Biodegradability and Biocompatibility of a Shape Memory Polymer Wrap to Improve Saphenous Vein Graft Patency in Peripheral and Coronary Artery Bypass Grafting Surgeries

PROJECT SUMMARY/ABSTRACT
Peripheral artery disease (PAD) affects nearly 12 million people in the United States. One of the most common
surgical therapies is peripheral artery bypass grafting (PABG). Some patients are eligible for less invasive
treatment options like angioplasty, but patients with calcified lesions are not. In patients that do receive PABG,
approximately 20% fail within the first year and 50% within 5 years. This proposal focuses on improving outcomes
in patients who require PABG.
There are a couple major shortcomings in current PABG procedures: the quality of the anastomosis is highly
dependent on surgeon experience, and vein grafts are not conditioned for the high pressure, high flow
environment of the arterial circulation. This proposal evaluates a shape memory polymer (SMP) external vein
wrap (SelfWrap) to address these shortcomings. SelfWrap is manufactured with a prescribed angle between the
artery and vein branches which can support the sutures, possibly reducing dependence on quality of the sutures
and surgical experience. More importantly, SelfWrap provides mechanical support to the vein upon its first
exposure to arterial pressures. Mitigating wall tension in the vein graft can reduce neointimal hyperplasia (NH),
thereby alleviating risk of graft failure. The shape memory characteristics of SelfWrap are a critical aspect that
enables the device to form-fit to the patient-specific vascular anatomy and provide non-constrictive mechanical
support, even as the artery and vein branches pulse throughout the cardiac cycle.
Preliminary results collected in sheep when evaluating SelfWrap as a perivascular wrap on arteriovenous fistulas
(AVF) used for hemodialysis access support these claims. At 28 days, AVFs treated with SelfWrap had
significantly higher flow rates and larger vessel diameters than untreated AVFs.
However, none of this is relevant towards commercializing SelfWrap if it has significant long-term degradation
and/or leachables issues. For this reason, biodegradation, a risk assessment following leachables testing, and
biocompatibility results from a 6-month implantation are evaluated in the present proposal. These tests will follow
pre-award activities assessing cytotoxicity, acute systemic toxicity, and implantable biocompatibility at earlier
timepoints. A Breakthrough Devices Designation decision from the FDA and a pre-submission meeting with the
FDA to further inform our regulatory testing strategy will also be completed pre-award. In addition to the first aim,
histological, hemodynamic, and biomechanical data will be collected in a rabbit model PABG model to further
validate that the SelfWrap device performs well in the PABG environment, both anatomically and physiologically.
Successful completion of the aims in this proposal will inform VenoStent, Inc. if there are any changes needed for
SelfWrap’s manufacturing process or design prior to continuing onto other GLP biocompatibility tests, furthering
manufacturing efforts, and testing in non-GLP and GLP large animal PABG models.Project Narrative
Peripheral artery disease (PAD) affects nearly 12 million people in the United States, representing a $21 billion
American healthcare cost annually, and 200 million people worldwide. Of the 8-900,000 American patients who
receive peripheral artery bypass grafts (PABG), 20% fail within the first year, necessitating expensive surgical
revisions that put the patient at a greater risk of complications and death. To address this, we propose a shape
memory polymer wrap that could be routinely applied during PABG surgeries to promote favorable adaptation of
the PABG, obviating the need for surgical revisions and, in turn, significantly reducing healthcare costs for
revision procedures.