4 | DISCUSSION
The purpose of the surgical treatment of FSV patient is to successful achieve the Fontan circulation. Depending on the anatomy, patients with single ventricle have four physiological modes, which are determined by excessive or insufficient pulmonary blood flow, that are inadequate pulmonary blood flow, excessive pulmonary blood flow with or without systemic outflow obstruction, and balanced pulmonary blood flow11. The primary goal of treatment for these patients is to establish a stable pulmonary blood flow as early as possible, and to avoid the adverse effects of continuous high blood flow and high pressure on pulmonary vascular bed, so that the Fontan circulation can be achieved in the later stage. Functional single ventricle patients combined with TAPVC makes the surgical treatment more complicated. Extracardiac TAPVC, especially with PVO, can cause pulmonary hypertension which makes patients in a worse situation. Surgical outcome of patients with FSV and TAPVC have a poor prognosis. Therefore, urgent simultaneous or staged surgical intervention should be performed in the infant stage or even the neonatal period. In our group of cases, the patients with FSV and TAPVC who came to our center for surgical treatment are all older. The median age were 32 months, range from 2 to 256 months. We retrospectively analyzed mid-term results and risk factors of petients with FSV and TAPVC in our center.
The management of patients with FSV and TAPVC remains challenging, a rate of in-hospital death increase significantly and the overall survival rate is low in this group6. Concomitant TAPVC repair significantly increased the risk for mortality. It was reported that operative mortalities of patients with FSV and TAPVC repair was 30% to 55%12,13, and the 5-year survival rate was 30%-60%2,4,10,14. Overall survival at 1 and 5 years were 89.5% and 83.3%, respectively (Figure 2). One year survival is 58.3% in TAPVC repair group and 87.1% in non-TAPVC repair group. Three years survival is 40% in TAPVC repair group and 87.1% in non-TAPVC repair group (Figure 3). In our study, totally mortality rate in TAPVC repair group was higher than that in non-TAPVC repair group (58.3% vs 12.9%, p = 0.002, HR:0.430) (Table 1). Type of TAPVC (p< 0.001) and preoperative PVO (p = 0.001) were significant difference between these two groups. In our study, univariate analysis identified that preoperative PVO (p = 0.047) and concomitant TAPVC repair (p = 0.007) were risk factors for mortality. Only concomitant TAPVC repair was risk factors for mortality by multivariate analysis (Table 2).
Type of TAPVC also affects the prognosis of patients with FSV and TAPVC. Nakayama Y and colleagues found that subcardiac and mixed TAPVC influenced the early surgical outcome of patients with FSV and TAPVC repair7. Nakata T and colleagues identified mixed TAPVC increased mortality of patients with FSV and TAPVC repair14. In our study, intracardiac and supracardia TAPVC are the main types of TAPVC (41/43, 95.3%). There are statistical differences between the two groups in the type of TAPVC (p< 0.001) (Table 1), but it is not a risk factor affecting mortality (Table 2). We consider that small proportion of mixed TAPVC may be the main reason.
Pulmonary venous obstruction is another factor that increases risk of mortality in patients with FSV and TAPVC1,7. Increased pulmonary vascular resistance due to PVO is unfavorable for achieving a successful Fontan circulation. Of 41 patients with FSV and extracardiac TAPVC, preoperative PVO was considered to be a risk factor for death1. Any significant PVO needs to be relieved at the first palliative stage, which can be staged or concurrent surgery11. In our study, all 6 patients with PVO were addressed during BDG procedure. Four of them died, but there was no direct correlation with PVO (Figure 1). No cases of postoperative pulmonary vein stenosis were found. Univariate analysis, but not multivariate analysis, indentified preoperative PVO as significant risk factors for mortality (Table 2). Cumulative survival rate in patients with preoperative PVO was lower than that in patients with no preoperative PVO (p = 0.03, HR:0.535) (Figure 4).