Results for primary bypass versus primary angioplasty/stent for intermittent claudication due to superficial femoral artery occlusive disease

Role of hemodynamic forces in the ex vivo arterialization of human saphenous veins

BACKGROUND

Human saphenous vein grafts are one of the salvage bypass conduits when endovascular procedures are not feasible or fail. Understanding the remodeling process that venous grafts undergo during exposure to arterial conditions is crucial to improve their patency, which is often compromised by intimal hyperplasia. The precise role of hemodynamic forces such as shear stress and arterial pressure in this remodeling is not fully characterized. The aim of this study was to determine the involvement of arterial shear stress and pressure on vein wall remodeling and to unravel the underlying molecular mechanisms.

METHODS

An ex vivo vein support system was modified for chronic (up to 1 week), pulsatile perfusion of human saphenous veins under controlled conditions that permitted the separate control of arterial shear stress and different arterial pressure (7 mm Hg or 70 mm Hg).

RESULTS

Veins perfused for 7 days under high pressure (70 mm Hg) underwent significant development of a neointima compared with veins exposed to low pressure (7 mm Hg). These structural changes were associated with altered expression of several molecular markers. Exposure to an arterial shear stress under low pressure increased the expression of matrix metalloproteinase (MMP)-2 and MMP-9 and tissue inhibitor of metalloproteinase (TIMP)-1 at the transcript, protein, and activity levels. This increase was enhanced by high pressure, which also increased TIMP-2 protein expression despite decreased levels of the cognate transcript. In contrast, the expression of plasminogen activator inhibitor-1 increased with shear stress but was not modified by pressure. Levels of the venous marker Eph-B4 were decreased under arterial shear stress, and levels of the arterial marker Ephrin-B2 were downregulated under high-pressure conditions.

CONCLUSIONS

This model is a valuable tool to identify the role of hemodynamic forces and to decipher the molecular mechanisms leading to failure of human saphenous vein grafts. Under ex vivo conditions, arterial perfusion is sufficient to activate the remodeling of human veins, a change that is associated with the loss of specific vein markers. Elevation of pressure generates intimal hyperplasia, even though veins do not acquire arterial markers.

CLINICAL RELEVANCE

The pathological remodeling of the venous wall, which leads to stenosis and ultimately graft failure, is the main limiting factor of human saphenous vein graft bypass. This remodeling is due to the hemodynamic adaptation of the vein to the arterial environment and cannot be prevented by conventional therapy. To develop a more targeted therapy, a better understanding of the molecular mechanisms involved in intimal hyperplasia is essential, which requires the development of ex vivo models of chronic perfusion of human veins.

Prosthetic graft infections involving the femoral artery

BACKGROUND

Prosthetic graft infection is a major complication of peripheral vascular surgery. We investigated the experience of a single institution over 10 years with bypass grafts involving the femoral artery to determine the incidence and risk factors for prosthetic graft infection.

METHODS

A retrospective cohort single-institution review of prosthetic bypass grafts involving the femoral artery from 2001 to 2010 evaluated patient demographics, body mass index, comorbidities, indications, location of bypass, type of prosthetic material, case urgency, and previous ipsilateral bypass or percutaneous interventions and evaluated the incidence of graft infections, amputations, and mortality.

RESULTS

There were 496 prosthetic grafts identified with a graft infection rate of 3.8% (n = 19) at a mean follow-up of 27 months. Multivariable analysis showed that redo bypass (hazard ratio [HR], 5.8; 95% confidence interval [CI], 2.2-15.0), active infection at the time of bypass (HR, 5.2; 95% CI, 1.9-14.2), female gender (HR, 4.5; 95% CI, 1.6-12.7), and diabetes mellitus (HR, 4.6; 95% CI, 1.5-14.3) were significant predictors of graft infection. Graft infection was predictive of major lower extremity amputation (HR, 9.8; 95% CI, 3.5-27.1), as was preoperative tissue loss (HR, 4.7; 95% CI, 1.8-11.9). Graft infection did not predict long-term mortality; however, chronic renal insufficiency (HR, 2.3; 95% CI, 1.6-3.4), tissue loss (HR, 1.4; 95% CI, 1.0-1.9), and active infection (HR, 2.3; 95% CI, 1.6-3.4) did. Infected grafts were removed 79% of the time. Staphylococcus epidermidis (37%) and methicillin-sensitive Staphylococcus aureus (26%) were the most common pathogens isolated.

CONCLUSIONS

Redo bypass, female gender, diabetes, and active infection at the time of bypass are associated with a higher risk for prosthetic graft infection and major extremity amputation but do not confer an increased risk of mortality. Autologous vein for lower extremity bypass and endovascular interventions should be considered when feasible in high-risk patients.