Variable Stiffness Helical Screw for Cardiac Implant Anchoring
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Solution Overview
Problem
Implantable cardiac devices face challenges in securely anchoring to thin walls, such as the atrial wall, without piercing, due to the risk of bleeding and difficulty in determining the exact thickness and angle of contact, which can lead to tissue damage and hemorrhagic tamponade.
Innovation Solution
An implantable medical device with a screw anchoring system featuring a deformable helix wire with a beveled end and variable stiffness, designed to deform non-helically and crush myocardium without piercing the visceral pericardium, and a torque limiter to prevent tissue laceration, ensuring secure and safe fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a helical screw anchoring system is used to securely fix the implantable device, then the anchoring strength and mechanical security are improved, but the risk of piercing the thin atrial wall and causing tissue damage increases
Solution Approach 1:
The helical screw features variable stiffness along its length, with the distal portion having lower stiffness and the proximal portion having higher stiffness. This local differentiation allows the distal end to flexibly adapt to thin atrial walls without piercing, while the proximal end provides strong anchoring force in the thicker myocardium.
Solution Approach 2:
The screw's bending stiffness parameter is varied along its length, transitioning from a lower stiffness value in the distal region to a higher stiffness value in the proximal region. This parameter change enables the screw to achieve both safety in thin tissues and strength in thicker tissues.
2Reliability
If the screw is made stiffer to ensure secure anchoring, then the anchoring reliability is improved, but the risk of exceeding the coring torque threshold and tearing tissues increases
Solution Approach 1:
The screw exhibits different mechanical properties at different locations: the distal portion has lower stiffness to allow gradual tissue engagement below the coring torque threshold, while the proximal portion has higher stiffness to provide reliable anchoring without requiring excessive torque.
Solution Approach 2:
The variable stiffness design预先 (in advance) prevents excessive torque generation by allowing the distal, more flexible portion to gradually engage the tissue, cushioning the engagement process and preventing sudden torque spikes that could cause tissue laceration.
3Strength
If the screw length is increased to improve anchoring in thin walls, then the anchoring security is improved, but the risk of piercing through the wall increases
Solution Approach 1:
Instead of uniformly increasing screw length, the invention changes the stiffness parameter along the screw length. The distal portion has lower stiffness to safely navigate thin atrial walls, while the proximal portion has higher stiffness to provide secure anchoring, achieving both goals without increasing overall piercing risk.
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 solution provides a mechanically secure and clinically safe anchoring mechanism that prevents piercing of the thin atrial wall, reducing the risk of bleeding and tissue damage, while maintaining effective fixation and pacing functions.
Implementation Method 1
the helix wire of the screw is a wire that is deformable in bending, and the screw includes, at its free distal end, a terminal region whose helix wire bending stiffness is lower than in a proximal region of the screw turns
Implementation Method 2
a terminal region whose helix wire bending stiffness is lower than in a proximal region of the screw turns
Implementation Method 3
the screw, once the visceral pericardium reached, produces a crushing of the myocardium without piercing of the visceral pericardium
Implementation Method 4
a torque limitation system making it possible to disengage the capsule body from the anchoring screw when the reaction torque exerted by the anchoring screw exceeds a predetermined threshold
Data Source
AI summary
The device has a device body with a front face at its distal end, and a means for the anchoring of the medical device to a patient's organ wall. The anchoring means includes a screw with a helix wire wound into a plurality of non-contiguous turns, the screw having a clamped end integral with the front face of the device body and a free end with a beveled end defined by at least one oblique surface. The helix wire includes, at its free distal end, a terminal region whose wire bending stiffness is lower than in a proximal region of the helix turns. The stiffness difference may, in particular, be obtained by varying the wire diameter over different successive portions, with decreasing diameters in a proximal to distal direction.