Sirolimus-eluting Stents for the Treatment of Atherosclerotic Ostial Lesions

This prospective observational study examines the use of sirolimus-eluting stents (SES) for the treatment of atherosclerotic ostial lesions.¹ Ostial lesions that involve the junction of the aorta and the origin of the right coronary artery, left main stem or a saphenous vein graft are called aorto-ostial. The other main type of ostial lesion occurs at the origin of the left anterior descending artery (LAD) or the left circumflex artery (LCX) arising from the bifurcation of the distal left main stem. The location of ostial lesions makes them difficult to treat by percutaneous coronary intervention (PCI). In those lesions involving the origin of the LAD or LCX, accurate stent positioning to avoid stent protrusion into the left main stem remains challenging. In aorto-ostial lesions, stent placement to cover the ostium without stent protrusion into the aorta requires fine manipulation of the guide catheter and stent. Long-term results of percutaneous transluminal coronary angioplasty (PTCA) for ostial lesions are limited by higher rates of restenosis compared to non-ostial lesions. Data from pathological series and atherectomy specimens have shown that ostial lesions are frequently sclerotic or calcified.² The more rigid character of these lesions makes them less amenable to treatment with direct coronary stenting. Direct stenting, although widely used in native and saphenous vein graft lesions, is frequently avoided in aorto-ostial lesions due to the frequent presence of tough or calcified plaque. In aorto-ostial lesions, the elasticity of adjacent aortic wall tissue contributes to suboptimal stent deployment and the development of restenosis.³ In an attempt to overcome these difficulties, operators have used rotational atherectomy, directional atherectomy and cutting balloon PTCA to “prepare” the lesions for coronary stenting.^4,5 More recently, another potential method for improving the long-term outcome of stenting in ostial lesions has arrived on the scene — the implantation of drug-eluting stents. In the original studies comparing SES with bare metal stents (BMS), ostial lesions were excluded and there are no randomized studies specifically addressing the benefits of SES in this group. The present study investigates the long-term clinical results of using SES in this challenging subgroup of lesions.¹ The study included a small sample size of 50 patients, with over half of the patients having treatment for ostial disease of the LAD or the LCX. Pre-dilatation was used in 50%, and post-dilatation of the stent in 30% of the cases. During a mean follow-up period of 414 days, target lesion revascularization (TLR) was required in 4 patients (8%), with one death during follow-up. Although routine angiographic follow-up was not performed, the low TLR rates suggest that SES are effective for the treatment of ostial lesions. Unfortunately, there is no clue as to whether any difference exists between aorto-ostial lesions and ostial lesions of LAD and LCX, or whether pre-treatment of ostial lesions prior to stenting has any additional benefit. It is also unclear as to whether vessel size, stent size and lesion length affect outcomes after SES when compared to BMS, but only a specifically designed, large, randomized trial could address these issues. A similar study examining the clinical and angiographic outcomes with SES in 32 patients with aorto-ostial lesions has been published.⁶ A control group consisted of 50 patients with aorto-ostial lesions treated with BMS. At 10-month follow-up, the angiographic restenosis rate was 11% in the SES group, compared with 51% in the BMS group. TLR was also reduced in the SES group compared to the BMS group (6.3% versus 28%). The aforementioned studies have only included small numbers of patients and larger randomized prospective studies are required to confirm the benefit of SES over BMS for the treatment of ostial coronary lesions. However, due to the not insignificant incidence of restenosis with BMS use at this location and the ischemic complications of ostial instent restenosis, it is likely that SES will have a major impact in improving the results of stenting ostial lesions. Lesion preparation may still remain an important determinant of success.

1. Vijayakumar M, Rodriguez Granillo GAA, Lemos PA, et al. Sirolimus-eluting stents for the treatment of atherosclerotic ostial lesions. J Invas Cardiol 2005;17:10–12. 2. Stewart JT, Ward DE, Davies MJ, Pepper JR. Isolated coronary ostial stenosis: Observations on the pathology. Eur Heart J 1987;8:917–920. 3. Tsunda T, Nakamura M, Wada M, et al. Chronic stent recoil plays an important role in restenosis of the right coronary ostium. Coronary Artery Disease 2004;15:39–44. 4. Muramatsu T, Tsukahara R, Ho M, et al. Efficacy of directional coronary atherectomy before stent implantation for coronary ostial lesions. J Invas Cardiol 2000;12:440–445. 5. Kurbaan AS, Kelly PA, Sigwart U. Cutting balloon angioplasty and stenting for aorto-ostial lesions. Heart 1997;77:350–352. 6. Iakovou I, Ge L, Michev I, et al. Clinical and angiographic outcome after sirolimus-eluting stent implantation in aorto-ostial lesions. J Am Coll Cardiol 2004;44:967–971.