Bidirectional Cam Mechanism for Pacemaker Lead Extraction
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Solution Overview
Problem
Current lead extraction devices face challenges in precisely controlling the extension, retraction, and rotation of blades within a vascular system, particularly in navigating tortuous paths and cutting through tough surrounding tissue, which can lead to jamming and increased difficulty in removing implanted leads due to scar tissue and fibrous tissue growth.
Innovation Solution
A surgical device featuring a barrel cam cylinder in the handle assembly that imparts rotation of the blade and a separate cam mechanism in the tip of the outer sheath assembly, allowing the blade to rotate in one direction during initial extension and retraction, and in an opposite direction during subsequent extensions, creating a slicing action to minimize jamming and facilitate lead removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a blade is extended and retracted in a single direction, then the cutting action is simple, but the blade becomes jammed in tough surrounding tissue
Solution Approach 1:
The blade performs periodic extension and retraction movements in alternating directions. The cam mechanism converts continuous rotation into periodic bidirectional linear motion, allowing the blade to cut through tough tissue more effectively by reversing direction periodically to prevent jamming.
Solution Approach 2:
The blade motion transitions from static or unidirectional to dynamic bidirectional movement. The cam-follower mechanism enables the blade to adapt its motion pattern dynamically, extending and retracting in both directions based on the rotational position, thereby maintaining cutting effectiveness and reducing jamming in fibrous tissue.
2Device complexity
If a single cam mechanism controls blade movement, then the device structure is simple, but precise control of extension, retraction, and rotation is difficult
Solution Approach 1:
The control mechanism is segmented into two independent cam mechanisms: one cam controls blade extension and retraction, while the other cam controls blade rotation. This segmentation allows each cam to be optimized for its specific function, achieving precise control over both linear and rotational movements independently.
Solution Approach 2:
The cam mechanisms act as intermediary elements between the motor's continuous rotation and the blade's complex motion requirements. The cams translate rotational motion into precise periodic linear motion and controlled rotational motion, enabling accurate control of blade extension, retraction, and rotation angles.
3Productivity
If the blade rotates continuously in one direction, then the cutting action is continuous, but the blade jams in scar tissue and fibrous attachments
Solution Approach 1:
The blade execution retraction movements periodically interspersed with cutting movements. The cam mechanism coordinates these periodic actions, allowing the blade to cut through scar tissue and fibrous attachments continuously while periodically retracting to clear debris and prevent jamming, maintaining both productivity and reliability.
Data Source
AI summary
Methods and devices for separating an implanted object, such as a pacemaker lead, from tissue surrounding such object in a patient's vasculature system. Specifically, the surgical device includes a handle, an elongate inner sheath and a circular cutting blade that extends from the distal end of the sheath upon actuating the handle. The circular cutting blade is configured to engage the tissue surrounding an implanted lead and cut such tissue in a coring fashion as the surgical device translates along the length of the lead, thereby allowing the lead, as well as any tissue remaining attached to the lead, to enter the device's elongate shaft. The surgical device has a barrel cam cylinder in the handle assembly that imparts rotation of the blade and a separate cam mechanism in the tip of outer sheath assembly that imparts and controls the extension and retraction of the blade. The barrel cam cylinder and cam mechanism cooperate to cause the blade to rotate in a first direction and extend from and retract in the outer sheath due to a first actuation of the handle and to rotate in a second direction and extend and retract in the outer sheath due to a second actuation of the handle. The inner sheath and outer sheath are constructed of laser-cut hypotubes, thereby allowing the surgical device, particularly the sheath assembly, to have a smaller profile for navigating smaller sized vasculature.