NDLI: Engineering Vein Grafts Using an External Electrospun Biodegradable Polymer Wrap to Gradually Impose Arterial Circumferential Wall Stress Over Time

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Mohammed, S. El-Kurdi Hong, Yi John, J. Stankus Soletti, Lorenzo William, R. Wagner David, A. Vorp
Copyright Year	2007
Abstract	Failure of vein grafts via intimal hyperplasia (IH) remains a critical problem, with the 5-year reoperation rate at 60% of all cases[1]. Vein segments transposed to the arterial circulation for use as bypass grafts are exposed to increased bloodflow and intraluminal pressure[2]. Indeed, Liu and Fung showed that the average circumferential wall stress (CWS) in an arterial vein graft (AVG) immediately upon reestablishing flow could be 140 fold that in a vein under normal circumstances[2]. The tissue often responds to this perceived injury by thickening, which is thought to be an attempt to return the stress to venous levels. However, this response is uncontrolled and can over-compensate, leading to stenosis instead of the desired thickening or “arterialization” of the AVG. It has been suggested that this hyperplastic response by AVGs is a direct result of a “cellular shock” related to their abrupt exposure to the harsh new biomechanical environment[3]. We hypothesize that the adverse hyperplastic response by AVGs may be reduced or eliminated by more gradually exposing them to the arterial biomechanical environment. We believe that an adventitially-placed electrospun polymer wrap will allow an AVG ample opportunity to adapt and remodel to the stresses of its new environment in situ, thereby reducing cellular injury and limiting the initiating mechanisms of IH. Previous work has shown that preventing acute distension of AVGs by adding an external support or sheath can improve various pathologic responses[4, 5], but clinical utility of such a wrap is unproven. Liu et al. used a polytetrafluoroethylene external support to reduce IH in AVGs[2]. However, the immunological response to a permanent wrap is unfavorable and led Vijayan et al. to develop a biodegradable polyglactin sheath. These polyglactin sheaths were loose-fitting and allowed the AVG to expand to their maximum diameters under arterial pressure and thus did not offer mechanical support or prevent increased levels of CWS.
Sponsorship	Bioengineering Division
Starting Page	135
Ending Page	136
Page Count	2
File Format	PDF
ISBN	0791847985
DOI	10.1115/SBC2007-175506
Conference Proceedings	ASME 2007 Summer Bioengineering Conference
Language	English
Publisher Date	2007-06-20
Publisher Place	Keystone, Colorado, USA
Access Restriction	Subscribed
Subject Keyword	Biodegradation Biomechanics Fittings Biological tissues Wounds Polymers Shock (mechanics) Pressure Flow (dynamics) Stress Failure
Content Type	Text
Resource Type	Article

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