Coronary artery bypass graft pseudoaneurysm from saphenous vein graft stent fracture

Abstract

Saphenous venous graft (SVG) pseudoaneurysms are a rare complication of coronary artery bypass grafting (CABG). An 85-year-old man with CABG and a distal SVG stent presented with dyspnea. Chest computed tomography (CT) revealed a large partially thrombosed pseudoaneurysm at the distal SVG with stent fracture. Endoluminal exclusion of the distal SVG pseudoaneurysm using a covered stent was performed. Follow-up chest CT and angiography showed persistent pseudoaneurysm filling and enlargement. The SVG proximal to the pseudoaneurysm was embolized with coils to reduce rupture risk. Following embolization, the patient’s left ventricular ejection fraction was moderately depressed but the patient remained stable and was discharged.

<Learning objective: Saphenous venous graft pseudoaneurysms are a rare post-operative complication of coronary artery bypass graft procedures with a risk of impending rupture if left untreated. Fracture of a vein graft stent is an even further unique etiology of pseudoaneurysms. Covered stents are a practical therapeutic option for the treatment of vein graft pseudoaneurysms, especially in high risk patients who are not surgical candidates.>

Introduction

Saphenous venous graft (SVG) pseudoaneurysms are a rare post-operative complication of coronary artery bypass graft (CABG) surgery. When they arise, the proximal or distal anastomoses are involved, typically occurring within the first 6 months of surgery [1]. While patients are often asymptomatic and the diagnosis is usually incidental, acute rupture of these pseudoaneurysms is associated with a high morbidity and mortality [2].

Case report

An 85-year-old man with a history of chronic obstructive pulmonary disease, hypertension, diabetes, CABG (SVG to right posterior descending artery 17 years previously), and myocardial infarction (status-post a 7 × 40 mm nitinol stent to the distal SVG 9 years ago) presented with progressive fatigue and dyspnea on exertion. Upon arrival, an echocardiogram demonstrated a right atrial mass. Contrast-enhanced computed tomography (CT) of the chest revealed a large partially thrombosed pseudoaneurysm at the distal SVG causing mass effect on the right atrium; the SVG stent was fractured with a large fragment floating in the pseudoaneurysm (Fig. 1). A subsequent coronary angiography confirmed this finding.

Fig. 1.

(A) Axial contrast-enhanced computed tomography (CT) image shows a partially thrombosed pseudoaneurysm in the region of the right atrium (*) with a large stent fragment floating posteriorly (arrow). (B) Curved coronal reformatted (left) and sagittal (right) CT images demonstrate fracture of the mid-portion of the saphenous venous graft stent (arrow) with the associated pseudoaneurysm. The large C-shaped fractured stent fragment is floating in the posterior portion of the pseudoaneurysm (arrow).

Since the patient was not a surgical candidate given his comorbidities, endoluminal exclusion of the pseudoaneurysm using a covered stent was performed. The following steps were involved in the procedure.

• 1.A 7F 90 cm Bright tip sheath was placed in the descending segment of the aortic arch.
• 2.A 5F MPA1 catheter was used to engage SVG to posterior descending artery (PDA).
• 3.A 0.014″ Grand slam wire was used to cross the pseudoaneurysm. Thereafter, the 7F sheath was advanced over the 5F MPA1 guide into the SVG. MPA1 was removed and intravascular ultrasound (Boston Scientific, Marlborough, MA) was performed to assess the vessel dimensions.
• 4.Delivery of a 7 × 100 mm Viabhan stent (WL Gore and Associates, Flagstaff, AZ) over the 0.014″ wire was unsuccessful.
• 5.A 0.014″ wire was exchanged for a 0.018″ wire over a Transit catheter. We then used a 7F dilator to advance the 7F sheath into the proximal segment of the fractured stent.
• 6.A 7 × 100 mm Viabhan stent was then advanced across the pseudoaneurysm and deployed.

Post stent deployment, the angiogram demonstrated diminished but persistent filling of the pseudoaneurysm via a distal anastomotic endoleak. Due to the discrepancy in sizes of the SVG and native PDA, the distal end of the covered stent could not be extended into the PDA to completely exclude the pseudoaneurysm.

At a 6-week follow-up, the patient had residual symptoms. Repeat angiography demonstrated enlargement of the pseudoaneurysm with widening of the neck. Given the rapid enlargement of the pseudoaneurysm, we performed coil embolization of the graft proximally, leading to an iatrogenic myocardial infarction and termination of flow into the pseudoaneurysm, thereby eliminating the risk of rupture and sudden cardiac death. Coiling was performed using four 14 cm Cook Nester Embolization Coils (Cook Medical Inc., Bloomington, IN). Contrast injection confirmed occlusion of the graft at the level of the coils with no flow distally (Fig. 2). The inferior wall infarction was an anticipated consequence of the procedure and there were no unexpected complications. The benefit of occluding the SVG (to reduce risk of pseudoaneurysm rupture, a fatal event) was felt to be greater than the sequelae of an inferior wall infarct. Post procedure, the left ventricular ejection fraction decreased from 50% to 35%. The patient was discharged home in stable condition.

Fig. 2.

(A) Coronary angiogram demonstrates the displaced stent fragment (arrow) and large pseudoaneurysm (asterisk). (B) Six-week follow-up coronal maximum intensity projection CT image demonstrates persistent filling of the pseudoaneurysm at the distal end of the new covered stent (arrow). (C) Coronary angiogram following placement of multiple endoluminal coils (arrow) within the saphenous venous graft demonstrates no filling of the pseudoaneurysm.

Discussion

SVG pseudoaneurysms are a rare complication of CABG surgery. Unlike an SVG aneurysm which is often a result of atherosclerotic degeneration, pseudoaneurysms are usually associated with an infection or leak; they usually occur at the proximal or distal anastomoses [2], [3]. Our case was unique given the etiology of SVG pseudoaneurysm was a fractured stent. This is only the second report of an aneurysmal SVG caused by a stent fracture; this is also the second case treated with distal covered stent deployment with proximal coil occlusion for eliminating risk of rupture [3]. Some factors that can lead to stent fracture include the stent architecture, biomechanical stress on the vessel wall, and implantation technique [3]. The etiology of stent fracture in this case was unclear.

The exact pathophysiology of SVG pseudoaneurysms and aneurysms remains unclear. First-line treatment for this type of complication is surgical repair. In patients unable to undergo repeat sternotomy, percutaneous covered stent placement, to exclude the pseudoaneurysm, may be a crucial management option. However, as demonstrated in our case, the difference in caliber of the SVG and native coronary vessel may limit extension of the covered stent far enough to adequately exclude the pseudoaneurysm.

Conclusion

Covered stents are a practical therapeutic option for the treatment of SVG pseudoaneurysms, especially in high-risk patients who are not surgical candidates. Coil occlusion of the vein graft, proximal to the pseudoaneurysm, may be utilized in select cases to minimize risk of rupture.

Conflict of interest

Authors declare no conflicts of interest.

Disclosures

The authors report no financial relationships or conflicts of interest regarding the content herein.