Unprotected Left Main Stenting: An Alternative to CABG in a DES World?

In this issue of the Journal of Invasive Cardiology, Eeckhout, et al. have described the adjunctive use of intravascular ultrasound to guide stent implantation in the treatment of symptomatic, “unprotected” left main coronary artery disease. While the use of stents or IVUS to guide stenting of left main stem disease are not novel, the experiences described by these investigators raise many important technical issues related to the optimal use of stents for left main percutaneous coronary intervention (PCI). As pointed out by the authors, angioplasty of unprotected left main coronary artery disease has historically been a taboo practice.¹ The fear of PCI to treat this form of coronary disease is largely related to very poor historical data with balloon angioplasty¹ and subotimal outcomes in the early experience using bare metal stents in high-risk patients.^2–4 However, “that was then, and now is now.” The availability of highly deliverable, radiopaque stents and effective drug-eluting stent (DES) technology, combined with the knowledge gained from published registry experiences and observational case reports, help to guide us closer to an optimal use of stents to treat unprotected left main disease. There are a number of important “key points” that can be made in 2005 regarding the safe and effective use of stents to treat left main disease. Perhaps one of the most important lessons from the case study of Eekhout et al. is the significant under-deployment observed when stents are implanted in the left main at “reasonable” deployment pressures. In this case study, the mean post-procedural diameter stenosis was 14% after post-dilatation. This should be considered as less than optimal. One of the most common causes of undersizing arises from a literal interpretation of the manufacturer balloon diameter/pressure compliance tables included in most stent packages. It needs to be emphasized that these balloon compliance data are obtained by measurements of balloon dimensions in air and without the constraining effect of a severely diseased and noncompliant segment of human coronary artery. We have recently presented data that demonstrate the marked under-deployment that will result from reliance on these compliance charts.5,6 This is particularly true of the BX VELOCITY™ and BX VELOCITY CYPHER^® drug-eluting stent systems (Cordis Corporation, Miami, Florida) due to the radial hoop strength of these stents and the very noncompliant nature of the RAPTOR™ (Cordis Corp.) balloon material of the stent delivery system (SDS). Our data demonstrate, for example, that a 3.5 mm BX VELOCITY stent, in vivo, attains a minimal stent diameter (mean) of only 2.98 mm at 12 atmospheres deployment pressure. These data are based upon QCA measurements of the stent delivery balloon during the treatment of native coronary lesions. This stent can be more optimally expanded in human coronary arteries at 17–18 atmospheres. At this deployment pressure, a 3.5 mm CYPHER stent then achieves a (mean) minimum lumen diameter (MLD) of 3.48 mm, in vivo (Figure 1). A similar, but less marked deviation of stent MLD from manufacturer compliance data is observed when stents, such as the NIR™ premounted stent (Boston Scientific Corporation, Maple Grove, Minnesota, are pre-mounted on a more compliant balloon.⁵ Therefore, if interventional cardiologists rely on printed compliance tables, this will routinely lead to stent under-deployment, particularly with the CYPHER DES. Under-deployment of stents is a very important issue, as clinical studies have identified this as an independent risk factor for both subacute stent thrombosis (SAT) and restenosis of both bare metal and DES. In addition, incomplete apposition of a CYPHER may limit delivery of drug to localized areas of injured vessel resulting in focal restenosis.⁷ Certainly, IVUS can be helpful to document optimal stent expansion. This may be even more critical in left main stenting, since either restenosis or thrombosis can result in a potentially fatal complication.^8,9 There are several other important take-home lessons about left main stenting from the current study and the historical literature. In addition to optimal expansion, left main stents must be precisely positioned to effectively alleviate the obstruction and to prevent acute recoil and late negative remodeling. This is particularly important in the treatment of aorto-ostial left main disease. It is likely that the higher failure rate of stents (bare metal and DES) in the treatment of aorto-ostial left main disease is related to a common error of “missing” the ostium. Most often, the geographic miss of the lesion occurs when the stent is placed just distal to the ostium. When this occurs, and if unrecognized, restenosis of the diseased, injured and non-stented true left main ostium is virtually inevitable. For the operator, if angiography or post-dilatation suggests suboptimal positioning at the ostium, then IVUS should be employed to confirm the position of the stent. In cases of geographic miss of the left main ostium, a second stent can be placed to optimize the acute clinical result. In our Center’s experience, however, a “miss” requiring a second (overlapping) stent is a risk factor for restenosis with bare metal stents. Less is known about this issue when using DES. There are a few final caveats and some important practical tips to consider when performing stenting of unprotected left main disease based upon our Center’s experience combined with the historical literature: 1) Avoid distal left main lesions that involve the bifurcation. Even though acceptable acute results can be achieved by highly experienced operators, the risks of a poor result, or death, is relatively high with the currently available technology. It may be best to send these patients for bypass surgery. 2) Do not undersize stents. Use high expansion pressures and post-dilate as needed to leave a 0% residual stenosis. Use IVUS if needed. 3) There are virtually no left main coronary arteries in adults that should be treated with less than a 3.5 mm diameter stent. 4) In ostial left main stenting, use a stent length > 10 mm. If 10 There are no current published data demonstrating safety and efficacy of a Taxus™ stent for this anatomy. Taxus stent deployment in vessels larger than 3.0 mm appears to be minimally effective.¹¹ (5) If the left main is large enough to accept a 4.25 mm result or larger, the restenosis rate with bare metal stents (when optimally expanded) is very low, and can achieve DES-like clinical results (Figure 2). 6) All patients who undergo coronary stenting of an unprotected left main should have mandatory angiographic follow-up at 3 to 4 months for bare metal stents, and 4 to 6 months for DES, in order to detect significant or aggressive in-stent restenosis. 7) If there is restenosis, especially with associated ischemia, it is our bias that CABG should be performed. There are little data to confirm the safety or efficacy of repeat PCI to treat restenosis of unprotected left main disease. 8) Finally, dual antiplatelet therapy with aspirin and clopidogrel is mandatory for a minimum of 6 months after the left main intervention, given the potential morbidity and mortality of a left main stent thrombosis. In summary, unprotected left main stenting is a viable alternative to bypass surgery in carefully selected patients, particularly if treated with DES. As always, meticulous stenting technique, including the appropriate use of IVUS guidance, will be predictive of the acute and long-term results achieved using this approach. Ultimately, a randomized clinical trial should be conducted to compare DES intervention with CABG in the management of left main coronary artery disease.

1. O'Keefe J, Hartzler G, Rutherford B. Left main coronary angioplasty: Early and late results of 127 acute and elective procedures. Am J Cardiol 1989;64:144–147. 2. Ellis S, Tamai H, Nobuyoshi M. Contemporary percutaneous treatment of unprotected left main coronary stenoses. Circulation 1997;96:3867–3872. 3. Park S, Park S, Hong M. Stenting of unprotected left main coronary artery stenosis: immediate and late outcomes. J Am Coll Cardiol 1998;31:37–42. 4. Wong P, Wong V, Chan W. A prospective study of elective stenting in unprotected left main coronary disease. Cathet Cardiovasc Intervent 1999;46:153–159. 5. Haller SD, Mirza R, Kucinich ME, et al. Overestimation of inflated balloon dimensions and risk of stent under-expansion using manufacturer compliance tables: The REALITY trial. Am J Cardiol TCT–59:26E. 6. Hehrlein C, DeVries J, Wood T, et al. Overestimation of stent delivery balloon diameters by the manufacturers’ compliance tables: A quantitative coronary analysis of Duet and NIR stent implantation. Cathet Cardiovasc Intervent 2001;53:474–478. 7. Fujii K, Mintz GS, Kobayashi Y, et al. Contribution of stent under expansion to recurrence after sirolimus-eluting stent implantation for in-stent restenosis. Circulation 2004;109:1085–1088. 8. Mudra H, di Mario C, de Jaegere P, et al. Randomized comparison of coronary stent implantation under ultrasound or angiographic guidance to reduce stent restenosis (OPTICUS study). Circulation 2001;104:1343–1349. 9. Fitzgerald PJ, Oshima A, Hayase M, et al. Final results of the Can Routine Ultrasound Influence Stent Expansion (CRUISE) study. Circulation 2000;102:523–530. 10. Arampatzis C, Lemos P, Tanabe K, et al. Effectiveness of sirolimus-eluting stent for treatment of left main coronary artery disease. Am J Cardiol 2003;92:327–329. 11. Stone CW, Ellis SG, Cox DA, et al. A polymer based, paclitaxel-eluting stent in patients with coronary artery disease. N Engl J Med 2003;350:221–231.