Asian Cardiovasc Thorac Ann 2008;16:381-386
© 2008 Asia Publishing EXchange Ltd
Factors Influencing Survival in Patients After Bidirectional Glenn Shunt
Suchaya Silvilairat, MD,
Yupada Pongprot, MD,
Rekwan Sittiwangkul, MD,
Surin Woragidpoonpol, MD1,
Suphachai Chuaratanaphong, MD1,
Weerachai Nawarawong, MD1
Division of Pediatric Cardiology
1 Division of Thoracic and Cardiovascular Surgery, Chiang Mai University, Chiang Mai, Thailand
For reprint information contact: Suchaya Silvilairat, MD, Tel: 66 89 761 2855, Fax: 66 53 94 6461, Email: ssamana{at}mail.med.cmu.ac.th, Department of Pediatrics, Chiang Mai University, Chiang Mai, 50200 Thailand.
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ABSTRACT
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Clinical characteristics, echocardiographic values, and catheterization data of 45 patients with a functional univentricular heart who had a bidirectional Glenn shunt instituted between November 1994 and October 2006 were retrospectively reviewed. Median age at operation was 20 months (range, 9 months to 19 years). Median follow-up time after the bidirectional Glenn operation was 4 years (range, 1 day to 11 years). The early mortality rate was 4/45 (8.9%); overall mortality was 24.4%. Actuarial survival after a bidirectional Glenn shunt was 73% ± 8% at 5 years and 55% ± 17% at 10 years. In multivariate Cox proportional hazards analysis, heterotaxy syndrome and systemic right ventricle were independent predictors of mortality after the bidirectional Glenn shunt. Age at operation, oxygen saturation, previous surgery, a pulsatile Glenn shunt, cardiopulmonary bypass, postoperative pulmonary artery pressure, bilateral superior venae cavae, and Nakata index were not predictive of mortality. The presence of heterotaxy syndrome and systemic right ventricle in patients with a functional univentricular heart should lead to aggressive investigation and management strategies.
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INTRODUCTION
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The prognosis for patients with a functional univentricular heart is quite poor.1 The modified Fontan operation has become the treatment of choice for univentricular heart, with favorable results.2–7 A bidirectional Glenn shunt has been used as an intermediate palliative step prior to the modified Fontan procedure. The advantages of this palliative surgery include relief of volume load on a functional single ventricle, reduced atrioventricular valve regurgitation, avoidance of pulmonary artery distortion from pulmonary artery banding or a systemic-to-pulmonary artery shunt, and prevention of pulmonary vascular obstructive disease.8–13 The bidirectional Glenn shunt is thought to have played a major role in improving outcomes for high-risk Fontan subgroups, with overall mortality rates of 5%–15%.14–19 However, mortality rates are higher in developing countries. Factors shown to influence mortality are abnormal pulmonary artery architecture, high pulmonary artery pressure, heterotaxy syndrome, systemic right ventricle, and anomalous pulmonary venous drainage.16–19 The aim of this study was to determine which factors influenced mortality in patients with a functional univentricular heart after a bidirectional Glenn shunt.
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PATIENTS AND METHODS
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A retrospective cohort study was performed in all 45 consecutive patients with a functional univentricular heart who had bidirectional Glenn shunt after 1994 at Chiang Mai University Hospital. Patients were identified by searching the surgical and echocardiographic database. The study protocol was reviewed and approved by the Chiang Mai University Review Board. Data were extracted regarding patient demographics, oxygen saturation, hemoglobin level, previous cardiovascular operation, surgical procedures, cardiopulmonary bypass time, aortic cross clamp time, and postoperative pulmonary artery pressure. Echocardiographic data were obtained from the final echo study prior to the operation. Details included ventricular morphology, atrioventricular valve regurgitation, and heterotaxy syndrome. Catheterization data included pulmonary artery pressure, pulmonary vascular resistance, pulmonary artery size, and ventricular end-diastolic pressure. The patients’ follow-up data were collected through October 2006.
All statistical calculations were performed using SPSS version 12.0 software (SPSS Inc., Chicago, IL, USA). Continuous data are expressed as median and range. Categorical data are summarized with the number and percentage. Survival was estimated using the Kaplan-Meier method, and differences were analyzed with the log-rank test. Multivariate Cox proportional hazards regression analysis was performed to assess all variables with a p value < 0.10 on univariate analysis. A p value < 0.05 was considered statistically significant.
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RESULTS
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The median age at diagnosis in the 45 patients who had a bidirectional Glenn shunt was 5 months (range, 1 day to 17 years). Table 1
summarizes their clinical characteristics. Previous surgical procedures were a modified Blalock-Taussig shunt artery banding in 1, and balloon atrial septostomy in 1. Median time from the previous surgical procedure to the bidirectional Glenn operation was 18 months (range, 11 months to 14 years). Bilateral bidirectional Glenn shunts were instituted in 17 (38%) patients with bilateral superior venae cavae. Three patients underwent a hemiFontan operation. Thirty (67%) patients had additional pulmonary blood flow from a modified Blalock-Taussig shunt or right ventricular outflow tract. Table 2 lists the associated surgical procedures. Echocardiographic and preoperative cardiac catheterization data are summarized in Table 3. Twenty-three patients have subsequently undergone a successful modified Fontan operation, and 7 will have a modified Fontan operation later. The Fontan operation cannot be carried out in 5 patients due to high pulmonary artery pressure and small pulmonary arteries. However, these patients’ symptoms have been relieved by the Glenn operation. Median follow-up after the bidirectional Glenn shunt was 4 years (range, 1 day to 11 years). The early mortality rate was 8.9% (4/45 patients). A further 7 patients died during follow-up; the overall mortality rate in this series was 24.4%. Actuarial survival was 73% ± 8% at 5 years and 55% ± 17% at 10 years (Figure 1). The results of univariate and multivariate Cox proportional hazards analyses of potential predictors of mortality are given in Table 4. In multivariate analysis, heterotaxy syndrome (hazard ratio = 6.7, p = 0.04) and systemic right ventricle (hazard ratio = 11.8, p = 0.009) were the only independent predictors of mortality after a bidirectional Glenn shunt. The risk of death was significantly greater in patients with heterotaxy syndrome (p = 0.0024) and a systemic right ventricle (p = 0.0018), using the log-rank test. Figure 2 shows the Kaplan-Meier survival plots in relation to heterotaxy syndrome and systemic right ventricle.
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Figure 1. Kaplan-Meier plot showing the probability of survival in patients with a functional univentricular heart after a bidirectional Glenn shunt.
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Figure 2. Kaplan-Meier plots showing the probability of survival after a bidirectional Glenn shunt in patients stratified by heterotaxy syndrome and systemic right ventricle (RV).
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DISCUSSION
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The overall mortality rates in previous reports were 5%–15%, and the factors influencing mortality were found to be heterotaxy syndrome, systemic right ventricle, anomalous pulmonary venous drainage, abnormal pulmonary artery architecture, and high pulmonary artery pressure.16–19 We observed lower actuarial survival rates after the bidirectional Glenn shunt operation in those who had heterotaxy syndrome and systemic right ventricle than in the other patients whose 5- and 10-year survival rates were 92% ± 5% and 92% ± 5%. All 4 early deaths in this series were in patients with heterotaxy syndrome or systemic right ventricle. The incidence of heterotaxy syndrome in this cohort was higher than that in previous reports, which may account for our higher early and overall mortality rates. Heterotaxy syndrome and systemic right ventricle in patients with a functional univentricular heart should lead to stringent investigation to preclude other risk factors such as abnormal pulmonary artery architecture, high pulmonary artery pressure, total anomalous pulmonary venous return, and separated hepatic venous connection. The causes of death in our patients were respiratory failure, heart failure, and pulmonary hypertension. Persistent deep cyanosis due to separated hepatic venous connection, ventricular dysfunction, pulmonary hypertension, and arrhythmia were observed in patients with heterotaxy syndrome after the bidirectional Glenn operation. In addition, the right ventricle eventually becomes inappropriate as the systemic ventricle. Systemic right ventricular dysfunction frequently occurred in these patients. Aggressive management of concomitant cardiovascular malformations, ventricular failure, arrhythmia, and pulmonary hypertension are warranted in patients with heterotaxy syndrome.
Our patients were relatively older than those in series from more developed countries because some presented later at the hospital and were diagnosed at an older age. Median age at diagnosis in this study was 5 months; however, age at operation was not predictive of mortality. Although ventricular end-diastolic pressure and pulmonary artery pressure did not predict mortality in this cohort, the patients with high pulmonary artery pressure or high ventricular end-diastolic pressure died or developed venous collaterals after the Glenn operation. In our opinion, patients with pulmonary artery pressure < 20 mm Hg and ventricular end-diastolic pressure < 15 mm Hg can successfully undergo a bidirectional Glenn shunt, although these criteria are somewhat higher than those generally used in clinical practice.
In this study, pulmonary artery banding was performed in only one patient who had no pulmonary stenosis. We recommend that pulmonary artery banding should be carried out before the Glenn operation in patients with high pulmonary artery pressure. Two patients who underwent total anomalous pulmonary venous return repair died after the Glenn operation; both had heterotaxy syndrome. Total anomalous pulmonary venous return was a significant risk factor in univariate analysis, but it was not predictive of mortality in multivariate analysis. The number of patients in this study may have been too small to detect the influence of this variable. In our opinion, total anomalous pulmonary venous return repair may be a risk factor for death. There was no difference in outcome between patients with and without associated surgical procedures. Atrioventricular valve repair was performed in only one case of severe valvular regurgitation in this series. Thus atrioventricular valve repair cannot be identified as a risk factor. Despite the lack of evidence that cardiopulmonary bypass time contributed to mortality, there is increasing confirmation that performing the bidirectional Glenn shunt on a beating heart without cardiopulmonary bypass leads to a much better outcome. This should probably be taken into consideration.
It is well established that appropriate preoperative selection of patients for the bidirectional Glenn shunt plays an important role in minimizing mortality and morbidity. Ventricular end-diastolic pressure, pulmonary artery pressure, and pulmonary artery size were not predictive of mortality in this cohort study, which might have been due to selection bias. In addition, our study patients were too few to detect the influence of these risk factors. However, our findings confirm that heterotaxy syndrome and systemic right ventricle pose high risks in patients with a functional univentricular heart, and their presence should trigger aggressive investigation and management strategies.
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ACKNOWLEDGMENTS
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This work was supported by Faculty of Medicine Research Fund, Chiang Mai University, Chiang Mai, Thailand.
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ABSTRACT
INTRODUCTION
