Pump-Outlet Tube Centering and Flow Direction in LVADs
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Solution Overview
Problem
Current ventricular assist devices face challenges in effectively centering the delivery tube within the aorta and efficiently directing blood flow through the blood-outlet openings.
Innovation Solution
The implementation of an expandable element, such as an expandable stent, braided element, or inflatable balloon, surrounding the delivery tube of a left-ventricular assist device. This expandable element is configured to center the delivery tube within the aorta and, when inflatable, can direct blood flow through the blood-outlet openings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an expandable element is added to center the delivery tube, then positioning accuracy is improved, but device complexity increases
Solution Approach 1:
An expandable element (balloon or stent) is introduced as an intermediary component between the delivery tube and the aorta wall. This mediator enables precise positioning by providing a mechanism to push the delivery tube against the aorta wall, while the expandable nature allows it to be delivered in a compressed state and then expanded at the target location, minimizing the increase in overall device complexity
Solution Approach 2:
The expandable element transitions from a compressed delivery state to an expanded functional state, providing dynamic adaptability. This allows the positioning mechanism to be compact during delivery and then provide sufficient outward force against the aorta wall when expanded, resolving the contradiction between compact delivery and effective positioning
2Ease of operation
If the expandable element is positioned within the pump-outlet tube, then blood flow direction is improved, but the risk of hemolysis and thrombosis increases
Solution Approach 1:
The expandable element is designed with specific local geometries (such as frustoconical distal ends) that create controlled flow patterns. The local quality of the surface and shape directs blood flow smoothly through the blood-outlet openings, reducing turbulence and stagnation zones that would otherwise cause hemolysis and thrombosis
Solution Approach 2:
The expandable element utilizes fluid pressure (pneumatics/hydraulics) to control its expansion and to guide blood flow. By inflating the element, blood is directed through the blood-outlet openings in a controlled manner, creating favorable flow conditions that reduce the risk of hemolysis and thrombosis while maintaining ease of operation
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 use of an expandable element enhances the positioning of the delivery tube within the aorta, ensuring proper blood flow and reducing the risk of complications such as hemolysis and thrombosis.
Implementation Method 1
the expandable element is configured to center a portion of the ventricular assist device (e.g., a portion of the delivery tube and, in particular, the portion of the delivery tube near the pump-outlet tube) within the aorta, by contacting the aorta wall
Implementation Method 2
the inflatable element is shaped to direct the blood through the blood-outlet openings. For example, the distal end of the inflatable element may have a width that decreases moving distally, e.g., the distal end may be frustoconical, such that the blood is directed by the distal end of the inflatable element, at an angle, through the blood-outlet openings
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
Apparatus and methods are described including a left-ventricular assist device that includes a pump-outlet tube (24) shaped to define one or more blood-outlet openings (109) and configured for insertion into a subject's left ventricle, such that the blood-outlet openings (109) are disposed within the subject's aorta and a distal portion of the pump-outlet tube (24) is disposed within the left ventricle. An impeller (50) is disposed within the pump-outlet tube (24) and is configured to pump blood of the subject proximally through the pump-outlet tube (24). A delivery tube extends from outside the subject's body to the distal portion of the pump-outlet tube (24). An expandable element (314) surrounds the delivery tube (142) proximally to the blood-outlet openings (109), a length of the delivery tube (142) between the expandable element (314) and the blood-outlet openings (109) being less than 30 mm. Other applications are also described.