Calcified plaque rupture and very late stent thrombosis after bare-metal stent implantation

Pathological assessment of very late bare metal stent thrombosis in the left main coronary artery: a case report

Background

Late catch-up phenomenon following stent implantation is a well-known complication. However, no report has evaluated thrombosis after 9 years with multi-modality and pathological evaluation.

Case summary

A 71-year-old man with stable angina underwent elective percutaneous intervention of the left main coronary artery with implantation of a bare metal stent (BMS) 9 years ago. At the 9-year follow-up, coronary computed tomography (CCT) and coronary angiography (CAG) findings revealed a thrombus-like structure in the BMS slightly protruding into the sinus of Valsalva. Therefore, the previously prescribed double-antiplatelet therapy was replaced with an anticoagulant and clopidogrel, and a potent statin treatment was initiated. After the changes in drug treatment, follow-up examinations with CCT at 1 and 3 months suggested a decrease in the size of the thrombus; however, it appeared to increase after 6 months. Subsequently, the patient underwent surgical intervention. Pathological assessment of the explanted stent showed a proteoglycan-dominated extracellular matrix with few smooth muscle cells suggesting an organized thrombus.

Discussion

It should be emphasized that multiple factors might be responsible for very late stent thrombosis, such as peri-stent strut chronic inflammation involving proteoglycans, stent protrusion, and poorly controlled type 2 diabetes mellitus, possibly further inducing inflammatory cells.

Acute Coronary Syndrome after 17 Years of Bare Metal Stent Implantation: "Very" Very Late Stent Thrombosis

Very late stent thrombosis (VLST) is a catastrophic and life-threatening complication after percutaneous coronary intervention which presents as an acute coronary syndrome with significantly high mortality and morbidity. VLST is a rare entity with drug-eluting stents and even rarer with bare metal stents. The exact pathophysiologic mechanism of VLST after BMS implantation is not known although various mechanisms have been proposed. Recently, in-stent neoatherosclerosis with intimal plaque rupture has been proposed as a potential mechanism of VLST after BMS. We report a rare case of VLST occurring 17 years after BMS implantation with angiographic and intravascular imaging evidence which provides insight into the mechanisms of VLST.