Mechanical stent failure as a cause of life-threatening left main restenosis

A 67-year-old woman with a history of diabetes, hy-pertension, severe obesity and hypercholesterolemia was admitted to our center with the diagnosis of non ST-segment elevation myocardial infarction. Electrocar-diography showed 3 mm ST-segment depressions in leads I, aVF, and V3–V6 and elevation in lead aVR. Tro-ponins were positive and ejection fraction assessed in echocardiography was 50%, without valve abnormalities. Five months earlier, the patient underwent elective percutaneous coronary intervention (PCI) of the left main coronary artery (LMCA) and left anterior descending artery (LAD) using 2 overlapping everolimus-eluting stents (Promus-Premier, Boston Scientific): 3.5/32 mm to the LMCA/LAD and 2.5/32 mm to the LAD with non-compliant 4.0 mm balloon high pressure postdilatation in the LMCA and with full expansion, an optimal angiographic result, unfortunately without intravascular ultrasound (IVUS) assistance. Qualification for PCI at that time followed the Heart Team meeting and discussion with the patient (low values of both Syntax-Score (21) and Euro-SCORE II (0.9%)) – she preferred the option of PCI more than coronary artery bypass grafting (CABG). Coronary angiography revealed critical in-stent re-stenosis in the calcified LMCA (Figure 1) with diffuse non-significant changes in the LAD, circumflex artery and right coronary artery. During angiography severe chest pain and hemodynamic instability occurred, so immediate in-stent balloon angioplasty with 3.0/15 mm and 3.5/15 mm balloons to 10 atm was performed, enough to improve the flow in the left coronary artery and with clinical stability. However, IVUS examination in the LMCA showed some features of mechanical stent failure – separation of struts on one side of the stent circumference, in place of vessel calcification, which could be the most likely cause of restenosis. Unfortunately, because of the lack of baseline IVUS, we could not clearly diagnose the type of stent deformation. We decided to implant another Biolimus-eluting stent, 3.5/14 mm with 4.0/8 mm non-compliant balloon postdilatation, and the final result was perfect (Figure 1). Mechanical stent failure (MSF) is a rare but potentially catastrophic complication in complex PCI procedures. The most common types are longitudinal stent deformation , stent fracture, stent underexpansion and stent recoil. The reported general MSF rate of everolimus-eluting stents is about 9.6%, the longitudinal stent deformation rate is about 5.4%, and the stent fracture rate is about 2.9% [1, 2]. However, in many cases angiography alone does not reveal the presence of MSF. Intravascular imaging techniques (IVUS, optical coherence tomography) appear to be more sensitive methods and are more useful …