Bifurcation Intervention: Keep it Simple
- Volume 18 - Issue 2 - February, 2006
- Posted on: 8/1/08
- 0 Comments
- 2446 reads
The percutaneous treatment of bifurcation lesions remains suboptimal. A frequent problem, accounting for 10–20% of coronary lesions undergoing percutaneous coronary intervention (PCI), the bifurcation is plagued by acute technical challenges, long-term restenosis, and more recently, early and late stent thrombosis.1–4 Generally defined as a lesion which involves a side branch of 2.0 mm or greater, the bifurcation is in part so complex due to its variability. This variability results from inconsistent plaque distribution, unpredictable side branch angulation and large differences in main branch and side branch diameters. Furthermore, these lesions are often noncompliant at the carina due to calcification and/or negative remodeling. A recent analysis of over 11,000 patients in whom 1,412 had bifurcation lesions suggested that PCI of the bifurcation was associated with an increased rate of death/MI/target vessel revascularization.5 Historically, bare metal stent restenosis rates of over 50% have been reported with no consistent favorable impact of systematic debulking.6,7 A significant reason for left main disease being unsuitable for PCI is involvement of the bifurcation.
Though this subset of lesions is challenging, progress has been made. The impact of drug-eluting stents appears favorable, though less dramatic than in noncomplex lesions. In this issue of the Journal, Lee and colleagues describe a single-center experience with drug-eluting stents in de novo bifurcation lesions, of which 39% were true bifurcations with plaque involving both the main and the side branches.8 In this report, 83 patients with 85 bifurcation lesions were treated with either CYPHER™ (Cordis Corp., Miami, Florida) or TAXUS® (Boston Scientific Corp., Natick, Massachusetts) stents. The type of stent was not randomly assigned. Procedural success was high, 93% and 96% for CYPHER and TAXUS stents, respectively. In the TAXUS group, 10 patients received side branch stenting (34%), while in the CYPHER group only 1 patient underwent side branch stenting (8%). Only 25% of the TAXUS patients received a final kissing balloon inflation. One patient in each group had a CK elevation postprocedure. At 30 days, there were 2 stent thromboses, both in the TAXUS group. The overall MACE rate was numerically higher in the TAXUS group (7 versus 4%), but not statistically different. Similar early positive results have been reported by others. Compared to historical controls, it appears that drug-eluting stents have lowered the rate of main branch restenosis and target lesion revascularization; however, the impact on the side branch has been less impressive. Yamachita and colleagues reported a restenosis rate of 33–39% for the main branch using bare metal stents. The event rates ranged from 38–51%, depending on the implantation strategy at 6-month follow up.6 With the use of drug-eluting stents, restenosis rates have been 10% or less in the main branch, particularly when the side branch is not stented.3
Various techniques have been devised to enhance the outcomes of the side branch. Bifurcation stenting techniques include the provisional T, the planned T, the V, the simultaneous kiss (SKS), the cullote, and most recently, the crush.1,9–11 Data from bare metal stent studies suggest no benefit of two stents versus one stent, and to the contrary, a consistent theme has been that one stent is superior.6,7 These analyses have been limited by a lack of prospective randomization, however, and do not exclude the possibility that those lesions receiving two stents are at inherently higher risk for restenosis. In one randomized study of systematic side branch stenting versus single main branch stenting, the single-stent group had lower overall restenosis rates (18.7% versus 28%) and fewer stent thromboses (6.6% in the two-stent group).3 Pan and colleagues reported similar findings in the other randomized study of single versus two stents in bifurcations.12
The “crush” technique was developed to improve ostial side branch coverage without compromising access to the side branch. This approach involves first delivering the side branch stent 5–10 mm proximal to the side branch ostium and then crushing the proximal portion of the side branch with the main branch stent.11 Although initially embraced, the technique appears to have substantial limitations. In a report by Ge et al., 181 patients were treated with bifurcation lesions using the crush technique. The overall restenosis rate (main and side branch) was 21.6%.13 The impact of a final kissing balloon (FKB) inflation was striking, reducing restenosis from 37.9% without FKB versus 11.1% with a final kiss. Even with a final kiss, the crushed portion of the stent was often not apposed and the minimum residual stenosis within in the main branch was nearly always at the site of the crush.14 Despite a final kiss, the ostium of the side branch was often inadequately dilated, resulting in a high restenosis rate.14 What was most sobering in this report was a 1.7% intraprocedural thrombosis rate coupled with an additional 2.8% of patients suffering stent thrombosis by 9 months; the overall thrombosis rate was 4.4%.13 This high rate of stent thrombosis compares to a 1–2% rate in other unselected cases of drug-eluting stents.13 These data suggest that the crushing technique should be used only in selected cases, if ever, and always with a final kissing inflation.
Further progress in this lesion subset will depend on developing effective bifurcation-specific stent platforms. Early devices include side branch access systems, which allow continued access and modest ostial branch scaffolding.15 Other devices allow for continued access and 1–2 mm of side branch scaffolding at the ostium. Another first-generation platform is a self-expanding modular system. These early devices have been limited by their large profile, suboptimal deliverability, incorrect side branch orientation and suboptimal scaffolding. Another hurdle is developing a system that is adaptable enough to approach the myriad of bifurcation geometries. Finally, a more robust true bifurcation system may be necessary for the left main application, where problems with deliverability are less frequent, and optimal coverage and scaffolding are paramount.
So what is today’s interventionalist to do before these true bifurcation systems become available? Clearly, drug-eluting stents reduce restenosis of the main branch. The clinical results in the main branch are likely even better in the real world, where routine angiography is not employed. The oculostenotic reflex is greater in bifurcation lesions than in nonbifurcations.5 It appears that many of the side branch lesions that seem to be angiographically significant are not hemodynamically significant by fractional flow reserve analysis.16 The size of the side branch is important, with those < 2.4 mm in diameter less frequently causing recurrent angina when restenosis occurs.17 If anything, interventionalists are guilty of being too aggressive with the side branch. The default strategy today appears to be one of main branch stenting and angioplasty of the side branch when necessary. When the side branch is very angulated or there is a high probability of closure with main branch stenting, leaving the side branch wire in place while deploying the main branch (at relatively low pressures) may facilitate rewiring the side branch. If the side branch is dilated through the struts of the main branch stent, a kissing inflation is mandatory, as this helps restore the main branch geometry and expansion.18 Although a provisional T-stent strategy is most often utilized when side branch stenting is required, there are true bifurcation lesions where the selected use of more complex bifurcation approaches seems appropriate, particularly when the main branch and side branch are larger vessels, having more diffuse side branch disease. If one of these complex bifurcation approaches is required, the use of GP IIb/IIIa inhibitors to avoid intraprocedural thrombosis appears to be prudent, along with meticulous implantation techniques, which should include intravascular ultrasound. Adequate predilatation with or without cutting balloon or rotational atherectomy is essential. Because the utilization of bifurcation stenting appears to be associated with higher stent thrombosis rates, prolonged/indefinite dual antiplatelet therapy is reasonable.
Bifurcation disease is the most common and one of the greatest challenges we face in intervention today. Until reliable bifurcation-specific systems are approved, be meticulous, use a drug-eluting stent and keep it simple.