Asian Cardiovasc Thorac Ann 2001;9:279-281
© 2001 Asia Publishing EXchange Pte Ltd
Bidirectional Cavopulmonary Shunt With Accessory Pulmonary Blood Flow
Pankaj Goel, MCh,
Kona Samba Murthy, MCh,
Kotturathu Mammen Cherian, FRACS
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Department of Cardiovascular Surgery Institute of Cardiovascular Diseases Madras Medical Mission Chennai, Tamil Nadu, India
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For reprint information contact: Kona Samba Murthy, MCh Tel: 91 44 656 5961 Fax: 91 44 656 5510 email: mmmbits{at}giasmd01.vsnl.net.in Department of Cardiovascular Surgery, Institute of Cardiovascular Diseases, Madras Medical Mission, 4A Dr. J Jayalalitha Nagar, Mogappair, Chennai, Tamil Nadu 600050, India.
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ABSTRACT
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Ninety-five patients underwent a bidirectional cavopulmonary shunt between 1995 and 1999. Group 1 (n = 38) had a shunt without an additional source of pulmonary blood flow. Group 2 (n = 57) had a shunt with accessory pulmonary flow. Patients with accessory pulmonary flow were better palliated (82% asymptomatic in group 2 versus 63% in group 1; p = 0.03). Intensive care stay was longer in group 2 (6.9 ± 7.5 days versus 4.6 ± 3.6 days; p = 0.05). There were no differences between the groups in terms of early postoperative oxygen saturation, incidence of pleural effusion, or the need for inotropic support. Leaving an additional source of pulmonary blood flow in selected patients is recommended. These findings are of special significance in developing countries where additional surgery is often unaffordable and a bidirectional cavopulmonary shunt may be the only procedure undertaken.
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INTRODUCTION
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A bidirectional cavopulmonary shunt (BCPS) is one of the palliative procedures for the management of patients with single ventricle and pulmonary stenosis.1,2 Although the surgical technique and long-term results have been described, the issue of leaving an additional source of pulmonary blood flow (APBF) at the time of the cavopulmonary shunt remains controversial. Proponents of APBF suggest that the oxygen saturations are higher, the associated pulsatility may promote pulmonary artery growth, and the incidence of pulmonary arteriovenous malformations is reduced.3–5 Opponents argue that the increased flow may lead to volume overload of the single ventricle and potentially elevate the pulmonary artery pressure, thus defeating the basic benefits of BCPS over the Blalock-Taussig shunt. Our experience of BCPS with and without APBF was assessed retrospectively.
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PATIENTS AND METHODS
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From January 1995 to March 1999, 95 patients underwent BCPS for various types of single ventricle physiology (Table 1
). An unstaged Fontan operation was not considered in these cases because of institutional policy. The patients were divided into 2 groups for the purpose of analysis. Group 1 (n = 38) had only a BCPS, and group 2 (n = 57) had a BCPS with an APBF in the form of persistent antegrade main pulmonary artery flow. The decision whether to leave an APBF was a surgical one. After completion of the BCPS, the mean superior vena cava (SVC) pressure was measured. If it was more than 15 mm Hg, the main pulmonary artery (MPA) was temporarily snared. If this led to a fall in SVC pressure with a rise in systemic oxygen saturation and improvement in hemodynamics, the MPA was interrupted. In all other cases, the MPA was left patent. The preoperative clinical characteristics are summarized in Table 2. Bilateral BCPS was established in 6 patients (4 in group 1, 2 in group 2) who had a large left SVC without a bridging vein. Previous palliative procedures are listed in Table 3.
All operations were performed via a median sternotomy. Cardiopulmonary bypass was not used in 8 patients (3 in group 1, 5 in group 2). Total circulatory arrest was employed in 19 patients (6 in group 1, 13 in group 2). All others underwent BCPS under moderate hypothermia using innominate vein or high SVC cannulation. Atrial sep-tectomy was carried out during a brief period of fibrillatory arrest through the atrial end of the cut SVC. All patients with a patent Blalock-Taussig shunt (6 in group 1, 7 in group 2) underwent shunt ligation. Additional surgical procedures were undertaken in 37 patients (Table 4).
Statistical analysis was performed using the SPSS statistical package (SPSS, Inc., Chicago, IL, USA). Comparisons between the groups were made with Fisher's exact test, the Mann-Whitney U test, or paired Student t test, as appropriate. A p value < 0.05 was considered significant.
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RESULTS
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There were 5 early deaths: in group 1, there was 1 death due to septicemia, and another was caused by intractable supraventricular arrhythmias; 1 patient in group 2 died of pneumonia, and 2 succumbed to recurrent shunt thrombosis and hypoxia. Both patients with shunt thrombosis presented with progressive desaturation, and intra-shunt streptokinase therapy failed to clear the thrombus. There was an additional death one month after the operation in a group-1 patient who had massive hemoptysis. Reexploration was required in 5 patients; 1 had excessive hemorrhage, and 4 patients in group 2 with high SVC pressures (> 20 mm Hg) underwent MPA ligation.
The clinical status of all patients improved after the operation. There was no statistical difference in the immediate postoperative oxygen saturation between the two groups (84% in group 1 versus 82.5% in group 2; p = 0.18). Group 1 had a shorter intensive care unit stay (4.6 days versus 6.9 days; p = 0.05). High inotropic support (defined as more than 5 µg•kg-1•min-1 of dopamine for > 48 hours) was required in 1 patient in group 1 and 6 in group 2 (p = 0.24). Recurrent pleural effusion requiring a drainage tube for more than 7 days occurred in 13% of group 1 and 21% of group 2 (p = 0.18). These patients underwent talc pleurodesis.
Follow-up was carried out by the patients' cardiologists. Pulse oximetry was performed while on room air. Symptomatic status was assessed according to the New York Heart Association guidelines. At a mean follow-up of 11.9 months, 24 (63%) of group 1 patients were asymp-tomatic, whereas at 8.3 months, 47 (82%) of group 2 patients were asymptomatic (p = 0.03). One patient in each group underwent completion of the Fontan procedure; both are doing well. One patient in group 1, and 2 in group 2 presented with desaturation and were found to have anastomotic stenosis that was stented with a satisfactory outcome. Two patients had desaturation due to a patent azygos vein; they underwent azygos vein ligation.
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DISCUSSION
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Although there are reports highlighting the benefit of leaving an APBF, the decision to leave an APBF has been arbitrary. The criteria used in this series were the effects of temporarily snaring the MPA. These criteria helped to identify patients who could not tolerate extra volume overload. Similar criteria were described by Albanese and colleagues,3 while other criteria have also been reported.2,5–7 The proponents of leaving an APBF postulate that oxygen saturation would be higher. In this series, patients with an APBF had slightly higher oxygen saturation, but it did not achieve statistical significance.
Kobayashi and colleagues4 emphasized the possible beneficial effects of pulsatile flow in preventing the late development of pulmonary arteriovenous malformations. Pulmonary arteriovenous malformations were observed in 2 patients in our series; both were in group 1, and one succumbed to intractable severe hemoptysis. None of the patients in group 2 developed pulmonary arteriovenous malformations.
Another potential advantage of leaving an APBF is that it may enhance pulmonary arterial growth. Uemura and colleagues8 showed that leaving an APBF with a BCPS prevented regression of pulmonary artery size. Although serial measurements of pulmonary artery size were not performed in our study, patients in group 2 with an APBF were found to be significantly better palliated, suggesting that the APBF might have prevented regression of pulmonary artery size.
Despite the potential advantages of leaving an APBF, most centers routinely perform BCPS with ligation of all sources of pulmonary blood flow. This reflects concern that accessory flow may result in high pulmonary arterial pressures, volume overload of the ventricle, and chronic effusion. Our data do not support these concerns. It was noted that when patients were chosen carefully, leaving an APBF afforded better palliation at follow-up. Kobayashi and colleagues4 demonstrated similar reductions in ventricular size and improvement in atrioventricular valve regurgitation in patients after BCPS with an APBF. In our experience, these patients required longer intensive care unit stays because of pleural effusion and the need for prolonged inotropic support. However, this had no influence on the outcome. The criteria for leaving an APBF should be strictly followed. Not all patients are suitable, and indiscriminate leaving of an APBF in patients with high pulmonary vascular resistance or poor ventricular function may lead to postoperative morbidity and mortality.
The limitations of this study were that it was non-randomized and retrospective; thus, it was subject to patient self-selection. The patients in group 1 were inherently more ill; 6 patients in group 2 who did not tolerate the APBF required pulmonary artery ligation and were subsequently analyzed in group 1. Nevertheless, it was concluded that an APBF was well tolerated in selected patients with BCPS. It gave higher oxygen saturations and better palliation. This is of special significance in developing countries where, due to economic constraints, secondary surgery is often not feasible, and BCPS may be the first and final procedure in the management of a majority of patients with single ventricle.
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ABSTRACT
INTRODUCTION
