Author + information
- aStructural Interventional Cardiology, Careggi University Hospital, Florence, Italy
- bInterventional Cardiology, Santi Antonio e Biagio e Cesare Arrigo, Alessandria, Italy
- ↵∗Address for correspondence:
Dr. Carlo Di Mario, Structural Interventional Cardiology, Careggi University Hospital, Largo Brambilla 3, Florence 50134, Italy.
After some negative initial experiences reported by the pioneers of angioplasty, for many years the left main coronary artery remained the forbidden fruit of interventional cardiology. Seung-Jung Park, the senior author of the paper by Lee et al. (1) in this issue of the Journal, has the historical merit of having drawn attention to the improved results that stents could achieve in this key coronary artery segment. Many studies in the drug-eluting stent era, from the SYNTAX (TAXUS Drug-Eluting Stent Versus Coronary Artery Bypass Surgery for the Treatment of Narrowed Arteries) left main substudy (2) to the recently reported full 3-year follow-up of EXCEL (Evaluation of XIENCE Versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularization) (3), confirmed safety and efficacy similar to those observed with coronary bypass surgery, at least in patients without very diffuse disease in other coronary segments.
The left main offers unique challenges for stents. First, diameters taper markedly from 4.5 to 6.0 mm of the left main to 3.0 to 4.0 mm of the proximal left anterior descending coronary artery. Stents able to expand far above the nominal diameter must be chosen (4), with a frequent need to use a larger balloon for post-dilation at the ostium. The prevention of early recoil after balloon deflation requires careful attention to stent design and mechanical properties of the selected alloy, as well as an optimal compromise between the lower thrombogenicity of thinner struts and the increased radial support thicker struts can give. Second, left main lesions involve the distal bifurcation in approximately 80% of cases, thus potentially jeopardizing a very large vital side branch, the left circumflex. When possible, experienced operators prefer to use only 1 stent and correct the carina shift leading to ostial left circumflex stenosis with a final kissing balloon dilation after the deployment of the main vessel stent. If a pre-existing left circumflex lesion involves a longer proximal segment, a 2-stent strategy may be required. In both cases, good expansion up to 3.0 to 3.5 mm of a left main stent cell is needed. Finally, perfect positioning at the ostium is required, making good stent visibility an essential pre-requisite. Excessive ostial protrusion complicates future catheter engagement and increases late thrombosis, a risk that has become more obvious with long protrusions of the left main stent to prevent coronary closure after transcatheter aortic valve replacement (chimney technique). The opposite problem, lack of ostium coverage, can develop in spite of perfect initial deployment because of longitudinal compression at the proximal edge of the stent that is often inadvertently caused by excessive guiding catheter manipulation.
With all these specific challenges, it should be logical to expect that some stents behave better than others for left main treatment. Discrepancies between the results of the 2 main recent randomized trials against surgery, EXCEL (3) and NOBLE (Coronary Artery Bypass Grafting Versus Drug Eluting Stent Percutaneous Coronary Angioplasty in the Treatment of Unprotected Left Main Stenosis) (5), can be explained by differences in study design, but differences in technique including stent selection can also play a role. The strengths of this nonrandomized comparison by Lee et al. (1) of 4 second-generation drug-eluting stents are the consistent selection of a large group of patients (n = 2,692), central core laboratory analysis, independent event adjudication, and sophisticated propensity score matching. The first observation is that the numbers confirm the expected low adverse event rates at 3 years of second-generation stents in left main trials and registries, with a 3.0% to 6.0% rate of cardiac death, a 5.4% to 8.0% rate of target vessel revascularization, and a 0% to 1.0% rate of definite or probable stent thrombosis. No striking differences emerged at 3 years among the various platforms tested. Lee et al. (5) rightly recommend great caution in the interpretation of the slight increase in target vessel failure in the platinum-coated everolimus-eluting stents or of the significant reduction in stent thrombosis, including late stent thrombosis, with the everolimus-eluting stent platforms. A first conclusion can be that patient and lesion selection and optimal technique are more important than the stent platform to determine early and late outcomes in left main stenting.
The rapid pace of technology development in interventional technology is such that at the time of the reported trials for none of the stents tested was there a 4.5-and/or a 5.0-mm version (available at least for the zotarolimus-eluting stent, Resolute Onyx, Medtronic, Inc., Dublin, Ireland). Moreover, some limitations of the stents tested, such as longitudinal compression affecting the early generation of platinum chromium-everolimus-eluting stents (Promus Element or Premier, Boston Scientific, Natick, Massachusetts), have been corrected in newer versions (Synergy), thus also minimizing the polymer and drug content and setting new standards in stent strut thickness.
Should we conclude that stents can be used interchangeably for left main lesions? It sounds illogical after the premises described here. We can certainly conclude, however, that the very low event rate of modern second-generation drug-eluting stents, especially in a coronary artery segment responding well to stent implantation such as the left main, seriously challenges our ability to demonstrate differences among various stent platforms with relatively large registries and trials. Operator preference, which practically means experience and familiarity with a given platform for the specific anatomy and technique chosen, should be valued as much as evidence from trials in stent selection.
↵∗ Editorials published in the Journal of the American College of Cardiology reflect the views of the authors and do not necessarily represent the views of JACC or the American College of Cardiology.
Dr. Di Mario received a grant to his institution for serving as the local principal investigator of the EXCEL trial, sponsored by Abbott Vascular. Dr. Secco has reported that he has no relationships relevant to the contents of this paper to disclose.
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