Long-term performance of an external stent for saphenous vein grafts: the VEST IV trial

Abstract

Background: Externally stenting saphenous vein grafts reduces intimal hyperplasia, improves lumen uniformity and reduces oscillatory shear stress 1 year following surgery. The present study is the first to present the longer-term (4.5 years) performance and biomechanical effects of externally stented saphenous vein grafts.

Methods: Thirty patients previously implanted with the VEST external stent in the randomized, within-patient-controlled VEST I study were followed up for adverse events; 21 of these were available to undergo coronary angiography and intravascular ultrasound.

Results: Twenty-one stented and 29 nonstented saphenous vein grafts were evaluated by angiography and ultrasound at 4.5 ± 0.3 years. Vein graft failure rates were comparable between stented and nonstented grafts (30 and 23% respectively; p = 0.42). All failures were apparent at 1 year except for one additional nonstented failure at 4.5 years. In patent vein grafts, Fitzgibbon perfect patency remained significantly higher in the stented versus nonstented vein grafts (81 and 48% respectively, p = 0.002), while intimal hyperplasia area (4.27 mm² ± 1.27 mm² and 5.23 mm² ± 1.83 mm² respectively, p < 0.001) and thickness (0.36 mm ± 0.09 mm and 0.42 mm ± 0.11 mm respectively, p < 0.001) were significantly reduced. Intimal hyperplasia proliferation correlated with lumen uniformity and with the distance between the stent and the lumen (p = 0.04 and p < 0.001 respectively).

Conclusions: External stenting mitigates saphenous vein graft remodeling and significantly reduces diffuse intimal hyperplasia and the development of lumen irregularities 4.5 years after coronary artery bypass surgery. Close conformity of the stent to the vessel wall appears to be an important factor.

Trial registration: NCT01415245 . Registered 11 August 2011.

Keywords: Coronary artery bypass graft surgery; External stent; Intimal hyperplasia; Saphenous vein graft.

Fig. 1

Angiographic images showing a within-patient comparison of stented and nonstented SVGs at 1 and 4.5 year follow-up. Stented SVG to obtuse marginal artery at 1 year (a) and after 4.5 years (b). Nonstented SVG to right coronary artery at 1 year (c) and 4.5 years (d)

Fig. 2

Perfect patency and graft failure rates of stented and nonstented vein grafts at 1 and 4.5 years post CABG. Green bars - perfect patency rates within each arm of stented (n = 40) and nonstented (n = 59) grafts (p = 0.002). Grey bars - graft failure rates within each arm of stented (n = 56) and nonstented (n = 72) grafts (p = 0.416)

Fig. 3

Within-patient comparison of intimal hyperplasia using IVUS. Segment of a nonstented SVG to the first obtuse marginal 4.5 years after implantation without (a) and with (b) marking of the lumen (red), EEM (purple) and outer vessel (green). Segment of externally stented SVG to the second obtuse marginal 4.5 years after implantation without (c) and with (d) marking of the lumen (red), EEM (purple) and stent (green)

Fig. 4

Comparison of intimal hyperplasia proliferation markers at 1 and 4.5 year follow-up. Data are mean ± SD. IH, intimal hyperplasia; 1Y, 1 year follow-up; 4.5Y, 4.5 year follow-up. Green square Stented grafts, grey square Non-stented grafts

Fig. 5

IVUS images showing a constrictive versus b loose fitting external stent (red arrows). Difference in wall thickness (yellow) and intima layer (blue) can be observed. In addition, there is formation of “neo-adventitia” between the loose-fitting stent and the original vessel wall

Fig. 6

Intimal hyperplasia thickness correlated with distance of the external stent from the lumen. grey circle 1 year (correlation coefficient 0.76, p < 0.001), green circle 4.5 years (correlation coefficient 0.84, p < 0.001). Baseline saphenous vein wall thickness (−--) is derived from relevant literature [30, 31]