Multilayer Flow Modulators Prevent Paraplegia in Type-B Aortic Dissection
Presenting Author: Farhad Rikhtegar Nezami 1
Institute for Medical Engineering and Science, Massachusetts Institutes of Technology, USA
Additional Authors: Farhan Khodaee 1, Lambros S. Athanasiou1,2, Elazer R. Edelman1,2
1 Institute for Medical Engineering and Science, Massachusetts Institutes of Technology, USA
2 Cardiovascular Division, Brigham and Women’s Hospital, Harvard Medical School, United States
BACKGROUND/PURPOSE: Management of aortic dissections (AD) is still challenging. Spinal Cord Ischemia (SCI) is the most distressing complication both post-surgery and following endovascular repairs. SCI can result in varying degrees of short-term and permanent disabilities, ranging from mild transient paraparesis to permanent flaccid paralysis. A verity of risk factors is associated with SCI following TEVAR, many of which result from the permanent interruption, imbalance and impairment in the spinal cord’s collateral blood supply network. Multilayer flow modulator (MFM) is becoming the method of choice for minimally-invasive treatment of AD patients; yet its performance in recovering physiologic perfusion to spinal cord has not been fully assessed.
METHOD: We used patient-specific geometry of Type-B AD obtained pre-intervention (PI), and post- TEVAR (PT) and MFM (PM) implantation. In-house semi-automatic segmentation routines were applied to computed-tomography images to reconstruct the lumen. MFM was numerically reconstructed, the covered device was modeled blocking the proximal entrance of the false lumen, and both were adapted to the post-surgical geometries. Computational methods were used to study the time-dependent flow patterns, shear stress metrics, and perfusion to vital organs and spinal cord. A three-element Windkessel module was coupled to the finite volume solver to dynamically assign appropriate outlet boundary conditions.
RESULTS: Both endovascular treatments were effective in maintaining physiological flow patterns in true lumen. However, MFM device not only eliminated local flow disturbances and globally regulated WSS distribution; but also maintained physiologic perfusion to peripheral vital organs and, more importantly herein, to spinal cord; thus promisingly reducing the risk of paraplegia.
CONCLUSION: MFM promisingly maintains the physiological intraluminal flow patterns with minimal compensation for vital organs and spinal perfusion. We propose further investigation in this field recruiting more clinical cases considering variety of anatomical features e.g. location and number of connecting tears. Those extensive numerical studies will focus on safety and efficacy of AD management assessing both modulation of blood flow and restoration of physiologic end-organ perfusion rather than mere restoration of vascular lamina morphology.