Design and Finite Element Analysis of a Novel Retrievable Vascular Stent / 医用生物力学

Objective In order to avoid early restenosis after drug-eluting stent (DES) implantation, the retrievable structure of the NiTi alloy stent and its biomechanical analysis were studied. Methods The geometric models of the retrievable vascular stent and the retrieval system were established. The retrieval part of the stent consisted of four symmetrically distributed tendons, which were designed as circular meshes. The distribution of the maximum strain during stent compression and its uniformity during compression and self-expansion were analyzed, and the simulation experiments of the retrieval process were also performed. Results The maximum strain of the stent was 3.7% and the index of non-uniformity (INU) was 0.62% when the stent was compressed to the minimum size. While the IBU was 1.31% after the self-expansion process completed. The maximum strain was 1.2% when half of the stent was retrieved into the outer sheath. Conclusions The stent could be safely and successfully retrieved into the outer sheath as the strain was within the bearable range of the material and the compression and self-expansion process was relatively uniform. The research findings provide important references for structural design, biomechanical analysis and potential clinical applications of the novel retrievable vascular stent.

Bioabsorbable Vascular Scaffolds Eluting with Everolimus: for Percutaneous Coronary Intervention of Patients with de-novo Coronary Artery Lesion: Our Experiences at a Tertiary Hospital.

Background: Aim of the study was to evaluate the primary procedural success of percutaneous coronary intervention (PCI) of de-novo coronary artery lesion by using Bioabsorbable Vascular Scaffold (BVS) ABSORB stents eluting Everolimus. Methods: Total 16 patients were enrolled in this very preliminary study of BVS absorb. Among them, Male: 11 and Female: 5. Total 20 stents were deployed. Mean age were for Male: 56 yrs, for Female: 60 yrs. Associated coronary artery disease (CAD) risk factors were Dyslipidemia, High Blood pressure, Diabetes Mellitus, Positive family history (FH) for CAD and Smoking. Patients were followed up clinically. Results: Among the study group; 13 (81%) were Dyslipidemic, 10(62.5%) were hypertensive; 6 (37.5%) patients were Diabetic, FH 3(18.75%), and 2(18%) were all male smoker. Female patients were more obese [Body Mass Index (BMI) M 25: F 27] and developed CAD in advance age. A common stented territory was for left anterior descending artery (LAD): 6 (37.5%), left circumflex artery (LCX) 5 (25%), right coronary artery (RCA) 6(37.5%). One patient had both LCX and LAD stenting. Total 3 patients had double/overlapping stent in RCA lesion. Territory wise distributions of BVS ABSORB stent were for LAD 6(30%), RCA 9 (45%), and LCX 5 (25%). There was no periprocedural or postprocedural complication. Conclusion: BVS ABSORB Everolimus eluting vascular scaffold showed favorable clinical outcome without any major cardiac events (acute or late stent thrombosis, MI or death) over a period of 9 month. Thus, BVS ABSORB would be favorable alternative to other available drug eluting metallic stents.

Mechanical performance of targeted drug eluting stent during compression process / 医用生物力学

Objective To investigate mechanical performances of two different drug eluting stents (DES) during compression process, so as to provide a scientific guideline for design of DES. Methods Using Solidworks, two kinds of stent models, namely the common DES without slots in outside surface (Stent I) and the targeted DES with slots in outside surface (Stent II) were established, respectively. The important mechanical properties of the two stents during compression process, such as rebound ratio of radial contraction, rebound ratio of axial contraction, the inhomogeneity of compression and the distribution of residual stress, were analyzed by ABAQUS. Results With the same outer radius, the difference values of rebound ratio of radial contraction, rebound ratio of axial contraction and inhomogeneity of compressing for the two stents were 0.07%-0.12%, 0.016%-0.033% and 0.013 %-0.048%, respectively; there was a bigger low-stress area on the support of Stent II. Conclusions Compared with the traditional DES, the targeted DES could maintain the same mechanical performances while reducing drug-loading capacity, which shows a good prospect in clinical application of the treatment for cardiovascular stenosis diseases.

Hemodynamic characteristics of arterial lesions after drug-eluting stent implantation / 医用生物力学

Objective To study the hemodynamic characteristics after vascular drug eluting stent (DES) implantation, so as to provide theoretical guidance for clinical application of DES as well as improving the design of DES. Methods The geometry models of vascular lesions implanted with DES were constructed to numerically analyze drug concentration and wall shear stress (WSS) distributions in vessel by computational fluid dynamics (CFD) method. The results were compared with flow characteristics of the model with bare metal stent (BMS) implantation. Results Low WSS accompanied by high drug concentration would occur during blood flow in some areas after DES implantation, and vice versa. The presence of DES significantly reduced appearing such areas as either with low WSS only or with low drug concentration only. Theoretically, DES had more advantages than BMS at the stage of drug release. Conclusions DES could dramatically reduce the ratio of in-stent restenosis. Understanding the regular pattern of blood flow field distributions after DES implantation in detail will be beneficial to improve the design of DES, and further advance the overall performance of the stent, which can provide the theoretical basis for clinical research.

A study to evaluate the clinical outcome of drug-eluting vs. bare-metal stents for acute coronary syndrome patients during commercial use in real setting.

Background: This study compared clinical outcome of Drug Eluting Stents (DES) versus Bare Metal Stents (BMS) in coronary arteries in patients with Acute Coronary Syndromes. Methods: A retrospective, observational study was carried out in an inpatient setting of the private tertiary care hospital. Patients with >18 years, diagnosed for Acute Coronary Syndromes (ACS), required intervention in coronary artery with implantation of Drug Eluting Stents (DES) or Bare Metal Stents (BMS) were recruited in the study. The data had been collected from file or database of the hospital. All subjects were followed for major adverse cardiac event. Results: A total of 202 patients who underwent percutaneous coronary intervention (PCI) were enrolled into DES group (n=101) and BMS group (n=101). All patients were followed up at 1 month, 3 months, 6 months & 12 months for Major Adverse Cardiac Events (MACE). Clinical outcomes during 12 months were compared between DES group & BMS group. Overall MACE rates were reported non-significantly high in BMS group patients (14.85%) compare to DES group patients (8.91%) (p=0.458). However, DES group had lower rates of death (0.99% vs 1.98%, p=0.57), rate of MI (3.96% vs 4.95% p=0.73), rate of revascularization (1.98% vs 3.96% p=0.42) & rate of sub acute thrombosis (1.98% vs 3.96% p=0.42) and higher rate of bleeding (1.98% vs 0.99% p=0.57) compare to cohort-II. Conclusions: The use of DES in the setting of Acute Coronary Syndrome is associated with lower Major Adverse Cardiac Event (MACE) rate compared to BMS without compromising the overall safety over the course of one-year follow-up. The long-term safety of drug-eluting stents needs to be ascertained in large, randomized trials.