Fabrication, characterization and numerical validation of a novel thin-wall hydrogel vessel model for cardiovascular research based on a patient-specific stenotic carotid artery bifurcation.

In vitro vascular models, primarily made of silicone, have been utilized for decades for studying hemodynamics and supporting the development of implants for catheter-based treatments of diseases such as stenoses and aneurysms. Hydrogels have emerged as prominent materials in tissue-engineering applications, offering distinct advantages over silicone models for fabricating vascular models owing to their viscoelasticity, low friction, and tunable mechanical properties. Our study evaluated the feasibility of fabricating thin-wall, anatomical vessel models made of polyvinyl alcohol hydrogel (PVA-H) based on a patient-specific carotid artery bifurcation using a combination of 3D printing and molding technologies. The model's geometry, elastic modulus, volumetric compliance, and diameter distensibility were characterized experimentally and numerically simulated. Moreover, a comparison with silicone models with the same anatomy was performed. A PVA-H vessel model was integrated into a mock circulatory loop for a preliminary ultrasound-based assessment of fluid dynamics. The vascular model's geometry was successfully replicated, and the elastic moduli amounted to 0.31 ± 0.007 MPa and 0.29 ± 0.007 MPa for PVA-H and silicone, respectively. Both materials exhibited nearly identical volumetric compliance (0.346 and 0.342% mmHg-1), which was higher compared to numerical simulation (0.248 and 0.290% mmHg-1). The diameter distensibility ranged from 0.09 to 0.20% mmHg-1 in the experiments and between 0.10 and 0.18% mmHg-1 in the numerical model at different positions along the vessel model, highlighting the influence of vessel geometry on local deformation. In conclusion, our study presents a method and provides insights into the manufacturing and mechanical characterization of hydrogel-based thin-wall vessel models, potentially allowing for a combination of fluid dynamics and tissue engineering studies in future cardio- and neurovascular research.

Identifying Factors Associated with Discontinuation of Infertility Treatment Prior to Achieving Pregnancy: Results of a Nationwide Survey.

The purpose of this mixed methods, cross-sectional patient survey was to characterize patient experience, to explore the frequency of and reasons for infertility treatment discontinuation and return to infertility treatments. Participants were recruited from United States patient support groups. Participants had received or were receiving ovulation induction (OI) with or without intrauterine insemination (IUI), with or without subsequent in vitro fertilization (IVF), or IVF with no other previous infertility treatment. Live birth was achieved by 62% of participants. Compared with participants treated with OI/IUI only, participants who underwent OI/IUI followed by ≥1 IVF cycle were less likely to consider discontinuing care (64% vs 77%; P = .014) or to discontinue treatment without achieving a pregnancy (40% vs 58%; P = .004). The most commonly cited reasons for treatment discontinuation were financial (62%) and psychological burden/treatment fatigue (58%). Expected versus actual time to pregnancy differed greatly. Continued desire for a child (60%) was the most frequently cited reason for continuing or resuming treatment. Expanded access to treatment, counseling and fostering realistic expectations regarding cumulative time to pregnancy may reduce treatment discontinuation.