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October/November 2008
Stenting for Left Main Stenosis
Ready for everyday practice?
Significant stenosis of the left main coronary artery (Figure 1) is discovered in about 4% of diagnostic coronary angiograms.1 Thus, a busy catheterization lab will encounter this clinical situation on approximately a weekly basis and will need to decide on appropriate management. Expert consensus guidelines2,3 recommend that management of such cases should include referral for coronary artery bypass graft (CABG) surgery, if the patient is a surgical candidate. This recommendation is based on data from the 1970s and 1980s that established that the treatment of left main stenosis with medical treatment alone led to unacceptable rates of adverse events and furthermore that there was a mortality benefit of CABG treatment compared to medical management.4-6
MANAGEMENT OF LEFT MAIN STENOSIS: TIME TO REVISIT THE QUESTION IN CAREFULLY SELECTED CASES?
Four recent developments in the field suggest that now might be an appropriate time to reconsider our management algorithms in carefully selected cases of left main stenosis (Table 1). In appropriate cases, it may be possible to treat left main stenosis with similar safety and efficacy by placement of drug-eluting stents (DES) as by CABG, thereby relieving the patient of the morbidity (increased risk of stroke and wound infection) and long hospital stay associated with cardiac surgery. The four developments in the field that have made such reconsideration possible are:
- The introduction of DES with markedly reduced rates of restenosis compared to bare-metal stents.7
- Data from multiple registries, including from our institution,8-19 a small, randomized trial20 and a meta-analysis21 indicating that stenting of the left main with DES is technically feasible with excellent procedural success rates (Table 2).
- Excellent long-term outcomes are being achieved in treating large numbers of left main stenosis cases in Korea with DES percutaneous coronary intervention (PCI),22 with no significant difference in follow-up rates of death compared to patients treated with CABG (Figure 2).
- The 1-year results of the randomized SYNTAX trial (SYNergy Between PCI With TAXUS and Cardiac Surgery) indicate that the combined rate of death, myocardial infarction, stroke, and revascularization at 1 year is similar whether left main is treated with DES PCI or CABG (15.8% vs 13.7%, respectively [Figure 3A]).23 Further data from this important dataset are keenly awaited. A closer breakdown shows higher rates of stroke and lower rates of revascularization in the CABG group at 12 months (Figure 3B).
THE SYNTAX TRIAL: A LANDMARK TRIAL
The SYNTAX trial, which has completed enrollment,24 contained a prespecified subset of more than 700 patients with left main disease randomized to treatment with either CABG or PCI. The 5-year mortality data are highly anticipated. If 5-year mortality were shown to be equivalent for the two treatment strategies, this would likely have a large effect on the treatment decisions of patients and physicians and possibly on the committees that write expert consensus guidelines for recommended management.
It is instructive to look at the situation of multivessel disease as a historical analogy. A number of randomized trials in 2000 and 2001, in the setting of multivessel disease with bare-metal stents,26-29 indicated that the choice of revascularization strategy was a tradeoff between a less invasive procedure—PCI—which needed to be "paid for" by an increased chance of repeat procedures compared to CABG. In that context, given the similar mortality of either approach,30 large numbers of physicians and patients "voted with their feet" and we witnessed the great shift from CABG to PCI for coronary revascularization over the past decade. If equivalent mortality of CABG and PCI was also to be demonstrated for left main stenosis in randomized trial(s), a similar shift in treatment patterns would also likely occur.
TECHNICAL CONSIDERATIONS
The angiographic anatomy of the left main lesion is a critically important factor in clinical decisions (Figure 4A). Outcomes of stenting are best if the left main stenosis can be dealt with using a single stent in the ostium or shaft of the left main,12 although this is occurs in a minority of cases (Figures 4B and 4C). If disease of the distal left main is present, there are four stenting techniques available to cover the lesion (Figures 4D through 4G). The technique used depends on a number of factors including presence of disease at the ostium of the circumflex, the angle at which the circumflex takes off from the left main, and operator preference. A detailed discussion of the relative merits of the different techniques is beyond the scope of this article. If restenosis occurs after bifurcation stenting, the ostium of the circumflex is the most common location.
Left main stenting should not be performed without the use of intravascular ultrasound to confirm adequate and accurate deployment.
The possibility of cardiovascular collapse during intervention in this position is a very real one, and the use of intra-aortic balloon pumps or newer percutaneous left ventricular assist devices31,32 should be considered.
A NOTE OF CAUTION
DES have clearly reduced the threshold for consideration of a percutaneous approach to treat left main stenosis, and a large amount of global experience now indicates that the procedure is feasible and safe when performed in experienced centers. Nonetheless, we should be wary of the widespread adoption of PCI to treat left main stenosis at this stage. Such cases should not be undertaken "on the fly" or in a haphazard manner. At this stage, left main PCI should only be tackled after careful consideration, by high-volume operators in high-volume centers with surgical back-up on site, and in a setting where outcomes are recorded and analyzed.
A patient's preference will always be for the less-invasive procedure, but at this point in time, we are still obliged to make conservative recommendations to our patients and explain that CABG is the current accepted treatment for left main stenosis.
CONCLUSION
Left main stenosis is a dangerous coronary lesion associated with high rates of adverse events if left untreated. Stenting of left main stenosis with DES, particularly if there is no involvement of the distal left main and its bifurcation, is technically feasible, with high acute procedural success rates. Furthermore, a body of observational literature now suggests that there is no large difference in clinical outcomes from those following treatment with coronary artery bypass surgery. Long-term follow-up of patients in the randomized SYNTAX trial will be an important advancement in our knowledge of the optimal approach to this lesion.
Is stenting for left main stenosis ready for everyday practice? The answer depends very much on the situation. If there is no involvement of the bifurcation of the left main and the operator is experienced, PCI may be a reasonable initial approach. Furthermore, an argument can be made on the basis of the presented 1-year follow-up left main subset SYNTAX data that cases of isolated left main, or with involvement of only one other vessel, may be particularly suited to consider a PCI approach (Figure 3). However, although stenting of the left main is a reasonable management strategy in very carefully selected cases, at this time, coronary artery bypass treatment will likely continue to be advised for the majority of our patients with this lesion.
Anthony White, MBBS, PhD, is Visiting Fellow, Cardiovascular Intervention Center, Cedars-Sinai Medical Center, in Los Angeles, California. He has disclosed that he holds no financial interest in any product or manufacturer mentioned herein. Dr. White may be reached at whiteaj@cshs.org.
Raj Makkar, MD, is Director, Cardiovascular Intervention Center, Cedars-Sinai Medical Center, in Los Angeles, California. He has disclosed that he receives grant/research funding from Cordis Corporation, Boston Scientific Corporation, and Medtronic, Inc. Dr. Makkar may be reached at raj.makkar@cshs.org.
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