Is Stenting Better Than CABG for Left Main Stenosis?
Abstract & Commentary
By Andrew 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: Buszman P, et al. Acute and late outcomes of unprotected left main stenting in Comparison With Surgical Revascularization. J Am Coll Cardiol. 2008;51:538-545.
Left main coronary artery stenosis is one of the primary indications for coronary artery bypass graft surgery (CABG). Recently, a number of non-randomized studies and registries have suggested that stenting, using current techniques and devices, may be a feasible alternative to CABG. However, the effect of the type of revascularization on left ventricular function remains unknown. Accordingly, Buszman and colleagues performed a multicenter, randomized trial comparing stenting of the left main with CABG in patients with > 50% stenosis of the left main, symptomatic angina, and documented ischemia. The primary outcome was left ventricular function at one year post procedure.
Of 347 patients screened, 122 were eligible for randomization and 105 were enrolled. Fifty-two patients underwent percutaneous coronary intervention (PCI) with stenting and 53 patients had CABG surgery performed. All procedures were performed by experienced operators at high volume centers. They excluded patients presenting with acute myocardial infarction, occluded left main, stroke, or transient ischemic attack within 3 months, renal impairment, contraindications to dual anti-platelet therapy, and those with a euroSCORE of 8 or more. All patients were treated with at least 12 months of dual anti-platelet therapy, regardless of whether they had CABG or PCI. Baseline characteristics were well matched between groups. PCI procedures used bare metal stents for left main arteries > 3.8 mm in diameter and drug-eluting stents for left main diameter < 3.8 mm. Distal left main disease was present in approximately 60% of patients in each group. The preferred strategy for PCI was direct stenting of the left main. Distal left main disease was treated with stenting into the left anterior descending coronary artery (LAD), with provisional stenting of the left circumflex (LCx) with culotte or T-stent techniques; the "crush" technique was specifically avoided. CABG surgery utilized left internal mammary artery grafts in 72% and radial artery grafts in 9%.
PCI and CABG achieved clinical success in 98% and 92% of cases, respectively. Thirty-day outcomes favored PCI, with no deaths and 1 MACCE (major adverse cardiac and cerebrovascular events), whereas CABG resulted in 2 deaths and 7 MACCE (p = NS for death, p = 0.03 for MACCE). Both PCI and CABG resulted in sustained improvements in exercise capacity and anginal status out to 12-month follow-up, and there was no difference between groups in these outcomes. At 12 months, the MACCE rates were no different between PCI and CABG treated patients. However, only PCI resulted in an improvement in left ventricular function. Left ventricular ejection fraction (LVEF) improved over 12 months in the PCI group (from 53.5 ± 10.7% to 58.0 ± 6.8%; p = 0.04) but did not change in the CABG group (53.7 ± 6.7 to 54.1 ± 8.9%; p = 0.84). Target vessel failure (TVF) was similar in PCI (9.6%) and CABG (9.4%) groups. Long-term survival to 28 ± 9.9 months showed a trend toward higher survival after PCI than CABG, with 3 deaths in the PCI group and 7 deaths in the CABG group (p = 0.08). However, this was not a pre-specified end point, and should be interpreted with caution. MACCE-free survival was similar in the two groups at long-term follow-up.
Commentary
This study was well designed and presents some exciting and thought-provoking results. The procedural outcomes compare well with previous studies, adding to the strength of the data. Several aspects of the study warrant specific mention. Firstly, only 35% of PCI patients received drug-eluting stents. This is lower than in contemporary US practice, but may reflect the fact that this study was performed in Europe. Secondly, all patients received at least 12 months of dual anti-platelet therapy, regardless of treatment assignment. It is notable that there were no cases of stent thrombosis reported. This may reflect prolonged dual anti-platelet therapy or the high rate of bare-metal stent usage, or both. Thirdly, the procedural methods of treating distal left main disease may have a dramatic effect on the outcomes, but may not be the same methods used by all operators in all circumstances. Buszman and colleagues chose a strategy of direct stenting into the LAD and provisional treatment of the LCx, with specific avoidance of the "crush" technique. However, there are many other approaches that have been successfully used in treating bifurcation left main disease. Therefore, the excellent results achieved in this study may not be generalizable to all clinical situations and all operators. Fourthly, PCI of left main disease has been plagued by high rates of restenosis in the past. In this study, 5 of the 52 PCI patients had in-stent restenosis and 4 of these were successfully treated with repeat PCI, with one requiring CABG. This compares favorably with previous studies and demonstrates that with contemporary practice, left main stent restenosis has a low and clinically acceptable incidence. Finally, it must be noted that the numbers in this study are small, with only 105 patients randomized.
Buszman et al conclude that PCI of left main coronary artery disease improves LVEF at 12-month follow-up, but CABG does not. Both procedures result in similar angina relief at 1 year and equal risk of left main TVF. In addition, PCI results in similar rates of MACCE-free survival for over 2 years compared to CABG, and a trend towards better survival. These findings support the need for larger randomized trials with clinical primary end points.