An Implantable Magnetic Drive Mechanism for Non-Invasive Arteriovenous Conduit Blood Flow Control
N.A. White (TU Delft - Medical Instruments & Bio-Inspired Technology)
Sander L. Van Der Kroft (Student TU Delft)
Koen E. Van Der Bogt (Haaglanden Medical Center, Leiden University Medical Center)
Timo J.C. Oude Vrielink (Leiden University Medical Center)
Christian Camenzuli (University of Malta)
Juan A. Sanchez-Margallo (Jesús Usón Minimally Invasive Surgery Centre)
Huybert J.F. Van De Stadt (Leiden University Medical Center)
J. Dankelman (TU Delft - Medical Instruments & Bio-Inspired Technology)
J.I. Rotmans (Leiden University Medical Center)
T. Horeman (TU Delft - Medical Instruments & Bio-Inspired Technology)
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Abstract
Objective: Hemodialysis patients usually receive an arteriovenous fistula (AVF) in the arm as vascular access conduit to allow dialysis 2-3 times a week. This AVF introduces the high flow necessary for dialysis, but over time the ever-present supraphysiological flow is the leading cause of complications. This study aims to develop an implantable device able to non-invasively remove the high flow outside dialysis sessions. Methods: The developed prototype features a magnetic ring allowing external coupling and torque transmission to non-invasively control an AVF valve. Mock-up devices were implanted into arm and sheep cadavers to test sizes and locations. The transmission torque, output force, and valve closure are measured for different representative skin thicknesses. Results: The prototype was placed successfully into arm and sheep cadavers. In the prototype, a maximum output force of 78.9 ± 4.2 N, 46.7 ± 1.9 N, 25.6 ± 0.7 N, 13.5 ± 0.6 N and 6.3 ± 0.4 N could be achieved non-invasively through skin thicknesses of 1-5 mm respectively. The fistula was fully collapsible in every measurement through skin thickness up to the required 4 mm. Conclusion: The prototype satisfies the design requirements. It is fully implantable and allows closure and control of an AVF through non-invasive torque transmission. In vivo studies are pivotal in assessing functionality and understanding systemic effects. Significance: A method is introduced to transfer large amounts of energy to a medical implant for actuation of a mechanical valve trough a closed surface. This system allows non-invasive control of an AVF to reduce complications related to the permanent high flow in conventional AVFs.
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