Our results suggest that APBF at BCPS helps maintain the Fontan circulation with high PAI, low PAP, low Rp, and low SVEDP without any major adverse event at the long-term follow-up after the Fontan procedure. However, our results also indicate that despite good Fontan conditions, liver fibrosis markers increase after the Fontan procedure.
BCPS can reduce cardiac volume overload and PAP [2, 15]. However, BCPS allows reduced pulmonary blood flow compared with normal circulation, leading to limited PA growth before Fontan completion (5). Moreover, PA growth after Fontan completion is reduced compared with somatic growth, and this phenomenon may disturb optimal long-term Fontan circulation [12]. Although APBF can preserve the potential of PA growth, excessive pulmonary blood flow could cause ventricular volume overload, atrioventricular valve regurgitation, and PAP elevation [16–18]. To avoid these concerns, Yoshida and colleagues developed a surgical management using an appropriately adjusted ABPF and reported its positive outcome compared with uncontrolled ABPF [19]. We reported a similar result when maximum APBF was regulated by a 3.5–4.0-mm SP shunt or retightened antegrade PA flow in our series [20]. After BCPS, the patients in the present series also showed good PA and ventricular condition throughout the follow-up.
Although PA and ventricular conditions are important factors for Fontan completion and its late outcome, some controversies remain. Lehner and colleagues reported that reduced PA diameters measured using the McGoon ratio and PAI did not adversely affect the early outcome of Fontan palliation [21]. However, Chowdhury and colleagues reported in their histomorphometric analysis that low PAI is significantly associated with the presence of severe intimal lesions, thrombus, abnormal smooth muscle extension, a reduced mean-indexed area of the intrapulmonary arteries, and poor postoperative outcome [22]. Hosein and colleagues [23] reported that preoperatively impaired ventricular function and elevated PAP have an adverse impact on both early and late outcomes. Ovroutski and colleagues reported that small PAs and low PAI are associated with elevated PAP as a late outcome after the Fontan procedure, with a correlation between low PAI and unfavorable late outcome [24]. Altogether, we believe that APBF is effective in Fontan circulation improvement based on our present results. Unfortunately, little data is available on the effects of BCPS with APBF on the Fontan circulation. Sugimoto and colleagues reported that patients who underwent BCPS with APBF had better-developed PA prior to the Fontan procedure, shorter pleural drainage duration, and shorter hospital stay after the Fontan procedure [25]. In our study, PA developed well and PAI was maintained at 485.1 ± 272.3 with low mean PAP (11.3 ± 3.8 mmHg) and Rp (1.1 ± 0.6 units) before the Fontan procedure. SVEDP decreased from 11.4 ± 3.2 to 8.2 ± 3.0 mmHg during the interstage of the Fontan procedure. In comparison with other reports (10,16,21), PAP, Rp, and SVEDP were similar or lower, whereas PAI was superior in our study. There were no intrapulmonary shunts or atrioventricular valve regurgitations that required intervention by the Fontan procedure. Adjusted ABPF prevented the decrease in PAI without increasing PAP and ventricular volume overload before the Fontan procedure. These parameters were maintained at the mid-to-long-term follow-up, resulting in good Fontan circulation in all patients with NYHA status I. However, it is noteworthy that although several researchers have reported better catheter data in APBF cases, no evident difference in mid-term survival rate between APBF and non-APBF cases has been observed. Furthermore, Schreiber and colleagues [26] achieved good outcomes in non-APBF cases; accordingly, we think that the long-term clinical data of both APBF and non-APBF cases require further evaluation in future studies.
Our results show that even in good Fontan condition, liver fibrosis markers increase after the Fontan procedure. The mechanism underlying Fontan-associated liver dysfunction is different from that of other liver diseases such as viral or alcoholic hepatitis. The evaluation of liver function is a challenge and there are various opinions on it. Nakano and colleagues reported that despite normal AST and ALT levels, a substantial number of patients show abnormally elevated levels of P-III-NP and collagen type IV, which are sensitive serum markers for liver fibrosis [27]. In this report, the mean CVP and SVEDP were 10 mmHg and 7.7 mmHg, respectively, at > 10 years after the Fontan procedure. Although these data support good Fontan condition at the mid-to-long-term follow-up, the liver fibrosis markers are elevated. In our study, collagen type IV, procollagen, and hyaluronic acid levels were elevated at the mid-to-long-term follow-up, although PAP and Rp were low, similar to the report by Nakano. Conversely, Wu et al. argued that the initial high levels of liver function markers, such as hyaluronic acid levels, may be unsuitable in Fontan patients because they did not correlate with the degree of hepatic fibrosis and did not predict cirrhosis in their research [28]. Further studies are necessary to evaluate liver dysfunction in Fontan patients at the long-term follow-up. We intend to examine the liver function and echo findings to clarify the effects of APBF on Fontan circulation during long-term follow-up. It is also important to develop surgical strategies to obtain reduced CVP after the Fontan procedure as much as possible.
The limitations of this study include the small size of the patient population, the homogeneity of the study group, and its retrospective nature. We did not compare the APBF cases with non-ABPF cases. In the future, larger cohorts and long-term studies must clarify whether APBF should be preserved at BCPS when considering the long-term prognosis of patients undergoing the Fontan procedure.