The effect of antegrade pulmonary blood flow following a late bidirectional Glenn procedure

The effect of antegrade pulmonary blood flow following a late bidirectional Glenn procedure Abstract OBJECTIVES The effect of antegrade pulmonary blood flow (APBF) has never been studied in the bidirectional Glenn (BDG) procedure performed late. METHODS Records of 112 consecutive patients who had a BDG procedure during a 10-year period were reviewed retrospectively. The patients were divided into 2 groups based on whether APBF occurred following the BDG procedure (APBF group, n = 81) or not (non-APBF group, n = 31). The median age at the BDG procedure was 6.16 ± 3.93 years in the APBF group and 6.12 ± 4.40 years in the non-APBF group. RESULTS Demographics and pre- and intraoperative variables were comparable for both groups. Follow-up data were obtained for patients at the BDG stage and for those who had undergone the Fontan completion. Both oxygen saturation levels (81.72 ± 1.976% vs 78.32 ± 2.344%, P < 0.01) and pulmonary pressure (13.59 ± 1.376 mmHg vs 12.90 ± 0.978 mmHg, P = 0.012) were higher in the APBF group immediately after the BDG procedure. Both the duration of chest tube drainage and the total length of stay were longer in the APBF group. The pre-Glenn measurements showed a mean McGoon ratio of 1.68 ± 0.114 in the APBF group and 1.67 ± 0.098 in the non-APBF group (P = 0.474). The McGoon ratios measured before the Fontan procedure were also comparable (1.669 ± 0.726 vs 1.685 ± 0.669, P = 0.576). At the pre-Fontan measurement, there was no significant difference in mean pulmonary artery pressures between the groups (13.72 ± 1.368 vs 13.50 ± 1.265, P = 0.653). Fifty-nine patients underwent the Fontan completion (43 from the APBF group and 16 from the non-APBF group) procedure with a median of 1.2 (APBF group) and 1.4 (non-APBF group) years after the BDG procedure. No significant differences between groups were observed in arterial oxygen saturation levels, incidence of systemic atrioventricular valve regurgitation or ventricular dysfunction in survivors at the last follow-up visit. CONCLUSIONS The BDG procedure can be safely performed at a relatively older age (∼6 years). APBF increases oxygen saturation but also prolongs pleural effusion and hospital stay. Medium-term outcomes and the Fontan completion rate in the APBF and the non-APBF groups are comparable. Further large studies and long-term follow-up are needed to clarify the effect of APBF in patients who have the late BDG. Bidirectional Glenn, Single ventricle, Antegrade pulmonary blood flow INTRODUCTION The bidirectional Glenn (BDG) operation is used as a standard palliative procedure in the staged surgical approach for palliation of a physiologically univentricular heart [1, 2]. Controversy remains regarding whether additional antegrade pulmonary blood flow (APBF) is beneficial in combination with BDG. The arguments for leaving an accessory source of pulsatile pulmonary blood flow include possible improvement in postoperative arterial oxygen saturation (SaO2) levels, promotion of the growth of pulmonary arteries and possible prevention of long-term development of an intrapulmonary shunt [3, 4]. However, APBF may also diminish ventricular unloading by the BDG procedure and elevate the systemic venous pressure, resulting in postoperative complications such as prolonged pleural effusion [5–7]. Despite the discrepancies in their conclusions, most current studies were performed in Europe and North America and focused on patient populations that were predominantly infants (<1 year), because the benefits of BDG are reduced in older children [8, 9]. However, for social and financial reasons, most BDG procedures performed in developing countries such as China and India occur when the children are much older, and this large group of patients is understudied [10, 11]. The objective of our study was to report our experience with the late BDG procedure and delineate the effect of APBF in this group of patients (average age 6.15 years). METHODS Patients Clinical data of patients undergoing the BDG procedure for palliation of a functionally univentricular heart were reviewed retrospectively. Two groups were formulated. This study was approved by the ethics committee of Guangzhou General Hospital of Guangzhou Military Command. From January 2006 to April 2010, 127 patients underwent BDG at our institution. Twelve patients who underwent repair of 1.5 ventricles and 3 patients who received a modified Blalock–Taussig shunt after the BDG procedure were excluded from this study. The 112 patients enrolled in this study were divided into 2 groups based on whether APBF existed following the BDG procedure (APBF group, n = 81) or not (non-APBF group, n = 31). Previous palliative procedures included modified Blalock–Taussig shunt placement in 10 patients and pulmonary artery banding in 1 patient. The median age at the BDG procedure was 6.16 ± 3.93 years (range 9 months to 18.4 years) in the APBF group (n = 81) and 6.12 ± 4.40 years (range 9 months to 21.5 years) in the non-APBF group (n = 31). There were no significant differences in age, gender, body weight, body surface area, McGoon index or pulmonary artery index between the 2 groups. Bidirectional Glenn The timing of the BDG procedure did not occur at a set age in our institution but rather was determined largely by when the patient presented to us. Treatment for many patients in developing countries can be delayed for social and financial reasons [10, 11]. All the surgical procedures were performed through a median sternotomy. Twenty-seven patients underwent the BDG procedure with the assistance of cardiopulmonary bypass and the remaining 85 patients underwent the BDG procedure with a passive shunt between the superior vena cava (SVC) and the right atrium. Any other forms of pulmonary blood flow such as major systemic to pulmonary collaterals, patent ductus arteriosus and previously placed modified Blalock–Taussig shunts were taken down. The SVC was anastomosed to the pulmonary artery branch in an end-to-side fashion. The bilateral BDG procedures were performed in 18 patients with significant persistent left SVC. The azygos vein was ligated in all cases to prevent untoward shunting from the SVC to the inferior vena cava vein. Three surgeons (M.T., X.W. and W.Z.) in our group performed the procedures. The decision to preserve the APBF or not was made intraoperatively. Both the patient’s disease and the surgeon’s preferences played a role in the decision. In general, APBF was more inclined to be preserved in patients with younger age, smaller pulmonary vessels, lower saturations and low pulmonary arterial pressure before the BDG procedure was performed. However, as listed in Tables 1 and 2, no significant differences were observed in these preoperative parameters. Table 1: Patient characteristics and diagnosis at the time of the bidirectional Glenn procedure Characteristics  APBF  Non-APBF  P-value  Age (years), mean ± SD  6.16 ± 3.93  6.12 ± 4.40  0.880  Male:female  44:37  15:16  0.574  Body weight (kg), mean ± SD  21.82 ± 10.17  20.00 ± 9.61  0.863  BSA (m2), mean ± SD  0.794 ± 0.28  0.813 ± .0.28  0.862  PAI (mm2/m2), mean ± SD  250.96 ± 67.11  252.65 ± 53.32  0.088  Single ventricle, n (%)  15 (18.5)  7 (22.5)  0.628   Left ventricle morphology  5 (6.2)  2 (6.5)  1.000   Right ventricle morphology  5 (6.2)  2 (6.5)  1.000   Biventricular or uncertain  5 (6.2)  3 (9.7)  0.683  DORV, n (%)  11 (13.6)  5 (16.1)  0.766  TA, n (%)  10 (12.3)  3 (9.7)  1.000  TGA, n (%)  9 (11.1)  2 (6.5)  0.724  Ebstein’s anomaly, n (%)  5 (6.2)  2 (6.5)  1.000  CAVC, n (%)  11 (13.6)  4 (12.9)  1.000  PA, n (%)  12 (14.8)  3 (9.7)  0.554  Others, n (%)  8 (9.9)  5 (16.1)  0.344  Characteristics  APBF  Non-APBF  P-value  Age (years), mean ± SD  6.16 ± 3.93  6.12 ± 4.40  0.880  Male:female  44:37  15:16  0.574  Body weight (kg), mean ± SD  21.82 ± 10.17  20.00 ± 9.61  0.863  BSA (m2), mean ± SD  0.794 ± 0.28  0.813 ± .0.28  0.862  PAI (mm2/m2), mean ± SD  250.96 ± 67.11  252.65 ± 53.32  0.088  Single ventricle, n (%)  15 (18.5)  7 (22.5)  0.628   Left ventricle morphology  5 (6.2)  2 (6.5)  1.000   Right ventricle morphology  5 (6.2)  2 (6.5)  1.000   Biventricular or uncertain  5 (6.2)  3 (9.7)  0.683  DORV, n (%)  11 (13.6)  5 (16.1)  0.766  TA, n (%)  10 (12.3)  3 (9.7)  1.000  TGA, n (%)  9 (11.1)  2 (6.5)  0.724  Ebstein’s anomaly, n (%)  5 (6.2)  2 (6.5)  1.000  CAVC, n (%)  11 (13.6)  4 (12.9)  1.000  PA, n (%)  12 (14.8)  3 (9.7)  0.554  Others, n (%)  8 (9.9)  5 (16.1)  0.344  APBF: anterior pulmonary blood flow; BSA: body surface area; CAVC: complete atrioventricular canal; DORV: double outlets of the right ventricle; PA: pulmonary atresia; PAI: pulmonary artery (Nakada) index; SD: standard deviation; TA: tricuspid atresia; TGA: transposition of the great arteries. Table 2: Perioperative data Characteristics  APBF  Non-APBF  P-value  Pre-BDG PA pressure, mean ± SD  11.37 ± 1.336  11.48 ± 1.208  0.681  Pre-BDG McGoon index, mean ± SD  1.68 ± 0. 114  1.67 ± 0.098  0.474  Post-BDG PA pressure, mean ± SD  13.59 ± 1.376  12.90 ± 0.978  0.012  Duration of ventilation (days), mean ± SD  1.63 ± 2.106  1.39 ± 1.054  0.542  Chest tube duration (days), mean ± SD  7.42 ± 4.477  4.35 ± 1.561  <0.01  Chylothorax, n (%)  5 (6.2)  3 (9.7)  0.683  ICU stay (days), mean ± SD  4.94 ± 7.703  8.13 ± 15.126  0.144  Length of stay (days), mean ± SD  17.30 ± 12.418  11.03 ± 3.381  <0.01  Hospital readmissions, n (%)  3 (3.7)  1 (3.2)  1.000  Characteristics  APBF  Non-APBF  P-value  Pre-BDG PA pressure, mean ± SD  11.37 ± 1.336  11.48 ± 1.208  0.681  Pre-BDG McGoon index, mean ± SD  1.68 ± 0. 114  1.67 ± 0.098  0.474  Post-BDG PA pressure, mean ± SD  13.59 ± 1.376  12.90 ± 0.978  0.012  Duration of ventilation (days), mean ± SD  1.63 ± 2.106  1.39 ± 1.054  0.542  Chest tube duration (days), mean ± SD  7.42 ± 4.477  4.35 ± 1.561  <0.01  Chylothorax, n (%)  5 (6.2)  3 (9.7)  0.683  ICU stay (days), mean ± SD  4.94 ± 7.703  8.13 ± 15.126  0.144  Length of stay (days), mean ± SD  17.30 ± 12.418  11.03 ± 3.381  <0.01  Hospital readmissions, n (%)  3 (3.7)  1 (3.2)  1.000  APBF: anterior pulmonary blood flow; BDG: bidirectional Glenn; ICU: intensive care unit; PA: pulmonary artery; SD: standard deviation. Statistical analysis Data were expressed as either the mean ± standard deviation or the median and range. Comparative univariate analysis was performed between the 2 groups of patients with the t-test for normally distributed continuous data. The χ2 test was used for ordinal data. The Kaplan–Meier survival estimates were plotted for the 2 groups and compared using a log-rank test. A P-value of <0.05 was considered significant. Statistical analyses were performed using SPSS 22.0 software (SPSS, Chicago, IL, USA). RESULTS Patient demographics Patient demographics are listed in Table 1. No significant differences between groups were noted in terms of age, body weight, body surface area, pulmonary artery index, pulmonary artery pressure and the McGoon ratio before the BDG procedure. As listed in Table 1, the anatomical diagnosis was similar in both groups. Chest drainage, postoperative ventilation time and length of stay in the intensive care unit and in the hospital No significant difference was noted between groups in postoperative time on a ventilator or length of stay in the intensive care unit (Table 2). However, the APBF group had significantly longer time with a chest tube drain in place compared with the non-APBF group (7.42 ± 4.477 days vs 4.35 ± 1.561 days, P < 0.01). The APBF group also had a significantly longer hospital stay compared with the non-APBF group (17.30 ± 12.42 days vs 11.03 ± 3.38 days, P < 0.01). Pulmonary artery pressure and systemic arterial oxygen saturation The mean pre-BDG pulmonary artery pressure was comparable between the groups (11.37 ± 1.336 mmHg vs 11.48 ± 1.208 mmHg, P = 0.681). The mean pulmonary artery pressure after the BDG procedure was higher in the APBF group (13.59 ± 1.376 mmHg vs 12.90 ± 0.978 mmHg, P = 0.012). In patients undergoing a total cavopulmonary connection (TCPC) procedure, pre-TCPC pulmonary artery pressure was comparable between groups (13.72 ± 1.368 mmHg vs 13.50 ± 1.265 mmHg, P = 0.653). There was no significant difference in pre-BDG SaO2 (67.52 ± 5.662% vs 68.19 ± 4.658%, P = 0.556). The SaO2 levels in both the APBF and the non-APBF groups were significantly improved following the BDG procedure (Table 3). However, post-BDG SaO2 levels were higher in the APBF group compared with the non-APBF group (81.72 ± 1.976% vs 78.32 ± 2.344%, P < 0.01). Table 3: Analysis of pre- and postoperative systemic arterial saturation SaO2  APBF  Non-APBF  P-value  Pre-BDG, mean ± SD  67.52 ± 5.662  68.19 ± 4.658  0.556  Post-BDG, mean ± SD  81.72 ± 1.976  78.32 ± 2.344  <0.01  SaO2  APBF  Non-APBF  P-value  Pre-BDG, mean ± SD  67.52 ± 5.662  68.19 ± 4.658  0.556  Post-BDG, mean ± SD  81.72 ± 1.976  78.32 ± 2.344  <0.01  APBF: anterior pulmonary blood flow; BDG: bidirectional Glenn; SaO2: arterial oxygen saturation; SD: standard deviation. Follow-up There were no early postoperative deaths. Two patients died before reaching the Fontan completion: 1 in the APBF group and 1 in the non-APBF group. The patient in the APBF group had double outlets of the right ventricle, pulmonary stenosis and ventricular septal defect and died of uncertain causes at home 15 months after the BDG procedure. The patient in the non-APBF group had pulmonary atresia and died 11 months after an episode of pneumonia in a local hospital. The actuarial survival rate did not significantly differ between the groups (Fig. 1). Figure 1 View largeDownload slide The Kaplan–Meier survival curves for the 2 groups of patients following the bidirectional Glenn procedure. APBF: antegrade pulmonary blood flow. Figure 1 View largeDownload slide The Kaplan–Meier survival curves for the 2 groups of patients following the bidirectional Glenn procedure. APBF: antegrade pulmonary blood flow. Forty-three patients in the APBF group (53.8% of survivors) and 16 in the non-APBF group (53.3% of survivors) have since undergone the Fontan completion procedure. The average interval for the Fontan completion procedure was 1.629 ± 0.7377 years. There was no difference in the TCPC completion rate (53.8% vs 53.3%, P = 0.969) or in the interval between groups (1.630 ± 0.7096 vs 1.625 ± 0.8331 years, P = 0.981). One early death occurred in each group following the Fontan procedure. The patient in the APBF group with severe Ebstein’s anomaly and hypoplastic RV died 3 days after a fenestrated Fontan procedure of multiple organ failure. The patient in the non-APBF group with a single ventricle died 2 days after a fenestrated Fontan procedure of a massive intracranial haemorrhage. There were 2 late deaths in the APBF group following the Fontan procedure and no late deaths in the non-APBF group following the Fontan procedure. The actuarial survival rates did not differ significantly between the groups (Fig. 1). Systemic SaO2 levels at the last follow-up visit were comparable between the groups (78.67 ± 1.971% vs 77.81 ± 3.375%, P = 0.156). In patients who had undergone the Fontan procedure completion, there was no difference in the oxygen saturation levels between the APBF group and the non-APBF group, either immediately before (78.67 ± 2.089% vs 77.56 ± 3.222%, P = 0.110) or after (92.73 ± 1.814% vs 92.94 ± 0.988%, P = 0.644) the TCPC operation (Table 4). Table 4: Analysis of systemic arterial saturation at follow-up SaO2  APBF  Non-APBF  P-value  Last follow-up, mean ± SD  78.67 ± 1.971  77.81 ± 3.375  0.156  Pre-Fontan, mean ± SD  78.67 ± 2.089  77.56 ± 3.222  0.110  Post-Fontan, mean ± SD  92.73 ± 1.814  92.94 ± 0.988  0.644  SaO2  APBF  Non-APBF  P-value  Last follow-up, mean ± SD  78.67 ± 1.971  77.81 ± 3.375  0.156  Pre-Fontan, mean ± SD  78.67 ± 2.089  77.56 ± 3.222  0.110  Post-Fontan, mean ± SD  92.73 ± 1.814  92.94 ± 0.988  0.644  APBF: anterior pulmonary blood flow; SaO2: arterial oxygen saturation; SD: standard deviation. Postoperative echocardiographic data from the last follow-up examination are listed in Table 5. There was no significant difference in the degree of ventricular or atrioventricular valve dysfunction between the 2 groups. Good ventricular function was preserved in 50 (67.6%) patients in the APBF group and in 18 (58.1%) patients in the non-APBF group. Ventricular function was mildly depressed in 21 (25.9%) patients in the APBF group and in 6 (19.4%) patients in the non-APBF group. Ventricular function was moderately depressed in 6 (7.4%) patients in the APBF group and in 5 (16.1%) patients in the non-APBF group. Severely depressed ventricular function was present in 4 (4.9%) patients in the APBF group and in 2 (6.5%) patients in the non-APBF group. At the last follow-up examination, mild atrioventricular valve regurgitation (AVVR) was recorded in 15 (18.5%) patients in the APBF group and in 6 (19.4%) patients in the non-APBF group. Moderate AVVR was recorded in 13 (13.6%) patients in the APBF group and in 4 (12.9%) patients in the non-APBF group. Severe AVVR was recorded in 4 (4.9%) patients in the APBF group and in 2 (6.5%) patients in the non-APBF group. Table 5: Postoperative echocardiography data Parameters  APBF  Non-APBF  P-value  Ventricular function, n (%)   Normal  50 (67.6)  18 (58.1)  0.492   Mildly depressed  21 (25.9)  6 (19.4)   Moderately depressed  6 (7.4)  5 (16.1)   Severely depressed  4 (4.9)  2 (6.5)  AV regurgitation, n (%)   None  51 (63.0)  19 (61.3)  0.983   Mild  15 (18.5)  6 (19.4)   Moderate  13 (13.6)  4 (12.9)   Severe  4 (4.9)  2 (6.5)  Parameters  APBF  Non-APBF  P-value  Ventricular function, n (%)   Normal  50 (67.6)  18 (58.1)  0.492   Mildly depressed  21 (25.9)  6 (19.4)   Moderately depressed  6 (7.4)  5 (16.1)   Severely depressed  4 (4.9)  2 (6.5)  AV regurgitation, n (%)   None  51 (63.0)  19 (61.3)  0.983   Mild  15 (18.5)  6 (19.4)   Moderate  13 (13.6)  4 (12.9)   Severe  4 (4.9)  2 (6.5)  APBF: anterior pulmonary blood flow; AV: atrioventricular. Pulmonary artery pressures and the McGoon ratio were measured by cardiac catheterization before completion of the Fontan procedure. These patients exhibited no differences in pulmonary artery pressure (13.72 ± 1.368 vs 13.50 ± 1.265, P = 0.653) or McGoon ratio (1.669 ± 0.726 vs 1.685 ± 0.669, P = 0.576) after BDG between groups (Table 6). Table 6: Pre-Fontan cardiac catheterization data Parameters  APBF  Non-APBF  P-value  McGoon ratio, mean ± SD  1.669 ± 0.726  1.685 ± 0.669  0576  Pulmonary artery pressure (mmHg), mean ± SD  13.72 ± 1.368  13.50 ± 1.265  0.653  Major intrapulmonary shunt, n (%)  2 (4.7)  1 (6.3)  1.000  Parameters  APBF  Non-APBF  P-value  McGoon ratio, mean ± SD  1.669 ± 0.726  1.685 ± 0.669  0576  Pulmonary artery pressure (mmHg), mean ± SD  13.72 ± 1.368  13.50 ± 1.265  0.653  Major intrapulmonary shunt, n (%)  2 (4.7)  1 (6.3)  1.000  APBF: anterior pulmonary blood flow; SD: standard deviation. DISCUSSION Two rival strategies are currently used in the management of APBF at the time the BDG procedure is done. In one strategy, all sources of APBF including the main pulmonary arteries are interrupted; consequently, the SVC becomes the sole source of blood flow to the lungs [12]. In the other strategy, the APBF is preserved. During systole, the inferior vena cava blood return reaches the pulmonary arteries by pulsatile pulmonary ventricular contraction [13]. The theoretical advantages of APBF include increases in oxygen saturation, stimulation of pulmonary artery growth, increased Fontan completion rates [14] and alleviated formation of the intrapulmonary shunt owing to the supply of ‘hepatic factor’. On the other hand, the APBF compromises the reduced volume overload that results from the BDG procedure and is associated with cardiac dysfunction, ventricular enlargement and AVVR. Whether APBF should be maintained in the BDG procedure remains controversial. The effect of APBF on patient survival is still debated. Mainwaring et al. [15] reported a significantly higher late mortality rate in the APBF group (15.1% vs 4.4%) and recommended elimination of APBF at the time of BDG. In a study by van de Wal et al. [16] concerning 205 patients whose age range (mean age 5.6 years, range 26 days to 34.2 years) was similar to that of our patients, APBF was associated with a higher late mortality rate. In a study focusing on long-term outcomes, Chen et al. [17] reported higher 5- and 10-year survival rates in the APBF group compared with the non-APBF group (96% and 96% vs 88% and 82%, log rank P = 0.03). In this study, the mean age was 10.2 months (range 2.3–166.9 months) in the APBF group and 11.7 months (range 5.6–92.1 months) in the non-APBF group. In this study, no difference in survival was observed. In this study, a higher incidence of prolonged chest tube duration was noted in the APBF group, presumably due to increased central venous pressure. This increase resulted in a longer hospitalization course after the BDG procedure; however, after discharge from the hospital, there was no significant difference in hospital readmissions between the groups. An increase in the incidences of pleural effusion and chylothorax was also noted by other researchers [5, 7, 15, 18] despite the report by Caspi et al. [19]. A recent study [17] showed no difference in pleural effusion with or without APBF. The major aim of excluding all other sources of pulmonary blood flow at the time of the BDG procedure is volume unloading of the single ventricle, which improves its function and reduces AVVR [20]. Superior aerobic capacity was shown in preadolescents with a single ventricle who underwent a volume unloading operation at an early age compared with those in whom the operation was delayed until they were older [21]. In a report by Zhang et al. [11], uncontrolled APBF was associated with ventricular enlargement and aggravation of valve regurgitation compared with those in whom APBF was titrated to a pulmonary arterial pressure <16 mmHg by pulmonary artery banding. Ferns et al. [7] demonstrated a trend towards a deterioration in cardiac function and AAVR in the APBF group, but the difference was not statistically significant. However, other studies showed that fractional shortening of the ventricle and lowering of ventricular end-diastolic pressure, as well as AVVR, were not adversely affected by additional pulmonary flow [3, 17, 19]. In this study, there was no significant difference in the degree of ventricular or atrioventricular valve dysfunction between the groups. Stimulation of pulmonary artery growth is a major theoretical advantage of preserved pulsatile blood flow. Caspi et al. [19] demonstrated a significant increase in the size of the pulmonary arteries in patients with controlled antegrade blood flow without adverse increases in the pulmonary artery pressure or pulmonary vascular resistance. Yoshida et al. [14] demonstrated that controlled antegrade blood flow increased the Fontan completion rate and attributed this result to stimulated growth of the pulmonary arteries by pulsatile blood flow. In this study, no significant increase in pulmonary artery index was observed in the APBF group compared with the non-APBF group. This discrepancy with previous studies may be explained by the relatively older ages of our patients. Age is negatively associated with a reduced potential for pulmonary artery growth [22, 23]. In this study, the potential benefit of PA stimulation by pulsatile APBF was most likely compromised by the diminished PA growth potential. We observed higher SaO2 levels early in the APBF group; this finding is in agreement with the results from previous reports [3, 6, 16, 17]. However, in our late follow-up examinations, although the trend towards higher oxygen saturation in APBF patients remained, it did not reach statistical significance. Mainwaring et al. [15] reported that in children aged  >4 or 5 years, the saturation levels may be considerably <80% and recommend APBF in this group of patients, given the fact that lower SaO2 rates early after the BDG procedure have been reported as a predictor of death or exclusion from the Fontan operation within 24 months in non-pulsatile patients having the BDG procedure [24]. In this study, although the levels were lower than those in the APBF group, non-ABPF patients had acceptable SaO2 (80–85%) levels and tolerated this SaO2 level throughout the follow-up period. Intrapulmonary shunts may develop shortly after a BDG procedure due to a lack of liver factors; some studies show reduced intrapulmonary shunts with APBF [25, 26]. However, others showed no difference. The only effective treatment for this condition is the Fontan completion procedure [27]. In this study, we did not observe the formation of any obvious intrapulmonary shunts. We believe this result can be at least partly attributed to the short interval (average 1.4 years, range 1.1–3.4 years) between BDG and TCPC in our patients. One theoretical advantage of APBF is that it may allow delayed TCPC with implantation of a larger extracardiac conduit at completion of the TCPC [28]. In this study, the time interval from the BDG procedure to the TCPC procedure (average time 1.8 years, range 1.3–3.4 years) was shorter than those found in most reports from developed countries where the BDG procedure is performed primarily in infancy, and TCPC has to be delayed until patients reach a certain age or body weight. Despite this short time interval, the patients in our series were already able to accommodate adult-sized conduits for subsequent extracardiac TCPC (age at TCPC average 8.7 years, range 3.4–21.4 years). There were no differences in age and time intervals before TCPC between the 2 groups. In developed countries, TCPC completion rates are as high as 80–90% [29, 30]. In contrast, the Fontan completion rates in developing countries are low and range from 15% to 50%, with a long interval (45–48 months) [10]. Given that most of our BDG procedures were performed late and the mortality rate of the 1-stage Glenn and Fontan procedure was relatively high (7.8%), we strongly encouraged patients’ families to revisit us routinely after completion of the BDG procedure so that we could assess the potential of the TCPC procedure. If the patient tolerated the BDG procedure well, we routinely started contemplating TCPC 1 year after the BDG procedure. By doing so, we achieved a 54% TCPC completion rate in all of our BDG procedures and found no difference between the APBF and the non-APBF groups in terms of TCPC completion rate. This completion rate is still lower than that reported in most developed countries, but this relatively low completion rate can be largely attributed to social or financial issues. Ferns et al. [7] reported lower PA pressure during TCPC in the APBF group. In this study, the PA pressure measured before the TCPC procedure did not differ between the groups. Further follow-up is needed to assess the long-term outcomes after TCPC. Limitations As a retrospective, non-randomized study focusing on patients with single ventricle morphology of inevitable anatomical and physiological variability, this report has its limitations. Selection bias can also exist, because patients were selected for APBF or non-APBF based on subjective and limited objective data as to the size and pressure of the pulmonary vascular bed. However, although these differences in themselves may not have a significant impact on the outcomes observed, our study does suggest that maintaining APBF after the BDG procedure is associated with improved systemic arterial saturation but also with prolonged pleural effusion and hospital stay. Ideally, multivariate analysis should be performed to understand these factors better, but the small number of patients and complications made such an analysis impossible. Further studies with a large number of patients and, ideally, defined morphological groups are necessary to understand better the effect of APBF in patients in whom BDG is performed late for single ventricular morphologies. CONCLUSION In conclusion, the BDG procedure can be safely performed in a child at a relatively older age (∼6 years). Leaving APBF at the time of the BDG procedure increases oxygen saturation but also prolongs pleural effusion and hospital stay. Medium-term outcomes and Fontan completion rates in the APBF and non-APBF groups are comparable. Further large studies with long-term follow-up are needed to clarify the effect of APBF in patients who have the BDG procedure when they are older. Funding This work was supported by the National Natural Science Foundation of China [81500183 to G.T., 81500298 to B.Z. and 81400366 to Z.S.], Military Medical Science Foundation [14QNP043 to X.Z.]; and Natural Science Foundation of Guangdong Province [2014A030310473 to B.Z., 2015A030310116 to X.Z.]; and the Pearl River Science and Technology Nova Program of Guangzhou [201610010094 to B.Z.]. Conflict of interest: none declared. REFERENCES 1 Hopkins RA, Armstrong BE, Serwer GA, Peterson RJ, Oldham HNJr. Physiological rationale for a bidirectional cavopulmonary shunt. A versatile complement to the Fontan principle. J Thorac Cardiovasc Surg  1985; 90: 391– 8. Google Scholar PubMed  2 Mazzera E, Corno A, Picardo S, Di Donato R, Marino B, Costa D et al.   Bidirectional cavopulmonary shunts: clinical applications as staged or definitive palliation. Ann Thorac Surg  1989; 47: 415– 20. Google Scholar CrossRef Search ADS PubMed  3 Berdat PA, Belli E, Lacour-Gayet F, Planche C, Serraf A. 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Appropriate additional pulmonary blood flow at the bidirectional Glenn procedure is useful for completion of total cavopulmonary connection. Ann Thorac Surg  2005; 80: 976– 81. Google Scholar CrossRef Search ADS PubMed  15 Mainwaring RD, Lamberti JJ, Uzark K, Spicer RL, Cocalis MW, Moore JW. Effect of accessory pulmonary blood flow on survival after the bidirectional Glenn procedure. Circulation  1999; 100: II151– 6. Google Scholar CrossRef Search ADS PubMed  16 van de Wal HJ, Ouknine R, Tamisier D, Levy M, Vouhe PR, Leca F. Bi-directional cavopulmonary shunt: is accessory pulsatile flow, good or bad? Eur J Cardiothorac Surg  1999; 16: 104– 10. Google Scholar CrossRef Search ADS PubMed  17 Chen Q, Tulloh R, Caputo M, Stoica S, Kia M, Parry AJ. Does the persistence of pulsatile antegrade pulmonary blood flow following bidirectional Glenn procedure affect long term outcome? Eur J Cardiothorac Surg  2015; 47: 154– 8; discussion 58. 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Google Scholar CrossRef Search ADS PubMed  29 Tanoue Y, Kado H, Boku N, Tatewaki H, Nakano T, Fukae K et al.   Three hundred and thirty-three experiences with the bidirectional Glenn procedure in a single institute. Interact CardioVasc Thorac Surg  2006; 6: 97– 101. Google Scholar CrossRef Search ADS PubMed  30 Rogers LS, Glatz AC, Ravishankar C, Spray TL, Nicolson SC, Rychik J et al.   18 years of the Fontan operation at a single institution: results from 771 consecutive patients. J Am Coll Cardiol  2012; 60: 1018– 25. Google Scholar CrossRef Search ADS PubMed  © The Author 2017. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Interactive CardioVascular and Thoracic Surgery Oxford University Press

The effect of antegrade pulmonary blood flow following a late bidirectional Glenn procedure

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Oxford University Press
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© The Author 2017. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
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1569-9293
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1569-9285
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10.1093/icvts/ivx325
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Abstract

Abstract OBJECTIVES The effect of antegrade pulmonary blood flow (APBF) has never been studied in the bidirectional Glenn (BDG) procedure performed late. METHODS Records of 112 consecutive patients who had a BDG procedure during a 10-year period were reviewed retrospectively. The patients were divided into 2 groups based on whether APBF occurred following the BDG procedure (APBF group, n = 81) or not (non-APBF group, n = 31). The median age at the BDG procedure was 6.16 ± 3.93 years in the APBF group and 6.12 ± 4.40 years in the non-APBF group. RESULTS Demographics and pre- and intraoperative variables were comparable for both groups. Follow-up data were obtained for patients at the BDG stage and for those who had undergone the Fontan completion. Both oxygen saturation levels (81.72 ± 1.976% vs 78.32 ± 2.344%, P < 0.01) and pulmonary pressure (13.59 ± 1.376 mmHg vs 12.90 ± 0.978 mmHg, P = 0.012) were higher in the APBF group immediately after the BDG procedure. Both the duration of chest tube drainage and the total length of stay were longer in the APBF group. The pre-Glenn measurements showed a mean McGoon ratio of 1.68 ± 0.114 in the APBF group and 1.67 ± 0.098 in the non-APBF group (P = 0.474). The McGoon ratios measured before the Fontan procedure were also comparable (1.669 ± 0.726 vs 1.685 ± 0.669, P = 0.576). At the pre-Fontan measurement, there was no significant difference in mean pulmonary artery pressures between the groups (13.72 ± 1.368 vs 13.50 ± 1.265, P = 0.653). Fifty-nine patients underwent the Fontan completion (43 from the APBF group and 16 from the non-APBF group) procedure with a median of 1.2 (APBF group) and 1.4 (non-APBF group) years after the BDG procedure. No significant differences between groups were observed in arterial oxygen saturation levels, incidence of systemic atrioventricular valve regurgitation or ventricular dysfunction in survivors at the last follow-up visit. CONCLUSIONS The BDG procedure can be safely performed at a relatively older age (∼6 years). APBF increases oxygen saturation but also prolongs pleural effusion and hospital stay. Medium-term outcomes and the Fontan completion rate in the APBF and the non-APBF groups are comparable. Further large studies and long-term follow-up are needed to clarify the effect of APBF in patients who have the late BDG. Bidirectional Glenn, Single ventricle, Antegrade pulmonary blood flow INTRODUCTION The bidirectional Glenn (BDG) operation is used as a standard palliative procedure in the staged surgical approach for palliation of a physiologically univentricular heart [1, 2]. Controversy remains regarding whether additional antegrade pulmonary blood flow (APBF) is beneficial in combination with BDG. The arguments for leaving an accessory source of pulsatile pulmonary blood flow include possible improvement in postoperative arterial oxygen saturation (SaO2) levels, promotion of the growth of pulmonary arteries and possible prevention of long-term development of an intrapulmonary shunt [3, 4]. However, APBF may also diminish ventricular unloading by the BDG procedure and elevate the systemic venous pressure, resulting in postoperative complications such as prolonged pleural effusion [5–7]. Despite the discrepancies in their conclusions, most current studies were performed in Europe and North America and focused on patient populations that were predominantly infants (<1 year), because the benefits of BDG are reduced in older children [8, 9]. However, for social and financial reasons, most BDG procedures performed in developing countries such as China and India occur when the children are much older, and this large group of patients is understudied [10, 11]. The objective of our study was to report our experience with the late BDG procedure and delineate the effect of APBF in this group of patients (average age 6.15 years). METHODS Patients Clinical data of patients undergoing the BDG procedure for palliation of a functionally univentricular heart were reviewed retrospectively. Two groups were formulated. This study was approved by the ethics committee of Guangzhou General Hospital of Guangzhou Military Command. From January 2006 to April 2010, 127 patients underwent BDG at our institution. Twelve patients who underwent repair of 1.5 ventricles and 3 patients who received a modified Blalock–Taussig shunt after the BDG procedure were excluded from this study. The 112 patients enrolled in this study were divided into 2 groups based on whether APBF existed following the BDG procedure (APBF group, n = 81) or not (non-APBF group, n = 31). Previous palliative procedures included modified Blalock–Taussig shunt placement in 10 patients and pulmonary artery banding in 1 patient. The median age at the BDG procedure was 6.16 ± 3.93 years (range 9 months to 18.4 years) in the APBF group (n = 81) and 6.12 ± 4.40 years (range 9 months to 21.5 years) in the non-APBF group (n = 31). There were no significant differences in age, gender, body weight, body surface area, McGoon index or pulmonary artery index between the 2 groups. Bidirectional Glenn The timing of the BDG procedure did not occur at a set age in our institution but rather was determined largely by when the patient presented to us. Treatment for many patients in developing countries can be delayed for social and financial reasons [10, 11]. All the surgical procedures were performed through a median sternotomy. Twenty-seven patients underwent the BDG procedure with the assistance of cardiopulmonary bypass and the remaining 85 patients underwent the BDG procedure with a passive shunt between the superior vena cava (SVC) and the right atrium. Any other forms of pulmonary blood flow such as major systemic to pulmonary collaterals, patent ductus arteriosus and previously placed modified Blalock–Taussig shunts were taken down. The SVC was anastomosed to the pulmonary artery branch in an end-to-side fashion. The bilateral BDG procedures were performed in 18 patients with significant persistent left SVC. The azygos vein was ligated in all cases to prevent untoward shunting from the SVC to the inferior vena cava vein. Three surgeons (M.T., X.W. and W.Z.) in our group performed the procedures. The decision to preserve the APBF or not was made intraoperatively. Both the patient’s disease and the surgeon’s preferences played a role in the decision. In general, APBF was more inclined to be preserved in patients with younger age, smaller pulmonary vessels, lower saturations and low pulmonary arterial pressure before the BDG procedure was performed. However, as listed in Tables 1 and 2, no significant differences were observed in these preoperative parameters. Table 1: Patient characteristics and diagnosis at the time of the bidirectional Glenn procedure Characteristics  APBF  Non-APBF  P-value  Age (years), mean ± SD  6.16 ± 3.93  6.12 ± 4.40  0.880  Male:female  44:37  15:16  0.574  Body weight (kg), mean ± SD  21.82 ± 10.17  20.00 ± 9.61  0.863  BSA (m2), mean ± SD  0.794 ± 0.28  0.813 ± .0.28  0.862  PAI (mm2/m2), mean ± SD  250.96 ± 67.11  252.65 ± 53.32  0.088  Single ventricle, n (%)  15 (18.5)  7 (22.5)  0.628   Left ventricle morphology  5 (6.2)  2 (6.5)  1.000   Right ventricle morphology  5 (6.2)  2 (6.5)  1.000   Biventricular or uncertain  5 (6.2)  3 (9.7)  0.683  DORV, n (%)  11 (13.6)  5 (16.1)  0.766  TA, n (%)  10 (12.3)  3 (9.7)  1.000  TGA, n (%)  9 (11.1)  2 (6.5)  0.724  Ebstein’s anomaly, n (%)  5 (6.2)  2 (6.5)  1.000  CAVC, n (%)  11 (13.6)  4 (12.9)  1.000  PA, n (%)  12 (14.8)  3 (9.7)  0.554  Others, n (%)  8 (9.9)  5 (16.1)  0.344  Characteristics  APBF  Non-APBF  P-value  Age (years), mean ± SD  6.16 ± 3.93  6.12 ± 4.40  0.880  Male:female  44:37  15:16  0.574  Body weight (kg), mean ± SD  21.82 ± 10.17  20.00 ± 9.61  0.863  BSA (m2), mean ± SD  0.794 ± 0.28  0.813 ± .0.28  0.862  PAI (mm2/m2), mean ± SD  250.96 ± 67.11  252.65 ± 53.32  0.088  Single ventricle, n (%)  15 (18.5)  7 (22.5)  0.628   Left ventricle morphology  5 (6.2)  2 (6.5)  1.000   Right ventricle morphology  5 (6.2)  2 (6.5)  1.000   Biventricular or uncertain  5 (6.2)  3 (9.7)  0.683  DORV, n (%)  11 (13.6)  5 (16.1)  0.766  TA, n (%)  10 (12.3)  3 (9.7)  1.000  TGA, n (%)  9 (11.1)  2 (6.5)  0.724  Ebstein’s anomaly, n (%)  5 (6.2)  2 (6.5)  1.000  CAVC, n (%)  11 (13.6)  4 (12.9)  1.000  PA, n (%)  12 (14.8)  3 (9.7)  0.554  Others, n (%)  8 (9.9)  5 (16.1)  0.344  APBF: anterior pulmonary blood flow; BSA: body surface area; CAVC: complete atrioventricular canal; DORV: double outlets of the right ventricle; PA: pulmonary atresia; PAI: pulmonary artery (Nakada) index; SD: standard deviation; TA: tricuspid atresia; TGA: transposition of the great arteries. Table 2: Perioperative data Characteristics  APBF  Non-APBF  P-value  Pre-BDG PA pressure, mean ± SD  11.37 ± 1.336  11.48 ± 1.208  0.681  Pre-BDG McGoon index, mean ± SD  1.68 ± 0. 114  1.67 ± 0.098  0.474  Post-BDG PA pressure, mean ± SD  13.59 ± 1.376  12.90 ± 0.978  0.012  Duration of ventilation (days), mean ± SD  1.63 ± 2.106  1.39 ± 1.054  0.542  Chest tube duration (days), mean ± SD  7.42 ± 4.477  4.35 ± 1.561  <0.01  Chylothorax, n (%)  5 (6.2)  3 (9.7)  0.683  ICU stay (days), mean ± SD  4.94 ± 7.703  8.13 ± 15.126  0.144  Length of stay (days), mean ± SD  17.30 ± 12.418  11.03 ± 3.381  <0.01  Hospital readmissions, n (%)  3 (3.7)  1 (3.2)  1.000  Characteristics  APBF  Non-APBF  P-value  Pre-BDG PA pressure, mean ± SD  11.37 ± 1.336  11.48 ± 1.208  0.681  Pre-BDG McGoon index, mean ± SD  1.68 ± 0. 114  1.67 ± 0.098  0.474  Post-BDG PA pressure, mean ± SD  13.59 ± 1.376  12.90 ± 0.978  0.012  Duration of ventilation (days), mean ± SD  1.63 ± 2.106  1.39 ± 1.054  0.542  Chest tube duration (days), mean ± SD  7.42 ± 4.477  4.35 ± 1.561  <0.01  Chylothorax, n (%)  5 (6.2)  3 (9.7)  0.683  ICU stay (days), mean ± SD  4.94 ± 7.703  8.13 ± 15.126  0.144  Length of stay (days), mean ± SD  17.30 ± 12.418  11.03 ± 3.381  <0.01  Hospital readmissions, n (%)  3 (3.7)  1 (3.2)  1.000  APBF: anterior pulmonary blood flow; BDG: bidirectional Glenn; ICU: intensive care unit; PA: pulmonary artery; SD: standard deviation. Statistical analysis Data were expressed as either the mean ± standard deviation or the median and range. Comparative univariate analysis was performed between the 2 groups of patients with the t-test for normally distributed continuous data. The χ2 test was used for ordinal data. The Kaplan–Meier survival estimates were plotted for the 2 groups and compared using a log-rank test. A P-value of <0.05 was considered significant. Statistical analyses were performed using SPSS 22.0 software (SPSS, Chicago, IL, USA). RESULTS Patient demographics Patient demographics are listed in Table 1. No significant differences between groups were noted in terms of age, body weight, body surface area, pulmonary artery index, pulmonary artery pressure and the McGoon ratio before the BDG procedure. As listed in Table 1, the anatomical diagnosis was similar in both groups. Chest drainage, postoperative ventilation time and length of stay in the intensive care unit and in the hospital No significant difference was noted between groups in postoperative time on a ventilator or length of stay in the intensive care unit (Table 2). However, the APBF group had significantly longer time with a chest tube drain in place compared with the non-APBF group (7.42 ± 4.477 days vs 4.35 ± 1.561 days, P < 0.01). The APBF group also had a significantly longer hospital stay compared with the non-APBF group (17.30 ± 12.42 days vs 11.03 ± 3.38 days, P < 0.01). Pulmonary artery pressure and systemic arterial oxygen saturation The mean pre-BDG pulmonary artery pressure was comparable between the groups (11.37 ± 1.336 mmHg vs 11.48 ± 1.208 mmHg, P = 0.681). The mean pulmonary artery pressure after the BDG procedure was higher in the APBF group (13.59 ± 1.376 mmHg vs 12.90 ± 0.978 mmHg, P = 0.012). In patients undergoing a total cavopulmonary connection (TCPC) procedure, pre-TCPC pulmonary artery pressure was comparable between groups (13.72 ± 1.368 mmHg vs 13.50 ± 1.265 mmHg, P = 0.653). There was no significant difference in pre-BDG SaO2 (67.52 ± 5.662% vs 68.19 ± 4.658%, P = 0.556). The SaO2 levels in both the APBF and the non-APBF groups were significantly improved following the BDG procedure (Table 3). However, post-BDG SaO2 levels were higher in the APBF group compared with the non-APBF group (81.72 ± 1.976% vs 78.32 ± 2.344%, P < 0.01). Table 3: Analysis of pre- and postoperative systemic arterial saturation SaO2  APBF  Non-APBF  P-value  Pre-BDG, mean ± SD  67.52 ± 5.662  68.19 ± 4.658  0.556  Post-BDG, mean ± SD  81.72 ± 1.976  78.32 ± 2.344  <0.01  SaO2  APBF  Non-APBF  P-value  Pre-BDG, mean ± SD  67.52 ± 5.662  68.19 ± 4.658  0.556  Post-BDG, mean ± SD  81.72 ± 1.976  78.32 ± 2.344  <0.01  APBF: anterior pulmonary blood flow; BDG: bidirectional Glenn; SaO2: arterial oxygen saturation; SD: standard deviation. Follow-up There were no early postoperative deaths. Two patients died before reaching the Fontan completion: 1 in the APBF group and 1 in the non-APBF group. The patient in the APBF group had double outlets of the right ventricle, pulmonary stenosis and ventricular septal defect and died of uncertain causes at home 15 months after the BDG procedure. The patient in the non-APBF group had pulmonary atresia and died 11 months after an episode of pneumonia in a local hospital. The actuarial survival rate did not significantly differ between the groups (Fig. 1). Figure 1 View largeDownload slide The Kaplan–Meier survival curves for the 2 groups of patients following the bidirectional Glenn procedure. APBF: antegrade pulmonary blood flow. Figure 1 View largeDownload slide The Kaplan–Meier survival curves for the 2 groups of patients following the bidirectional Glenn procedure. APBF: antegrade pulmonary blood flow. Forty-three patients in the APBF group (53.8% of survivors) and 16 in the non-APBF group (53.3% of survivors) have since undergone the Fontan completion procedure. The average interval for the Fontan completion procedure was 1.629 ± 0.7377 years. There was no difference in the TCPC completion rate (53.8% vs 53.3%, P = 0.969) or in the interval between groups (1.630 ± 0.7096 vs 1.625 ± 0.8331 years, P = 0.981). One early death occurred in each group following the Fontan procedure. The patient in the APBF group with severe Ebstein’s anomaly and hypoplastic RV died 3 days after a fenestrated Fontan procedure of multiple organ failure. The patient in the non-APBF group with a single ventricle died 2 days after a fenestrated Fontan procedure of a massive intracranial haemorrhage. There were 2 late deaths in the APBF group following the Fontan procedure and no late deaths in the non-APBF group following the Fontan procedure. The actuarial survival rates did not differ significantly between the groups (Fig. 1). Systemic SaO2 levels at the last follow-up visit were comparable between the groups (78.67 ± 1.971% vs 77.81 ± 3.375%, P = 0.156). In patients who had undergone the Fontan procedure completion, there was no difference in the oxygen saturation levels between the APBF group and the non-APBF group, either immediately before (78.67 ± 2.089% vs 77.56 ± 3.222%, P = 0.110) or after (92.73 ± 1.814% vs 92.94 ± 0.988%, P = 0.644) the TCPC operation (Table 4). Table 4: Analysis of systemic arterial saturation at follow-up SaO2  APBF  Non-APBF  P-value  Last follow-up, mean ± SD  78.67 ± 1.971  77.81 ± 3.375  0.156  Pre-Fontan, mean ± SD  78.67 ± 2.089  77.56 ± 3.222  0.110  Post-Fontan, mean ± SD  92.73 ± 1.814  92.94 ± 0.988  0.644  SaO2  APBF  Non-APBF  P-value  Last follow-up, mean ± SD  78.67 ± 1.971  77.81 ± 3.375  0.156  Pre-Fontan, mean ± SD  78.67 ± 2.089  77.56 ± 3.222  0.110  Post-Fontan, mean ± SD  92.73 ± 1.814  92.94 ± 0.988  0.644  APBF: anterior pulmonary blood flow; SaO2: arterial oxygen saturation; SD: standard deviation. Postoperative echocardiographic data from the last follow-up examination are listed in Table 5. There was no significant difference in the degree of ventricular or atrioventricular valve dysfunction between the 2 groups. Good ventricular function was preserved in 50 (67.6%) patients in the APBF group and in 18 (58.1%) patients in the non-APBF group. Ventricular function was mildly depressed in 21 (25.9%) patients in the APBF group and in 6 (19.4%) patients in the non-APBF group. Ventricular function was moderately depressed in 6 (7.4%) patients in the APBF group and in 5 (16.1%) patients in the non-APBF group. Severely depressed ventricular function was present in 4 (4.9%) patients in the APBF group and in 2 (6.5%) patients in the non-APBF group. At the last follow-up examination, mild atrioventricular valve regurgitation (AVVR) was recorded in 15 (18.5%) patients in the APBF group and in 6 (19.4%) patients in the non-APBF group. Moderate AVVR was recorded in 13 (13.6%) patients in the APBF group and in 4 (12.9%) patients in the non-APBF group. Severe AVVR was recorded in 4 (4.9%) patients in the APBF group and in 2 (6.5%) patients in the non-APBF group. Table 5: Postoperative echocardiography data Parameters  APBF  Non-APBF  P-value  Ventricular function, n (%)   Normal  50 (67.6)  18 (58.1)  0.492   Mildly depressed  21 (25.9)  6 (19.4)   Moderately depressed  6 (7.4)  5 (16.1)   Severely depressed  4 (4.9)  2 (6.5)  AV regurgitation, n (%)   None  51 (63.0)  19 (61.3)  0.983   Mild  15 (18.5)  6 (19.4)   Moderate  13 (13.6)  4 (12.9)   Severe  4 (4.9)  2 (6.5)  Parameters  APBF  Non-APBF  P-value  Ventricular function, n (%)   Normal  50 (67.6)  18 (58.1)  0.492   Mildly depressed  21 (25.9)  6 (19.4)   Moderately depressed  6 (7.4)  5 (16.1)   Severely depressed  4 (4.9)  2 (6.5)  AV regurgitation, n (%)   None  51 (63.0)  19 (61.3)  0.983   Mild  15 (18.5)  6 (19.4)   Moderate  13 (13.6)  4 (12.9)   Severe  4 (4.9)  2 (6.5)  APBF: anterior pulmonary blood flow; AV: atrioventricular. Pulmonary artery pressures and the McGoon ratio were measured by cardiac catheterization before completion of the Fontan procedure. These patients exhibited no differences in pulmonary artery pressure (13.72 ± 1.368 vs 13.50 ± 1.265, P = 0.653) or McGoon ratio (1.669 ± 0.726 vs 1.685 ± 0.669, P = 0.576) after BDG between groups (Table 6). Table 6: Pre-Fontan cardiac catheterization data Parameters  APBF  Non-APBF  P-value  McGoon ratio, mean ± SD  1.669 ± 0.726  1.685 ± 0.669  0576  Pulmonary artery pressure (mmHg), mean ± SD  13.72 ± 1.368  13.50 ± 1.265  0.653  Major intrapulmonary shunt, n (%)  2 (4.7)  1 (6.3)  1.000  Parameters  APBF  Non-APBF  P-value  McGoon ratio, mean ± SD  1.669 ± 0.726  1.685 ± 0.669  0576  Pulmonary artery pressure (mmHg), mean ± SD  13.72 ± 1.368  13.50 ± 1.265  0.653  Major intrapulmonary shunt, n (%)  2 (4.7)  1 (6.3)  1.000  APBF: anterior pulmonary blood flow; SD: standard deviation. DISCUSSION Two rival strategies are currently used in the management of APBF at the time the BDG procedure is done. In one strategy, all sources of APBF including the main pulmonary arteries are interrupted; consequently, the SVC becomes the sole source of blood flow to the lungs [12]. In the other strategy, the APBF is preserved. During systole, the inferior vena cava blood return reaches the pulmonary arteries by pulsatile pulmonary ventricular contraction [13]. The theoretical advantages of APBF include increases in oxygen saturation, stimulation of pulmonary artery growth, increased Fontan completion rates [14] and alleviated formation of the intrapulmonary shunt owing to the supply of ‘hepatic factor’. On the other hand, the APBF compromises the reduced volume overload that results from the BDG procedure and is associated with cardiac dysfunction, ventricular enlargement and AVVR. Whether APBF should be maintained in the BDG procedure remains controversial. The effect of APBF on patient survival is still debated. Mainwaring et al. [15] reported a significantly higher late mortality rate in the APBF group (15.1% vs 4.4%) and recommended elimination of APBF at the time of BDG. In a study by van de Wal et al. [16] concerning 205 patients whose age range (mean age 5.6 years, range 26 days to 34.2 years) was similar to that of our patients, APBF was associated with a higher late mortality rate. In a study focusing on long-term outcomes, Chen et al. [17] reported higher 5- and 10-year survival rates in the APBF group compared with the non-APBF group (96% and 96% vs 88% and 82%, log rank P = 0.03). In this study, the mean age was 10.2 months (range 2.3–166.9 months) in the APBF group and 11.7 months (range 5.6–92.1 months) in the non-APBF group. In this study, no difference in survival was observed. In this study, a higher incidence of prolonged chest tube duration was noted in the APBF group, presumably due to increased central venous pressure. This increase resulted in a longer hospitalization course after the BDG procedure; however, after discharge from the hospital, there was no significant difference in hospital readmissions between the groups. An increase in the incidences of pleural effusion and chylothorax was also noted by other researchers [5, 7, 15, 18] despite the report by Caspi et al. [19]. A recent study [17] showed no difference in pleural effusion with or without APBF. The major aim of excluding all other sources of pulmonary blood flow at the time of the BDG procedure is volume unloading of the single ventricle, which improves its function and reduces AVVR [20]. Superior aerobic capacity was shown in preadolescents with a single ventricle who underwent a volume unloading operation at an early age compared with those in whom the operation was delayed until they were older [21]. In a report by Zhang et al. [11], uncontrolled APBF was associated with ventricular enlargement and aggravation of valve regurgitation compared with those in whom APBF was titrated to a pulmonary arterial pressure <16 mmHg by pulmonary artery banding. Ferns et al. [7] demonstrated a trend towards a deterioration in cardiac function and AAVR in the APBF group, but the difference was not statistically significant. However, other studies showed that fractional shortening of the ventricle and lowering of ventricular end-diastolic pressure, as well as AVVR, were not adversely affected by additional pulmonary flow [3, 17, 19]. In this study, there was no significant difference in the degree of ventricular or atrioventricular valve dysfunction between the groups. Stimulation of pulmonary artery growth is a major theoretical advantage of preserved pulsatile blood flow. Caspi et al. [19] demonstrated a significant increase in the size of the pulmonary arteries in patients with controlled antegrade blood flow without adverse increases in the pulmonary artery pressure or pulmonary vascular resistance. Yoshida et al. [14] demonstrated that controlled antegrade blood flow increased the Fontan completion rate and attributed this result to stimulated growth of the pulmonary arteries by pulsatile blood flow. In this study, no significant increase in pulmonary artery index was observed in the APBF group compared with the non-APBF group. This discrepancy with previous studies may be explained by the relatively older ages of our patients. Age is negatively associated with a reduced potential for pulmonary artery growth [22, 23]. In this study, the potential benefit of PA stimulation by pulsatile APBF was most likely compromised by the diminished PA growth potential. We observed higher SaO2 levels early in the APBF group; this finding is in agreement with the results from previous reports [3, 6, 16, 17]. However, in our late follow-up examinations, although the trend towards higher oxygen saturation in APBF patients remained, it did not reach statistical significance. Mainwaring et al. [15] reported that in children aged  >4 or 5 years, the saturation levels may be considerably <80% and recommend APBF in this group of patients, given the fact that lower SaO2 rates early after the BDG procedure have been reported as a predictor of death or exclusion from the Fontan operation within 24 months in non-pulsatile patients having the BDG procedure [24]. In this study, although the levels were lower than those in the APBF group, non-ABPF patients had acceptable SaO2 (80–85%) levels and tolerated this SaO2 level throughout the follow-up period. Intrapulmonary shunts may develop shortly after a BDG procedure due to a lack of liver factors; some studies show reduced intrapulmonary shunts with APBF [25, 26]. However, others showed no difference. The only effective treatment for this condition is the Fontan completion procedure [27]. In this study, we did not observe the formation of any obvious intrapulmonary shunts. We believe this result can be at least partly attributed to the short interval (average 1.4 years, range 1.1–3.4 years) between BDG and TCPC in our patients. One theoretical advantage of APBF is that it may allow delayed TCPC with implantation of a larger extracardiac conduit at completion of the TCPC [28]. In this study, the time interval from the BDG procedure to the TCPC procedure (average time 1.8 years, range 1.3–3.4 years) was shorter than those found in most reports from developed countries where the BDG procedure is performed primarily in infancy, and TCPC has to be delayed until patients reach a certain age or body weight. Despite this short time interval, the patients in our series were already able to accommodate adult-sized conduits for subsequent extracardiac TCPC (age at TCPC average 8.7 years, range 3.4–21.4 years). There were no differences in age and time intervals before TCPC between the 2 groups. In developed countries, TCPC completion rates are as high as 80–90% [29, 30]. In contrast, the Fontan completion rates in developing countries are low and range from 15% to 50%, with a long interval (45–48 months) [10]. Given that most of our BDG procedures were performed late and the mortality rate of the 1-stage Glenn and Fontan procedure was relatively high (7.8%), we strongly encouraged patients’ families to revisit us routinely after completion of the BDG procedure so that we could assess the potential of the TCPC procedure. If the patient tolerated the BDG procedure well, we routinely started contemplating TCPC 1 year after the BDG procedure. By doing so, we achieved a 54% TCPC completion rate in all of our BDG procedures and found no difference between the APBF and the non-APBF groups in terms of TCPC completion rate. This completion rate is still lower than that reported in most developed countries, but this relatively low completion rate can be largely attributed to social or financial issues. Ferns et al. [7] reported lower PA pressure during TCPC in the APBF group. In this study, the PA pressure measured before the TCPC procedure did not differ between the groups. Further follow-up is needed to assess the long-term outcomes after TCPC. Limitations As a retrospective, non-randomized study focusing on patients with single ventricle morphology of inevitable anatomical and physiological variability, this report has its limitations. Selection bias can also exist, because patients were selected for APBF or non-APBF based on subjective and limited objective data as to the size and pressure of the pulmonary vascular bed. However, although these differences in themselves may not have a significant impact on the outcomes observed, our study does suggest that maintaining APBF after the BDG procedure is associated with improved systemic arterial saturation but also with prolonged pleural effusion and hospital stay. Ideally, multivariate analysis should be performed to understand these factors better, but the small number of patients and complications made such an analysis impossible. Further studies with a large number of patients and, ideally, defined morphological groups are necessary to understand better the effect of APBF in patients in whom BDG is performed late for single ventricular morphologies. CONCLUSION In conclusion, the BDG procedure can be safely performed in a child at a relatively older age (∼6 years). Leaving APBF at the time of the BDG procedure increases oxygen saturation but also prolongs pleural effusion and hospital stay. Medium-term outcomes and Fontan completion rates in the APBF and non-APBF groups are comparable. Further large studies with long-term follow-up are needed to clarify the effect of APBF in patients who have the BDG procedure when they are older. Funding This work was supported by the National Natural Science Foundation of China [81500183 to G.T., 81500298 to B.Z. and 81400366 to Z.S.], Military Medical Science Foundation [14QNP043 to X.Z.]; and Natural Science Foundation of Guangdong Province [2014A030310473 to B.Z., 2015A030310116 to X.Z.]; and the Pearl River Science and Technology Nova Program of Guangzhou [201610010094 to B.Z.]. Conflict of interest: none declared. REFERENCES 1 Hopkins RA, Armstrong BE, Serwer GA, Peterson RJ, Oldham HNJr. Physiological rationale for a bidirectional cavopulmonary shunt. A versatile complement to the Fontan principle. J Thorac Cardiovasc Surg  1985; 90: 391– 8. Google Scholar PubMed  2 Mazzera E, Corno A, Picardo S, Di Donato R, Marino B, Costa D et al.   Bidirectional cavopulmonary shunts: clinical applications as staged or definitive palliation. Ann Thorac Surg  1989; 47: 415– 20. Google Scholar CrossRef Search ADS PubMed  3 Berdat PA, Belli E, Lacour-Gayet F, Planche C, Serraf A. 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Interactive CardioVascular and Thoracic SurgeryOxford University Press

Published: Mar 1, 2018

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