Giant Aneurysm with Stent Thrombosis: A Very Rare Complication of Stent Fracture

Iacopo Muraca1, Matteo Pennesi1, Fernando Scudiero2, Nazario Carrabba1, Giacomo Virgili3, Filippo Bruscoli3, Angela Migliorini1, Giulia Pontecorboli1, Niccolò Marchionni3 and Renato Valenti1* 1Interventional Cardiology Unit, Cardiovascular Department, Careggi University Hospital, Italy 2Cardiology Unit, Medical Science Department, ASST Bergamo Est Bolognini Hospital Seriate, Italy 3Department of Clinical and Experimental Medicine, University of Florence, Italy


Introduction
Stent fracture (SF) represents a rare complication after coronary stent implantation. This complication is commonly associated with restenosis/reocclusion or late/very late stent thrombosis; conversely cases of stent fracture associated with aneurysms or pseudoaneurysm are rarely reported. Low incidence of this complication can lead to a very challenging diagnosis. Intravascular imaging in these situations can be useful to promptly achieve the diagnosis and even more in the planning of an appropriate interventional strategy with the aim to obtain an optimal result and to improve patient's outcome.

History of Presentation
A 77-year-old patient, previously treated with multivessel percutaneous revascularization, presented with inferior STsegment elevation myocardial infarction. In his medical history there was multiple coronary risk factors, including hypertension, hyperlipidemia, type-2 diabetes mellitus, smoking history, chronic kidney disease, peripheral artery disease; furthermore, the patient was affected by paroxysmal atrial fibrillation on oral anticoagulant therapy. In the CathLab, proximal stent thrombosis of right coronary artery (RCA) ( Figure 1A) and good patency of previously implanted stents on the left coronary artery were detected. After comparison with previous procedure, it was possible to identify the presence of a stent fracture with very long displacement ( Figure 1B).

Management
Using "mother-and-child" extension catheter technique to maximize backup due to shepherd crook origin of RCA, we

Discussion
SF is an uncommon complication in new generation DES era, ranging from 1.7 to 7.7% [1]. SF is the result of the interactions between multiple factors: stent structure, stented segment length, pulsatile and non-pulsatile forces and plaque morphology. Multiple variables have been associated with an increased rate of SF: RCA lesions treated with sirolimus eluting stents (SES), stent length, stents in angulated/tortuous vessels (hinge points), calcific lesions, vein grafts, and overlapping stents [1]. The clinical presentation of a SF is variable, ranging from asymptomatic to sudden cardiac death. SF may result in perforation, restenosis or reocclusion, migration of the stent segments, pseudoaneurysm formation, embolization and late and very late thrombosis associated with acute coronary syndrome and poor prognosis [1]. Due to the low incidence of this complication, it becomes evident the difficulty in diagnostic and therapeutic management. In our case the SF presented in an acute setting with massive thrombosis of a giant aneurysm. The SF of the case reported, was a type IV according to Allie et al. classification [2] with a very long stent displacement. Complete SF (type III or IV) are often associated with coronary aneurysm, but a prompt identification and an "optimal" procedural management of this complication allow a successful technical result and a good clinical outcome [3]. In our patient, after the vessel recanalization, it was crucial the differential diagnosis between coronary perforation and giant coronary aneurysm. Imaging played a key role: absence of pericardial effusion by transthoracic echocardiography, and IVUS images, sustained the hypothesis of giant coronary aneurysm.
The possible therapeutic strategies included: surgical resection, balloon or stent-assisted coil embolization or covered stent exclusion [4]. In our case, in an acute setting, we opted for the covered stent exclusion, adopting a new procedural planning. The first step was the implantation of a long EES (48 mm) to provide a supporting structure, to avoid covered stent dislocation inside the aneurysm/pseudoaneurysm and to prevent a new fracture due to the continuous mechanical stress. As expected, after the everolimus-eluting stent implantation there was no aneurysm sealing. The second step was the implantation of covered stents; we had to use an overlap of two stents in order to completely exclude the aneurysm, since the maximum length available of those devices was inferior to the aneurysm length. All the diagnostic and therapeutic steps were pursued with a multimodality imaging including angiography and IVUS [5].

Conclusion
SF is an uncommon adverse event, and its management is still not well established, given its low incidence and wide variety of presentation. In our case, the differential diagnosis between wall perforation and giant aneurysm has been crucial for the interventional procedure strategy. Multimodality imaging confirms its fundamental support for complex coronary percutaneous procedures.

Disclosure
The authors have nothing to disclose.