A Novel Abluminal Grouve-filled Biodegradable Polymer Sirolimus-eluting Stent For The Treatment Of Coronary Artery Disease: A Clinical And Angiographic Follow-up Study

Background: The durable polymer of the drug-eluting stents have caused a sustained partial vascular inflammatory reaction which increase the risk of late and very late stent thrombosis events. The purpose of this study is that through a variety of angiographic method to evaluate the efficacy and safety of the Firehawk abluminal grouve-filled biodegradable polymer sirolimus-eluting stent for the treatment of coronary artery disease.Methods and Results: A total of 78 patients with de novo native coronary lesions ≤60mm in length and a coronary artery ≥2.25 mm to ≤4.0mm in diameter implanted Firehawk abluminal grouve-filled biodegradable polymer sirolimus-eluting stent were enrolled in the current study. Clinical follow-up was performed at thirty days, six months, nine months and one year. Angiographic follow-up at one year was completed in 39 patients(50%), of which 33 patients underwent IVUS post-procedure and IVUS at one-year follow-up, 34 patients underwent OCT at one-year follow-up.A total of 151 Firehawk stents were implanted and the clinical follow-up rate is 100%. The target lesion failure rate is 1.28% and there’s no ARC definite or probable stent thrombosis event happened. The in-stent late lumen loss is 0.17±0.66 mm in QCA at one-year follow-up. The comparison of IVUS follow-up and post-procedure showed that there was a reduce of the volume of plaque and media(P&M)(p=0.035) and a increase of stent eccentricity ratio(0.12±0.02 vs. 0.14±0.03, p=0.007), but there was no significant vascular remodeling. The OCT at one-year follow-up demonstrated a good performance of the inhibition of neointimal hyperplasia(NIH), the coverage and apposition of struts. The mean NIH thickness was 0.098±0.059mm; the percentage of NIH volume obstruction was 9.02±6.04%; the percentage of uncovered struts was 4.06±5.02% and the percentage of malapposition was 0.067±0.161%. 7 overlapped segments were analysed in OCT: the mean percentage of NIH obstruction was 7.32±4.85%; the percentage of uncovered struts was 1.38±2.47%; no malapposition or cross-section with uncovered struts > 30% were found. The percentage of malapposition was lower in overlapped segments compared with that of non-overlapped segments(0% vs. 0.07±0.16%, p=0.013).Despite similar baseline clinical characteristics, clinical outcomes and baseline target lesions percentage of stenosis, the target vessel diameter(3.15±0.47 mm vs. 2.74±0.44 mm, p<0.001), the length of lesion(31.54±17.58 mm vs. 25.27±13.76 mm, p=0.035) were higher in the patients with angiographic follow-up than the patients without angiographic follow-up. In addition, the acute gain post procedure was lower(1.32±0.58 mm vs. 1.64±0.48 mm, p=0.002) and the residual stenosis was higher(26.44±7.21% vs. 8.46±4.59%, p<0.001) in patients with angiographic follow-up. Futhermore, compared with non-DM patients, OCT revealed that DM patients had a greater percentage of well-apposed strut(98.82±0.85% vs. 99.34±0.67%, p=0.039). The percentage of embedded strut(85.09±11.74% vs. 71.05±16.45%, p=0.004) was higher in ACS patients than non-ACS patients. OCT and IVUS showed that the in-stent diameter stenosis(DS) and distal edge DS was higher in long lesion group post procedure and at follow-up. Moreover, the percentage of NIH obstruction was higher(11.26±7.24% vs. 7.10±4.05%, p=0.040) and the percentage of cross-section with any uncovered strut was lower(14.38±14.91% vs. 25.11±17.41%, p=0.048) in long lesion group. However, there were no significant differences in strut apposition and NIH between small vessel group and non-small vessel group.Conclusions: The study demonstrated the feasibility, initial safety and efficacy in percutaneous coronary intervention using the novel abluminal grouve-filled biodegradable polymer sirolimus-eluting stent for treating patients with moderate complexity coronary artery lesions. The QCA, IVUS and OCT analysis revealed a low late lumen loss, a reduce of the P&M volume, an increase of the stent eccentricity ratio, a high strut well-apposition rate and coverage rate with a low NIH volume. The overlapping segments had a better strut apposition than the non-overlapping segments. The diabetes mellitus related to a higher strut malapposition rate and the long lesion length related to more NIH probably. The performance of the Firehawk abluminal grouve-filled sirolimus-eluting stent justifies the conduct of a large, randomized trial in complex patients for long-time follow up.