CASE REPORTS

Stent Fracture and Collapse in a Saphenous Vein Graft Causing Occlusive Restenosis

*Micha F. Dorsch, MD, Peter H. Seidelin, MD, *Daniel J. Blackman, MD
*Micha F. Dorsch, MD, Peter H. Seidelin, MD, *Daniel J. Blackman, MD
Percutaneous coronary intervention has revolutionized the management of coronary artery disease since its inception in 1977. Initial problems with acute vessel closure were largely solved with the advent of stenting.1 Recurrent stenosis and/or occlusion in the stent era occur almost exclusively due to in-stent restenosis caused by neointimal hyperplasia. We report a rare case in which late vessel occlusion was caused by complete fracture and collapse of the stent. Case Report. A 66-year-old woman presented with a 2-week history of progressive exertional angina. Her medical history was significant for 4-vessel coronary artery bypass grafts (1989), hypertension and hyperlipidemia. Two months previously, she had undergone successful percutaneous coronary intervention to a saphenous vein graft to the right coronary artery for de novo disease. Overlapping 3.5 x 28 mm and 3.5 x 18 mm bare metal stents were deployed in the proximal body of the graft, achieving an excellent result (Figure 1). On admission, 12-lead ECG and serial cardiac enzymes were negative for myocardial ischemia. However, symptoms of chest pain persisted. Procedure. Coronary angiography was undertaken and demonstrated in-stent occlusion of the right coronary artery saphenous vein graft, with evidence of fracture and collapse of the proximal stent at the site of occlusion (Figure 2). Intra-arterial heparin (60 Units/kg) was administered at the onset of the procedure. The vein graft to the right coronary artery was engaged with a 7 Fr MPA2 guiding catheter (Boston Scientific Corp., Natick, Massachusetts). Initial attempts to cross the lesion with a Balance Middleweight™ guidewire (Guidant Corp., Indianapolis, Indiana) were unsuccessful. The occlusion was finally passed with a Cross-It 100 guidewire (Guidant). Predilatation was performed within the stent and throughout the length of the graft using a 1.5 x 20 mm Maverick™ balloon (Boston Scientific) and subsequently with a 2.0 x 20 mm Maverick balloon, each to 10 atmospheres (atm.). No improvement in flow was achieved and the vessel was further assessed by intravascular ultrasound (IVUS) using a Galaxy II (Boston Scientific) system. After administration of 200 µg intracoronary glyceryltrinitrate, an Atlantis™ (Boston Scientific) 40 MHz IVUS catheter was advanced 10 mm beyond the distal stent and automated pullback at 0.5 mm/second was performed. IVUS images demonstrated excellent deployment of the stents proximally and distally (Figures 3A and 3E), but complete fracture of the proximal stent in its mid-portion (Figure 3C), with no struts visible on IVUS cross-section. Immediately proximal and distal to the site of fracture, there was apparent collapse of the stent struts, leaving a small residual lumen (Figures 3B and 3D). Angiography and IVUS also revealed extensive thrombus within the distal portion of the stents and distal body of the vein graft. Further balloon dilatations were performed throughout the vessel with 2.5 x 20 mm and 3.0 x 20 mm Maverick balloons to 14 atm. Subsequently, thrombectomy was performed using the X-Sizer® system (ev3, Inc., Plymouth, Minnesota). Coronary angiography was repeated and revealed recanalization of the vessel, but with angiographic evidence of residual thrombus. New 3.0 x 32 mm, 3.0 x 32 mm, and 3.0 x 24 mm overlapping Driver stents (Medtronic, Inc., Minneapolis, Minnesota) were deployed to 16 atm from the distal vessel back to the ostium. Postdilatation was performed throughout the stented segments using a 3.5 x 15 mm noncompliant Quantum™ balloon (Boston Scientific). The final angiographic result was excellent (Figure 4). The patient recovered well and was discharged from hospital 2 days later. Discussion Complete stent fracture is well recognized as a complication of peripheral vascular intervention. Scheinert et al.2 reported stent fracture detected by systematic fluoroscopic screening in 45/121 (37.2%) patients 11 months after femoro-popliteal stenting. In 25.0% of stents, there was complete separation of stent segments. In contrast, overt stent fracture after coronary intervention is very rare. There have been only two reports3,4 both in vein grafts. Chowdhury and Ramos3 described complete fracture of a stent in a saphenous vein graft causing vessel occlusion one year after percutaneous coronary intervention. The operators were unable to cross the lesion and the patient required repeat surgical intervention. Brilakis et al.4 reported stent fracture in a vein graft causing stenosis that required repeat intervention. More recently, partial stent fracture, identifiable only by intravascular ultrasound, has been described as a potential cause of in-stent restenosis affecting drug-eluting stents due to failure of drug delivery to the vessel wall.5,6 Reviewing these and our cases, one can make some interesting observations. Firstly, complete coronary stent fracture has only been described in vein grafts. This may be explained by the higher mechanical stresses in vein grafts caused by the curvature of the graft, the presence of perigraft fibrosis and the limited intrathoracic space available.5 Secondly, in both our case and in Chowdhury’s report,3 stented segments were long and overlapping stents were used. Stent length and the use of multiple overlapping stents is a known predictor of stent fractures after peripheral interventions, probably due to increased axial stiffness of the stented segment.2 In summary, we have presented a case of complete stent fracture as a rare cause of late vessel occlusion with subsequent successful percutaneous management. Complete stent fracture is a rare, but recognized, phenomenon in vein grafts due to increased mechanical stress, particularly with long and overlapping stents.
References
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