Third-generation drug-eluting stents: can they be used in chronic total occlusions?

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Through local delivery of antiproliferative drugs from stent coatings, drug-eluting stents (DES) very effectively reduced the relatively high rates of restenosis of bare-metal stents (BMS). Engineering improvement from first-generation DES, with paclitaxel or sirolimus drugs and durable polymers, to second-generation DES, using everolimus or zotarolimus drugs and more biocompatible durable polymers, has been associated with enhanced clinical outcomes 1–5. The contemporary third-generation DES were developed with more refined stent designs, possibly facilitating stent deliverability in challenging coronary anatomies, and more biodegradable polymers, with promising results toward better outcomes 6–8.
Within the context of coronary chronic total occlusion (CTO) interventions, where the operator faces highly hostile coronary anatomies, including severe tortuosity, long occlusions with heavy calcifications leading to multiple long overlapping stents, suboptimal stent expansion, subadventitial stent implantation, and/or coronary recoil, new stent technology may offer additional advantages.
The study published in this issue of Coronary Artery Disease by Markovic and colleagues assesses the outcomes of a third-generation sirolimus-eluting stent (Orsiro; Biotronik AG, Bülach, Switzerland) when used in more complex lesions such as CTOs. The authors compared the newer technology with a second-generation zotarolimus-eluting stent (Resolute Integrity; Medtronic Vascular, Santa Rosa, California, USA) after successful recanalization of CTOs. The primary surrogate endpoint of late lumen loss after 9 months was lower with the Orsiro DES compared with the Resolute Integrity (0.24±0.53 vs. 0.59±0.72 mm; P=0.01). However, it should be noted that postprocedural minimal lumen diameter (2.82±0.51 vs. 3.06±0.48 mm; P=0.01) and diameter stenosis (7.6±10.0 vs. 3.7±8.3%; P=0.001) were worse in the Orsiro group, leading to similar minimal lumen diameter (1.99±0.63 vs. 1.87±0.8; P=0.86) and diameter stenosis (24.7±19.2 vs. 27.7±28.7; P=0.58) between the groups at the 9-month angiographic follow-up. In other words, it appears that a worse acute result with the Orsiro, likely attributable to a thinner-strut design and perhaps higher stent recoil, was compensated by improved neointimal proliferation attenuation. However, it is important to acknowledge alternative explanations, such as higher CTO lesions complexity in the Orsiro group (J-CTO Score: 2.6±1.1 vs. 1.9±1.0; P<0.01) that may have further prevented optimal expansion of the stent. Despite this, it is reassuring to find that this new DES performed very well in the long term despite slightly worse initial results (Table 1).
However, the study results should be considered in the context of the available data. The PRISON series trials performed an angiographic follow-up comparison between different devices. The superiority of DES over BMS was established in the PRISON II trial 9. Despite having a higher diameter stenosis after the procedure (14.5±8.7 vs. 19.3±12.0; P=0.001), the first-generation sirolimus-eluting stent Cypher had a markedly smaller late lumen loss compared with BMS (1.09±0.91 vs. 0.05±0.81; P<0.0001), leading to a significantly smaller diameter stenosis on follow-up (48.8±26.5 vs. 22.0±21.0; P<0.0001). Going against the hypothesis of ‘newer is better’, the PRISON III trial 10 showed that the Cypher compared with the second-generation zotarolimus-eluting stent Endeavor had similar minimal lumen diameter postprocedure (2.17±0.43 vs. 2.49±0.44; P=0.07), but better minimal lumen diameter (2.38±0.63 vs. 1.79±0.39; P=0.01) and late lumen loss (−0.21±0.50 vs. 0.70±0.40; P<0.0001) on follow-up. Only the Resolute second-generation zotarolimus-eluting stent design, with better drug delivery, could match the Cypher stent outcomes. Finally, the randomized multicenter PRISON IV trial failed to show noninferiority of the third-generation Orsiro stent, as used in the present study, compared with the Xience second-generation DES, which had shown remarkable and superior outcomes in many other lesion subsets 3,11. The primary noninferiority endpoint of in-segment late lumen loss was not fulfilled (0.13±0.63 mm for Orsiro vs. 0.02±0.47 mm for Xience; P=0.08, two sided; difference=0.11 mm; 95% confidence interval, −0.01–0.25; Pnoninferiority=0.11, one sided). However, in-stent late lumen loss was comparable with both stents (0.12±0.

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