Original title: Tissue coverage and neointimal hyperplasia in overlap versus nonoverlap segments of drug-eluting stents 9 to 13 months after implantation: In vivo assessment with optical coherence tomography. Reference: Juan Luis Gutiérrez-Chico et al. Am Heart J 2013;166:83-94.e3.

The drug-eluting stent’s (DES) overlapping effect over neointimal healing is not completely understood. Drug overdose, large amounts of polymer and metal bilayer, produce an important change in the intimal coverage, in fact angiographic studies showed greater late lumen loss and binary restenosis in overlapping segments.

The aim of this study was to compare, using optical coherence tomography (OCT), the overlapping intimal coverage versus non-overlapping segments in different types of DES. The data came from the randomized trials; LEADERS and RESOLUTE-All comers including per protocol an angiographic follow-up and by OCT.

In total 42 overlapping segments were analyzed corresponding to 11 sirolimus-eluting stents (Cypher SELECT, Cordis, Miami Lakes, FL), 3 biolimus eluting stents (BioMatrix Flex, Biosensors International, Morges, Switzerland), 11 zotarolimus-eluting stents (Resolute, Medtronic Inc, Santa Rosa, CA) and 17 everolimus-eluting stents (Xience V, Abbott Vascular, Santa Clara, CA). There were 5.1% of uncovered struts in overlapping segments increasing to 6.2% when excluding the outermost layer struts, compared to only 2.3% of struts not covered by non-overlapping segments. Intimal thickness was 109 µm over the overlapping segments versus 150 µm in the non-overlapping. This effect was independent of the type of DES analyzed. 

Conclusion:

The neointimal growth by the DES overlapping is markedly heterogeneous and although on average tend to be a thin layer, with the most uncovered struts there are cases where the overlap leads to exaggerated and thicker proliferation. These results may help us to understand why drug-eluting stents overlapping is associated with worse outcomes in terms of both thrombosis and restenosis. 

Commentary:

One of the points that could cause the inconsistency between different studies is the analysis of the outermost layer of struts, (some are included and some not), and that obviously it will be better positioned and covered than the innermost layer. One limitation of this work is the post hoc analysis view with relatively few patients and no data about the anatomical complexity prior to angioplasty. Perhaps the need for stents overlapping is given by a more complex anatomy and that might explain the worst results in these segments. 

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