Approximately 30% of the patients operated upon with bypass surgery experience a graft occlusion within one year. This may in turn induce a recurrence of organ ischemia with dramatic increased incidence of heart-infarction and amputation of legs.
The development of a graft-stenosis is due to an excessive response with scar tissue. Recent evidences have shown that physical forces exerted by the blood flow are the major contributors to the development. Low shear stress and turbulence accelerate the development.
Bypasses are today implanted end-to-side to the recipient artery. This gives rise to a reduced shear stress and turbulence at the connection sites, which induces the production of the scar-tissue. The development is further increased by the suturing of the anastomoses. The trauma imposed by the stitches in the vessel wall and the flow characteristics induce cellular growth in concert through different mechanisms at the same location.