Modified Z Stents for Iliac Vein Interdigitation

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Solution Overview

Problem

The existing Z stents face challenges in the common iliac vein due to compression by the overlying artery, requiring sufficient stiffness to resist collapse, and when extended into the vena cava, they can 'jail' the opposite vein, impeding flow or provide incomplete coverage of stenosis, due to their design limitations.

Innovation Solution

Modifications to the Z stent design include angled top surfaces and the use of intermediary sutures to allow interdigitation of top struts in the vena cava, reducing the apparent size of bilateral stents and preventing jailing, along with beveled or tapered designs to minimize interference and enhance radial strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If Z stents are extended into the vena cava to cover stenosis, then coverage of stenosis is improved, but the stents can jail the opposite vein impeding flow

Engineering Contradiction:

Improvecoverage of stenosisVSAvoidjailing of opposite vein

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a new dimensional characteristic by angling the top surfaces of stacked Z stents relative to the cylindrical axis. This angular orientation (e.g., 45 degrees) allows the stents to interdigitate with contralateral stents in the vena cava, transforming the spatial arrangement from parallel to intersecting, thereby reducing the apparent diameter and preventing vein jailing while maintaining stenosis coverage

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent applies asymmetry by making the top surfaces of the stacked Z stents asymmetric relative to the cylindrical axis. Instead of symmetric circular tops, the stents have angled tops that create an asymmetric profile, enabling them to interlock with opposing stents and reduce the overall diameter in the vena cava

Inventive Principle:

Principle #4Asymmetry

2Strength

If Z stents are made stiffer to resist collapse from artery compression, then radial strength is improved, but fluid flow through the stent decreases

Engineering Contradiction:

Improveradial strengthVSAvoidfluid flow

Core Design Contradiction:

StrengthVSQuantity of substance

Solution Approach 1:

The patent applies local quality by maintaining the stiff, closed-cylinder Z stent structure in the common iliac vein region where radial strength is needed to resist arterial compression, while using angled, interdigitating configurations only in the vena cava region where flow preservation is prioritized. This localized application of different structural qualities optimizes both radial strength and fluid flow in their respective locations

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS11666466B2Modified Z stents for iliac vein stenting

Publication Date: 2023.06.06 RAJU SESHADRI

AI summary

The invention includes modifications of a Z stent to allow the top struts of two Z stents deployed in the vena cava in a bilateral relationship, to interleave. One embodiment includes Z stents with angled top surfaces. A second embodiment includes Z stents having an intermediary suture but lacking the top suture in the topmost stent of a stacked stent module.