Graft geometry and venous intimal-medial hyperplasia in arteriovenous loop grafts

Abstract

This study explores graft geometry and hemodynamics in a reproducible canine arteriovenous loop graft model of intimal-medial hyperplasia. Untapered 6 mm diameter polytetrafluoroethylene grafts (n = 10) were paired with 4 to 7 mm taper (n = 5) or 7 to 4 mm taper (n = 5) grafts for a 12-week period. Several hemodynamic variables were assessed at multiple locations, and venous intimal-medial thickness was measured at locations corresponding to the hemodynamic measurements. Color Doppler imaging demonstrated energy transfer out of the vessel in the form of perivascular tissue vibration. This was quantitated by the distance required for Doppler signal attenuation or volume of the detected vibration signal. Differences among graft types were noted for pressure, flow velocity, tissue vibration, and venous intimal-medial thickness. Hyperplasia was significantly decreased in 4 to 7 mm taper grafts. Stepwise deletion regression indicated volume of the vibration signal had a better correlation with venous intimal-medial thickness than any other variable (r 0.9, p less than 0.001). We conclude that graft geometry can have a significant impact on hemodynamic factors and venous intimal-medial hyperplasia in arteriovenous loop grafts. Flow disturbances appear to cause energy transfer through the vessel wall and into perivascular tissue. Kinetic energy transfer in the form of perivascular tissue vibration was quantitated in vivo and correlates strongly with venous intimal-medial thickness.

Hemodynamics and Complications Encountered with Arteriovenous Fistulas and Grafts as Vascular Access for Hemodialysis: A Review

“…Perivascular tissue vibration was less in the vein near the heel where the fewest IH development was observed. Loth et al 56 repeated the experiments of Fillinger et al 17 by implanting PTFE-grafts in swines. They discovered mitogen-activated protein kinases (MAPK), more specifically: ERK1 and ERK2 in regions of increased vein wall vibrations.…”

“…Fillinger et al 17 correlated kinetic energy transfer to intimal hyperplasia development. The kinetic energy transfer causes perivascular tissue vibration that can induce chronic vascular injury and subsequent IH development.…”

The effect of in-plane arterial curvature on blood flow and oxygen transport in arterio-venous fistulae

“…[10][11][12][13][14] The results presented above suggest that forming an AVF via a vein graft onto a straight artery, or onto the inner-curvature of a curved artery, will result in unsteady blood flow patterns and WSS distributions within both the artery (50-60 Hz) and potentially (depending on the venous diameter) within the vein (up to 650 Hz). However, forming an AVF via a vein graft onto the outer-curvature of a curved artery can suppress such unsteadiness.…”

“…In particular regions of low Wall Shear Stress (WSS), highly oscillatory flow, and low Lumen-to-Wall Oxygen Flux (LWOF), leading to wall hypoxia, are all implicated in the initiation of IH. [5][6][7][8][9][10][11][12][13][14][15][16][17] There have been various computational studies of blood flow within AVF and Arterio-Venous Grafts (AVG). In 2003, Loth et al 18 simulated blood flow within idealized AVG and compared results with those obtained in vivo.…”

Cell Attachment–Detachment Control on Temperature-Responsive Thin Surfaces for Novel Tissue Engineering

“…Based on these observations, tissue-engineering techniques that can re-create adequate blood supplies are essential for properly reconstructed tissues that possess the structure and function of the native organs. 15,37,59,73 In order to overcome these problems, an innovative approach to tissue engineering using temperatureresponsive culture surface has been developed since 1990. 64,70 PIPAAm and its copolymers exhibit a LCST in aqueous media in the vicinity of 32°C.…”