Three hundred and thirty-three experiences with the bidirectional Glenn procedure in a single institute
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《血管的通路杂志》
a Department of Cardiovascular Surgery, Fukuoka Children's Hospital Medical Center, 2-5-1 Tojin-machi, Chuo-ku, Fukuoka 810-0063, Japan
b Department of Cardiovascular Surgery, Kyushu University Fukuoka, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
Presented at the joint 19th Annual Meeting of the European Association for Cardio-thoracic Surgery and the 13th Annual Meeting of the European Society of Thoracic Surgeons, Barcelona, Spain, September 25–28, 2005.
Abstract
Objective: Introduction of the bidirectional Glenn procedure (BDG) in low-risk Fontan candidates would improve clinical outcomes. Over the last decade, not only high-risk Fontan candidates, but all candidates underwent BDG and staged Fontan operation (TCPC) in our hospital. Methods: Three hundred and thirty-three consecutive patients (age range, 42 days to 16 years old) underwent BDG at Fukuoka Children's Hospital Medical Center from 1992 to 2004. Diagnoses included hypoplastic left heart syndrome in 47, pulmonary atresia with intact ventricular septum in 32, tricuspid valve atresia in 35, and other complex univentricular heart defects in 219 patients (right dominant in 166, left dominant in 53). Results: There were three hospital deaths and 27 late deaths (five after TCPC). Six patients underwent takedown operation. Two hundred and thirty patients underwent TCPC, while 66 patients were waiting for TCPC. In five patients, completion of TCPC was contraindicated. A univariate analysis revealed that for patients less than six months old, diagnoses besides tricuspid atresia, right ventricular morphology, mean pulmonary arterial pressure, pulmonary vascular resistance, ventricular end-diastolic pressure, atrioventricular valve regurgitation greater than moderate, atrioventricular valvuloplasty/valve replacement in concomitant procedure, and total anomalous pulmonary venous connection repair in concomitant procedure were significant predictors of death, takedown, or out of indication for completion of TCPC. A stepwise logistic regression analysis showed that mean pulmonary arterial pressure and heterotaxy were independent predictors. Conclusions: The staged strategy used for all Fontan candidates provides excellent clinical results. The main risk factor for death, takedown, or out of indication for completion of TCPC was elevated pulmonary arterial pressure. Appropriate surgical interventions such as atrioventricular valvuloplasty and total anomalous pulmonary venous connection repair, before and/or on BDG for the control of pulmonary circulation are of great importance to prevent elevation of pulmonary arterial pressure.
Key Words: Bidirectional Glenn procedure; Fontan; Pulmonary arterial pressure
1. Introduction
The Glenn operation involving anastomosis of the superior vena cava to the pulmonary artery, has been performed for palliative operations of many cyanotic congenital heart diseases in addition to the single ventricle since the 1960s [1]. The bidirectional Glenn procedure (BDG) involving bidirectional superior cavopulmonary anastomosis, has been mainly performed instead of the classical Glenn shunt (unidirectional superior cavopulmonary anastomosis) [2,3]. This operation improves efficiency of gas exchange without volume or pressure overload of the ventricle unlike the systemic-pulmonary arterial shunt or the pulmonary trunk band. Following the clinical introduction of the concept of total cavopulmonary connection (TCPC) [4], BDG has been performed as a partial procedure of TCPC, or a prior procedure to staged TCPC (staged strategy) [5–7].
BDG is a useful intermediate palliative procedure before the Fontan operation. For high-risk candidates, introduction of BDG preceding Fontan operation (TCPC) may extend indications for the Fontan procedure, and revealed excellent clinical results [5–7]. Introduction of BDG to low-risk Fontan candidates would improve clinical outcomes. Over the last decade, not only high-risk Fontan candidates, but all candidates underwent BDG and staged TCPC in our hospital. In the present study, we reviewed our experiences of the staged strategy for all Fontan candidates.
2. Methods
2.1. Patient information
Three hundred and thirty-three consecutive patients underwent BDG at Fukuoka Children's Hospital Medical Center from 1992 to 2004. Patient age ranged from 42 days to 16 years old (median, 15 months). Thirty-three patients were less than six months old, and 13 were less than three months old. Diagnoses included hypoplastic left heart syndrome in 47, pulmonary atresia with intact ventricular septum in 32, tricuspid valve atresia in 35, other complex univentricular heart defects in 219 patients (right dominant in 166, left dominant in 53). Precedent surgeries of BDG included systemic-pulmonary shunt in 167 patients, pulmonary artery banding in 81 patients, atrioventricular valvuloplasty or valve replacement in 13 patients, repair of total anomalous pulmonary venous connection in 12 patients, atrial septectomy in 64 patients, repair of coarctation or interrupted aortic arch in 18 patients, repair of Cor triatriatum in one patient, Brock operation in one patient, palliative arterial switch operation in one patient, tricuspid valve closure due to infective endocarditis in one patient, and Norwood or Norwood-like operation in 42 patients (right ventricular-pulmonary artery conduit modification [8] in 26 patients). Informed consent for operation and cardiac catheterization, and our strategy that all Fontan candidates undergo BDG and staged TCPC in our hospital was obtained from all parents of the children.
2.2. Operative techniques
All patients underwent surgery using median sternotomy and cardiopulmonary bypass with moderate hypothermia. Cardiopulmonary bypass was instituted by a heart-lung machine consisting of a roller pump and a membrane oxygenator. Myocardial protection was achieved using cold crystalloid cardioplegic solution containing 5% albumin (modified Kyushu University solution) combined with topical cooling, when cardiac arrest was necessary. Bidirectional cavopulmonary shunt was performed by direct end-to-side anastomosis between the superior vena cava and the pulmonary artery. When bilateral superior venae cavae were present, bidirectional cavopulmonary anastomoses were done in a separate fashion.
Concomitant procedures included bilateral BDG in 93 patients, total cavopulmonary shunt in 11 patients, augmentation and plasty of the pulmonary artery in 125 patients (unifocalization in two patients), atrioventricular valvuloplasty or valve replacement in 74 patients, repair of total anomalous pulmonary venous connection in 36 patients, atrial septectomy in 92 patients, Damus-Kaye-Stansel operation in 19 patients, Norwood or Norwood-like operation in 10 patients, and plasty of the ascending aorta in one patient.
Additional pulmonary blood flow was maintained in 163 patients. Systemic-pulmonary shunt was maintained in 50 patients, and ventricular-pulmonary shunt was maintained in 113 patients (main pulmonary trunk in 101, right ventricular-pulmonary artery conduit in 12). Additional flow was adjusted to elevate the superior vena cava pressure around 1 mmHg.
2.3. Statistical analysis
All preoperative and intraoperative variables were first analyzed using a univariate analysis to determine whether any single factor influenced problematic cases for mortality and morbidity (operative death, late death, takedown of BDG, or out of indication for completion of TCPC). A P-value of <0.05 was considered statistically significant. Continuous variables were expressed as means ± standard deviation or median (25%, 75%), and were analyzed using the Mann-Whitney U test. Categoric variables were presented as case numbers, and were analyzed with the 2 test or Fisher exact test when appropriate. A stepwise logistic regression analysis was performed to evaluate independent risk factors for problematic cases. Statistical analysis was performed with the SAS software, version 8.2 (SAS Inc).
3. Results
Clinical results following BDG are summarized in Fig. 1. A total of 230 patients underwent TCPC at a mean duration after BDG of 23 months, and 66 patients were waiting for TCPC. For the inferior cavopulmonary anastomosis, the lateral tunnel technique was performed in 17 patients, the intracardiac conduit approach using a 16- or 20-mm polytetrafluoroethylene graft was performed in four patients, and the extracardiac conduit approach using a 16-, 18- or 20-mm polytetrafluoroethylene graft was performed in 209 patients. Fenestration was created in three patients. Following BDG, three patients died in hospital due to hypoxia (two patients) or pulmonary venous obstruction (one patient). Twenty-two patients involved late death due to upper respiratory infection (12 patients), heart failure (five patients), arrhythmia (four patients), or cerebral infarction (one patient). Six patients underwent takedown, six patients were contraindicated completion of TCPC due to ventricular dysfunction (one patient), high pulmonary arterial pressure (one patient), poor development of pulmonary arteries (one patient), hepatitis (one patient), or non-cardiac malformation (two patients), and five patients were late death after staged TCPC due to heart failure (three patients), upper respiratory infection (one patient), or hepatitis (one patient). A total of 42 patients were problematic cases. No patient died in hospital after staged TCPC. Fontan-achievement rate was 88.9%, and the 10-year survival rate was 89.8% (Fig. 2).
A univariate analysis revealed that age less than 6 months old (P=0.037), diagnosis besides tricuspid atresia (P=0.0127), right ventricular morphology (P=0.0097), mean pulmonary arterial pressure (P<0.0001), pulmonary vascular resistance (P=0.0015), ventricular end-diastolic pressure (P=0.0223), atrioventricular valve regurgitation greater than moderate (P=0.0027), atrioventricular valvuloplasty or valve replacement in concomitant procedure (P=0.0402), and repair of total anomalous pulmonary venous connection in concomitant procedure (P=0.0075) were significant predictors of problematic cases (Table 1). A stepwise logistic regression analysis was performed for 281 cases in whom all values were available, and showed that mean pulmonary arterial pressure (P<0.0001; odds ratio [OR], 1.143; 95% confidence interval [CI], 1.070–1.221) and heterotaxy (P=0.0322; OR, 4.184; 95% CI, 0.819–0.935) were independent predictors of problematic cases.
4. Discussion
Clinical results of the 333 experiences of BDG using the proposed strategy that all Fontan candidates underwent BDG and staged TCPC were satisfactory, and promising. Fontan-achievement rate was 88.9%, and the 10-year survival rate was 89.8%. The main risk factor for death, takedown, or out of indication for completion of TCPC was elevated pulmonary arterial pressure. To the best of our knowledge, this is the largest clinical report of BDG in Fontan candidates who were treated with the staged strategy in a single institute. The main objective of this study was to re-elucidate the significance of the introduction of BDG in Fontan candidates.
Current significances of BDG in an operative strategy are: (1) shunt operation increases pulmonary blood flow without volume overload of the ventricle, (2) feasibility in correcting systemic venous return disorder or anomalous pulmonary venous connection, if complicated, and (3) clinical effectiveness to be used as the preceding operation of TCPC in high-risk Fontan candidates [5–7]. We previously reported correction of afterload mismatch during the interval period between BDG and staged TCPC [9], and minimization of afterload mismatch by cavopulmonary anastomosis on staged TCPC [10] using the approximation method of the end-systolic elastance (contractility) and the effective arterial elastance (afterload) validated by a canine right-heart-bypass model with a conductance catheter [10]. We also speculated that the staged strategy might avoid the deleterious effect of a sudden decrease in the diastolic ventricular volume, which might be fatal in some high-risk patients [7]. From these viewpoints, the staged strategy (BDG and staged TCPC) for all Fontan candidates was adopted in our hospital, and any concomitant procedures were terminated on BDG as far as possible. Although the staged strategy inherently has the disadvantage of re-operation, this strategy enables TCPC with an extracardiac conduit under the beating heart in almost all patients [11].
Fenestration of the Fontan circuit has been reported to decrease postoperative morbidity and mortality rates and the length of hospital stay, and the routine use of fenestration was comparatively introduced in many institutions [12–14]. The benefit of fenestration is attributable to an increase in [6] cardiac output resulting from the right-to-left shunt at the atrial level. However, fenestration inherently involves lower systemic oxygenation, and then a potential need for closure of shunt. In this series, fenestration was created in only three patients on staged TCPC, and there was no hospital death after staged TCPC. The non-requirement of fenestration is one of the best advantages of the strategy, i.e. all Fontan candidates underwent BDG and staged TCPC.
The introduction of BDG reduces volume load of the ventricle, and would diminish arrhythmia and improve exercise performance. Long-term survival and quality of life may conceivably be improved as well. BDG should be performed between three to six months to achieve maximum benefits [15]. We confirmed the use of this concept for urgent cases complicated with severe lesions such as atrioventricular valve regurgitation and/or total anomalous pulmonary venous connection. Thirty-three patients less than six months old underwent BDG, and 13 other patients were less than three months old in this series. However, we consider that BDG could be performed at more than six months old up to two years old [16], in elective cases from the point of view of safety for invasion by operation and cardiopulmonary bypass.
The role of additional pulmonary blood flow after BDG remains unclear [17–19]. The problem of volume overload to the ventricle and the expecting effect to increase the saturation level, and to promote pulmonary artery growth are always controversial. However, additional pulmonary blood flow is considered to be necessary for children who suffer from any problems of unexpected desaturation. We previously reported the comparative study of the ventricular performance after BDG and stage TCPC in hypoplastic left heart syndrome patients who underwent Norwood procedure with right ventricular-pulmonary artery conduit and Norwood procedure with systemic-pulmonary shunt [20]. We mentioned in this repot that the large systemic right ventricular volume whose patients underwent the Norwood procedure with right ventricular-pulmonary artery conduit after BDG and TCPC would be due to volume overload by the additional pulmonary blood flow. Although additional pulmonary blood flow was not a significant risk factor in this series, further studies comparing patients with or without a systemic-to-pulmonary shunt and with or without a forward flow from the ventricle are required.
Incidence of pulmonary arteriovenous fistula increases with time, and desaturation progresses in the long term after BDG. Quality of life in patients after Blalock-Taussig shunt operation would be better than that in patients after BDG, as BDG is not used as the final operation for patients who cannot be completed by the Fontan circulation. Therefore, indication of BDG should be decided according to the surgical strategy aiming at the Fontan operation. In this clinical report, elevated pulmonary arterial pressure was the most important significant factor for risks of death, takedown, or out of indication for completion of TCPC, as revealed by previous reports [6,7]. Young age on operation and total anomalous pulmonary venous connection were also important risk factors, and these results were well comparable to previous other reports [21–23]. Atrioventricular valve regurgitation which was a risk factor in our series was controversial in some reports [24,25]. However, atrioventricular valvuloplasty should be performed when atrioventricular valve regurgitation is more than moderate to control pulmonary circulation [7]. Both total anomalous pulmonary venous connection repair and atrioventricular valvuloplasty, before and/or on BDG are of great importance to prevent elevation of pulmonary arterial pressure.
Recently, surgical treatments of single ventricular morphology aiming at Fontan operation have dramatically progressed due to improvements in treatment strategies, especially the introduction of BDG preceding TCPC. In our experiences, Fontan-achievement rate which was about 20% of that 20 years ago, improved to almost 90% in the last decade. Further expansion of BDG and establishment of a treatment system aiming at improving quality of life in Fontan candidates are expected.
In conclusion, the staged strategy for all Fontan candidates provided excellent clinical results. The main risk factor for death, takedown, or out of indication for completion of TCPC was elevated pulmonary arterial pressure. Appropriate surgical interventions such as atrioventricular valvuloplasty and total anomalous pulmonary venous connection repair, before and/or on BDG for the control of pulmonary circulation are of great importance to prevent elevation of pulmonary arterial pressure.
Acknowledgements
This study was prepared in consultation with Tomomi Yamada, MS, Department of Medical Information Science Kyushu University Hospital, for statistical analyses.
References
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b Department of Cardiovascular Surgery, Kyushu University Fukuoka, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
Presented at the joint 19th Annual Meeting of the European Association for Cardio-thoracic Surgery and the 13th Annual Meeting of the European Society of Thoracic Surgeons, Barcelona, Spain, September 25–28, 2005.
Abstract
Objective: Introduction of the bidirectional Glenn procedure (BDG) in low-risk Fontan candidates would improve clinical outcomes. Over the last decade, not only high-risk Fontan candidates, but all candidates underwent BDG and staged Fontan operation (TCPC) in our hospital. Methods: Three hundred and thirty-three consecutive patients (age range, 42 days to 16 years old) underwent BDG at Fukuoka Children's Hospital Medical Center from 1992 to 2004. Diagnoses included hypoplastic left heart syndrome in 47, pulmonary atresia with intact ventricular septum in 32, tricuspid valve atresia in 35, and other complex univentricular heart defects in 219 patients (right dominant in 166, left dominant in 53). Results: There were three hospital deaths and 27 late deaths (five after TCPC). Six patients underwent takedown operation. Two hundred and thirty patients underwent TCPC, while 66 patients were waiting for TCPC. In five patients, completion of TCPC was contraindicated. A univariate analysis revealed that for patients less than six months old, diagnoses besides tricuspid atresia, right ventricular morphology, mean pulmonary arterial pressure, pulmonary vascular resistance, ventricular end-diastolic pressure, atrioventricular valve regurgitation greater than moderate, atrioventricular valvuloplasty/valve replacement in concomitant procedure, and total anomalous pulmonary venous connection repair in concomitant procedure were significant predictors of death, takedown, or out of indication for completion of TCPC. A stepwise logistic regression analysis showed that mean pulmonary arterial pressure and heterotaxy were independent predictors. Conclusions: The staged strategy used for all Fontan candidates provides excellent clinical results. The main risk factor for death, takedown, or out of indication for completion of TCPC was elevated pulmonary arterial pressure. Appropriate surgical interventions such as atrioventricular valvuloplasty and total anomalous pulmonary venous connection repair, before and/or on BDG for the control of pulmonary circulation are of great importance to prevent elevation of pulmonary arterial pressure.
Key Words: Bidirectional Glenn procedure; Fontan; Pulmonary arterial pressure
1. Introduction
The Glenn operation involving anastomosis of the superior vena cava to the pulmonary artery, has been performed for palliative operations of many cyanotic congenital heart diseases in addition to the single ventricle since the 1960s [1]. The bidirectional Glenn procedure (BDG) involving bidirectional superior cavopulmonary anastomosis, has been mainly performed instead of the classical Glenn shunt (unidirectional superior cavopulmonary anastomosis) [2,3]. This operation improves efficiency of gas exchange without volume or pressure overload of the ventricle unlike the systemic-pulmonary arterial shunt or the pulmonary trunk band. Following the clinical introduction of the concept of total cavopulmonary connection (TCPC) [4], BDG has been performed as a partial procedure of TCPC, or a prior procedure to staged TCPC (staged strategy) [5–7].
BDG is a useful intermediate palliative procedure before the Fontan operation. For high-risk candidates, introduction of BDG preceding Fontan operation (TCPC) may extend indications for the Fontan procedure, and revealed excellent clinical results [5–7]. Introduction of BDG to low-risk Fontan candidates would improve clinical outcomes. Over the last decade, not only high-risk Fontan candidates, but all candidates underwent BDG and staged TCPC in our hospital. In the present study, we reviewed our experiences of the staged strategy for all Fontan candidates.
2. Methods
2.1. Patient information
Three hundred and thirty-three consecutive patients underwent BDG at Fukuoka Children's Hospital Medical Center from 1992 to 2004. Patient age ranged from 42 days to 16 years old (median, 15 months). Thirty-three patients were less than six months old, and 13 were less than three months old. Diagnoses included hypoplastic left heart syndrome in 47, pulmonary atresia with intact ventricular septum in 32, tricuspid valve atresia in 35, other complex univentricular heart defects in 219 patients (right dominant in 166, left dominant in 53). Precedent surgeries of BDG included systemic-pulmonary shunt in 167 patients, pulmonary artery banding in 81 patients, atrioventricular valvuloplasty or valve replacement in 13 patients, repair of total anomalous pulmonary venous connection in 12 patients, atrial septectomy in 64 patients, repair of coarctation or interrupted aortic arch in 18 patients, repair of Cor triatriatum in one patient, Brock operation in one patient, palliative arterial switch operation in one patient, tricuspid valve closure due to infective endocarditis in one patient, and Norwood or Norwood-like operation in 42 patients (right ventricular-pulmonary artery conduit modification [8] in 26 patients). Informed consent for operation and cardiac catheterization, and our strategy that all Fontan candidates undergo BDG and staged TCPC in our hospital was obtained from all parents of the children.
2.2. Operative techniques
All patients underwent surgery using median sternotomy and cardiopulmonary bypass with moderate hypothermia. Cardiopulmonary bypass was instituted by a heart-lung machine consisting of a roller pump and a membrane oxygenator. Myocardial protection was achieved using cold crystalloid cardioplegic solution containing 5% albumin (modified Kyushu University solution) combined with topical cooling, when cardiac arrest was necessary. Bidirectional cavopulmonary shunt was performed by direct end-to-side anastomosis between the superior vena cava and the pulmonary artery. When bilateral superior venae cavae were present, bidirectional cavopulmonary anastomoses were done in a separate fashion.
Concomitant procedures included bilateral BDG in 93 patients, total cavopulmonary shunt in 11 patients, augmentation and plasty of the pulmonary artery in 125 patients (unifocalization in two patients), atrioventricular valvuloplasty or valve replacement in 74 patients, repair of total anomalous pulmonary venous connection in 36 patients, atrial septectomy in 92 patients, Damus-Kaye-Stansel operation in 19 patients, Norwood or Norwood-like operation in 10 patients, and plasty of the ascending aorta in one patient.
Additional pulmonary blood flow was maintained in 163 patients. Systemic-pulmonary shunt was maintained in 50 patients, and ventricular-pulmonary shunt was maintained in 113 patients (main pulmonary trunk in 101, right ventricular-pulmonary artery conduit in 12). Additional flow was adjusted to elevate the superior vena cava pressure around 1 mmHg.
2.3. Statistical analysis
All preoperative and intraoperative variables were first analyzed using a univariate analysis to determine whether any single factor influenced problematic cases for mortality and morbidity (operative death, late death, takedown of BDG, or out of indication for completion of TCPC). A P-value of <0.05 was considered statistically significant. Continuous variables were expressed as means ± standard deviation or median (25%, 75%), and were analyzed using the Mann-Whitney U test. Categoric variables were presented as case numbers, and were analyzed with the 2 test or Fisher exact test when appropriate. A stepwise logistic regression analysis was performed to evaluate independent risk factors for problematic cases. Statistical analysis was performed with the SAS software, version 8.2 (SAS Inc).
3. Results
Clinical results following BDG are summarized in Fig. 1. A total of 230 patients underwent TCPC at a mean duration after BDG of 23 months, and 66 patients were waiting for TCPC. For the inferior cavopulmonary anastomosis, the lateral tunnel technique was performed in 17 patients, the intracardiac conduit approach using a 16- or 20-mm polytetrafluoroethylene graft was performed in four patients, and the extracardiac conduit approach using a 16-, 18- or 20-mm polytetrafluoroethylene graft was performed in 209 patients. Fenestration was created in three patients. Following BDG, three patients died in hospital due to hypoxia (two patients) or pulmonary venous obstruction (one patient). Twenty-two patients involved late death due to upper respiratory infection (12 patients), heart failure (five patients), arrhythmia (four patients), or cerebral infarction (one patient). Six patients underwent takedown, six patients were contraindicated completion of TCPC due to ventricular dysfunction (one patient), high pulmonary arterial pressure (one patient), poor development of pulmonary arteries (one patient), hepatitis (one patient), or non-cardiac malformation (two patients), and five patients were late death after staged TCPC due to heart failure (three patients), upper respiratory infection (one patient), or hepatitis (one patient). A total of 42 patients were problematic cases. No patient died in hospital after staged TCPC. Fontan-achievement rate was 88.9%, and the 10-year survival rate was 89.8% (Fig. 2).
A univariate analysis revealed that age less than 6 months old (P=0.037), diagnosis besides tricuspid atresia (P=0.0127), right ventricular morphology (P=0.0097), mean pulmonary arterial pressure (P<0.0001), pulmonary vascular resistance (P=0.0015), ventricular end-diastolic pressure (P=0.0223), atrioventricular valve regurgitation greater than moderate (P=0.0027), atrioventricular valvuloplasty or valve replacement in concomitant procedure (P=0.0402), and repair of total anomalous pulmonary venous connection in concomitant procedure (P=0.0075) were significant predictors of problematic cases (Table 1). A stepwise logistic regression analysis was performed for 281 cases in whom all values were available, and showed that mean pulmonary arterial pressure (P<0.0001; odds ratio [OR], 1.143; 95% confidence interval [CI], 1.070–1.221) and heterotaxy (P=0.0322; OR, 4.184; 95% CI, 0.819–0.935) were independent predictors of problematic cases.
4. Discussion
Clinical results of the 333 experiences of BDG using the proposed strategy that all Fontan candidates underwent BDG and staged TCPC were satisfactory, and promising. Fontan-achievement rate was 88.9%, and the 10-year survival rate was 89.8%. The main risk factor for death, takedown, or out of indication for completion of TCPC was elevated pulmonary arterial pressure. To the best of our knowledge, this is the largest clinical report of BDG in Fontan candidates who were treated with the staged strategy in a single institute. The main objective of this study was to re-elucidate the significance of the introduction of BDG in Fontan candidates.
Current significances of BDG in an operative strategy are: (1) shunt operation increases pulmonary blood flow without volume overload of the ventricle, (2) feasibility in correcting systemic venous return disorder or anomalous pulmonary venous connection, if complicated, and (3) clinical effectiveness to be used as the preceding operation of TCPC in high-risk Fontan candidates [5–7]. We previously reported correction of afterload mismatch during the interval period between BDG and staged TCPC [9], and minimization of afterload mismatch by cavopulmonary anastomosis on staged TCPC [10] using the approximation method of the end-systolic elastance (contractility) and the effective arterial elastance (afterload) validated by a canine right-heart-bypass model with a conductance catheter [10]. We also speculated that the staged strategy might avoid the deleterious effect of a sudden decrease in the diastolic ventricular volume, which might be fatal in some high-risk patients [7]. From these viewpoints, the staged strategy (BDG and staged TCPC) for all Fontan candidates was adopted in our hospital, and any concomitant procedures were terminated on BDG as far as possible. Although the staged strategy inherently has the disadvantage of re-operation, this strategy enables TCPC with an extracardiac conduit under the beating heart in almost all patients [11].
Fenestration of the Fontan circuit has been reported to decrease postoperative morbidity and mortality rates and the length of hospital stay, and the routine use of fenestration was comparatively introduced in many institutions [12–14]. The benefit of fenestration is attributable to an increase in [6] cardiac output resulting from the right-to-left shunt at the atrial level. However, fenestration inherently involves lower systemic oxygenation, and then a potential need for closure of shunt. In this series, fenestration was created in only three patients on staged TCPC, and there was no hospital death after staged TCPC. The non-requirement of fenestration is one of the best advantages of the strategy, i.e. all Fontan candidates underwent BDG and staged TCPC.
The introduction of BDG reduces volume load of the ventricle, and would diminish arrhythmia and improve exercise performance. Long-term survival and quality of life may conceivably be improved as well. BDG should be performed between three to six months to achieve maximum benefits [15]. We confirmed the use of this concept for urgent cases complicated with severe lesions such as atrioventricular valve regurgitation and/or total anomalous pulmonary venous connection. Thirty-three patients less than six months old underwent BDG, and 13 other patients were less than three months old in this series. However, we consider that BDG could be performed at more than six months old up to two years old [16], in elective cases from the point of view of safety for invasion by operation and cardiopulmonary bypass.
The role of additional pulmonary blood flow after BDG remains unclear [17–19]. The problem of volume overload to the ventricle and the expecting effect to increase the saturation level, and to promote pulmonary artery growth are always controversial. However, additional pulmonary blood flow is considered to be necessary for children who suffer from any problems of unexpected desaturation. We previously reported the comparative study of the ventricular performance after BDG and stage TCPC in hypoplastic left heart syndrome patients who underwent Norwood procedure with right ventricular-pulmonary artery conduit and Norwood procedure with systemic-pulmonary shunt [20]. We mentioned in this repot that the large systemic right ventricular volume whose patients underwent the Norwood procedure with right ventricular-pulmonary artery conduit after BDG and TCPC would be due to volume overload by the additional pulmonary blood flow. Although additional pulmonary blood flow was not a significant risk factor in this series, further studies comparing patients with or without a systemic-to-pulmonary shunt and with or without a forward flow from the ventricle are required.
Incidence of pulmonary arteriovenous fistula increases with time, and desaturation progresses in the long term after BDG. Quality of life in patients after Blalock-Taussig shunt operation would be better than that in patients after BDG, as BDG is not used as the final operation for patients who cannot be completed by the Fontan circulation. Therefore, indication of BDG should be decided according to the surgical strategy aiming at the Fontan operation. In this clinical report, elevated pulmonary arterial pressure was the most important significant factor for risks of death, takedown, or out of indication for completion of TCPC, as revealed by previous reports [6,7]. Young age on operation and total anomalous pulmonary venous connection were also important risk factors, and these results were well comparable to previous other reports [21–23]. Atrioventricular valve regurgitation which was a risk factor in our series was controversial in some reports [24,25]. However, atrioventricular valvuloplasty should be performed when atrioventricular valve regurgitation is more than moderate to control pulmonary circulation [7]. Both total anomalous pulmonary venous connection repair and atrioventricular valvuloplasty, before and/or on BDG are of great importance to prevent elevation of pulmonary arterial pressure.
Recently, surgical treatments of single ventricular morphology aiming at Fontan operation have dramatically progressed due to improvements in treatment strategies, especially the introduction of BDG preceding TCPC. In our experiences, Fontan-achievement rate which was about 20% of that 20 years ago, improved to almost 90% in the last decade. Further expansion of BDG and establishment of a treatment system aiming at improving quality of life in Fontan candidates are expected.
In conclusion, the staged strategy for all Fontan candidates provided excellent clinical results. The main risk factor for death, takedown, or out of indication for completion of TCPC was elevated pulmonary arterial pressure. Appropriate surgical interventions such as atrioventricular valvuloplasty and total anomalous pulmonary venous connection repair, before and/or on BDG for the control of pulmonary circulation are of great importance to prevent elevation of pulmonary arterial pressure.
Acknowledgements
This study was prepared in consultation with Tomomi Yamada, MS, Department of Medical Information Science Kyushu University Hospital, for statistical analyses.
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