Long-term follow-up Biolimus A9TM stents with optical coherence tomography: strut apposition and tissue coverage analysis

Introdução: Os stents farmacológicos (SF) de primeira geração surgiram com o intuito de reduzir as taxas de reestenose intra-stent e de revascularização da lesão-alvo, sendo mais eficazes quando comparados aos stents não-farmacológicos (SNF), porém com aumento de risco de trombose do stent (TS) muito tardia. A cobertura tecidual incompleta e a má aposição tardia das hastes dos stents podem estar vinculadas à TS. O SF de segunda geração BioMatrix®, que utiliza um polímero bioabsorvível, surgiu na expectativa de redução da TS. Devido à alta acurácia e reprodutibilidade e à análise precisa da cobertura tecidual e da aposição das hastes dos stents, a tomografia de coerência óptica (TCO) vem se tornando um método útil na análise desses aspectos. O objetivo desse estudo foi avaliar a cobertura tecidual e a aposição das hastes do SF BioMatrix® após longo período do implante. Métodos: Vinte pacientes submetidos ao implante do SF BioMatrix® (n = 15) ou do SNF S-Stent® (n = 5) foram acompanhados por um período mínimo de cinco anos e avaliados por meio da angiografia coronária quantitativa (ACQ), da ultrassonografia intracoronária (USIC) e da TCO. Para a análise estatística, foram utilizados os programas SPSS® versão 16.0 e SAS versão 9.2. O valor de p < 0,05 era considerado estatisticamente significante. As variáveis categóricas foram expressas em números absolutos e porcentuais e comparadas pelo teste exato de Fisher. As variáveis contínuas foram expressas em média e desvio padrão e/ou mediana e intervalo interquartílico e foram comparadas pelo teste não paramétrico de Mann-Whitney. Resultados: A ACQ demonstrou diferença, porém não significativa na perda tardia da luz entre o SF BioMatrix® e o S-Stent® [0,40 (0,21; 0,77) mm vs 0,68 (0,66; 0,82) mm, p = 0,205]. Os pacientes tratados com o SF BioMatrix® apresentaram porcentual de obstrução do stent significativamente menor quando comparados àqueles que receberam o S-Stent® [5,6 (4,4; 9,7)% vs 28,6 (24,7; 29,0)%, p =0,001]. A análise da TCO demonstrou 126 (8,7%) hastes não cobertas nos stents BioMatrix® e 23 (4,0%) nos S-Stents® (p = 0,297), estando a maioria delas bem apostas (117/126 e 21/23, respectivamente, p = 0,292). Apenas nove (0,6%) hastes nos SF e duas (0,4%) hastes nos SNF estavam simultaneamente sem cobertura tecidual e mal apostas (p = 0,924). No grupo BioMatrix®, apenas 1 (11,1%) paciente teve todas as hastes cobertas. Já no grupo S-Stent, 66,7% dos pacientes (2/3) apresentaram cobertura completa das hastes (p = 0,127). Conclusões: A avaliação tardia do SF BioMatrix® pela TCO mostrou cobertura tecidual e aposição em quase a totalidade de suas hastes, de maneira similar àquela encontrada nos SNF S-Stents®.Introduction: First generation drug-eluting stents (DES) have emerged as a strategy to prevent in-stent restenosis and the need of target-vessel revascularization when compared to bare metal stents (BMS); but at the expense of a higher risk of very late stent thrombosis (ST). Uncovered and malapposed struts may be associated with both late and very late ST. It has been postulated that the second generation DES, the biolimus-eluting stent BioMatrixTM with biodegradable polymer, may reduce the incidence of ST. Given its high accuracy and reproducibility with precise analysis of the complete strut apposition and strut coverage, the optic coherence tomography (OCT) has been extensively used for stent analysis. The aim of this study was to assess the struts coverage and apposition of DES BioMatrixTM in a long-term follow up. Methods: Twenty patients undergoing a BioMatrixTM (n = 15) or BMS S-StentTM (n = 5) implantation were followed up for a period of at least five years and evaluated by means of OCT, quantitative coronary angiography (QCA) and intravascular ultrasound (IVUS). All statistical analyses were performed using SPSSTM (v.16.0) and SAS (v.9.2) software. Statistical significance was considered at p values < 0.05. Categorical variables were expressed as counts and percentages, and continuous variables as mean SD and/or median and interquartile range. For per-patient level comparison, the difference between two stent types was evaluated by nonparametric Mann-Whitney U test while categorical variables were evaluated by the Fisher exact test. Results: QCA analysis showed no differences in the occurrence of intrastent late loss between the groups [0.40 (0.21; 0.77) mm vs 0.68 (0.66; 0.82) mm, p = 0.205 for BioMatrixTM and S-StentsTM, respectively]. The vessel, stent and lumen volumes assessed by IVUS after the procedure and 5 years later were similar between the two groups. Patients treated with BioMatrixTM had significantly less stent obstruction percentage when compared to those treated with S-StentTM [5.6 (4.4; 9.7)% vs 28.6 (24.7; 29.0)%, p = 0.001]. OCT analysis demonstrated 126 (8.7%) uncovered struts in the BioMatrixTM group compared to 23 (4.0%) in the S-StentsTM group (p = 0.297), being the majority of them well apposed (117/126 and 21/23, respectively, p = 0.292). Only 9 (0.6%) struts in the DES and 2 (0.4%) struts in the BMS groups were imultaneously uncovered and malapposed (p = 0.924). Among the BioMatrixTM patients, 55.6% (5/9) had more than 95% of covered struts and in only 1 (11.1%) patient all struts were covered. On the other hand, among the S-StentTM patients, 66.7% (2/3) had complete covered struts (p = 0.127). Conclusion: Long term assessment of DES BioMatrixTM by OCT showed tissue coverage and apposition in almost all struts, similary to those found in the BMS S-StentsTM