## 4 Discussion  
According to previous studies [4; 5; 6; 7], the novel stent developed in this study is expected to achieve specific clinical outcomes and advantages in fistula maturation, including the following:  
1. After implantation, the stent can expand the vein diameter of the arteriovenous fistula (AVF) to over 4.2 mm [4], thereby facilitating AVF maturation.
2. The stent maintains good flexibility even after implantation and vein expansion, preventing damage to the stent and vein obstruction caused by external forces. Furthermore, the stent adapts to the vein's natural maturation process, accommodating the vein's increasing diameter.
3. The stent is designed to fully degrade after AVF maturation, thereby avoiding long-term vascular obstruction and related complications.  
Given that current nitinol vein stents have undergone extensive clinical validation and proven effective in achieving the first and second clinical outcomes [7; 9], the primary experimental model used in this study involved mechanical function comparisons between the developed stent and existing nitinol vein stents using stent crimping equipment. The  
Figure 20: Comparison between this study’s stent and other brands’ stents [9].  
diameter of nitinol self-expanding stents used in AVFs is typically based on the diameter of blood vessels, and currently, common AVF stent diameters are mostly between 4.5 mm and 6.5 mm [9]. Experimental results demonstrated that the developed stent provides expanded diameter, radial force performance, and post-expansion flexibility comparable to those of current nitinol vein stents. Compared with balloon-expandable stents, self-expanding metal stents are more flexible after expansion and can avoid being damaged by external forces from the outside of the arm [8; 9]. These findings suggest that the developed stent can reasonably be expected to achieve the first and second clinical objectives when implanted in AVF veins. However, further animal studies are required to validate these outcomes in vivo.  
PLA vascular stents have been shown to be biocompatible and typically degrade within one to two years in vivo [31; 32; 33]. For an AVF stent designed to assist maturation, however, an ideal degradation period is considered to be six months to one year. Therefore, exploring the use of poly(lactic-co-glycolic) acid or other suitable biodegradable materials with shorter degradation times may be a worthwhile approach for the proposed AVF stent in the future. Additionally, potential drawbacks associated with inflammation mediated during the resorption process were not investigated in this study. Future in vivo studies are necessary to address this issue and to explore the possibility of incorporating anti-platelet or anti-inflammatory drugs into the stent material.  
The present study has certain limitations that require further investigation in future experiments. The PLA structure and TPU elastic lines of the stent developed in this study gradually degrade over time following implantation into the vein of an arteriovenous fistula (AVF). This degradation may potentially impact the stent's ability to facilitate AVF maturation. Additionally, prolonged cyclic compression and expansion of the stent within the vein could lead to structural fatigue damage, potentially affecting its functionality and reliability.  
To address these limitations, in vitro experiments are proposed to evaluate fatigue behavior under pulsatile loading, investigate the impact of TPU degradation on the stent's self-expanding capability, and examine other factors influencing the stent's long-term reliability. Furthermore, ongoing research involves establishing an AVF model in pigs to enable in vivo testing of the developed stent. The experimental results will be used to refine the stent's design.  
In addition, future studies should include hemocompatibility testing and explore the effects of sterilization methods, such as gamma irradiation and ethylene oxide, on the stent's structural integrity and biocompatibility.