Resolution of intrapulmonary arteriovenous shunting after restoration of pulmonary inflow.
Central Message.
Systemic-to-pulmonary shunt recruited reversible intrapulmonary arteriovenous shunting in isolated UAPA, with PAH; the phenotype resolved after restoration of pulmonary inflow.
The concept of a hepatic factor emerged from observations that the exclusion of hepatic venous effluent from the pulmonary circulation, particularly in passive-flow cavopulmonary physiology, is associated with the development of pulmonary arteriovenous malformations.1 Reversal of this phenotype after restoration of hepatic venous flow to the affected lung supports an important role for hepatic venous effluent in pulmonary vascular homeostasis.2 Intrapulmonary arteriovenous pathways may, however, also be recruited under distinct physiologic stresses beyond hepatic venous effluent exclusion.3 We report a child with isolated unilateral absence of the right pulmonary artery4 in whom intrapulmonary shunting and pulmonary arterial hypertension (PAH) emerged after a systemic-to-pulmonary shunt and resolved after restoration of right ventricular pulmonary arterial inflow, suggesting an early functional and potentially reversible component. This study was approved by the institutional review board of Shizuoka General Hospital (SGHIRB #2024027, September 18, 2025). Written informed consent was obtained.
Case Report
A boy was noted to have mediastinal rightward shift on radiography in infancy. Cardiac catheterization at 2 years showed absence of continuity between the proximal pulmonary artery (PA) and the main PA without cardiac anomalies. Oxygen saturation was 96% on room air. Selective angiography showed a diminutive intraparenchymal right PA supplied by bronchial arterial flow and systemic-pulmonary collaterals.
At 4 years, recurrent respiratory infections prompted augmentation of right lung perfusion. At the initial operation, a long, completely occluded ligamentous segment extended from the base of the innominate artery to the hilar right PA. After opening this segment at the hilar level and performing partial endarterectomy, we discovered that the branch pulmonary arteries measured only 2 to 3 mm. This anatomy suggested a native but markedly hypoplastic right pulmonary arterial pathway, making immediate single-stage anatomic revascularization unfavorable; therefore, a 5-mm modified Blalock-Taussig shunt was selected as a staged approach to promote right pulmonary arterial growth. Follow-up catheterizations at 1, 2, and 4 years showed increasing right PA pressures with minimal distal growth (Table 1). Right pulmonary angiography showed early pulmonary venous opacification, corroborated by selective contrast echocardiography, consistent with intrapulmonary shunting; this persisted at 2 and 4 years (Figure 1; Video 1).
Table 1.
Catheter findings
| Measurement site | Postshunt |
Postrepair |
|||
|---|---|---|---|---|---|
| 1 y | 2 y | 4 y | 1 y | 4 y | |
| Right PA | 76/48 (61) | 60/37 (48) | 44/33 (40) | 38/7 (19) | 26/12 (18) |
| Left PA | 30/12 (21) | 30/9 (20) | 35/13 (22) | 38/2 (19) | 26/12 (16) |
| Aorta | 95/49 (73) | 94/37 (64) | 95/50 (72) | 124/72 (98) | 100/60 (80) |
Values are shown as systolic/diastolic mm Hg (mean). PA, Pulmonary artery.
Figure 1.
Right pulmonary angiography showing early pulmonary venous opacification during systemic-to-pulmonary shunt (A) with resolution after restoration (B, 1 year; C, 4 years). The white arrow indicates early opacification of the pulmonary vein.
Four years later, the shunt was taken down, and a 14-mm expanded polytetrafluoroethylene conduit was interposed between the main and right PAs, restoring hepatic venous effluent and pulsatile inflow. Although the proximal hilar pulmonary arterial region had enlarged somewhat, the feasibility of using a larger conduit at reoperation reflected oblique reconstruction of the proximal hilar anastomotic site using the surrounding adhesions, rather than substantial growth of the distal native PAs. No postoperative deoxygenation occurred. At 1 year, catheterization showed a patent conduit without PAH, and the shunt phenotype was no longer detectable. This remained absent at 4 years (Figure 1). Over 8 years, the child remained asymptomatic; magnetic resonance imaging showed persistently lower right than left pulmonary flow (0.57-0.89 vs 3.9-4.1 L/min).
Comment
This case highlights an unusual response to systemic-to-pulmonary shunting. Rather than promoting normal pulmonary arterial growth, the shunt produced PAH and recruited intrapulmonary right-to-left shunting. In isolated unilateral absence of the right pulmonary artery, parenchymal growth may outpace the development of the pulmonary arterial bed, predisposing the affected lung to pressure elevation under augmented flow.
In this patient, the shunt delivered blood that had already traversed the left pulmonary circulation and lacked direct hepatic venous effluent exposure, altering inflow characteristics beyond oxygen content alone. After restoration of right ventricular–pulmonary arterial continuity, the shunt phenotype resolved, and right pulmonary flow increased despite low pressures. The absence of postoperative deoxygenation further supported that the shunt phenotype had functionally regressed soon after restoration of physiologic pulmonary inflow. Comparable reversibility after pulmonary inflow rerouting has been described in hemitruncus repair.5 Although the importance of hepatic venous effluent in maintaining pulmonary vascular tone has been established mainly in single-ventricle venous shunt physiology, this case extends that concept to biventricular circulation with restored right ventricular–driven pulmonary flow. Consistent with a recent conceptual framework for acquired intrapulmonary shunting,E1 This reversibility may reflect functional recruitment of low-resistance intrapulmonary pathways before fixed anatomic remodeling becomes established.
Declaration of Generative AI and AI-Assisted Technologies in the Writing Process
During the preparation of this work, the authors used ChatGPT in order to edit language, grammar, and style. After using this tool/service, the authors reviewed and edited the content as needed and take full responsibility for the content of the publication.
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
Serial right pulmonary angiography demonstrating disappearance of early pulmonary venous opacification after restoration. Video available at: https://www.jtcvs.org/article/S2666-2736(26)00337-2/fulltext.
References
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E-Reference
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Associated Data
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Supplementary Materials
Serial right pulmonary angiography demonstrating disappearance of early pulmonary venous opacification after restoration. Video available at: https://www.jtcvs.org/article/S2666-2736(26)00337-2/fulltext.