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Objectives: To assess and quantify coating irregularities on unexpanded and expanded durable polymer-based drug-eluting stents (DES) to gain insights into the origin of coating irregularities., Background: Previous scanning electron microscopy (SEM) studies in various expanded DES revealed differences in frequency and size of coating irregularities between DES types and specific distribution patterns, however, the origin of these irregularities is unclear., Methods: We assessed at bench side a total of 1,200 SEM images obtained in 30 DES samples (15 expanded and 15 unexpanded) of Cypher Select Plus, Taxus Liberté, Endeavor, Xience V, and resolute., Results: For most coating irregularities seen on expanded DES (72%; 23/32), a matching irregularity (n = 18/23) and/or its precursor (n = 11/23) was observed in unexpanded DES. Unexpanded Cypher select showed (small) crater lesions and cracks together with precursors of "peeling." On unexpanded Taxus Liberté, thinning of polymer, small bare metal areas, wrinkles, and one precursor type were found. Unexpanded endeavor showed cracks, small bare metal areas, crater lesions, and precursors of the latter. Unexpanded Xience V and resolute mainly revealed crater lesions and their precursors. On unexpanded versus expanded DES, there was no difference in measured frequency of coating irregularities and precursors (P = ns) with the exception of more bare metal areas on expanded Taxus Liberte (P = 0.01)., Conclusions: Most coating irregularities, or the potential to develop them, are inherent to the unexpanded DES. Important determinants of the formation of coating irregularities may be the stent geometry and the physical properties of the coating, while stent-balloon interaction plays no major role., (Copyright © 2011 Wiley Periodicals, Inc.)

Background:  Oversized postdilation of drug-eluting stents (DES) is often performed to avoid stent malapposition. In stents implanted in long lesion or major bifurcations, extremely oversized partial postdilation may be required, which exposes DES coating to extreme forces. This study aims to assess shape and incidence of coating irregularities on durable polymer-based DES following extremely oversized partial postdilatation., Methods:  Fifteen DES samples (3 3.5 mm stents of Cypher Select plus [Cordis Europa, Roden, the Netherlands], Taxus Liberté[Boston Scientific Corp., Natick, MA, USA], Endeavor Sprint [Medtronic Vascular, Santa Rosa, CA, USA], Endeavor Resolute [Medtronic Vascular, Santa Rosa, CA, USA], and Xience V [Abbott Vascular, Santa Clara, CA, USA]) were deployed in sterile water (37 °C) at 14 atm, followed by a proximal postdilation with noncompliant 5.0-mm balloons at 18 atm. Stents were then examined with scanning electron microscopy., Results:  Thorough examination of a total of 660 scanning electron microscopic images demonstrated that shape and incidence of coating irregularities in the postdilated and/or transitional DES regions differed only mildly from the nonpostdilated regions. Cypher Select plus showed more peeling without bare metal aspect in the postdilated and transitional regions, and cracks were wider (P < 0.001) in the postdilated and transitional regions; in Taxus Liberté one additional irregularity (torn webbing) and more wrinkles were observed (P < 0.05 for both); in Endeavor Resolute wider cracks were found in the extremely postdilated region only (P < 0.001). Endeavor Sprint and Xience V showed no differences in shape or incidence of coating irregularities between oversized and nonoversized stent regions., Conclusions:  Bench side assessment of five contemporary durable polymer-based DES with scanning electron microscopy suggests that even very aggressive stent postdilatation results in no more than mild differences in coating irregularities between postdilated and nonpostdilated stent regions. , (©2010, Wiley Periodicals, Inc.)

Aims: To classify and quantify post-expansion irregularities in durable polymer-based coatings of drug-eluting stents (DES)., Methods and Results: Taxus Liberté, Endeavor Sprint, Endeavor Resolute and Xience V DES (three samples of each) were explored by light microscopy and scanning electron microscopy (SEM) following expansion at 14 atm in water. Incidence and size of irregularities were measured during thorough quantitative examinations of a 360 SEM images. DES types examined showed a significant difference in the incidence of irregularities (p<0.0001; 6.6+/-4.2/image at 60-fold magnification) with typical patterns specific for each DES. All types showed areas with bare metal-aspects, but incidence, shape, and size differed largely: Sprint showed the largest areas. Cracks were only found in Sprint and Resolute, while wrinkles were seen exclusively in Taxus Liberté and Xience V (p<0.0001). The coating of each DES type showed some inhomogeneity of distribution, but the incidence differed (p<0.0001) and was least in Taxus Liberté, which, on the other hand, was the only DES that showed webbing with large bare-metal exposure., Conclusions: The incidence and size of various coating irregularities on different types of DES varied widely. These data may be considered in ongoing discussions on the differences between DES and may serve as reference to compare novel DES.