure, and conversion to the Fontan circulation, deserve consideration when deciding on the optimal surgical management for patients with discordant atrioventricular connections, interventricular communications, and pulmonary stenosis or atresia. At present, both options could potentially result in better long-term functional outcomes. A larger number of patients, nonetheless, and longer follow-up, is required fully to assess the long-term benefits of these surgical alternatives.
