More Stents, Fewer LIMAs?

Since Robert Goetz first performed a single mammary artery bypass to the anterior descending artery in 1960, its evolution has been associated with unparalleled clinical benefit in terms of symptom relief and a favorable effect on mortality, particularly in diabetics and those with multivessel disease. In fact, there have been few, if any, treatment strategies in all of modern vascular medicine that rival the beneficial impact of the mammary artery anastamosis, specifically when used to treat disease involving the left anterior descending (LAD) coronary artery.^2–10 The current study, as well as others published and/or presented recently in abstract form, provide further evidence of a continued evolution in the treatment strategies for multivessel coronary artery disease and/or complex proximal LAD disease. Can we forecast the potential impact of modern percutaneous coronary interventions on the future of surgical revascularization? As many answers as we have ascertained from studies such as these, a surfeit of new questions have been raised, both scientific and economic. In an unprecedented fashion, drug-eluting stents have rapidly advanced vascular science and become a mainstay of cardiovascular care. The direct patient benefit is underscored by the results of clinical trials such as the present one. However, even during the earliest drug-eluting clinical trials prior to FDA approval, the potential adverse economic repercussions on hospital systems resulting from an anticipated reduction in coronary artery bypass surgery were expected, but appear to have been underestimated. The empiric evidence has uniformly established that the contribution margin of coronary artery bypass surgery far exceeds that of percutaneous coronary intervention. While Medicare and third party payors may see potential benefits from a relative reduction in bypass surgery (shorter hospital stays, less costly procedures), the economic fallout on healthcare systems around the country is obvious. Those institutions which have historically relied upon open heart surgery to carry other hospital programs, have been left scrambling to find another service line “sugar daddy” or risk a reduction in the breadth of services provided. Hospital systems cannot be left shouldering the burden. If this is to be avoided, The Centers for Medicare & Medicaid Services (CMS) must quickly implement its rumored initiative to favorably redefine and restructure reimbursement related to drug-eluting stent usage. This must be fixed directly so that the advancement of science and economic security can smoothly run parallel paths. While the current study need not directly reference any head-to-head comparisons to bypass surgery, the implications are clear. The present study, prima facie, may appear to be only a soft affirmation of what we have come to suspect regarding the benefits of the antiproliferative interventions. However, critical analysis of these data more than merely suggest a potential broadening of the clinical application of the percutaneous interventions, particularly in the utilization of drug-eluting stents. Specifically, in treating the most exigent proximal LAD lesions, this study poses the question of a credible challenge to the scientifically justified, two decades-long, sacramental-like devotion to the LIMA. Does this mark a paradigm shift when considering revascularization strategies in the modern era? The real answer awaits the scientific establishment of a LIMA-like durability of drug-eluting stents long-term via a randomized trial. It must be conclusively demonstrated in these, the most complex coronary lesions, that drug-eluting stents truly abolish restenosis, not merely delay it. In contradistinction to the early landmark drug-eluting stent trials^11–14 where long-term benefits have been established, but lesion complexity might be considered dubious, the present study adequately demonstrates increasingly complex proximal LAD disease treated safely and successfully with the sirolimus drug-eluting stent, achieving acceptable short- and intermediate-term results. Recently, Stone et al. published a subgroup analysis of the TAXUS IV study evaluating patients with LAD disease. In the group who underwent Taxus stent implantation for proximal LAD disease, the one-year TVR rate was 7.9%.¹⁵ The TAXUS V trial arguably represents the most complex patient and lesion cohort yet subjected to a blinded, randomized drug-eluting stent trial. Some consider TAXUS V the “gold standard” for validating the resilience of drug-eluting stents in a somewhat harsher coronary milieu with stent lengths up to 84 mm (mean stent length 28.68 mm, B2/C lesions 75.4%). Similarly, the present study of the sirolimus-eluting stent distinguishes itself by virtue of the fact that 90% of the lesions treated were Type B2/C lesions. The 6.3% long-term TLR rate also compares favorably with TAXUS V (8.6% TLR), though mean lesion lengths between the two studies differ. It is obvious that this study could realize even further scientific credibility, depending on the length of angiographic followup the authors are willing to pursue.

1. Goetz R, Rhoman M, Haller J, et al. Internal mammary-coronary anastomosis. A nonsuture method employing tantalum ring. J Thorac Cardiovas Surg 1961;41:378–386. 2. Dignan RJ, Yeh T, Dyke CM, et al. The influence of age and sex on human internal mammary artery size and reactivity. Ann Thorac Surg 1992;53:792–797. 3. Loop FD, Lytle BW, Cosgrove DM, et al. Influence of the internal mammary artery graft of 10-year survival and other cardiac events. N Engl J Med 1986;314:1–6. 4. Cameron AAC, Green GE, Brogno DA, et al. Internal thoracic artery grafts: 20-year clinical follow-up. J Am Coll Cardiol 1995;25:188–192. 5. Edwards FH, Clark RE, Schwartz M. Impact of the internal mammary artery conduits on operative mortality in coronary revascularization. Ann Thorac Surg 1994;57:27–32. 6. Leavitt BJ, O’Connor GT, Olmstead EM, et al. Use of the internal mammary artery graft and in-hospital mortality and other adverse outcomes associated with coronary artery bypass surgery. Circulation 2001;103:507–512. 7. Navia D, Cosgrove DM, Lytle BW, et al. Is the internal thoracic artery the conduit of choice to replace a stenotic vein graft? Ann Thorac Surg 1994;57:40–44. 8. O’Connor GT, Plume SK, Olmstead EM, et al. A regional intervention to improve the hospital mortality associated with coronary artery bypass graft surgery: The Northern New England Cardiovascular Disease Study Group. JAMA 1996;275:841–846. 9. Gardner TJ, Greene PS, Rykiel MF, et al. Routine use of the left internal mammary artery graft in the elderly. Ann Thorac Surg 1990;49:188–194. 10. Fiore AC, Naunheim KS, Dean P, et al. Results of the internal thoracic artery grafting over 15 years: Single versus double grafts. Ann Thorac Surg 1990;49:202–209. 11. Sousa JE, Costa MA, Abizaid A, et al. Four-year angiographic and intravascular ultrasound follow-up of patients treated with sirolimus eluting-stents. Circulation 2005;111:2326–2329. 12. Regar E, Serruys PW, Bode C, et al. Angiographic findings of the multicenter randomized study with the sirolimus-eluting BX velocity balloon expandable stent (RAVEL). Circulation 2002;106:1949–1956. 13. Colombo A, Drzewiecki J, Banning A, et al. Randomized study to assess the effectiveness of slow and moderate release polymer-based paclitaxel-stents for coronary lesions (TAXUS II Study Group). Circulation 2003;108:788–794. 14. Stone G, Ellis SG, Cox DA, and the TAXUS-IV Investigators. One-year clinical results with the slow-release, polymer-based, paclitaxel-eluting TAXUS stent: The TAXUS-IV Trial. Circulation 2004;109:1942 –1947. 15. Dangas G, Ellis SG, Shlofmitz R and the TAXUS IV Investigators. Outcomes of paclitaxel-eluting stent implantation in patients with stenosis of the left anterior descending coronary artery. J Am Coll Cardiol 2005;45:1206–1212.