Department of Biomedical and Chemical Engineering and Sciences, Florida Institute of Technology, Melbourne, FL, 32901, USA.
Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, 44106, USA.
J Mech Behav Biomed Mater. 2021 Sep;121:104609. doi: 10.1016/j.jmbbm.2021.104609. Epub 2021 May 28.
Stent deployment in a calcified coronary artery is often associated with suboptimal outcomes such as stent underexpansion and malapposition. Post-dilation after stent deployment is commonly used for optimal stent implantation. There is no guideline for choosing the post-dilation balloon diameter and inflation pressure. In this work, ex-vivo/in-silico experiments were performed to investigate the efficacy of post-dilation balloon diameter and inflation pressure in improving the stent expansion in a calcified lesion. Post-dilations with three balloon diameters (3 mm, 3.5 mm, and 4 mm) were performed. For each balloon diameter, three inflation pressures (10 atm, 20 atm, and 30 atm) were sequentially applied. In ex-vivo experiments, optical coherence tomography images were acquired during the stenting procedure, i.e., pre- and post-deployment of 3 mm diameter stent, as well as after each post-dilation. The results from in-silico experiments were compared with ex-vivo experiments in terms of lumen area. In addition, stretch ratio analysis was developed to predict the stent-induced lumen area, along with the strain analysis and the in-silico experiments. Results have shown that target lumen area could be achieved with an oversized nominal balloon diameter of +0.5 mm (i.e., 0.5 mm greater than reference lumen diameter) at an inflation pressure of 20 atm. After each post-dilation, fibrotic tissue demonstrated a larger strain, contributing to improved lumen gain. However, minimal changes were observed in calcification. Moreover, a strong correlation (R = 0.95) between the stretch ratio of fibrotic tissue and lumen area after each post-dilation was observed. This indicated that the morphology of the fibrotic tissue could be a potential marker to predict the lumen gain. The detailed mechanistic quantifications of a single lesion cannot be generalized to all clinical cases. However, this work could be used to provide a fundamental understanding of the post-dilations, to develop experimental protocols for producing generalized guidelines, and to exploit their potential for optimal pre- and post-stent strategies.
支架在钙化冠状动脉中的植入通常会导致不理想的结果，如支架扩张不足和贴壁不良。支架植入后通常会进行后扩张以实现最佳的支架植入。然而，目前并没有选择后扩张球囊直径和充气压力的指南。在这项工作中，进行了离体/数值模拟实验，以研究后扩张球囊直径和充气压力对改善钙化病变中支架扩张的效果。进行了三种球囊直径（3mm、3.5mm 和 4mm）的后扩张。对于每种球囊直径，依次施加三种充气压力（10atm、20atm 和 30atm）。在离体实验中，在支架置入过程中获得光学相干断层扫描图像，即在 3mm 直径支架置入前后，以及每次后扩张后。数值模拟实验的结果与离体实验的管腔面积进行了比较。此外，还开发了拉伸比分析来预测支架引起的管腔面积，以及应变分析和数值模拟实验。结果表明，在充气压力为 20atm 时，可以使用标称球囊直径+0.5mm（即比参考管腔直径大 0.5mm）的过大球囊直径来实现目标管腔面积。每次后扩张后，纤维组织表现出较大的应变，有助于增加管腔面积。然而，在钙化部位观察到的变化很小。此外，还观察到每次后扩张后纤维组织的拉伸比与管腔面积之间存在很强的相关性（R=0.95）。这表明纤维组织的形态可以作为预测管腔增益的潜在标志物。单个病变的详细机械量化不能推广到所有临床病例。然而，这项工作可以用来提供对后扩张的基本理解，为制定通用指南的实验方案，并利用它们在最佳支架置入前后策略中的潜力。
