Interventions Involving the Use of Covered Coronary Artery Stents for Pseudoaneurysms of Blalock-Taussig Shunts

Introduction

One of the most dangerous complications associated with a modified Blalock-Taussig shunt involves the formation of a pseudoaneurysm. A pseudoaneurysm is a rare and potentially fatal complication for which the primary treatment has traditionally been surgery. However said surgery may also be associated with significant morbidity and mortality. Aneurysmal sacs involve the outer arterial layers and the surrounding tissue. They are rare. The primary complications of shunt-related pseudoaneurysm include rupture and massive pulmonary hemorrhage. ^{1 -4} We describe two children herein who had recurrent pulmonary hemorrhage secondary to pseudoaneurysms of the left subclavian artery following modified Blalock-Taussig shunt procedures.

Case 1

A three-year and ten-month-old girl with double-outlet right ventricle and severe subpulmonary and pulmonary stenosis underwent a left modified Blalock-Taussig shunt through a left thoracotomy because of severe cyanosis. Two months later, she was referred to our facility from another intensive care unit because of new onset of intermittent massive pulmonary hemorrhage. Her oxygen saturation level was approximately 70%. Her chest X-ray was significant for an enlarged upper left mediastinum (Figure 1A). None of the laboratory parameters or clinical findings were indicative of the presence of an infection. Lung tomography demonstrated an aneurysmal lesion that originated from the left subclavian artery in the left upper area of the chest. Upon her first catheterization, we observed a pseudoaneurysm arising from the left subclavian artery end of the modified Blalock-Taussig shunt and occupying the posterior portion of the left chest (Figure 1B). The shunt was completely occluded. The pseudoaneurysm measured 22 × 17 mm. We initially thought that there was no active hemorrhage and that coil embolization would provide enough protection by promoting thrombosis within the pseudoaneurysm. We placed 3 PFM Nıt-Occlud coils (11 × 4, 5 × 4, and 4 × 4), 2 Gianturco coils (35-4-3 and 35-4-3), and 3 Cook coils (8-PDA5, 8-PDA4, and 6.5-PDA5). Following coil embolization, the passage of contrast inside of the pseudoaneurysm appeared to have slowed and eventually stopped, resulting in stasis (Figure 1C). At this time, we considered the pseudoaneurysm to have been occluded. The patient was progressing well, with stable vital signs, and she had not had any further episodes of hemoptysis. Three-dimensional computed tomography demonstrated that the pseudoaneurysm was occluded by the various coils (Figure 1D). The patient was discharged three days later. However, 21 days later, the patient presented again with massive hemoptysis. We subsequently performed a second catheterization with vascular access via the right femoral artery and observed a new pseudoaneurysm within the same vascular region opposite the site of the previous pseudoaneurysm, and its dimensions were 30 × 15 mm. Surgery was deemed to be very risky. The length of the left subclavian artery was 17 mm. The intact vessel radius was 4.4 mm but decreased to 1.4 mm because of the mass effect of pseudoaneurysm. We inserted a 0.014-in floppy coronary guidewire into the vertebral artery and advanced a 4 × 17 mm pericardium covered coronary artery stent (Itgi Med or Akiva, Israel) from the beginning of the vertebral artery to the aortic arch, eventually reaching the left subclavian artery, where the sac of the pseudoaneurysm was covered by the stent, which was dilated with a 4.5 noncompliant coronary balloon (Figure 1E and F). The patient has been followed one year and has not had any additional episodes of hemoptysis following the procedure. Corrective surgery is planned for her cardiac anomaly.

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Figure 1.

A pseudoaneurysm, which formed following a left modified Blalock-Taussig shunt and subsequent transcatheter intervention for case 1. A, A chest X-ray depicting a mass effect. B and C, The first transcatheter intervention, using various types of coils. D, Three-dimensional volume rendering multisliced computerized tomography following coil embolizations. E and F, The occlusion of the pseudoaneurysm using a covered coronary stent.

Case 2

A seven-month-old boy with tricuspid atresia and pulmonary atresia, hypoplastic right ventricle, and patent ductus arteriosus-dependent pulmonary circulation underwent a left modified Blalock-Taussig shunt through a left thoracotomy. Five months after the shunt operation, the patient was referred to our clinic because of massive hemoptysis. The left lung was completely nonaerated as determined by chest X-ray. The patient had portal vein thrombosis for which he had been receiving aspirin and low-molecular-weight heparin. None of the laboratory parameters or clinical findings were indicative of the presence of an infection. Based on our experience with our previous patient, we suspected that the boy’s hemorrhage had been caused by a pseudoaneurysm of the left subclavian artery. Upon cardiac catheterization, the dimensions of the pseudoaneurysm were found to be 33 × 37 mm, and because of its size, the risk of rupture of the pseudoaneurysm was considered to be high (Figure 2A). A small number of collateral arteries were visible near the distal portion of the aneurysm. The pseudoaneurysm’s mass effect caused the trachea to deviate to the right and the left pulmonary artery to move downward. The boy’s oxygen saturation was 50%. We subsequently inserted a Flexor Ansel 5F sheath (Cook Medical Incorporated, Bloomington, Indiana) and advanced a coronary floppy wire into the left subclavian artery. A 3 × 16 mm polytetrahydrofuran covered stent (InSitu Tech, St Paul, Minnesota) was subsequently placed. However, we appreciated residual flow into the aneurysmal sac (Figure 2B and C). Therefore, a second covered stent was advanced to the proximal portion of the first stent via the telescopic method. Following dilatation with a 3.5 × 8 mm noncompliant balloon, residual flow was again visualized. We subsequently placed a third (3.5 × 23 mm) pericardial covered stent (Itgi Med or Akiva, Israel) inside the other devices (Figure 2D-F). Residual flow ceased following this portion of the procedure. The patient’s oxygen saturation subsequently increased to 66%. Seven days later, he underwent surgical construction of a right modified Blalock-Taussig shunt. A small amount of residual flow from the left subclavian artery into the aneurysmal sac was appreciated during a diagnostic catheterization performed ten days later. The patient subsequently underwent a surgical aneurysmal excision. During the operation, a segment of the left lung was found surrounding the pseudoaneurysm. The graft of the Blalock-Taussig shunt was completely separated from the left subclavian artery, and the covered coronary stent was closed at the aneurysmal neck. Following the operation, however, the patient passed away secondary to respiratory failure and metabolic problems.

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Figure 2.

A large pseudoaneurysm, which formed following a left modified Blalock-Taussig shunt and subsequent transcatheter intervention for case 2. A-F, The occlusion of the pseudoaneurysm using three covered coronary stents with the telescopic method.

Discussion

Pseudoaneurysm formation is a rare complication of the modified Blalock-Taussig shunt operation. The factors that are related to pseudoaneurysm formation include infection, structural weakness of the artery or the graft, type of suturing material used, and mechanical stress at the anastomotic site or dehiscence. ^1,5 In several reported cases, the exact pathological mechanism of the cases was unknown, and vascular infection could be one explanation. In our cases, however, we did not detect any positive infection-related parameters. In the second case, the surgical team observed that the shunt length was slightly shorter than expected and that the aortic end of the graft had completely dehisced from the anastomotic site. Therefore, in our opinion, the use of the short shunt created stress at the suture line and caused it to dehisce. In one reported case, Demyanchuk et al detected a pseudoaneurysm a long period of time after the shunt operation, and they suggested that the main cause was that the relatively short shunt did not grow simultaneously with the somatic growth of the patient. ³

In our case 1, lung computerized tomography showed that the left subclavian artery was associated with the pseudoaneurysm. In case 2, based on our experiences, we first performed cardiac catheterization. After the stenting procedure and construction of the right modified Blalock-Taussig shunt in case 2, the mass effect of the pseudoaneurysm persisted, the pseudoaneurysm did not resolve, and thus the patient had difficulty breathing. Therefore, we opined that placing a fourth stent to stop the tiny residual aneurysmal flow would not have been helpful in case 2. Our plan included the surgical resection of the pseudoaneurysm sac.

In 2012, Srivastava et al reported the use a covered stent to treat an infected pseudoaneuryem. ⁴ An Advanta V12 balloon expandable covered stent (Atrium Medical Corporation, Hudson, New Hampshire) was deployed to eliminate the pseudoaneurysm. ⁴ However, their patient was older than our patient. Because of the small size of the involved vessels, we chose to use pericardium and polytetrahydrofuran covered coronary artery stents to occlude the entering site of the pseudoaneurysms in our two cases.

Pseudoaneurysms can be treated using either the surgical or the transcatheter approach. ² The transcatheter approach is preferred in patients who are critically ill or having active hemorrhage. Both of our patients had massive hemoptysis; therefore, an operation with or without cardiopulmonary bypass may have been more risky for them.

Conclusion

These cases highlight the use of pericardial and polytetrahydrofuran covered coronary artery stents as an alternative option in the treatment of pseudoaneurysms associated with modified Blalock-Taussig shunts. We have concluded that covered coronary artery stent placement, with or without coil embolization of the pseudoaneurysm cavity, represents a promising new tool for treating pseudoaneurysms via endovascular methods. It also makes it possible to preserve the patency of both the vessels and their side branches.