Drug-Eluting Stents and Saphenous Vein Graft Intervention

The sting in the tail of successful saphenous vein graft (SVG) intervention is the high rate of in-stent restenosis. Not only are the procedures themselves fraught with technical challenges and a high rate of periprocedural adverse cardiovascular events, there is also a late downside due to frequent restenosis.^1–3 Bypass surgery, like angioplasty, is merely a palliative procedure with the majority of vein grafts showing significant stenoses by 10 years after the surgery.^4–6 Redo bypass grafting in patients with recurrent angina is often unattractive due to the older age of the patients,⁷ higher risk and lower success rates as compared with first bypass operation.⁸ Thus the appeal of SVG angioplasty despite the acknowledged difficulties. Management of the initial intervention in SVGs has reached something of a plateau. A number of technologies with early promise have subsequently proved disappointing. Debulking strategies are a case in point.^9–11 Somewhat surprisingly, the use of glycoprotein IIb/IIIa receptor antagonism has been a disappointment in the setting of SVG intervention.^12,13 However, some technologies do appear to reduce adverse procedural events. Embolic protection devices have been proven effective.^12,14,15 Direct stenting may be desirable.^16,17 While some of these newer approaches may reduce peri-procedural events they do nothing to prevent the longer-term problem with restenosis. With SVG intervention carrying such high initial risk and cost, it is all the more important to achieve a durable benefit. While stents have reduced the rate of restenosis,18 the improvement has generally been modest.^2,3,19 When SVG in-stent restenosis (ISR) occurs, there are few options. Intravascular brachytherapy is of value and is widely available, but enthusiasm is muted due to limited benefit, late thrombosis, procedural complexity, inconvenience and expense.²⁰ In this issue of The Journal of Invasive Cardiology, Hoye et al. (see pages 230–233) present data suggesting a low rate of repeat SVG intervention in patients treated with sirolimus-eluting stents. Drug-eluting stents have been widely adopted after their benefits were proven in native vessels.²¹ If they also improve the risk-benefit ratio in SVG intervention, their use is to be welcomed. The intravascular milieu of vein grafts differs greatly from native vessels. Plaque morphology in SVGs is lipid-rich, soft and more prone to rupture than plaque in native coronary arteries.¹⁵ Furthermore, the pathology of ISR^22,23 differs from that in native vessels.^24,25 A mixture of cellular hyperplasia, progression of atherosclerosis, local inflammatory reaction to stent material and thrombosis appears responsible for vein graft restenosis. The local conditions after stent implantation in SVGs are prothrombotic for much longer than after stenting in native vessels.^22,23 In addition, there are differences between the time-course of restenosis of native coronary arteries, treated with either balloon^26,27 or stent,²⁸ and that of vein grafts.²⁹ It remains possible that drug-eluting stents will as much delay as prevent SVG restenosis. Successful long-term treatment for degenerative vein grafts may require several simultaneous and disparate actions to prevent restenosis or further degeneration. The goal posts continue to move and the use of historical controls may not be valid. Some investigators have recently reported more favorable results with bare metal stenting,³⁰ citing a respectable 76% one year event-free survival; perhaps due to more modern stent systems, better procedural techniques and improved case selection. More information is needed with respect to the place of drug-eluting stents in the setting of saphenous vein graft angioplasty. However the movement towards routine application of drug-eluting stent technology appears inexorable.