Sirolimus-Eluting Stents vs. MIDCAB for Isolated Proximal LAD Disease
Abstract & Commentary
By Andrew J. Boyle, MBBS, PhD, Assistant Professor of Medicine, Interventional Cardiology, University of California, San Francisco. Dr. Boyle reports no financial relationships relevant to this field of study.
Source: Thiele H, et al. Randomized comparison of minimally invasive direct coronary artery bypass surgery versus sirolimus-eluting stenting in isolated proximal left anterior descending coronary artery stenosis. J Am Coll Cardiol. 2009;53:2324-2331.
The debate continues as to whether coronary artery bypass graft (CABG) surgery with left-internal mammary artery (LIMA) or stenting is the best treatment for proximal left-anterior descending coronary artery (LAD) lesions. Prior studies of bare-metal stents (BMS) vs. CABG with standard midline sternotomy and cardiopulmonary bypass (CPB) show equivalent rates of death and myocardial infarction (MI), but increased need for repeat revascularization in patients receiving stents. However, both approaches have undergone improvements in recent years. The advent of drug-eluting stents has dramatically reduced restenosis rates. The evolution of MIDCAB (minimally invasive direct coronary artery bypass), using mini-thoracotomy and not requiring CPB, has made bypass surgery less invasive. With the rapid evolution of both stenting and surgical techniques, the best approach for revascularization of proximal LAD lesions is, once again, unknown. Accordingly, Thiele et al performed a randomized, controlled trial of sirolimus-eluting stents (SES) vs. MIDCAB in patients with isolated proximal LAD disease, using a non-inferiority design.
Thiele et al screened 213 patients with isolated proximal LAD stenosis and either symptomatic angina or documented ischemia. All patients were deemed suitable for either percutaneous coronary intervention (PCI) with SES or MIDCAB by both the interventional cardiologist and the cardiac surgeon. Exclusion criteria were acute coronary syndromes requiring immediate treatment, prior PCI, CABG or valve surgery, significant carotid stenosis requiring treatment, renal failure requiring dialysis, total LAD occlusion, overt congestive heart failure, upper gastro-intestinal bleeding within four weeks, contra-indication to anti-platelet therapy, or any condition limiting life-expectancy. PCI was performed via the femoral artery using heparin, and all patients were pre-loaded with clopidogrel 600 mg the day before the procedure; the use of glycoprotein IIb/IIIa inhibitors is not mentioned. MIDCAB was performed via left-anterolateral mini-thoracotomy; mechanical stabilizers were used to immobilize the anastomotic site. Patients were followed for at least 12 months (median 41 months after MIDCAB and 43 months after SES), and had a 12-month stress test; 87% had a 12-month angiogram. Angiography was analyzed at a core laboratory. The primary endpoint was freedom from MACE (major adverse cardiac events cardiovascular death, MI, repeat target vessel revascularization within 12 months). Secondary endpoints included each component of the primary composite endpoint, as well as peri-procedural adverse events occurring within 30 days post-procedure.
The baseline characteristics were similar between the patients receiving SES (n = 65) and those receiving MIDCAB (n = 65) by intention-to-treat. Two patients did not undergo MIDCAB because of clinical instability requiring more urgent intervention, four patients required conversion to standard thoracotomy, and one had a vein graft instead of LIMA because of a poor-quality artery. In the SES group, three patients did not undergo SES implantation because of inability to cross the lesion, and had bare-metal stents implanted instead. After MIDCAB, peri-procedural adverse events occurred more frequently (16.2% vs. 3.1%; p = 0.02) and length-of-stay post-procedure was longer (eight days vs. one day; p < 0.001). Discharge medication was similar between groups in terms of aspirin, statin, beta-blocker, and angiotensin-converting enzyme inhibitors/receptor blockers. However, more patients with SES were discharged on clopidogrel (100% vs. 34%; p < 0.001).
At 12 months, there was no difference in the primary endpoint rates of MACE, which occurred in 7.7% of the SES group and 7.7% of the MIDCAB group and satisfied the non-inferiority criteria (p = 0.03 for non-inferiority). This held true when analyzed on an intention-to-treat basis or on a per-protocol basis. There were no cardiac deaths in either group at 12 months. The rates of MI were 1.5% in the SES group and 7.7% in the MIDCAB group (p < 0.001 for non-inferiority). Repeat revascularization was performed in 6.2% of the SES group, and none of the MIDCAB group did not meet non-inferiority criteria. Importantly, both stenting and MIDCAB significantly improved angina and quality of life; there were no differences in the extent of benefit between treatment groups, as assessed by Canadian Cardiovascular Society angina class, work capacity on bicycle ergometry, SF-36, and MacNew domain quality-of-life scores. Thiele et al conclude that in patients with isolated proximal LAD lesions, SES is non-inferior to MIDCAB at 12 months with respect to freedom from MACE, with similar relief of symptoms and fewer peri-procedural complications.
Commentary
Revascularization technologies continue to evolve, both in CABG surgery and PCI, and clinical trial data struggles to keep pace with this rapid progress. The current study by Thiele et al presents medium-term data to support the use of either MIDCAB or SES in proximal LAD lesions. The excellent long-term outcomes of patent LIMA to LAD grafts is well known, but the long-term outcomes of SES are still being evaluated. There is a need for continued anti-platelet therapy in the SES group, and this was seen as higher rate of clopidogrel therapy at discharge in the SES group. This reduces the rate of stent thrombosis and may also reduce the rate of events from other lesions, improving long-term prognosis. Alternatively, this may lead to worse outcomes due to the small but significant increased risk of bleeding. Long-term follow-up is needed to adjudicate this issue.
The randomized study design is a strength of this paper. Several potential confounders need to be acknowledged in this study. The results presented herein are from a single center highly experienced in MIDCAB and may not represent the outcomes in all centers. In the SES group, we are not told about glycoprotein IIb/IIa inhibitor use, which may have influenced the results. Furthermore, the use of alternative anti-thrombins, such as bivalirudin, or the use of transradial access, may have reduced the complication rate further. Thiele et al present important data, which can guide us in offering our patients alternative strategies for revascularization of proximal LAD lesions.
The debate continues as to whether coronary artery bypass graft (CABG) surgery with left-internal mammary artery (LIMA) or stenting is the best treatment for proximal left-anterior descending coronary artery (LAD) lesions.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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