1.3 The Forgotten Side Branch in Bifurcation Lesions

These proceedings summarize the educational activity of the 17th Biennial Meeting of the International Andreas Gruentzig Society held January 30 to February 2, 2024 in Chiang Rai, Thailand.

Faculty Disclosures     Vendor Acknowledgments

2024 IAGS Summary Document

Statement of the problem or issue

Does every bifurcation lesion require 2 stents, or only just 1? That is, should operators routinely stent both the main branch (MB) and the side branch (SB), or the main branch only? And if judgement and selectivity with SB treatment are needed, then, in which cases, and how do we judge? If we do use 2 stents, are there major differences in stent-placement techniques? Perspectives on these questions have shifted back and forth over the years. For a long time, there was a myth that a near-perfect angiographic result in a bifurcation lesion ensured the best long-term outcome. But the reality is, angiographically, a bifurcation lesion is going to look much better with two stents, however, the long-term outcome is a totally different matter.

Gaps in current knowledge

Early data showed that restenosis was more frequent in the SB than the MB, until the DEFINITION trial was published, which showed the opposite. In that trial, the expectation was that 2 stents would be better, but then it turned out, for example, there was no difference in mortality. The main issues were target vessel MI and TLR: The differences in these 2 outcomes were dramatic beginning the first day.

The same finding was observed in the DK-CRUSH trial where provisional stenting for left main bifurcation lesions was compared to a routine 2-stent strategy using DK-crush technique. There was improvement in target lesion failure (TLF), but, importantly, the difference emerges from the first day onward (Figure 2).

Figure 1. Target lesion failure (TLF) in the DK-CRUSH trial. From: J Am Coll Cardiol. 2017;70(21):2605–2617.

The concordant findings on early outcomes in these 2 trials suggest there were problems, and very likely it's an operator-dependent issue. This is an enormous gap area, and it confounds objective evaluation and hinders reproducibility.

Possible solutions and future directions

There are many different types of side branches. Are they all relevant? Are they all equally important? Should we put a lot of effort into trying to determine if we need to treat both branches? There are 2 important considerations that may point the way to future directions. First, there is length of the lesion in the SB. A network meta-analysis showed that with longer lesions in the SB (≥10 mm) a 2-stent strategy may be better than a provisional strategy.

Figure 2. Influence of side branch lesion length on clinical outcomes. From: JACC Cardiovasc Interv. 2020;13(12):1432-1444.

The second consideration is the amount of myocardium supplied by the SB. This can be characterized as fractional myocardial mass, that is, the fraction of total myocardial mass supplied by the SB. Comparing SBs to MBs, the SBs very often perfuse much smaller amounts of myocardium, and therefore may not be “significant” in about 80% of cases. Avoidance of the SB may then simplify the procedure. Figure 3 illustrates the issue.

Figure 3. Fractional myocardial mass (FMM) of coronary artery bifurcations. From: JACC Cardiovasc Interv. 2017;10(6):571–581.

In the present era, it seems that provisional stenting of bifurcation lesions is indicated, reserving treatment of SBs to certain specific situations. A typical recommendation is shown in Table 1 below.

Table 1. When to treat the side branch (SB) after treating the main branch in coronary bifurcations.

Finally, we don’t know which 2-stent technique is better. Clinical trials comparing DK-crush operators to Culotte operators would be helpful to better understand the influence of operator experience and bias.

References

1. Zhang JJ, Ye F, Xu K, et al. Multicentre, randomized comparison of two-stent and provisional stenting techniques in patients with complex coronary bifurcation lesions: the DEFINITION II trial. Eur Heart J. 2020;41(27):2523-2536. doi: 10.1093/eurheartj/ehaa543 PMID: 32588060

2. Chen, S, Zhang, J, Han, Y. et al. Double kissing crush versus provisional stenting for left main distal bifurcation lesions: DKCRUSH-V randomized trial. J Am Coll Cardiol. 2017;70(21):2605–2617. Epub 2017 Oct 30. doi: 10.1016/j.jacc.2017.09.1066

3. Di Gioia G, Sonck J, Ferenc M, et al. Clinical outcomes following coronary bifurcation PCI techniques: A systematic review and network meta-analysis comprising 5,711 patients. JACC Cardiovasc Interv. 2020;13(12):1432-1444. doi: 10.1016/j.jcin.2020.03.054 PMID: 32553331

4. Kim, H, Doh, J, Lim, H. et al. Identification of coronary artery side branch supplying myocardial mass that may benefit from revascularization. JACC Cardiovasc Interv. 2017;10(6):571–581. doi: 10.1016/j.jcin.2016.11.033