Transcatheter coil embolization of an idiopathic systemic-to-pulmonary artery fistula using a combined systemic arterial and pulmonary arterial approach

Abstract

Systemic-to-pulmonary artery fistula is a rare vascular anomaly characterized by a direct communication between the systemic and pulmonary arteries, carrying a risk of rupture and life-threatening hemoptysis, for which transcatheter embolization has been proposed as a minimally invasive treatment option. We report a case of a 46-year-old woman with an incidentally detected idiopathic SA-PAF arising from a tortuous mediastinal branch of the aorta and forming a fistula with the A7 pulmonary artery of the right lower lobe. Due to the high tortuosity of the feeding artery, embolization from the systemic side alone was anticipated to result in incomplete occlusion due to persistent retrograde flow from the pulmonary arterial side. We therefore performed coil embolization via a combined approach from both the systemic and pulmonary sides. Complete obliteration was achieved without complications, and magnetic resonance angiography at 3 months confirmed no residual flow.

Introduction

Systemic-to-pulmonary artery fistula (SA‐PAF) is a rare vascular anomaly characterized by abnormal communication between the systemic and pulmonary circulations [1,2]. Due to its rarity, the long-term prognosis remains unclear, and consensus on its optimal management has yet to be established [2,3]. Although transcatheter embolization is a recognized non-surgical treatment option, such cases are rarely reported [2,3]. In this report, we present a case of idiopathic SA‐PAF that was successfully treated with coil embolization performed from both the systemic and pulmonary arterial sides.

Case report

A 46-year-old woman with no significant medical history was referred to our hospital for an abnormal finding incidentally detected on screening chest computed tomography (CT). Chest CT performed at our institution revealed a tortuous vascular structure in the right lower lobe (Fig. 1). Contrast-enhanced CT showed that this structure was continuous with the A7 pulmonary artery and appeared to receive its supply via the pleura from a mediastinal branch arising from the aorta at the Th8 level. These findings were consistent with SA-PAF. The dilated vessel measured 4.7 mm in maximum diameter, and the A7 pulmonary artery and the mediastinal branch adjacent to the dilated vessel measured 1.9 mm and 1.7 mm in maximum diameter, respectively. Considering the risks of rupture and hemoptysis, we decided to proceed with treatment after shared decision-making with the patient. Transcatheter embolization was selected owing to its lower invasiveness compared with surgical ligation or pneumonectomy.

Fig. 1.

(A) A chest CT image (lung window setting) reveals a tortuous vascular structure in the right lower lobe (arrow). (B) 3D reconstructed CT images show the structure continuous with the A7 pulmonary artery (arrowhead) and supplied by a mediastinal branch arising from the aorta at the Th8 level (arrow), diagnosed as a systemic-to-pulmonary artery fistula.

The feeding mediastinal branch arising from the aorta was highly tortuous, making it technically challenging to advance the catheter sufficiently far distally toward the pulmonary artery. If embolization had been performed from the systemic arterial side alone, occlusion would have been limited to the proximal portion of the feeding artery, and retrograde blood flow from the draining A7 pulmonary artery branch was anticipated to persist, potentially resulting in incomplete occlusion of the fistula. This raised concern that the risks of rupture and hemoptysis would remain. Therefore, we decided to approach the fistula vessel from both the systemic arterial side and the pulmonary arterial side to achieve complete embolization.

The right femoral vein was punctured, and a 6-Fr guiding catheter (Mach1; Boston Scientific, Marlborough, MA) was placed, followed by a 4-Fr catheter (C2; Hanako Medical, Saitama, Japan) advanced into the right pulmonary artery. A microcatheter (2.2-Fr Breakthrough; Boston Scientific) was then advanced to the dilated portion of the SA-PAF continuous with the A7 pulmonary artery using a 0.014-inch microwire (ASAHI Meister; ASAHI INTECC, Aichi, Japan). Simultaneously, through a left femoral artery approach with a 4-Fr sheath, the mediastinal branch was selected using a 4-Fr catheter (CJ1; Hanako Medical). Angiography revealed the fistula between the systemic and pulmonary arteries (Fig. 2A). A microcatheter (1.9-Fr Progreat Lambda; Terumo, Tokyo, Japan) was then advanced into the abnormal vessel using a 0.014-inch microwire (ASAHI Meister; ASAHI INTECC) as distally as possible (Fig. 2B). Coil embolization was initiated from the systemic arterial side; 2 detachable hydrogel microcoils (AZUR Soft 3D; Terumo) and 4 bare platinum pushable microcoils (C-stopper 14; Piolax, Yokohama, Japan) were deployed (Fig. 2C). Subsequently, through the microcatheter placed in the A7 pulmonary artery, the fistula vessel was further embolized using 4 detachable hydrogel microcoils (AZUR Soft 3D; Terumo), and post-embolization aortography demonstrated complete disappearance of the fistula (Figs. 2D and 2E).

Fig. 2.

(A) Angiography from the systemic arterial side using a 4-Fr catheter shows the tortuous fistula vessel continuing into the dilated vessel (arrow), with retrograde opacification of the A7 pulmonary artery. (B) Angiography from the systemic arterial side using a 1.9-Fr microcatheter advanced as far as possible into the fistula vessel (arrow). (C) Embolization from the systemic arterial side was performed using microcoils until complete flow stasis was achieved. (D) A 2.2-Fr microcatheter was advanced into the dilated vessel from the pulmonary arterial side (arrow), followed by embolization using microcoils. (E) Post-embolization angiography from the A7 pulmonary artery demonstrates complete occlusion of the dilated vessel.

The patient was discharged 3 days later without complications. Magnetic resonance angiography (MRA) was selected for follow-up assessment of residual blood flow within the fistula to minimize beam-hardening artifacts from the coils and to avoid additional radiation exposure. MRA performed 3 months post-procedure confirmed the absence of blood flow within the fistula (Fig. 3).

Fig. 3.

Magnetic resonance angiography performed 3 months later confirmed disappearance of the systemic-to-pulmonary artery fistula (circle).

Discussion

In this report, we present a case of idiopathic SA‐PAF in which a tortuous mediastinal branch of the aorta formed a fistula with the A7 pulmonary artery. Due to the high tortuosity of the feeding artery, distal catheter advancement from the systemic side was technically challenging, and we therefore performed coil embolization via a combined systemic and pulmonary arterial approach, achieving complete obliteration of the fistula.

SA‐PAF is a rare vascular anomaly characterized by a direct communication between the systemic and pulmonary arteries, resulting in a left-to-right fistula. While some cases are congenital, others are acquired secondary to conditions such as chronic inflammation or trauma [2,3]. Although SA‐PAF is typically diagnosed in patients presenting with symptoms such as hemoptysis, advances in CT technology have led to its increasing incidental detection in asymptomatic individuals [1,3]. However, the natural history of untreated SA-PAF remains unclear, and neither the rupture rate nor a size-based threshold for treatment has been established. Some patients can be managed conservatively without complications; for example, Alsafi et al. reported 10 conservatively managed patients who remained clinically well during a median follow-up of 4.5 years [4]. Nevertheless, because SA-PAF is continuously exposed to high systemic arterial pressures, untreated cases carry a significant risk of aneurysmal enlargement, rupture, and subsequent life-threatening hemoptysis. Indeed, serious hemorrhagic complications, including massive hemoptysis and hemothorax, have been reported in patients with SA-PAF [5,6], indicating that rupture can occur despite an initially benign course. Therefore, even in asymptomatic patients, therapeutic intervention is considered justified to prevent future bleeding complications.

When embolization is performed exclusively from the systemic arterial side, proximal occlusion of the feeding artery reduces systemic arterial pressure, which may result in relatively higher pressure on the pulmonary artery side, driving retrograde flow through the fistula. This may lead to incomplete fistula closure, leaving the patient at continued risk of rupture and life-threatening hemoptysis [7]. Therefore, controlling both the systemic artery and pulmonary artery is considered essential for safe and complete occlusion in the transcatheter management of SA‐PAF. A previous report described embolization from both sides to prevent embolic materials from migrating into the pulmonary circulation, with the pulmonary artery embolized first, followed by the systemic artery [8]. However, embolizing the pulmonary artery first may elevate pressure within the fistula, which could potentially increase the risk of intraprocedural rupture. In our case, we therefore chose to embolize the systemic artery first, followed by the pulmonary artery, with the aim of avoiding this risk.

The exact origin of the feeding mediastinal branch remained unclear, as cone-beam CT angiography of this branch was not performed. Because the feeder ran close to the esophagus on CT, a connection to an esophageal artery could not be entirely excluded. Although the esophagus has a rich collateral blood supply, esophageal infarction has been reported as a potential complication of bronchial artery embolization [9]. N-Butyl-2-cyanoacrylate was therefore avoided, given the potential risk of nontarget embolization into esophageal branches or migration through the fistula into the pulmonary artery. Coils were selected instead to minimize this risk.

In conclusion, a combined systemic and pulmonary arterial approach may serve as a viable therapeutic option for the management of idiopathic SA‐PAF, particularly in cases where embolization from the systemic arterial side alone is insufficient.

Patient consent

Written informed consent was obtained for the publication of this article.