Cannula Self-Retaining Mechanism for Cardiac Blood Flow
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Solution Overview
Problem
Current cannula systems for cardiac blood pumping face issues such as clot formation, atrial tissue suction, secure attachment challenges, and the need for suturing, which can lead to complications like embolization and reduced blood flow rates.
Innovation Solution
A cannula system with a self-expandable distal end and a retaining mechanism that promotes tissue ingrowth, providing a secure fluid-tight seal without suturing, and a flared shape to reduce turbulence and suction risks, allowing for higher blood flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a cannula tip projects into the left atrium to enable blood flow, then blood pumping function is achieved, but atrial tissue is suctioned into the cannula causing obstruction and clotting
Solution Approach 1:
The cannula is divided into distinct functional zones: a proximal segment with a larger diameter inflow port that directs flow away from the atrial wall, and a distal segment with a smaller diameter that interfaces with the atrial septum. This segmentation allows the inflow port to be positioned optimally for blood capture while preventing tissue suction into the narrower cannula body.
Solution Approach 2:
The cannula incorporates a flared or angled inflow port that redirects blood flow in a different spatial dimension, away from the atrial wall and toward the cannula lumen. This dimensional redirection of flow prevents the suction effect that would otherwise draw tissue into the cannula opening.
2Reliability
If a purse string suture is used to secure the cannula to the atrial septum, then the cannula is held in position, but the incision size increases and suturing complexity is required
Solution Approach 1:
The mechanical suturing system is replaced with a self-retaining cannula design that uses elastic memory, friction, or interlocking geometric features to secure itself to the atrial septum. The cannula may incorporate expansion elements, barbs, or a compliant distal end that naturally anchors in the tissue without requiring external sutures.
Solution Approach 2:
The cannula is designed to self-secure to the atrial septum through its own structural features, such as an expandable distal end that engages with the tissue or a friction-fit mechanism. This eliminates the need for external suturing devices and procedures, allowing the cannula to hold itself in position reliably.
3Reliability
If the cannula is secured with a purse string suture, then the cannula is held in position, but bleeding and dislodgement risks remain
Solution Approach 1:
The cannula incorporates a sealing mechanism that is activated during insertion or immediately after placement, creating a fluid-tight seal before bleeding can occur. This may involve self-expanding elements that conform to the atrial septum or sealing flanges that prevent blood leakage at the insertion site.
Solution Approach 2:
The suture-based fixation system is replaced with a mechanical self-retaining system that provides both secure positioning and hemostasis simultaneously. The cannula may use friction-fit, elastic memory, or interlocking features that prevent dislodgement while maintaining a sealed interface with the atrial tissue.
4Reliability
If a large incision is made to pass sutures and expose the region, then secure cannula attachment is achieved, but surgical trauma and recovery time increase
Solution Approach 1:
The suture-based attachment system requiring large incisions is replaced with a percutaneous or minimally invasive self-retaining cannula design. The cannula can be inserted through a small puncture and secured using elastic memory, friction, or interlocking features that do not require suture passage through large tissue defects.
Solution Approach 2:
The cannula is designed to self-secure through its own structural features, allowing insertion through minimal incisions. The self-retaining mechanism activates automatically during or after insertion, providing secure attachment without requiring extensive surgical exposure or traumatic tissue dissection.
5Productivity
If the cannula flows at high rates (2-3 liters per minute or more), then pump performance is improved, but atrial tissue suction and cannula obstruction increase
Solution Approach 1:
The cannula incorporates a larger diameter inflow port or chamber that separates the high-flow region from the narrower cannula body. This segmentation allows high flow rates to be achieved at the inflow interface without creating excessive suction velocity that would draw tissue into the smaller cannula lumen.
Solution Approach 2:
The inflow port is designed with a flared or angled geometry that redirects high-velocity blood flow in a different spatial direction, away from the atrial wall. This dimensional flow redirection maintains high pump flow rates while preventing the suction effect that causes tissue obstruction at high flow conditions.
Data Source
Figure 1A~1B
Figure 1C
Figure 2A
AI summary
Disclosed herein is a cannula assembly for directing the flow of material from an organ chamber, e.g., blood from the left chamber of the heart, and methods of placing the cannula assembly in fluidic communication with the chamber. The cannula assembly includes an elongate tubular member (110) and a coupling assembly (120) disposed at the distal end of elongate tubular member. The elongate tubular member includes a lumen extending from a distal opening at the distal end to a proximal opening at the proximal end. The coupling assembly includes a retaining element (122) and a retention member (124) configured to cooperate with each other and with the portion of the organ wall surrounding the opening in the wall to couple or anchor cannula system (100) to the wall and to provide fluidic communication between the distal opening of the elongate tubular member and the organ chamber.