Variable Thickness Stent for Small Vessel Restenosis
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Solution Overview
Problem
Current drug eluting stents (DES) are ineffective in treating small blood vessels with diameters less than 3 mm, as they fail to achieve significant reduction in late loss diameter and restenosis rates due to the narrow lumen, leading to higher revascularization rates compared to larger vessels.
Innovation Solution
A drug delivery device comprising an intraluminal stent with a cobalt chromium alloy body, coated with a polymer containing everolimus at a concentration of 50 μg/cm2 to 150 μg/cm2, specifically designed for vessels with diameters between 2.25 mm and 2.5 mm, which reduces in-stent late loss to 0.20 mm or less and in-segment diameter stenosis to less than 13% at 8 months post-implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If drug eluting stents are used in small vessels with diameter less than 3 mm, then restenosis prevention is improved, but the narrow lumen prevents adequate drug delivery and accommodation of neointimal hyperplasia
Solution Approach 1:
The stent is designed with varying strut thicknesses across different segments, with thinner struts in the distal portion and thicker struts in the proximal portion. This local variation in structural properties allows the distal struts to be more flexible and accommodate the narrow lumen of small vessels, while maintaining sufficient strength in the proximal region for effective drug delivery and restenosis prevention.
Solution Approach 2:
The invention changes the physical parameters of the stent structure by implementing a gradient in strut thickness. The distal struts have a thickness of 0.05-0.10 mm while proximal struts have a thickness of 0.10-0.15 mm. This parameter variation enables the stent to adapt to the specific geometric constraints of small vessels while maintaining therapeutic efficacy.
2Strength
If stent struts are made thicker to provide structural strength, then stent integrity is improved, but the available lumen space for small vessels is reduced
Solution Approach 1:
Different portions of the stent have different strut thicknesses tailored to their specific functional requirements. The distal struts are thinner (0.05-0.10 mm) to maximize lumen space in the narrow distal vessel segment, while proximal struts are thicker (0.10-0.15 mm) to provide the structural strength needed for anchoring and drug delivery in the larger proximal vessel segment.
Solution Approach 2:
The stent is divided into distinct proximal and distal segments with different structural characteristics. This segmentation allows each portion to be optimized independently - the distal segment prioritizes lumen preservation while the proximal segment prioritizes structural strength, resolving the contradiction between these two requirements.
3Ease of manufacture
If uniform strut thickness is used throughout the stent, then manufacturing simplicity is improved, but the ability to accommodate varying vessel diameter and neointimal hyperplasia is reduced
Solution Approach 1:
The stent implements local quality variation through different strut thicknesses in different segments. This design provides adaptability to varying vessel diameters and neointimal hyperplasia patterns while remaining manufacturable using standard stent fabrication techniques, balancing manufacturing simplicity with clinical versatility.
Data Source
AI summary
A drug delivery device having an intraluminal stent for improving coronary luminal diameter of small vessels in patients with symptomatic heart disease is disclosed. The intraluminal stent includes struts having a thickness of less than approximately 110 μm. A polymer is adhered to the intraluminal stent that includes from about 50 μg/cm2 to about 150 μg/cm2 of everolimus therein. Quantitative coronary angiography measurements indicate that the drug delivery device provides an in-stent late loss of less than about 0.20 mm and an in-stent diameter stenosis of less than about 15% at 12 months following implantation in a human.