Incomplete Stent Apposition Causes High Shear Flow Disturbances and Delay in Neointimal Coverage as a Function of Strut to Wall Detachment Distance

Abstract

13are common morphological findings in fatal cases of LST after DES.9-14 DES can interfere with this physiological healing process through different mechanisms: first, the antiproliferative drug released by the device prevents the cellular mitosis required to restore the endothelial continuity; second, the polymer carrying the drug exerts a proinflammatory effect itself 15 ; finally, in Background-Lack of re-endothelialization and neointimal coverage on stent struts has been put forward as the main underlying mechanism leading to late stent thrombosis. Incomplete stent apposition (ISA) has been observed frequently in patients with very late stent thrombosis after drug eluting stent implantation, suggesting a role of ISA in the pathogenesis of this adverse event. The aim of this study was to evaluate the impact of different degrees of ISA severity on abnormal shear rate and healing response with coverage, because of its potential implications for stent optimization in clinical practice. Methods and Results-We characterized flow profile and shear distribution in different cases of ISA with increasing strutwall detachment distance (ranging from 100 to 500 μm). Protruding strut and strut malapposed with moderate detachment (ISA detachment distance <100 μm) have minimal disturbance to blood flow as compared with floating strut that has more significant ISA distance. In vivo impact on strut coverage was assessed retrospectively using optical coherence tomography evaluation on 72 stents (48 patients) sequentially at baseline and after 6-month follow-up. Analysis of coverage revealed an important impact of baseline strut-wall ISA distance on the risk of incomplete strut coverage at follow-up. Malapposed segments with an ISA detachment <100 μm at baseline showed complete strut coverage at follow-up, whereas segments with a maximal ISA detachment distance of 100 to 300 μm and >300 μm had 6.1% and 15.7% of their struts still uncovered at follow-up, respectively (P<0.001). Conclusions-Flow disturbances and risk of delayed strut coverage both increase with ISA detachment distance. Insights from this study are important for understanding malapposition as a quantitative, rather than binary phenomenon (present or absent) and to define the threshold of ISA detachment that might benefit from optimization during stent implantation. (Circ Cardiovasc Interv. 2014;7:180-189.)

Optical Coherence Tomography Guided Percutaneous Coronary Intervention With Nobori Stent Implantation in Patients With Non–ST-Segment–Elevation Myocardial Infarction (OCTACS) Trial

“…However, culprit lesions from patients with MI are severely diseased coronary vessel wall sites more prone to suboptimal apposition, 4,5 probably explanatory to our acute ISA findings. In previous OCT studies, 8,9,27,28 coverage of ISA struts has been found to be delayed when compared with well-apposed 8 found a 9× higher risk of incomplete coverage for ISA struts versus well-apposed struts. Our results are in line with these previous findings, as the improved strut coverage observed at 6-month follow-up in the OCT-guided group is interpreted caused by the better apposition of the stents at baseline.…”

Mechanisms of Very Late Drug-Eluting Stent Thrombosis Assessed by Optical Coherence Tomography

“…23 Of note, in vitro investigations directly assessing thrombogenicity could not confirm a correlation between the perpendicular ISA distance and clot mass volume. 24 In addition, the impact of ISA length or volume was not assessed in previous studies and should be assessed in future flow models or in vitro investigations to corroborate our in vivo findings.…”

Predictors and Long‐Term Clinical Impact of Acute Stent Malapposition: An Assessment of Dual Antiplatelet Therapy With Drug‐Eluting Stents (ADAPT‐DES) Intravascular Ultrasound Substudy

“…Acute stent malapposition (ASM) is common at the time of stent implantation1, 2, 3, 4, 5, 6; however, it is still controversial whether ASM impacts long‐term clinical outcomes in patients undergoing percutaneous coronary intervention (PCI). For example, Kimura et al7 reported that although most ASM after sirolimus‐eluting stent implantation did not resolve completely, the incidence of restenosis or thrombosis was not affected.…”