Promoting the growth of unbalanced pulmonary artery using an intrapulmonary-artery baffle fenestration

Significant growth of the right pulmonary artery was observed by 6 months postoperation.

Central Message.

Intrapulmonary-artery baffle fenestration may serve as a viable interim strategy for Fontan candidates with a functional single ventricle and unbalanced pulmonary artery.

Functional single ventricle (FSV), accounting for 2% to 3% of all congenital heart disease, comprises a heterogeneous group of congenital heart defects characterized by having only 1 fully developed ventricle. The Fontan operation represents the final step for patients with FSV, and its outcomes have significantly improved as a result of advances in surgical techniques and perioperative strategies. Among the “Ten Commandments” guiding Fontan candidacy, the diameter of pulmonary artery (PA) is considered one of the most critical determinants for a successful Fontan circulation. Severely unbalanced PA may render patients either ineligible for the Fontan operation or the 1-lung Fontan operation.¹ We herein report a modified technique named “intrapulmonary-artery baffle fenestration” (IPABF) combined with a Blalock-Thomas-Taussig (BTT) shunt to promote the growth of the poorly grown PA in a patient with FSV for whom we achieved satisfactory results. The institutional review board of our hospital waived ethical approval for this case report, and written informed consent for publication was obtained from the patient's parents.

Technique Procedure

Computational Fluid Dynamics (CFD) Analysis

To determine the fenestration and the shunt diameter preoperatively, CFD analysis was used to assess hemodynamic changes. To summarize, using computed tomography (CT)-derived geometry, we reconstructed the pulmonary bifurcation with IPABF and a BTT shunt, fixing pulmonary outlet pressure. Vessel walls were assumed rigid and no-slip, and the blood was modeled as an Eulerian-Eulerian 2-phase mixture with non-Newtonian viscosity via a modified Carreau-Yasuda law. Interphase momentum exchange incorporated Schiller-Naumann drag and Saffman-Mei lift to represent red blood cell lateral migration and near-wall hematocrit. Peak Reynolds numbers exceeded 2 × 10⁴; accordingly, a mixture k-ω shear stress transport model was adopted to resolve separation and secondary flows. Robustness was verified via mesh-independence tests, turbulence-model cross-checks, and a pipe-flow benchmark. The primary indicators included the flow-distribution ratio (FDR), wall shear stress, oscillatory shear index, energy loss, to mention a few. Detailed information on the methods was presented in our previous study.²

Surgical Procedure

After general anesthesia is administered, a midline sternotomy is performed, and cardiopulmonary bypass (CPB) is established. Vessel clamps are applied to block the PA trunk and its main branches. The PA bifurcation is then opened, and the dilated PA is appropriately trimmed for the subsequent reconstruction. A biological patch is tailored to match the diameter of the dilated PA and sutured into its lumen. A BTT shunt is constructed using a prosthetic graft to connect the right subclavian artery to the hypoplastic PA, providing additional blood flow. Fenestration and BTT shunt diameter are preselected on the basis of CFD results. Finally, the PA bifurcation is closed, and vessel clamps are sequentially released to restore the blood flow. After meticulous hemostasis, CPB is removed, and the thoracic cavity is closed (Figure 1, Video 1).

Figure 1.

The schematic diagram of intrapulmonary-artery baffle fenestration.

Case Presentation

A 4-year-old boy was admitted to our department for cyanosis. Echocardiography revealed right ventricular hypoplasia, tricuspid valve atresia, pulmonary valve atresia, patent ductus arteriosus, and unbalanced PA, characterized by a poorly grown right PA (RPA) and a dilated left PA (LPA). Contrast-enhanced CT further confirmed the unbalanced PA, with RPA measuring 4.4 mm in diameter (Figure 2, A). Because of severe RPA hypoplasia, the patient was deemed unsuitable for the Glenn or Fontan procedure. Thus, strategies to promote RPA growth were essential to meet the criteria for further intervention. Generally, constructing a systemic shunt is a conventional method to promote the growth of a hypoplastic PA. However, in this case, the LPA was significantly dilated, and an additional shunt risked preferential flow to the LPA, potentially leading to pulmonary overcirculation. Thus, an approach was required to selectively augment blood flow to the RPA while minimizing volume overload to the LPA. To achieve this, we used an IPABF technique to redirect blood flow preferentially into the hypoplastic PA, thus facilitating its growth.

Figure 2.

Pre- (A) and postoperative (B) contrast-enhanced CT images at 6 months. The growth of the RPA was significant, while the LPA remained at normal perfusion. CT, Computed tomography; RPA, right pulmonary artery; LPA, left pulmonary artery; IPABF, intrapulmonary-artery baffle fenestration.

CFD analysis indicated a diameter ratio (fenestration diameter/hypoplastic PA diameter) of 0.91 to achieve an FDR of 50% with a low oscillatory shear index and moderate energy loss. By contrast, hematocrit and the BTT shunt diameter had little influence on FDR. During the operation, an IPABF was successfully performed within the LPA, a 5-mm artificial vessel was used to construct a BTT shunt, and the patent ductus arteriosus was also ligated. After these procedures, the patient was transferred to the pediatric intensive care unit and was returned to the general ward after 3 days. The postoperative course was uneventful, and the patient was discharged 5 days later without complication. Postoperative contrast-enhanced CT and pulmonary arteriography at 6 months indicated a significant growth of the RPA (Figure 2, B, and Figure 3). Table 1 presents the cardiac catheterization findings obtained 9 months and 24 months after the IPABF surgery (before the Glenn procedure and Fontan procedure, respectively). No adverse events occurred during the follow-up.

Figure 3.

Pulmonary arteriography at 1 month (A) and 6 months (B) postoperation.

Table 1.

Cardiac catheterization findings obtained 9 months and 24 months after the IPABF surgery (before the Glenn procedure and Fontan procedure, respectively)

Parameters	9 mo	24 mo
RPA diameter, mm	9	10
Mean RPA pressure, mm Hg	19	8
Mean SVC pressure, mm Hg	14	10

IPABF, Intrapulmonary-artery baffle fenestration; RPA, right pulmonary artery; SVC, superior vena cava.

Discussion

Poorly grown PA presents a critical obstacle to achieving successful Fontan circulation in patients with FSV. Furthermore, unbalanced PA contributes to the formation of collateral circulation, which can increase pulmonary vascular resistance, predisposing patients to PA hypertension and eventually right heart failure. Thus, relieving unbalanced PA is crucial for optimizing outcomes of patients with FSV.

Patch enlargement is effective for relieving the stenosis of hypoplastic PA. However, Gao and Zhu³ reported that restenosis still occurred in 40% of patients who underwent patch enlargement from the origin to the hilum, and in 33% of those with enlargement limited to the origin. This may be attributed to scar formation and the limited potential for further development. Consequently, promoting the natural growth of hypoplastic PA may be preferable. Ishidou and colleagues⁴ proposed a technique called “intrapulmonary-artery septation” for Fontan candidates with unbalanced PA. This method involves creating a septation within the unaffected PA and connecting it with a Glenn shunt. Simultaneously, a systemic-pulmonary shunt is constructed between the innominate artery and the poorly-grown PA to enhance blood flow and improve oxygenation.⁴ Although widely adopted, the primary drawback of this technique is its complexity and time-consuming nature. Another lower-cost and easier approach is using a band to restrict the diameter of the unaffected PA, thereby directing more blood through the hypoplastic PA.⁵ This approach may also lead to scar formation after the band is removed, leaving negative impacts on long-term outcomes.

We developed a simplified approach to promote the growth of hypoplastic PA. Instead of completely separating the unaffected PA, we created a baffle fenestration within it, allowing more blood into the hypoplastic PA and promoting its growth. A BTT shunt was also constructed to increase blood flow and improve oxygenation. This technique is simpler to adopt, significantly reducing the CPB duration, and the result was satisfactory, as presented in our case. Because the baffle fenestration size and the shunt diameter should be determined preoperatively, and previous studies addressing these issues were lacking, we performed CFD analysis to simulate hemodynamic changes after surgery and provide quantitative evidence to guide surgical planning. Notably, our results revealed little impact of the BTT shunt on FDR, and its diameter primarily affected total pulmonary flow and energy loss; thus, its size can be selected following general principles for acceptable oxygenation. Furthermore, the effectiveness of our technique may be limited when the hypoplastic PA diameter is ≤3 mm, a condition in which a fenestration <3 mm can produce a high-shear, high-energy-loss flow state that increases thrombotic risk and reduces growth potential.²

Despite the advantages, we acknowledge 2 limitations: First, our technique remains under investigation and may be an individualized procedure. The diameter ratio of 0.91 and the hypoplastic PA diameter threshold were derived from a single case; further validation is required to confirm generalizability, effectiveness, and safety. Second, perioperative anticoagulant therapy is essential to prevent thrombosis around the IPABF.

Conclusions

In this study, we presented a modified technique to promote the growth of hypoplastic PA. Given its simplicity and efficiency, IPABF may serve as a viable interim strategy for Fontan candidates with a FSV and unbalanced PA.

Conflict of Interest Statement

The authors reported no conflicts of interest.

The Journal policy requires editors and reviewers to disclose conflicts of interest and to decline handling or reviewing manuscripts for which they may have a conflict of interest. The editors and reviewers of this article have no conflicts of interest.

Supplementary Data

Video 1

The surgical procedures of the intrapulmonary-artery baffle fenestration. Video available at: https://www.jtcvs.org/article/S2666-2507(25)00429-8/fulltext.