Extended Stenting of Distal Left Main Coronary Artery for
the Treatment of Branch Ostial Disease — Belling the Cat or
Bearding
Besides the inherent risk involved in an angioplasty of a major vessel supplying a large myocardial area, percutaneous coronary intervention (PCI) of left main coronary artery (LMCA) branch ostial disease is fraught with some unique problems, namely, high elastic recoil, excessive plaque burden, plaque shift or plaque redistribution, melon-seeding effect, calcification, retrograde dissection of the left main or the other major branch artery, and the technical challenge of a very precise stent placement when attempting the conventional focal stenting of the affected branch ostium. The stent, if placed too distally, would not cover the ostium adequately, thus predisposing to restenosis or occlusion. And if placed too proximally, the stent may compromise the ostium of the other branch vessel, thereby not only predisposing it to acute or delayed stenosis or occlusion but also making its angioplasty difficult, for the hardware may not pass through the projecting stent struts. Furthermore, with branch ostial disease there is frequent involvement of the distal LMCA1 and thus, the impending danger of incomplete lesion coverage if stenting is not extended to the involved left main.
Intravascular ultrasound has shown the mechanism of lumen enlargement during intracoronary stent implantation as involving significant axial redistribution of the plaque from the center of lesion towards the proximal and distal reference segments adjoining the stent, thus increasing the plaque burden in these segments.2 With ostial lesions of LMCA branch vessels, this would imply a plaque shift into the left main and/or the other branch artery. Debulking the lesion may reduce this plaque shift. While studying the effectiveness of stent implantation following directional coronary atherectomy (DCA) for treatment of left anterior descending (LAD) ostial stenosis, a high success rate of 98%, a low angiographic binary restenosis rate of 14.5%, and a good long-term outcome was shown on a follow-up of 30 ± 29 months.3 In a randomized comparison of debulking by DCA followed by stenting versus stenting alone under intravascular ultrasound guidance for ostial LAD stenosis, the DCA followed by stenting achieved greater lumen gain than stenting alone, though overall angiographic restenosis was not dissimilar in the two groups.4 In a recent study it was shown that left circumflex (LCX) ostium remains unaffected during PCI of LAD ostium by DCA using the Flexi-Cut atherectomy catheter.5 Similarly, high-speed rotational atherectomy has shown promise as a debulking strategy in lesions affecting the LAD ostium.6,7 Based on its capability of giving microsurgical stress relief at scoring sites, cutting balloon may reduce plaque shift and thereby improve results of PCI in LAD or LCX ostium. Overall, the strategy of cutting balloon followed by stenting in de novo coronary lesions was shown to be effective in reducing the restenosis rate in a randomized Japanese multicenter trial.8
In this issue of the Journal, Cubeddu et al report their 2-year follow-up results of the PCI of the isolated disease of LAD or LCX ostium using a bifurcation technique in which a drugeluting stent (DES) was deployed from the distal LMCA across the stenosis into the main branch.9 Post-deployment kissing balloon inflation with provisional side branch stenting was performed. The mean duration of clinical follow up was 24 months and follow up angiography was performed in 91% patients at a mean of 11 months. The strategy was safe and effective with one cardiac death and one non-fatal myocardial infarction while the TLR rate due to restenosis was 15% and the overall event-free survival was 79% at 2 years.
The concept of extending the stenting to involve the distal left main and then treating the left main bifurcation is interesting, in so far as it is a logical extension of the fact that in ostial disease of LAD or LCX the plaque frequently extends into LMCA. From this perspective, left main branch ostial disease is necessarily a bifurcation disease and therefore should be treated in a similar manner.
Though balloon predilation or atherectomy was discretionary, direct stenting was the preferred strategy and half the patients underwent direct stenting. This is an optimal approach since plaque debulking by atherectomy or cutting balloon angioplasty loses its importance if the possibility of plaque shift in the left main or the side branch ostium is annulled by extending the stenting into the LMCA and treating the side branch with kissing dilation and provisional stenting. Further, according to the inclusion criteria, the side branch was relatively normal as only patients with side branch disease comprising less than 50% stenosis were included, and therefore, the entry of the wire into the side branch through the main branch stent would not have necessarily been an issue influencing the methodology adopted. Predilation of the side branch in order to facilitate the wire passage through the mainbranch stent does help in tight side branch ostial-proximal stenosis. Another advantage of direct stenting is that it saves time and makes the procedure simpler. There is a caveat, however — sometimes the proximal ends of the left main branches are calcified, and in this situation adequate lesion preparation before stenting is warranted to avoid inadequate stent expansion, particularly with drug-eluting stents.
Kissing balloon dilation was done in every case followed by a strategy of provisional stenting. Provisional stenting strategy was carefully adhered to and only one-fourth of the patients received a stent in the side branch. While a breakdown of these patients is not available, it might have been interesting to see if the two branches behaved differently with respect to plaque shift or dissection that finally necessitated a stent. Numerous studies have shown the virtues of provisional stenting both with bare metal stents and DES in non left main coronary bifurcation lesions,10,11 and although it would be tempting to extend the same inference for left main bifurcations, this has not been backed by solid evidence in a randomized manner. Two of the 3 patients who experienced restenosis in the side branch had, in fact, restenotic lesions within the stents. In other words, of the 9 patients that had side branch stents, 2 experienced restenosis, while only one instance of side branch restenosis was seen in the remaining patients who underwent plain balloon dilation in a kissing fashion.
The value of doing a kissing balloon dilatation religiously in each and every case cannot be overemphasized. It prevents stent distortion, consequently reducing chances of stent thrombosis and restenosis. Moreover, it performs the allimportant task of relieving the side branch from stent jail, which in turn facilitates future interventions in the branch. It is not unusual to face problems pushing hardware through a stent jailed branch ostium at a later date if kissing dilation to open the stent struts was not performed in the initial procedure. We reported a patient with intractable angina in whom we had to resort to rotational atherectomy in an attempt to dilate a large stent jailed septal perforator through a previously deployed LAD stent.12 In another patient we had to do a similar procedure while performing PCI in a stent-jailed LCX ostium.
Some other points are noteworthy. Two thirds of the interventions were done through the radial access using 6 French (Fr) guide catheters. This showcases the versatility of radial access in doing complicated interventions. With the new guide catheter designs, a larger lumen size allows kissing technique to be performed in 6 Fr guide catheters that can be introduced safely through the radial artery. Furthermore, an overwhelming majority of stents were paclitaxel-eluting Taxus® stents (Boston Scientific, Natick Massachusetts) while sirolimus-eluting Cypher® stents (Cordis, Miami, Florida) were deployed in the remaining 15% of patients. It is conjectural to say if stent type would impact the outcome in a substantial manner in the present scenario, but with continuing efforts to improve the stent designs this might well play a role in future.
Finally, it is a small non-randomized study comprising of 33 patients and should essentially be considered a feasibility study to substantiate the hypothesis of extended stenting of LMCA in isolated branch ostial disease. While the PCI of left main ostial and mid-shaft lesions with DES has been shown to be safe and effective,13 the results are less favorable for left main bifurcation lesions. In fact, major registries with DES implantation in LMCA lesions have demonstrated that restenosis is essentially confined to distal bifurcation lesions. The ostium of the LCX is particularly susceptible, accounting for about onehalf of the restenosis cases. Stent fracture in the LCX at the sharp bend leaving the left main during simultaneous kissing may contribute to focal restenosis at this location.14 To this extent, the data in the present study could be skewed in favor of a better performance, considering the fact that only one-fourth of the patients had LCX ostial disease while the great majority had stenosis of the LAD ostium. In the light of the unproven safety and efficacy of LMCA bifurcation PCI, the strategy of stenting LMCA in isolated branch ostial disease will have to stand the test of randomized trials comparing it with conventional focal single branch stenting. Moreover, considering the scourge of late thrombosis with DES and the catastrophic consequences of LMCA late stent thrombosis, a long-term followup would be needed to substantiate the merits of this strategy.
References
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