Expandable Introducer Sheath Structure for Low-Trauma Device Passage
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Solution Overview
Problem
Existing introducer sheaths for medical devices, particularly for intracardiac blood pumps, are prone to tearing, require excessive force for removal, and lead to larger vessel openings, increasing the risk of bleeding and vascular complications, while expandable sheaths for short-term use risk clot formation and lack rigidity, causing kinking or buckling during insertion.
Innovation Solution
An expandable introducer sheath with a frame and coating configuration that allows for a smaller initial size, minimizes friction, and maintains position, featuring a coating on the inner or outer surface to facilitate expansion and contraction, compatible with a dilator assembly for long-term use, reducing the need for multiple sheaths and minimizing vessel trauma.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a peel away introducer sheath is used, then the pump assembly can be inserted through the femoral artery, but the sheath tears too easily or requires excessive force to remove, leading to bleeding or vascular complications
Solution Approach 1:
The introducer sheath incorporates a shape memory alloy frame that enables dynamic transformation between compressed and expanded states. The frame automatically transitions from a compressed delivery state during insertion to an expanded operational state, providing controlled expansion without manual tearing while maintaining reliability and ease of operation.
Solution Approach 2:
The sheath utilizes phase transition of shape memory alloy material to change its physical parameters (shape, rigidity, expandability). The material transforms from austenite to martensite phases, enabling the sheath to change from a rigid expanded state during insertion to a flexible compressed state for delivery, eliminating the tearing problem while maintaining ease of use.
2Ease of operation
If a peel away introducer sheath is used, then the pump assembly can be inserted, but a larger vessel opening is created, complicating vessel closure
Solution Approach 1:
The introducer sheath dynamically adjusts its diameter through shape memory alloy frame transformation. During insertion, the frame is in a compressed state allowing narrow profile access. Upon deployment, the frame expands to the required diameter, minimizing the initial vessel opening while maintaining the ability to accommodate the pump assembly, thereby reducing vessel trauma.
Solution Approach 2:
The sheath utilizes temporal dimension by introducing a phase transition process. The shape memory alloy frame transitions from compressed to expanded state over time during the procedure, allowing the vessel opening to be minimized initially and then expanded only when necessary, reducing overall vessel trauma while maintaining insertion capability.
3Adaptability or versatility
If an expandable sheath with longitudinal fold or crease is used, then the sheath can expand radially to allow passage of devices, but the sheath may kink or buckle during insertion or withdrawal
Solution Approach 1:
The sheath combines shape memory alloy frame with biocompatible polymer coating to create a composite structure. The shape memory alloy provides structural stability and kink resistance through its superelastic properties, while the polymer coating provides flexibility and expandability. This composite construction maintains structural integrity during insertion and withdrawal while enabling radial expansion when needed.
Solution Approach 2:
The shape memory alloy frame changes its mechanical parameters (rigidity, elasticity) through phase transition. In the austenite phase, the frame exhibits high rigidity and kink resistance during insertion. During expansion, the material transitions to allow radial deformation. This parameter change enables the sheath to maintain structural stability while achieving the required expandability without kinking or buckling.
4Ease of operation
If the inner diameter of the introducer sheath is large enough to accommodate the pump head, then the pump assembly can be inserted, but the introducer creates an opening wider than necessary, requiring replacement with a lower-profile repositioning sheath
Solution Approach 1:
The introducer sheath dynamically transforms from a compressed state during insertion to an expanded state during device passage. The shape memory alloy frame allows the sheath to temporarily expand to accommodate the pump head, then contract to a lower profile after device insertion. This eliminates the need for replacement with a repositioning sheath while minimizing the vessel opening size at all times.
Solution Approach 2:
The sheath utilizes the temporal dimension by introducing phase transition over time. The shape memory alloy frame transitions from compressed to expanded state during the brief period when device passage is needed, then returns to compressed state. This time-dependent dimensional change allows adequate device passage while minimizing vessel opening size before and after the procedure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The expandable sheath reduces the risk of tearing and clot formation, maintains vessel access, and improves procedural efficiency by eliminating the need for multiple sheaths, minimizing vessel trauma and bleeding, and allowing accurate device repositioning.
Implementation Method 1
The frame is constructed from a shape memory alloy and has transformed from an austenite phase to a martensite phase
Implementation Method 2
The dilator assembly is configured to expand the sheath from a compressed state to an expanded state during insertion of the sheath into the vessel
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
An introducer sheath (200) for the insertion of a medical device into a blood vessel having an expandable sheath (202). The sheath has a length, a thickness, and proximal and distal ends. The expandable sheath has a frame extending longitudinally between the proximal and the distal ends, and having an exterior surface and an interior surface that forms an interior lumen along the length of the frame. The frame is configured to achieve an expanded state and a contracted state, the expanded state forming an expanded cross- section in the lumen for passing a medical device therethrough. The frame has a smooth coating about the exterior surface and protrusions extending into the lumen along the interior surface. The introducer sheath can be introduced into a patient in the contracted state, with the distal end of the introducer sheath prevented from moving in the proximal direction by an abutment against a dilator end surface.