Flow patterns from metallic vascular endoprostheses: in vitro results

Area of Science:

• Biomedical Engineering
• Cardiovascular Research
• Medical Device Technology

Background:

• Vascular stents are crucial for treating stenotic lesions.
• Understanding stent hemodynamics is vital for preventing complications like restenosis.
• Previous studies have not comprehensively compared various stent types in standardized flow models.

Purpose of the Study:

• To evaluate and compare the flow characteristics and pressure gradients of different balloon- and self-expandable vascular stents.
• To assess the impact of stent design and deployment on hemodynamic parameters in vitro.
• To correlate flow disturbances with potential risks of thrombus formation and restenosis.

Main Methods:

• Seven vascular stents (Bridge, Cragg, Memotherm, Palmaz PS 784, Sinus, Symphony, Wallstent) were tested in a closed in vitro flow model.
• Stents were deployed in a 9 mm inner diameter tube, simulating 25% and 50% stenosis.
• Flow patterns (1.5 and 6 L/min) were visualized, and pressure gradients were measured using anionic particles and lasers.

Main Results:

• Stent implantation significantly reduced laminar flow and increased pressure gradients compared to an unstented tube, especially at 6 L/min and higher stenoses.
• The 'Sinus' stent demonstrated the highest laminar flow, while 'Palmaz' showed the minimum across tested conditions.
• No stent maintained laminar flow at 50% stenosis; inadequate deployment exacerbated negative hemodynamic effects.

Conclusions:

• Vascular stent implantation alters blood flow dynamics, increasing pressure gradients and reducing laminar flow.
• Stent design and complete expansion are critical factors influencing hemodynamic performance and potentially reducing restenosis.
• Inadequate stent deployment poses a risk for adverse flow conditions, contributing to thrombus formation and post-interventional restenosis.