Results of the SOS (Stenting of saphenous vein grafts) study published in the 17 March, 2009 issue of the Journal of the American College of Cardiology showed that the Taxus paclitaxel-eluting stent (Boston Scientific) reduced angiographic restenosis, target lesion revascularisation, and target vessel failure compared with bare metal stents in saphenous vein graft lesions.
The trial randomised 80 patients with 112 lesions to either bare metal stents (n=39, 43 grafts, 55 lesions) or Taxus stents (n=41, 45 grafts, 57 lesions) in five centres (four in the USA, one in Greece) between 2005 and 2007. The inclusion criteria was age >18 years; one or more 50% to 99% de novo or restenotic lesions in an saphenous vein graft that were between 2.5 and 4mm in diameter; need for percutaneous coronary intervention in the opinion of the attending cardiologist; and willingness to return for repeat graft angiography at 12 months and be contacted after one, six, 12, and 24 months for clinical follow-up. The study was led by Dr Emmanouil S Brilakis, VA North Texas Healthcare System and University of Texas Southwestern Medical Center, Dallas, USA.
The results showed that the primary endpoint, binary angiographic restenosis at 12 months, was significantly lower in Taxus-treated lesions vs. bare metal stents-treated lesions (9% vs. 51% for both in-segment and in-stent restenosis, p<.0001). During a median follow-up of 1.5 years the Taxus patients had less target lesion revascularisation (28% vs. 5%, p =.003) and target vessel failure (46% vs. 22%, p=.03), a trend toward less target vessel revascularisation (31% vs. 15%, p=.08) and myocardial infarction (31% vs. 15%, p =.10), and similar mortality (5% vs. 12%, p=.27).
“The most important finding of this trial is that paclitaxel-eluting stents reduce angiographic restenosis rates and target vessel failure in saphenous vein graft lesions compared with bare metal stents,” the authors wrote. “Drug-eluting stents have been shown to reduce restenosis in many lesion types and clinical syndromes. However, there is a paucity of prospective data on drug-eluting stents in saphenous vein graft interventions, although bare metal stenting is associated with high restenosis rates in saphenous vein graft lesions. The results of mostly retrospective observational series comparing drug-eluting with bare metal stents in saphenous vein grafts have been conflicting: six studies showed better results with drug-eluting stents and nine suggested no difference between bare metal and drug-eluting stents.”
The RRISC (Reduction of restenosis in saphenous vein grafts with Cypher sirolimus-eluting stents) trial, the only other published, prospective, randomised trial investigating drug-eluting stents vs. bare metal stents in saphenous vein graft lesions, showed restenosis and target vessel revascularisation were lower with Cypher (Cordis) vs. bare metal stent BxVelocity (Cordis) at six months, but after 36 months, mortality was higher with Cypher (29% vs. 0%, p= .001). In addition, any early benefits with the sirolimus-eluting stent had disappeared, as evidenced by equivalent rates of infarction (18% Cypher vs. 5% BxVelocity, p=.15) and target vessel revascularisation (34% Cypher vs. 38% BxVelocity, p=.74).
As in the RRISC trial, the authors affirmed, a significant reduction in late loss was observed in the drug-eluting stent arm of SOS. The in-stent late loss in the drug-eluting stent group was similar in the two studies (.38 ± .51mm in the RRISC trial, and .42 ± .57mm in the SOS trial) but was less in the bare metal group in the RRISC study (.79 ± .66mm) than in the SOS trial (1.29 ± 1.03mm). Accordingly, angiographic restenosis occurred more frequently in the bare metal stent arm of the SOS trial (51% vs. 33% in the RRISC trial). “This was likely in part due to the performance of follow-up coronary angiography at 12 months in the SOS trial versus at six months in the RRISC trial. The higher prevalence of diabetes (44% in the SOS trial vs. 15% in the RRISC trial) and smoking (26% in the SOS trial vs. 8% in the RRISC trial) might have also played a role. In contrast to the RRISC study, where most restenoses were nonocclusive, nearly one-half of the restenotic lesions in the SOS trial were occlusive, in which repeat PCI is often not attempted, explaining in part why the difference in target vessel revascularisation did not reach statistical significance in the SOS trial.”
The paclitaxel-eluting stent group in the SOS trial, the authors continued, had less target lesion revascularisation without attenuation of benefit during follow-up, as was seen in the RRISC trial. “Both the Express2 bare metal stent used in SOS and the BxVelocity used in the RRISC trial are thick strut stents (strut thickness 132 and 140µm, respectively); therefore, bare metal stent design is unlikely to explain the higher in-stent restenosis rates in the bare metal stent arm of the SOS trial.”
The researchers of the SOS study concluded that the use of paclitaxel-eluting stent in saphenous vein graft lesions is associated with lower rates of angiographic restenosis and target vessel failure than bare metal stents. “Large, prospective, multicentre, randomised-controlled clinical trials that use a clinical rather than angiographic end point are needed to confirm the beneficial role of drug-eluting stents in saphenous vein graft lesions.” Such a study (VA Cooperative Study 571, Drug eluting stenting in saphenous vein graft angioplasty – DIVA) is currently in final stages of planning and may begin enrolment in 2009.