Coronary artery bifurcation lesions are one of the difficulties in interventional therapy. Among them, the left main trunk bifurcation lesion has a wider blood supply range than other bifurcation lesions. Therefore, the protection and treatment of side branches are particularly important. So, what is the significance of side branches protection, and how to deal with the side branches occlusion after the main stent is placed? On this related issue, Prof. Rongchong Huang from the Friendship Hospital of Capital Medical University and Prof. Debabrata Dash from UAE Hospital had a dialogue.
Prof. Huang: Coronary bifurcation lesions are one of the difficulties of interventional therapy. Would you please share with us the latest research developments in the field, including the use of IVUS, OCT and FFR?
Prof. Dash: As all of us know, bifurcation is one of the most challenging subsets of PCI, accounting for 15-20% of cases in the cathlab. The current recommendations still support provisional stenting, based on large trials like BBC ONE and NORDIC I, which found that provisional stenting was better than the two-stent technique. However, they did not differentiate between true and non-true bifurcation. The EBC TWO trial also found that the two-stent technique did not improve outcomes compared to the provisional technique. In NORDIC IV, the two-stent technique was as good as provisional. However, there was a lack of the proximal optimization technique, lack of IVUS, and at that time, ticagrelor was not available so clopidogrel was used. Then came the DKCRUSH series of trials. In DKCRUSH-I the DK crush technique was found to be superior to the provisional technique in terms of MACE, in-stent restenosis and stent thrombosis. Similarly, in DKCRUSH-II, DK crush was found to be superior to provisional at five years in terms of target lesion failure (TLF) and TVR. DKCRUSH-III was a landmark study for complex left main bifurcation, where DK crush was found to be superior compared to culotte in terms of stent thrombosis and MACE. Then came DKCRUSH-V. Again, this was a very good study that compared DK crush to provisional and found it to be superior in terms of TLF, target vessel MI, stent thrombosis and in-stent restenosis. Now we have the DEFINITION-II trial in complex bifurcation lesions where DK crush was the most used technique and found to be superior compared to other stenting techniques, as far as target lesion failure is concerned. IVUS plays an important role in bifurcation lesions, mainly left main bifurcations. There are many comparative studies demonstrating better outcomes for death and MACE where IVUS is used compared to angiographic results alone. DKCRUSH-VI is a trial that actually looked at FFR guidance bifurcation angioplasty and found to be superior compared to angiographic guidance.
Prof. Huang: I think IVUS or OCT are very important in left main bifurcation lesions.
Prof. Dash: I do agree. OCT can direct the entry of the guidewire and whether it is likely to cross the proximal strut or distal strut. That can be clearly visualized. It will also optimize results in terms of stent apposition and expansion.
Prof. Huang: Sometimes, the size of the main branch and the side branch can be very different, so protection and treatment of the side branches are particularly important. Would you please share with us the significance and skills involved in side branch protection in bifurcation lesion treatment?
Prof. Dash: Sometimes the side branch is small and sometimes it can be big, as in the case of left main bifurcation. In left main bifurcation, the side branch is as important as the main branch as far as the blood supply to the myocardium is concerned. It is important to define the degree of ischemia originating from the side branch so the patient will benefit from revascularization by PCI. In Korea, they have calculated the sectional myocardial mass supplied by specific vessels. It is calculated using CT, and if it is >10% then that will mean the side branch is significant. In the case of left main, most of the time, the side branch is >10% of the sectional myocardial mass. But in non-left main bifurcation, 1 in 5 cases may have a significant side branch, so side branch protection becomes important. There are a few techniques. One is the jailed wire technique, which is the most commonly used. Then the jailed balloon technique where a semi-compliant balloon is placed in the side branch, either with or without partial inflation. The other is a balloon-stent kissing technique. For this technique, a compliant balloon is placed in the side branch and an extended stent in the main branch. Initially, we inflate the side branch balloon followed by inflation of the stent. Then both the main and side branch balloons are deflated and the wire and balloon are removed and a proximal optimization technique applied to the main branch. There is also the modified balloon-stent kissing technique. Here, the stent and balloon are inflated at the same time. After deflation and the balloons taken out, the main branch is post-dilated as per the proximal optimization technique. This prevents side branch occlusion. These the three main techniques.
Prof. Huang: In recent years, coated balloons have been used in left main bifurcations to protect the side branch. What are you thoughts on this approach?
Prof. Dash: I agree the drug-eluting balloons are very good, but we need data on the degree of benefit. We need more trials. But you are right, balloons can be used in the side branch as a provisional technique, followed by proximal optimization in the main branch. It is a good technique but we need more data.
Prof. Huang: To date, we have no solid evidence for drug-coated (drug-eluting) balloons (DCBs) being used for protection. But after the jailed balloon technique, maybe we could use DCBs to treat after the main stent is implanted.
Prof. Dash: That is a good idea. The concept was first introduced in Italy and then Germany, I think. I think China uses a lot of drug-eluding balloons as well, and there have been recent randomized controlled trials from China in that regard.
Prof. Huang: Our Chinese factories can produce DCBs much more cost-effectively, which means manufacturers can support ongoing research. In my experience, it is still early days using DCBs for this indication, but maybe as the devices get cheaper, we can all get more experience with them.
Prof. Dash: It may be cheaper but it can still work well. When you don’t want another stent layer and there are patients at high bleeding risk, and in situations when other stents will not be useful, this is another option.
Prof. Huang: For bifurcation lesions, what should be done when side branch occlusion occurs after the main branch stent is inserted?
Prof. Dash: When there is side branch occlusion following the main branch stent, the first approach is to extend the wire and a kissing balloon inflation, or a side port with proximal optimization and side vein inflation followed by proximal optimization of the main branch. If it doesn't work, we can consider a second stent, using T and protrusion (TAP), provisional culotte or internal crush techniques. The selection of the technique depends on the operator’s experience, the angle of bifurcation, and the diameter of the side branch. If the angle is >90 degrees, then T-stenting is very good. However, these techniques can suffer from incomplete coverage of the side branch ostium leading to incomplete side branch scaffolding leading to thrombosis and in-stent restenosis. Secondly, if the angle is narrow, we can consider T and protrusion (TAP), extending the stent into the side branch with a 2 mm protrusion into the main branch, followed by kissing balloon afterwards. With this technique, there may be a neocarina that can lead to stent thrombosis. Another technique is the provisional culotte. You can do a mini-culotte with less overlap, a mini-overlap of the stent with mini-kissing, but sometimes it can be difficult to cross the the two-stent layer at the carina. These techniques would be done when the main branch and side branch are of similar diameter and the angle is narrow.
Prof. Huang: We need to assess the bifurcation lesions before we perform our procedure, so you are giving good advice on how to proceed. I agree with you.
Prof. Dash: The reverse culotte technique a good technique I think. With the DK crush, in some situations it is rather similar to the reverse culotte.
Prof. Huang: In the future, is DCB angioplasty for both main branch and branch vessels a new trend in clinical treatment of bifurcation lesions?
Prof. Dash: More and more, we are being able to treat the main branch with DCBs alone. This is called the DCB-only strategy, with DCB in the main branch as well as in the side branch. There is a provisional strategy with DS (direct stenting) in the main branch and DCB in the side branch, similar to provisional stenting. For the latter technique, there is a randomized trial ongoing in Europe, the PRO-DAVID study, looking at whether the provisional DCB technique is better than the provisional stenting technique. For the DCB-only strategy, I don’t have data, but that may come in the future and we may be surprised, because the less stent metal used the better. Maybe we will see biodegradable stents or DCBs in the future to take care of the bifurcation lesions.
Prof. Huang: I think we have more new devices to discover to perform PCI in the very near future. That will give us more choices.
Prof. Dash: I think we will see biodegradable stents in the future. I predict we will soon see this type of new technology.
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