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a Department of Pediatrics, Division of Pediatric Cardiology, Morgan Stanley Children's Hospital, New York, New York
b Department of Surgery, Morgan Stanley Children's Hospital, New York, New York
Accepted for publication April 7, 2008.
* Address correspondence to Dr Liberman, Morgan Stanley Children's Hospital, 3959 Broadway, 2 North, New York, NY 10032 (Email: ceresnak{at}yahoo.com).
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Abstract |
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Methods: This is a retrospective review of our institutional experience from October 1991 through August 2006 on single-ventricle patients with transposition of the great vessels and systemic outflow tract obstruction who underwent a palliative arterial switch procedure.
Results: Nine patients underwent an initial palliative switch procedure. Six of 9 patients underwent completion of palliation with the Fontan procedure and are alive and well. One patient is well and is awaiting the next stage of palliation (78%). There was 1 early operative death (11%) and 1 late death (11%). There was 1 case of recoarctation (11%).
Conclusions: The palliative switch procedure appears a reasonable surgical option for patients with functional single-ventricle lesions, transposition of the great vessels, and systemic outflow tract obstruction. Patients who have undergone a palliative switch procedure are suitable candidates for completion of palliation with the Fontan procedure.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Surgical Technique
All procedures were performed by the same cardiothoracic surgeon (J.M.Q.). In all patients, the chest was entered through a vertical midsternal incision. The heart was cannulated in the aorta and in the right atrium using a single venous cannula. The aorta was then transected in its midportion. Aortic coarctation and arch reconstruction were performed first using hypothermic circulatory arrest. In the patients with tubular hypoplasia of the aortic arch or large discrepancy in the size between the aorta and the pulmonary artery, or both, a cryopreserved pericardial patch was used to enlarge the arch and to augment the distal ascending aorta.
The remainder of the procedure was then performed on cardiopulmonary bypass with flows at 1.6 L/min/m2 and the temperature set at 28°C. The pulmonary artery (PA) was then transected just above the commissures. The usual coronary artery pattern (left anterior descending and circumflex from sinus 1 and the right coronary artery from sinus 2) was encountered in 7 of the 9 patients. The coronary arteries were excised as buttons from the aorta and reimplanted in the corresponding sinus of the PA. The Lecompte maneuver was performed in all patients. The enlarged (if necessary) distal aorta was then anastomosed to the neoaortic root. The neopulmonary root was repaired with two autologous pericardial patches and anastomosed to the PA bifurcation. Cardiopulmonary bypass was then discontinued.
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Results |
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There was 1 early operative death (11%). This patient (no. 7) was noted to have good ventricular function after removal from cardiopulmonary bypass. Arterial hypotension occurred after chest closure with decreased ventricular function on transesophageal echocardiography. The patient's coronary anatomy was normal, but the left coronary artery was short and bifurcated early. In addition, there was a large size discrepancy between the aorta and the pulmonary artery, with the pulmonary artery being more than 50% larger than the aorta. This size discrepancy between the aorta and pulmonary artery, coupled with the short, early bifurcating left coronary artery, made the coronary transfer more challenging. At reexploration, we could not confirm kinking of the left coronary artery; however, the left coronary artery was then "tacked up" anteriorly, resulting in improved ventricular function. The patient died on postoperative day number 16 of persistently poor ventricular function despite maximal inotropic and medical support. No postmortem examination was performed.
Follow-Up
Three of the 9 patients (33%) needed augmentation of pulmonary blood flow with a modified Blalock-Taussig shunt. One patient had the Blalock-Taussig shunt placed on postoperative day 5, whereas the other 2 patients had the shunts placed 2 and 3 months postoperatively (Table 1). None of the patients required a PA band because of excessive pulmonary blood flow.
Six of the 9 patients ultimately underwent Fontan palliation. Four patients initially underwent a bidirectional Glenn (BDG) operation, and 2 did not have an intermediate BDG staging and had Fontan as their second procedure after palliative switch. The median age of the BDG procedure was 8 months (range, 4 to 19). The median age of the Fontan procedure was 32 months (range, 27 to 37). One patient is currently doing well and awaiting the next stage of palliation. The 6 patients who have completed Fontan palliation are alive and well on most recent follow-up. The median time to most recent follow-up is 4.83 years (range, 0.5 to 15.3).
Pre-Fontan cardiac catheterizations were performed on all patients before the Fontan procedure. The median PA pressure was 10 mm Hg (range, 9 to 14 mm Hg) and the median ventricular end-diastolic pressure was 8 mm Hg (range, 5 to 11 mm Hg). There were no patients with pulmonary hypertension or other problems that prevented surgical palliation with the Fontan procedure. The pulmonary artery anatomy was assessed angiographically on all patients, and the median PA index (Nakata index) was 347 mm2/BSA (range, 167 to 740 mm2/BSA) [19]. Three of the 6 patients (50%) had concomitant PA enlargements at the time of the Fontan. The median PA index of the patients requiring PA enlargement was 203 mm2/BSA (range, 167 to 490 mm2/BSA) and the median PA index of the patients who did not require PA enlargement was 545 mm2/BSA (range, 190 to 740 mm2/BSA]. The difference between these two groups was not statistically significant (p = 0.34).
There was 1 late death (11%) that occurred 3 months after the initial arterial switch procedure (patient 9). This patient presented with signs and symptoms of heart failure and had recoarctation of the aorta with severely decreased ventricular function. The patient was taken to the cardiac catheterization laboratory for successful balloon angioplasty of the coarctation and was then transferred to the pediatric cardiac intensive care unit. After catheterization, the patient was hypoxic and went to surgery for placement of Blalock-Taussig shunt. Three days postoperatively, the patient died after respiratory arrest despite maximal inotropic and medical support. No postmortem examination was performed, and the cause of death was believed to be secondary to respiratory acidosis in the setting of severely decreased ventricular function.
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Comment |
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There are numerous potential theoretical benefits of an arterial switch procedure [2, 14, 15]. These benefits may include the following: (1) the creation of laminar flow through the systemic outflow tract, potentially decreasing the risk of recoarctation; (2) relief of subaortic stenosis, thus preventing myocardial hypertrophy of the single ventricle and helping to prevent diastolic dysfunction of the single ventricular chamber; (3) decreased need for a systemic to PA shunt, as a shunt carries the risk of shunt occlusion, distortion of PA anatomy, and decreased diastolic pressure with potentially poorer coronary perfusion; and (4) protection of the pulmonary vascular bed through effective "banding" due to subpulmonary stenosis or a restrictive bulboventricular foramen.
There are several theoretical drawbacks of the palliative switch procedure. These drawbacks include the difficulty in predicting pulmonary blood flow, and the possibility of long-term coronary artery problems after coronary transfer as part of the arterial switch procedure.
There is limited experience reported in the literature about the utility of an arterial switch as the first stage of palliation for single-ventricle lesions [2, 14, 16–18]. The initial palliative arterial switch procedure reported in the literature was in 1980 by Freedom and colleagues [16], who described 2 patients with tricuspid atresia who underwent arterial switch and simultaneous Fontan procedure. Karl and associates [2] reported 6 patients with univentricular hearts and subaortic stenosis, 2 of whom went on to BDG and 1 who underwent a Fontan procedure. Lacour-Gayet and colleagues [14] reported 7 patients who underwent palliative arterial switch. The short-term results in this series were good, but suitability for ultimate Fontan palliation has not been reported.
Outcomes
Estimates on the operative mortality for the Norwood Procedure and the DKS procedure vary according to the era of reporting, the anatomy of the patient undergoing the procedure, the presence of additional medical or genetic problems, the weight of the patient, and the institution [20]. Estimates for mortality for both procedures vary and have ranged from 30% during the early years of the procedure to as low as 10% in current surgical practice [5, 6, 9, 11, 21]. In contrast, the arterial switch operation has evolved to a standard and safe procedure, with mortality rates ranging from 5% to 7% for patients with biventricular hearts [20, 21]. During the early period, the mortality rate for a standard arterial switch operation in our center was 2% [22]. It was because of this dramatic difference in operative mortality between the Norwood and DKS procedures and the arterial switch operation procedure that a palliative switch was considered in these high-risk patients. In univentricular hearts, Lacour-Gayet and colleagues [14] reported an overall mortality with the palliative switch to be 29%. In this study, the early operative mortality was 11%, and the 1 death was related to poor ventricular function after bypass. The late mortality was also 11%, and the late death was secondary to a respiratory arrest. The overall mortality, therefore, seems comparable to that for both the DKS and Norwood procedures.
Recoarctation
One of the theoretical benefits of the palliative switch procedure is the creation of laminar flow through the aortic outflow tract, with a potential decreased risk of coarctation. Clarke and associates [9] described a recoarctation rate as high as 33% among patients who have underwent DKS (4 of 12 patients). In our series, recoarctation developed in only 1 of the 9 patients (11%). More laminar flow through the "true" aortic outflow tract and across the aortic arch has been postulated to potentially result in a decreased risk of recoarctation.
Pulmonary Blood Flow
Prior reports in the literature have described that one of the problems with the palliative arterial switch operation is that it is difficult to predict and control pulmonary blood flow. In prior studies it has been shown that most of the patients undergoing palliative switch required augmentation of pulmonary blood flow with a Blalock-Taussig shunt [5, 14]. Lacour-Gayet and colleagues [14] showed that the majority of patients (6 of 7) needed a systemic to PA shunt for decreased pulmonary blood flow. In addition, there was 1 patient in that series who needed a pulmonary artery band placed owing to excessive pulmonary blood flow. In that series, all patients undergoing palliative switch needed an intervention to help control or augment pulmonary blood flow. In our series, 3 of the 9 patients (33%) required a Blalock-Taussig shunt to augment pulmonary blood flow, and none of the patients required a PA band. The surgical switch thus created pulmonary outflow tract obstruction, either in the form of pulmonary or subpulmonary stenosis or through a restrictive buloventricular foramen that was adequate to provide appropriate pulmonary blood flow. In the majority of the patients in our series (67%), therefore, the pulmonary outflow tract obstruction offered adequate protection of the pulmonary bed and offered a natural "banding" and restriction of pulmonary blood flow.
Conclusion
In conclusion, the palliative arterial switch procedure may be a reasonable surgical option for patients with univentricular lesions and SOTO. Operative mortality is similar to that for the Norwood and DKS procedures. The arterial switch procedure may offer long-term benefits that make patients with single ventricles good candidates for future palliation with the Fontan procedure. Further studies are needed to compare the different surgical techniques.
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