Staged Stenting of a Long Aneurysm of a Saphenous Vein
Coronary Artery Bypass Graft

Aneurysms of saphenous vein grafts (SVG) to coronary arteries were first reported in 1975, but remain an unusual complication of coronary artery bypass graft (CABG) surgery.^1,2 There are different, mostly surgical, treatment modalities, but in some cases percutaneous coil embolization, covered stent implantation and Amplatzer vascular plug occlusion have been attempted.^3,4 We report on a case of a long SVG aneurysm 21 years after CABG surgery, which was treated with a Magic Wallstent (Boston Scientific, Maple Grove, Minnesota) and PTFE-covered stents.
Case Report. A 65-year-old male who underwent CABG surgery 21 years ago and received a mitral valve annuloplasty 5 years ago, presented with recurrent angina. The anatomy for the repeat CABG was a SVG to the left anterior descending artery (LAD), a SVG to the marginal branch, a SVG to the proximal part of the right coronary artery (RCA) and a sequential SVG to the diagonal branch, the posterior left ventricular branch and the distal part of the RCA. A chest X-ray showed mild cardiomegaly. Computed tomography showed an aneurysm of the SVG (measuring approximately 43 x 33 mm with mural thrombus) (Figure 1). Diagnostic catheterization showed no significant LAD disease and an occluded RCA and left circumflex artery (LCX). The SVG to the LAD and the sequential SVG to the diagonal branch, the posterior left ventricular branch and the distal RCA were also occluded. However, the SVG to the marginal branch of the LCX showed a large aneurysm with mural thrombus, which measured 32 x 45 mm (Figure 2A). Intravascular ultrasound showed an enormous aneurysm with massive thrombus (Figure 3D).

Because of the high-risk associated with surgical correction, the decision was made to treat the aneurysm. A 7 Fr left coronary bypass guiding catheter and a0.014 inch Confianza guidewire (Asahi Intecc, Seto, Japan) were chosen for support and stent delivery. The lesion was pretreated with a 5.5 x 47 mm Magic Wallstent followed by 4.0 x 26, 4.0 x 26, 4.0 x 19 and 4.0 x 16 mm PTFE-covered stents (Figure 2B). The preference for a long Wallstent was to secure mid-segment axial strength where there was no mechanical support from the adjacent vascular wall. Postdilatation was performed using a 5.0 x 20 mm balloon, which yielded an acceptable final angiographic and IVUS outcome with minimal flow into the aneurysm at the proximal and distal ends of the aneurysm (Figures 2B and 3A, 3B and 3C). Repeat coronary angiography at 6 months showed some residual flow into the aneurysm from the proximal and distal ends of the stents (Figure 2C). Because flow from the distal end was significant, although potentially not harmful, we implanted an additional 4.0 x 26 mm PTFE-covered stent at the distal edge of the previous stent and performed balloon dilatation with a 5.5 x 20 mm balloon to reduce the flow that was facilitating the thrombus organization. Final angiography and IVUS showed no significant flow into the aneurysm. (Figures 2D and 4).

Discussion
Approximately 130 cases of SVG aneurysms or pseudoaneurysms have been published since 1975. The aneurysms have been of various sizes, ranging from between 10 to 130 mm in diameter. The interval between operation and the occurrence of the aneurysm varied from 11 days to 21 years.^1–37
Etiology and pathology. True aneurysms are a localized dilatation of an entire blood vessel wall, are atherosclerotic in nature and appear as a late postoperative complication more than 5 years after CABG.⁵ Reported possible explanations for the formation of SVG aneurysms include atherosclerotic change of the SVG, mycotic vasculitis, vein wall weakness and suture line breakdown due to suture material or technical failure.^6–8 True aneurysms tend to occur more commonly in the body of the graft.^9,10

Pseudoaneurysms are a rupture in the vascular wall which lead to an extravascular hematoma, freely communicating with the intravascular space; they may occur early as well as late after initial surgery, and at the anastomotic site in most cases.⁵ Potential causes of pseudoaneurysms include animperfect surgical technique and damage to the graft wall during initial surgery, weakness in the veins themselves at branch sites or in the areas of the vein valves, stenting of aged veins and infection.¹¹
Clinical presentation. Patients with SVG aneurysms usually present with chest pain, which may be related to angina, myocardial infarction or rupture. In some cases, detection of a mediastinal mass upon chest radiography or echocardiography, a superior caval venous obstruction or worsening dyspnea leads to the diagnosis.
The natural history of aneurysms includes thrombosis, embolization and rupture. A ruptured aneurysm communicating with a bronchus may cause hemothorax or hemoptysis. The SVG aneurysm may extrinsically compress the right atrium. Intraluminal thrombus formation can result in myocardial infarction either by embolization or by complete occlusion.¹² The myocardial infarction can be caused by a mass effect.¹³ Other serious complications include spontaneous late rupture with resultant pseudoaneurysm, fistula development between the right ventricle and the SVG or the right atrium and the SVG, hemothorax or fatal dehiscence secondary to bacterial infection and superior vena cava obstruction.^8,14,16–18

Diagnosis. Several SVG aneurysms have initially presented as mediastinal masses on plain chest X-rays.^19–25 Magnetic resonance imaging can correctly identify and localize a radiographic abnormality such as an aneurysm.²⁶ Transesophageal echocardiography provides serial assessment of size as well as intraluminal pathology.²⁷ Computed tomography can reveal the extent of the aneurysm and its relation to, and impression upon, surrounding structures. ^13,28,29 IVUS provides unique insight into the morphology, pathogenesis and management of SVG aneurysms.³⁰ Finally, angiography demonstrates the vascular nature of SVG aneurysms and can detect other lesions in the native coronary circulation.
Management. Treatment of SVG aneurysms includes excision, or ideally, resection of the aneurysm with replacement of the diseased graft when the native coronary artery requires further revascularization. However, the risk of requiring reintervention may be high. Embolization of these aneurysms may be a good alternative.^3,4,30,31 The Amplatzer vascular plug, and vein-covered and PTFE-covered stents have been used successfully for the treatment of SVG aneurysms.^33–37 In our case, and because current covered stents compatible for coronary intervention were not of adequate length, we used a long Wallstent as a backbone over which we were able to serially implant covered stents.

Conclusion
Nonsurgical management of a long SVG aneurysm using PTFE-covered stents with IVUS guidance is an alternative method to surgery. Although the restenosis rate of PTFEcovered stents in SVGs appears similar to that of bare-metal stents, it is associated with a higher incidence of nonfatal myocardial infarction.¹⁰ The use of PTFE-covered stents in SVGs should therefore be judicious. The technical challenges of aneurysm correction deserve continued interest. Application of IVUS yields a unique picture to appreciate the final result.