Vein graft stenoses <50% are believed to be clinically "insignificant" because they cause little decrement in blood flow. However, the possible deleterious effects of minor flow disturbances on long-term cellular proliferation are unknown. The purpose of this study was to evaluate the effect of artificially created 50% stenoses on neointimal thickening in experimental vein grafts. Fifteen male New Zealand White rabbits underwent carotid interposition bypass grafting using the external jugular vein. Mid-graft 50% stenoses were created in eight grafts by the application of a two-millimeter internal diameter stainless steel clip. After four weeks, the grafts were perfusion-fixed, excised, and histologic sections were examined for neointimal thickening. Application of the clip caused a 50% reduction in external diameter (3.9 ± 0.4 mm to 2.0 mm), causing only slight perturbations in pressure gradient (ΔP = 2.1 ± 1.1 to 2.3 ± 1.5 mmHg) and mean blood flow (flow 16 ± 3.0 to 14 ± 4.4 ml/min). After four weeks, four grafts had occluded (two from each group) and one clip had become dislodged, leaving ten grafts for analysis. Neointimal thickness was minimal in control grafts (88 ± 12 μm), but was significantly increased in stenotic grafts both immediately proximal (200 ± 39 μm; p = 0.03) and immediately distal to the stenosis (230 ± 50 μm; p = 0.02). Hemody-namically "insignificant" stenoses stimulate vein graft neointimal thickening. These results support the continued use of graft surveillance and an aggressive approach to the treatment of "minimal" vein graft lesions.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine