Left Main Stenting

Abstract & Commentary

By Andrew J. Boyle, MBBS, PhD

Source: Buszman P et al. Early and long-term results of unprotected left main coronary artery stenting. The LE MANS (Left Main Coronary Artery Stenting) registry. J Am Col Cardiol. 2009;54:1500-1511.

Stenosis of the left main coronary artery has traditionally been an indication for coronary artery bypass graft (CABG) surgery. However, recent studies have shown that percutaneous coronary intervention (PCI) of unprotected left main (ULM) lesions can achieve similar short- and medium-term results to CABG. Accordingly, the ACC/AHA guidelines for PCI were revised last month to include PCI of left main coronary stenoses as a class IIb indication, instead of class III. The revised guidelines state that "PCI of the left main coronary artery with stents as an alternative to CABG may be considered in patients with anatomic conditions that are associated with a low risk of PCI procedural complications and clinical conditions that predict an increased risk of adverse surgical outcomes" [Kushner et al. J Am Coll Cardiol. 2009;54:2205-2241]. With little long-term outcome data to support the revised guidelines, this report from the LE MANS registry was published at around the same time the guidelines were changed, and gives us some insight into the long-term outcomes of ULM stenting. The LE MANS study randomized 105 patients to PCI with stenting or CABG for ULM stenosis (> 50%), and these results have been previously published. Patients who were not deemed suitable for randomization were enrolled in either PCI or CABG registries; herein, Buszman et al present the results of their PCI registry.

From 1997-2008, 252 patients were enrolled after undergoing ULM stenting with either bare-metal stents (BMS, n=158) or drug-eluting stents (DES, n=94). Exclusion criteria were ST elevation myocardial infarction (STEMI) presentation, occluded left main, and the presence of any patent bypass grafts to the left coronary artery. The mean age of subjects was 69 years, 24% were diabetic, and 69% were male. Mean EuroSCORE was 62.8, and distal left main involvement was present in 59%. Reasons not to perform CABG were high surgical risk in 52%, patient preference in 12%, and anatomical suitability (ostial or mid-shaft) of ULM lesion for PCI in 35%. In the PCI procedure, direct stenting was the preferred technique, with lesion predilatation reserved for critical and calcified lesions. Distal ULM disease was preferentially treated with stenting across the ostium of the circumflex into the left anterior descending artery, with provisional angioplasty, T-stenting or culotte of the circumflex ostium, according to the operator's discretion. DES were recommended for vessels with reference diameter < 3.8 mm and BMS if > 3.8 mm. Within the DES group, paclitaxel-eluting stents were used in 64% and limus derivatives in the remainder. Intra-aortic balloon counterpulsation was used in 6.3%, heparin was the anti-thrombin for all cases, and glycoprotein IIb/IIIa inhibitors were used in 24%. All patients received aspirin therapy (300 mg loading followed by 150 mg daily for life) and thienopyridine loading followed by maintenance dose, early in the study ticlopidine and later clopidogrel. Dual anti-platelet therapy was continued in 55%, 21%, and 17% at one year, two years, and beyond two years from the index procedure, respectively. Patients were followed from 1-11 years (mean 3.8 years). The primary endpoint was death; major adverse cardiovascular and cerebral events (MACCE — a composite of death, myocardial infarction [MI], stroke, target lesion revascularization [TLR], and stent thrombosis) and comparisons between DES and BMS were secondary endpoints.

Within 30 days from the index procedure, mortality was 1.6%; MACCE occurred in 4.8%. Acute stent thrombosis occurred in two patients, and sub-acute stent thrombosis occurred in one patient. At one year after the index procedure, survival was 93% and MACCE-free survival was 82%. Fifty-six percent of patients had surveillance angiography at 6-12 months, and 12% were found to have restenosis. At long-term follow-up, after a mean of four years, mortality was 14%, of which 11% were considered cardiac in origin. According to Kaplan-Meier analysis, the five-year survival was 78%, and the 10-year survival was 69%. There was one definite, very late stent thrombosis, probable stent thrombosis occurred in 1.2% late (30-days to 1-year), and 2% was very late (> 1 year). Survival was significantly better in patients with isolated left main disease or left main + single or double vessel disease, compared to patients with left main + triple vessel disease (p = 0.02). Multivariate analysis showed the only independent predictor of death was depressed ejection fraction < 50%.

Patients receiving DES were more often diabetic (31% vs. 20%, p = 0.06), more likely to present with acute coronary syndromes (ACS; 69% vs. 54%, p = 0.04), had higher surgical risk (EuroSCORE 6.8 3.9 vs. 5.6 3.8, p = 0.01), had smaller caliber left main (3.4 0.5 vs. 3.7 1.0mm, p = 0.01), and more involvement of the distal bifurcation (72% vs. 51%, p = 0.001). Despite the higher-risk profile of patients receiving DES, DES use was associated with lower incidence of MACCE (15% vs. 26%, p = 0.04) and TLR (3% vs. 10%, p = 0.04) at four-year follow-up. There was no difference in mortality or risk of MI between DES and BMS. Sub-group analysis of patients with distal left main disease also revealed higher survival and MACCE-free survival with DES use. The authors conclude that stenting of ULM lesions is feasible and offers good long-term outcome. Implantation of DES decreased the risk of long-term MACCE and, particularly, improved survival in patients with distal ULM lesions.

Commentary

Buszman et al present data from their registry that strengthens the argument in favor of PCI for ULM stenosis. Their early, 30-day mortality rate of 1.6% compares favorably against historical surgical controls, based upon the EuroSCORE risk profile. However, the absence of a randomized control group of patients undergoing CABG surgery reduces our ability to draw firm conclusions from their data, as in any registry series. Several factors are important to highlight from their data. Firstly, as in the SYNTAX study, the patients who had left main + triple vessel disease did worse than those with isolated left main or left main + single- or double-vessel disease. These patients should still have CABG surgery considered as the first option for revascularization. Secondly, the rates of definite or probable stent thrombosis were low but not insignificant (nine patients out of 252) over a mean of four years. They were seen late in three and very late (i.e., more than 1 year from the index procedure) in six patients. This underscores the need for long-term dual anti-platelet therapy. The ability to comply with extended dual anti-platelet therapy should be a critical part of decision-making in deciding on the most appropriate revascularization strategy in all patients. Finally, it is important to note that sub-group analyses should be interpreted with caution in this study, because the study was not specifically designed to compare DES and BMS for patient outcomes. However, with a subtle shift in the treatment paradigm for ULM disease, this longer-term safety data is reassuring.