COMMENTARY:Provisional Side Branch Stenting: A Justified Approach in the Era of Drug-Eluting Stents

Percutaneous coronary intervention of bifurcation lesions poses technical challenges beyond conventional approaches. The difficulties lie with various anatomic variants including the takeoff angle, size and presence of disease of the side branch, as well as various proposed techniques to ensure complete stent coverage of the carina such as “crush”, “kissing”, “culottes”, “double-barrel”, “Y”, “T” and “V”-stenting. The more complex procedures, however, may lead to higher rates of complications, exposure to radiation and contrast, and cost. The decision to stent a side branch is highly individualized based on the angiographic appearance, the degree of technical difficulty and comparison with the natural history of left-alone “jailed” side branches. Hence, the rationale for the consideration of provisional side branch stenting.
The natural history of “jailed” side branches appears to be fairly benign. From the early days of the Palmaz-Schatz stent to the current technology of bare-metal stents, left-alone side branches arising from stented segments of the parent vessels have shown no discernible major adverse clinical events.^1,2 A powerful predictor of side branch occlusion following parent-vessel stenting was found to be ostial narrowing of >50%,³ however, side branch occlusion in this study was not associated with a worsened clinical outcome in the 9-month follow-up period. Clinical relevance of the side branch increases with its size. Even in the presence of larger-sized side branches, however, various studies including treatments with plain-old balloon angioplasty (POBA) and stenting in the parent vessels alone have suggested safety without added adverse clinical outcomes.^4–6 Function studies such as fractional flow reserve by Koo et al⁷ and scintigraphy in the current study by Vigna et al further support the relative clinical insignificance of “jailed” side branches.
The concept of provisional stenting began with nonbifurcation coronary lesions. An axiom of provisional stenting is if a stent-like result is achieved with POBA, it will likely last as a stent. Provisional stenting for the most part was found to be equivalent to primary stenting after percutaneous tansluminal coronary angioplasty, and potentially at a lower cost.⁸ Aside from using angiography alone, the success of provisional stenting was further strengthened when performed under the guidance of intravascular ultrasound, physiologic measurement and quantitative angiography.^9–11 Conversely, there were a handful of negative studies of provisional stenting including a meta-analysis.^12,13 In conjunction with the reality of the difficulty to achieve a “stent-like” result with a high crossover rate, provisional stenting did not become a mainstay approach for nonbifurcation lesions.
Provisional stenting of the side branch in bifurcation lesions, however, deserves further considerations. As alluded to earlier, bifurcation stenting, as compared with nonbifurcation interventions, is associated with a lower rate of procedural success, higher procedural costs, longer hospitalization and a higher rate of clinical and angiographic restenosis. Along with the relatively benign natural history of small-to-medium sized “jailed” side branches, the reason for a careful decision to stent the side branch is apparent. An important randomized study utilizing sirolimus-eluting stents comparing stenting both the main vessel and side branch (MV + SB) with stenting of the main vessel (MV) only, with an option for side branch stenting (Nordic Bifurcation Study),⁵ is of interest. With similar baseline clinical characteristics of the cohorts, there was no difference in major adverse cardiac events (MACE) over 6 months. The MV group had reduced procedural and fluoroscopy times, reduced contrast volumes, and a lower rate of procedure-related biomarker elevation. The crossover rate is low, with only 9 of the 207 patients in the MV group undergoing side branch stenting. Regarding the largest coronary side branch, Park et al⁶ studied left main bifurcations with sirolimus-eluting stents comparing simple (stenting of the LM into the LAD only) with a complex technique (stenting both LAD and LCX using either “kissing stents” or “crush”). Target lesion revascularization (TLR) and restenosis rates were higher in the complex group, however, these findings may be somewhat skewed by the slight predominance of multivessel disease and smaller LCX arteries in the complex group. Nonetheless, the simple group had easier procedures, which appeared to be effective and safe without undue adverse outcomes. A recent multicenter French registry of provisional T-stenting with kissing balloon (TULIPE)¹⁴ showed a high procedural success rate with a relatively low 7-month TLR rate. Even though the crossover rate was fairly high at 34% for side branch stenting, this approach was found to be safe and effective. Similar results were found in the current study. In a small cohort of patients, the crossover rate was low at 4/53 patients needing side branch stenting, and the findings demonstrated a high procedural success rate, low mid-term TLR and safety of provisional T-stenting with either drug-eluting stents in coronary bifurcation lesions. The addition of scintigraphy for follow up in this study is an attractive feature. For medium-to-large side branch vessels, Sharma et al¹⁵ had contrary results demonstrating superiority of the simultaneous kissing stents (SKS) technique to a provisional side branch stenting strategy in improvement in 30-day MACE, TLR and procedural time. The SKS technique deserves further focus in future studies.
Recent concern regarding thrombosis and drug-eluting stents in off-label use, and the report by Colombo et al¹⁶ of a 3.5% stent thrombosis rate in sirolimus stented bifurcation lesions, further raise caution in routine side branch stenting. Until proven and reliable techniques or bifurcation stents are available, provisional side branch stenting is currently an attractive approach to coronary bifurcation lesions.

References

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