Bifurcation left main stenting- Elias Hanna

I want to talk about digital left main bifurcation stenting. This stock complements my prior bifurcation talks, as well as my talk about LV supporting complex PCI and left main static technique. So I suggest you review those three talks.

For each left main PCI, as I explained in that talk, there are five major questions and three additional questions. Need for atherectomy, left main bifurcation technique, LV support, sedation plan. LV support is decided on two major features and six additional features. The two major features are hemodynamics, including blood pressure, LVEDP, and clinical heart failure and hypoxemia, and the complexity of your left main intervention, which you can modify depending on which stenting technique, digital bifurcation, static technique, you use.

The three additional questions you ask are: if you have RCA stenosis, should I stent it first or after? Usually RCA stenting is done after left main PCI, as an EXCEL trial, unless you have a critical large, super dominant RCA with a stenosis over 90 percent, while the left main stenosis is relatively moderate. For downstream disease deemed necessary to treat, you may stent it before stenting left main, unless you have a critical osteo left main with a guide ventricularization and ischemia, or unless you have ongoing left main ischemia as your wiring and advancing balloons. The third additional question is: is it difficult to wire left main and/or proximal LAD, and you have a critical 99 percent stenosis, so much so that flow is expected to shut down during wiring? In which case this may further favor LV support.

Regarding bifurcation left main stenting, the same general approach applies. Most of this is a left main bifurcation should be treated with provisional stenting. And I'm talking about true left main bifurcation involving the ostium of the left circumflex. So you do crossover stenting into the LAD. Then you rewire and balloon the left circumflex only if it is more than 75 percent narrow. Then you stent it only if it remains narrow after ballooning, especially narrower than 75 to 90 percent. You want a higher threshold to stent that left circumflex than to balloon it. In the EBC main trial, the side branch was stented only for a cutoff of 90 percent despite ballooning, or for the presence of dissection. Also, proximal part of the main branch stent reduces side branch narrowing and the need for side branch post-dilatation, according to EBC main analysis. And you only go for upfront two-stent strategy in complex true bifurcation where not only the main and side branch are involved, but the involvement is very complex; meaning the circumflex is more than 70 percent and it's a long disease, not just the ostium, but longer than 10 millimeter, and you have heavy calcium or heavy plaque burden in the main branch. The risk of side branch occlusion here after main vessel stenting is up to 20 percent.

There are two major left main bifurcation trials you need to know: EBC Main and DK Crush 5. EBC main took true digital left main bifurcations and randomized them to provisional stenting versus upfront two-stent strategy. Those were true left main bifurcations but not very complex. The side branch stenosis length was 7 plus or minus 6 millimeters, and the baseline side branch stenosis was around 52 plus or minus 18 percent. Importantly, provisional stenting did as well, if not better, than the two-stent strategy. And in fact, at one year the need for revascularization trended to be better in the provisional strategy, and at three years the need for revascularization was actually better with provisional strategy. And there was a trend toward better MACE with a provisional strategy in true left main bifurcation. And importantly, even in true left main bifurcation in that trial, only 22 percent of the provisional arm require dual stent, even though almost all of them received left circumflex dilatation, which tells you that dilating the side branch, which is a left circumflex in this case, does not mean it has to be stented. Even a large left circumflex, you frequently need to dilate in a true bifurcation stenting, but you frequently do not need to stent it.

So side branch post-dilatation is frequently done in provisional true bifurcation using a 75 percent side branch cutoff, as per the landmark bifurcation trials such as DK Crush 5 and EBC Main. And stenting of the side branch is reserved for a 90 percent cutoff despite side branch ballooning or for side branch dissection.

Now regarding 3D rotation of the side branch, this is more controversial. Side branch pre-dilatation was done in 40 to 50 percent of the provisional arm in left main bifurcation trials such as the two major ones, EBC Main and DK Crush 5. I perform side branch pre-dilatation usually for side branch more than 70 to 80 percent stenotic or heavily calcified side branch in order to reduce side branch occlusion post main branch stent and to ensure that the lesion yields. However, systematic side branch pre-dilatation may increase the risk of dissection of the side branch, which makes it more difficult to rewire that side branch. That is why in EBC main, side branch pre-dilatation increased the risk of conversion to two-stent because of side branch dissection. So you may pre-dilate the side branch when it's critical, otherwise try to avoid it. So even in true left main bifurcation, you often don't need to stent the left circumflex, even if you balloon it. Now even more in non-true left main bifurcation where the left circumflex is not involved, try to not even touch at all the side branch, which is usually the left circumflex. Wire it, but do not pre- or post-dilate. There is no evidence that leaving a grid of metal struts stent across the left circumflex ostium is harmful, so you can just stent across and not even rewire and balloon. You can leave that grid of metal without opening it at the end of your procedure. This likely applies to non-true bifurcation that are mainly going to the circumflex, where mainly your disease is left main and circumflex and the LAD is the practically non-diseased side branch. Even in that case, you can stent directly into left circumflex and not rewire and balloon the LAD unless it becomes severely narrow. So you can leave that grid of metal across it, although you do have a lower threshold to balloon or stent if your LAD is what you have considered a side branch.

There is indirect evidence that even dilating the side branch in those non-true bifurcation cases is not beneficial and may worsen main branch outcome unless the side branch becomes occluded. Most of the data is from non-left main studies. You have the CROSS and Nordic 3, and the recent KISS trial, all those showing that in non-true bifurcation, do not touch the side branch unless it occludes. And there is also the KOBUS 3 one-stent arm showed that kissing balloon leads to more target lesion revascularization of the main branch in the left main arena. You have the left main EXCEL sub-analysis showing that kissing balloon inflation, no benefit in the one-stent strategy, and there was a trend to more stent thrombosis. All this suggests that you should reserve left circumflex post-dilatation for stenosis over 75 to 90 percent, even more so in the case of non-true bifurcation at baseline. Importantly, side branch post-dilatation or kiss may be harmful in non-true bifurcation or non-complex bifurcation at baseline unless the side branch eventually occludes, because that side branch dilatation or kiss may distort the main branch stent. Okay, that is why data from CROSS trial and from left main EXCEL analysis suggests possible harm from kiss in patients who undergo one-stent strategy.

This is a case from EuroPCR from Dr. Hildik Smith, who's the primary investigator of EBC Main. He shows a case here where you have a trifurcation left main, but the main disease is this is a left main into that OM. The LAD and the diagonal are not severely diseased, so he did a simplified approach here. He just stented from left main into that OM while just wiring the LAD, and he got a great result and he did not need to rewire and balloon that LAD. So he just did provisional stenting into the OM1 and did not even rewire and balloon the grid across the LAD, again in favor of a very simplified strategy, particularly in non-true bifurcation, but even in true bifurcations that aren't very complex where you don't have heavy disease burden and long disease on the side branch.

Only DK Crush 5 showed that in this left main two-stent strategy may be better than provisional strategy, but only in complex digital left main disease where again the circumflex is more than 70 percent, not just 50 percent stenosis, and the disease is long, more than 10 millimeter, and you have heavy plaque and/or calcium burden in that left main LAD system.

Now the question I want to mainly address here: what two-stent strategy to use, whether as upfront approach or when two stents are needed in the provisional approach. So in the upfront two-stent strategy, you may choose one of the following four: DK Crush, culotte, T, and protrusion Tab in a planned fashion as a two-stent strategy, because this may be used also as a provisional strategy. But simplest and maybe best of all is the perfect T strategy, which is almost like a nano Crush, as I will explain. So those are the four, and my preferred is perfect T and second is TAP.

If provisional stenting is needed after main branch stent and you haven't obtained a good result with just ballooning the side branch, left circumflex, then you may choose reverse Crush, which is similar to DK Crush, but you're starting with main branch stenting rather than side branch stenting. You can do kilot technique, but simplest of all is the TAP technique. So you have three options, but simplest is TAP. With both planned culotte and Tab, you may start by placing your first stent in the left main to the LAD. Then you place your left circumflex stent in TAP or kilot, or you may start by placing your first stent from the left main to the left circumflex, then you place your LAD stent whether in TAP or culotte. And in those cases we would call them inverted TAP and inverted culotte, starting with stenting from the left main to left circumflex versus left main to LAD. Really depends on the severity of that left circumflex stenosis compared to the LAD stenosis and how likely it is to occlude that left circumflex if you start by putting a stent from the left main to the LAD, and how difficult it will be to rewire the left circumflex once you put a stent from the left main to the LAD. In perfect T, nano Crush, and in standard Crush single case or DK Crush, you start by stenting whichever branch you consider a side branch, typically the left circumflex, and there is no risk of side branch or main branch loss at any time unlike with TAP and kilot, and that is an advantage of those techniques; no concern of branch occlusion in the middle of your procedure.

Yeah, I will move on to describe data. Even though there is an American fascination with a DK Crush technique, if you look at the data, it's actually weak for DK Crush. And let's go by the major trials of left main. You have the EXCEL trial that put left main stenting on the map as an alternative to CABG. And in EXCEL trial, for provisional stenting, T and TAP were the biggest techniques, nearly 80 percent, and even in planned two-stent strategy, T or TAP were applied in 50 percent of the cases. Then you had kilot in 23 percent. Crush was a minority, 14 percent. And in EBC main trial, which compared a provisional to two-stent strategy, and the planned two-stent, they used kilot in 53 percent of the time and true TAP 33 percent of the time. DK Crush was only using 5 percent of the cases. And this is the big NOBLE trial, again stent versus CABG, a major trial like EXCEL, and in that trial 87 percent were distal left main. Two-stent strategy was only using 35 percent, again arguing in favor of provisional stenting in most distal left main. And the two-stent strategies that were used were kilot first and T stent second. Crush was the least used. So again, in both NOBLE and EXCEL, Crush was the least used strategy.

Only DK Crush 5 supports the use of DK Crush in complex distal left main, and in DK Crush 5, DK Crush was compared to provisional in complex distal left main and show that DK Crush was better in terms of stent failure and target vessel MI. But if anything, the DK Crush 5 suggests that in complex distal left main that I explained, two-stent strategy is superior to provisional strategy. It doesn't establish that DK Crush is superior to other two-stenting strategy. There is only one study that compared two different two-stent strategy. The DK Crush 3 compared DK Crush with kilot in distal left main, and in that trial DK Crush was superior, articulate with less DVR at one year, significantly less, and even more so at three years with less target vessel MI and less stent thrombosis. But it is speculated that the DK Crush 5 operators, which are mainly from one country, uh, used sub-optimal culotte technique, no part and too much metal overlap instead of miniclot, which made the culotte result look a lot worse than the European culotte results. And more importantly than the actual two-stent strategy that you use in provisional and in upfront two-stent, the most important thing is a rather proper vessel preparation and stent post-dilatation, especially at the ostium of LAD and left circumflex. This is what improves outcomes rather than particular two-stent strategy, rather than DK Crush is better than T or kilot. This is what improves outcomes, particularly that the ostium of the left circumflex is the Achilles heel of left main stenting. It's the site where you get the most restenosis, target vessel revascularization, and where you get the most severe and refractory under expansion when you do two stents. So it's extremely important to prepare the vessel properly. And these are five ideas: one, you need high-pressure pre-dilatation or rotablation or lithotripsy of the left circumflex ostium and/or LAD. Two, you need to do post-proximal optimization after each main branch stenting before you rewire and after side branch stenting. You need to always pull back the balloon and post-dilate the ostium at high pressure. So side branch stenting is always two-step: you deploy the side branch, then you immediately pull back and inflate it at high pressure over 18 atmosphere in all techniques, including the DK Crush technique. Before you eventually crush that side branch, you post-dilate high pressure before you crush it. Another idea: when we do the kiss, always do sequential kiss, not just simultaneous kiss. So you double balloon, you inflate the balloon in each branch, the side branch and the main branch at over 18 atmosphere sequentially, then you do your simultaneous kiss at 8 to 12 atmosphere. And always you have that sequence throughout your procedure, whatever technique you use, you do part of the proximal extension of the stent into the main branch, then you rewire and kiss, then you repot afterwards. So pot, rewire, kiss, repot.

I will describe those TAP and T stents, which I believe are the better technique, particularly in distal left main, and they are the simpler techniques and the better tolerated hemodynamically, and they are also the techniques that lead to least metal overlap, and they are the techniques that have been most used in EXCEL landmark trial. So TAP in distal left main consists of placing a stent from your left main to the LAD, crossover stent. Then you rewire once, and you deploy your left circumflex stent. Well, you have a balloon stationed into the left main, then you inflate simultaneously the left circumflex and the left main balloon. So really your left circumflex stent deployment is seamlessly followed by kissing balloon dilatation without the need for rewiring. For both TAP stenting and final kissing balloon, you use the same rewiring that you have already done for side branch post-dilatation, and you will end up with a small neocarina of metal inside the left main. That's the only downside of TAP. And TAP is only done after you've deployed the main vessel stent, in this case crossover left main to LAD.

So I'll give you more details. So you start to deploy that stent, left main to LAD, then you pot the proximal left main, then you rewire the left circumflex. It's easy rewiring through one stent layer, then you balloon it, then you deploy the TAP stent while you have a balloon stationed in the main branch, then you pull back the TAP stent balloon and you post-dilate that ostium circumflex. Like I said, always whenever you deploy side branch stent, you deploy it, then you pull back the balloon and do high-pressure dilatation of that side branch, then you do simultaneous kissing balloon dilatation with the main branch balloon that was waiting. Importantly, unlike the common misconception in the U.S., TAP can be used in shallow angle, like 30-degree angle, if you use a proper technique. It does not have to be over 70 degrees. It's easier if it is over 70 degrees, but it absolutely doesn't have to be, and I've done it in shallow angles, and I'll show you the the proper tips for that. And this is an illustration of the TAP steps. Use stent boost very importantly to position the TAP stent. So you deploy your main vessel stent, then you pot the proximal main vessel, then you rewire and position your TAP stent and that side branch TAP stent. The DOT should be just inside the main branch, not touching or barely touching the main branch. Wire balloon without missing the ostium. So it's barely inside the main branch, then you deploy it, then you pull back the balloon and do high-pressure inflation of that ostium. Then you pull back the main vessel balloon and do kissing balloon dilatation. Then it preferably you should do final pot. It is recommended to do final pot, but I worry if the pot balloon in the main branch extends a little bit to the carina, it will end up crushing the TAP stent and it's no longer TAP, it becomes like a crush technique. So it is key to use stent boost to position that pot balloon just before the carina and before the origin of the TAP stent. And it's nice if your lab has short, six-millimeter balloon for pot. This slide shows you that TAP may be applicable for angles that aren't close to 90 degrees. This here is about 30 degrees. You can also do inverted TAP where you start your stent from left main to left circumflex and then you do the TAP stent in the LAD. This inverted TAP is done if the left circumflex disease is critical while the LAD disease is moderate and it's easy to wire. In which case you may just stent left main to left circumflex and do provisional balloon and provisional TAP stenting of the LAD, or you may be planning to do upfront two-stent strategy. But even if you're doing upfront two-stent strategy, you're starting with the left main, left circumflex, then you put your TAP LAD stent afterward. The second condition where inverted TAP may be preferred is when the left circumflex caliber better matches the left main caliber than the LAD caliber does; meaning you have a big left circumflex that is almost the size of the left main, whereas the LAD is small. Again, the TAP stent can only be deployed after your main branch stent has been deployed. And this is a video animation by Dr. Stankovic that I obtained from a PCR webinar in 2020. It illustrates the provisional steps nicely and it shows you how to do the TAP technique. So here you're doing your main branch stent, then you were pot, then you rewire the side branch, you do balloon dilatation and kissing balloon, then you advance and properly position your TAP stent, then you pull the balloon of that TAP stent, do high-pressure inflation, then you inflate that balloon in the main branch that was stationed. Watch it again. TAP stent position deployed while a balloon is waiting here. You post-dilate the TAP stent, then you do a kissing balloon, then you do a final pot. And see, here's a small piece of TAP protruding the main vessel, but it should only be small. And note how the kissing balloon dilatation positions the carina in the center allowing normal flow in both directions. That's the role of the kissing balloon, to center that carina and provide normal flow both ways, and it will allow you to advance digital devices if needed without hindrance.

This slide shows you the difference in side branch strut overhang between TAP, Crush, and kilot. TAP leaves a small neocarina, a piece of metal hanging in the middle of the main branch. Crush, on the other hand, the side branch is smashed to the wall and there is no neocarina in the lumen. That side branch stent is crushed to the wall whether before main branch stenting as in standard SK single kiss or double kiss crush, or it may be smashed to the wall after main branch stenting as in reverse Crush. In kilot, the side branch stent goes all the way to the opposite main branch wall and touches that opposite wall. The full circumference of the side branch is overlapped with the full circumference of the main branch stent, and you get two full circumferential layers of stent against the main branch wall. Keep that kilot overlap as short as possible. TAP is very different from what I call the perfect T. In perfect T, you're deploying your side branch, left circumflex stent before you've deployed your main vessel stent. In this

Case: the angle must be close to 90 degrees, unlike tab, which can be applied to any angle. Imperfect; you have to be close to 90 degrees. You position it perfectly, and you have a balloon station in the main vessel. After you deploy your circumflex tent, you balloon the main vessel to crush any potential protrusion. Then you deploy your main vessel stand. So you're starting with a side branch; then you put the main branch stand. After that, you have to part the main branch as usual; then you have to rewire, but it's an easy rewiring across one stand layer because that osteum only has one stent layer, the main vessel stent layer. So you rewire, then you do a kissing balloon; then ideally you repot.

So again, perfect T is different from top, and actually sequentially the steps are very close to the single case Nano Crush. Perfect T is actually almost a Nano Crush. In Nano Crush, the angle is not perfectly 90 degrees. So when you position your t-stand in the circumflex, in order to fully cover the awesome, a piece of that stent will hang into the main vessel. So if the perfect T hangs a tiny bit into the main vessel, you end up having less than one millimeter Nano Crush, but it is almost impossible to distinguish a perfect T from a Nano Crush, as it's only 0.5 to 1 millimeter difference and how far the stand extends into the main branch. So practically, I consider them the same. And in that case, the side branch stent may have a tiny piece, by definition less than one millimeter piece, that is hanging in the main vessel, and that gets crushed by the main vessel balloon, then the main vessel stand. Then after main vessel standing, you rewire and you do simultaneous kiss. Nano Crush is more similar to the perfect T than to standard Crush because you have very little crushed area, which is almost like having no crushed area. Most of the side branch osteum is only covered by struts of the main vessel stand, the red one, with a tiny area of double layers of stand toward the carina. This is different from the three layers of stent you get with a standard crush on the upper arm and two layers toward the carina. You see here three layers and two layers here in the standard, whether single case or double kiss Crush. But in terms of rewiring and doing eventually simultaneous Kissing Balloons, are closer in steps to the standard SK Crush than to the top.

These are summary key ideas for perfect T, for tab, for Perfect T: you need 90-degree angle, but it's okay for over 60 to 70-degree angle as it will end up being a Nano Crush. And you start by stenting the side branch before you do your main branch standing. Then you stand main branch. You may even do Standalone t-stand in isolated osteal left circumflex disease. Now for tap, you can only deploy the top stand after main branch standing. It can be applied for shallow Side branch angle, like 30 degrees, as long as you do good part to make the main branch large. You request the distal strut; you use a stand boost technology. And the fourth idea: it's even more successful at shallow angle if your side branch is significantly smaller than main branch, so the relative amount of overhang will be small. Top may also be done for angles close to 90 degrees instead of a perfect T if you have already deployed your main branch stand. If you've already deployed your main branch send and your angle is close to 90 degrees, you can still do top; you may not end up with much protrusion at all, but the sequence of treatment is like a tab where you recross, deploy your stand and do simultaneous balloon stand balloon inflation.

This is an illustration of the key concept to allow you to do tap successfully in all cases, particularly in Shallow angles. After main vessel standing, you have to do a good part to create a good bulge of the proximal main vessel stand into the side branch. And then when you rewire into the side branch, you have to rewire across the distal stent struts; that's very important. When you cross distally, then balloon the side branch, you push those main branch struts toward the upper arm of the side branch, as in here, which creates good scaffolding of the upper the top arm of the side branch with your main branch stand. And the upper arm is actually the one that is more difficult to cover with your TAP stand. So when you create a scaffolding already before you put your TAP stand, it's easier to position your TAP stand with a lot less protrusion. Conversely, if you cross proximally, you're not going to create a scaffolding of that upper arm of the side branch, and when you position your TAP stand in order to cover that upper arm, you have to make it protrude further, more. So proximal Crossing: more protrusion; distal Crossing: more scaffolding of that upper arm of Side branch and easier positioning without protrusion. This ends up being top with minimal protrusion. The so-called actually t-stand is not the perfect T, but in the EBC, European bifurcation Club, they call that top with minimal protrusion or practical note protrusion; they call it t-stand. I prefer to resolve the t-stand terminology for that perfect T that you position before main vessel standing.

And in order to cross the distal stand struts, it's not very difficult: make your wire tip Bend larger than the side branch and go distally with your wire, then pull back. That's how you end up Crossing distally, and you can verify the digital strut Crossing and the amount of metal overhang using stand boost as in here. This was distal stratri wiring and minimal overhang by stand boost. Again, tap is applied here to a shallow angle, 30 degrees, and here is the EBC where they call tap with minimal protrusion t-stand versus the top with more protrusion. And for the same side branch and the same bifurcation, you can do a less perfect top as in here versus a more perfect top with no stand protrusion. The difference is how you cross distally versus proximally and how good your path is. Another note: when you have tap with some protrusion, you may have difficulty advancing devices in the main branch distal to that neocarina, especially stand, as you're trying to Advance stand somewhere distally in the vessel in the future. Your stent may have a friction around that neocarina; it may have difficulty advancement. However, if you cannot Advance a balloon past that neocarina, it means you may be going through the neocarina stent struts. So in this case, you need to rewire your main vessel, and you can keep that first wire over which you could not Advance a balloon, keep it and Advance the second wire. That first wire means are to deflect away the second wire from the neocarina. You may even keep the first balloon hanging around here and rewire and Advance another balloon. That first wire balloon will deflect you away from the neocarina.

This is an illustration from a case I did. It was led diagonal top. This is a top in the diagonal, and the angle is very shallow here; is less than 30 degrees, but with the stand boost and with rewiring the side branch across distal struts, I had very little neocarana in the main vessel. See here how top was well done, and this sorry Crossing created scaffolding into that side branch. We deploy the top stand here while a balloon is positioned in the main branch to prevent the tap stand from touching the wall and becoming a lot. Then after we deploy that side branch stand, we pull its balloon; we inflate it at high pressure; then we do simultaneous kissing balloon of the main branch Side branch leaving potentially little neocarina. This was an excellent result; we had excellent side Brands coverage; we did not miss the awesome of the side branch; yet we had minimal strength overlap and practically no overhang. Keep in mind how much stent and metal overlap you get with culotte and Crush. Look how much with kilot you get; how much for the crush we got here: practically no stand overlap, much less metal, probably translate into less ristenosis by all data we know, not directly in bifurcation but overall in instantly stenosis data.

And this is a summary of the advantages of T and tap compared to DK crush and kilot. You only rewire Side branch once after stenting versus two times with DK crush. And with clock, you only do one kissing balloon; and in case of tap, you're using the top stand balloon itself for your kissing balloon versus needing two kissing balloon inflation with DK crush and one or preferably two with kilot, the so-called Decay collage. And another Advantage: you rewire through only one stand layer versus two layers with kilot and two to three layers with DK Crush. With kilot, after deploying your second stand, the blue, you have to rewire into this stand potentially through two stent layers. One note here: I describe that with provisional standing in general. And with top, you need to request the distal stand struts across the side branch to obtain good scaffolding of the upper arm of the side branch and easy to position the top stand. In crush, however, when you rewire the crushed stent, it's best to cross proximally or mid stand layers, not this study. You want to avoid the distal stent layers. Why? Because in crush you already have Side branch stand covering the upper arm of the side branch with actually most metal in dust area. You have two layers of stand in that upper arm of the side branch and even three layers after you position your main vessel stand. So this upper arm in crush actually has a lot of stent layers, so rewiring distally and ballooning will push more stent struts over that crushed area that already has too much stent causing too much metal overlap. It can also cause the wire to go to distally in the gap between the Karina and the side branch stand struts and cause Mala position upon inflation. Regarding culotte, like in provisional and in tap, you cross this study; you don't want to re-cross the stand layers proximally because this will push too much metal toward the Karina. When you do your kissing balloon, you will end up with something like this: too much metal pushed toward that Karina, which is what we call neocarina, compared to how it should be.

If you cross proximally, and I mentioned the importance of vessel preparation and proper stenting technique, more importantly than the actual technique you choose. The worst thing you can do is do DK crush with an under expanded left circumflex tent. You end up with a three metal layers at the left circumflex osseum with an under expansion. Most stent failure at the Karina are not instant tissue growth; they are rather stand under expansion, especially at the Austria and at that Karina. And the problem is exaggerated if you're doing DK crush or culotte with multiple layers of under expanded stents. And you should always verify in this cell left main bifurcation standing proper stand expansion with imaging. These are MSA Dimension from a Korean paper that indicated for your left main, the main left main should be at least eight millimeters Square, the Karina seven millimeter square, ocel LED 6, and ostel circumflex 5; that 8765 rules. And those who are using the renovate Imaging trial. However, in addition to that, I believe it's important to have proper relative stunt expansion over 90 percent stent expansion in the LED compared to the digital led a reference Lumen area and the left main compared to the reference left main luminal area. Also, those numbers may be too small for the general European and American population. Fact: in Noble I was analysis, the best result were with MSA over 13 for the left main or at least over 10 millimeter square. So shoot for those absolute values and preferably a little higher, particularly in European American population, and aim also for relative stunt expansion more than 90 percent of the reference. Aside from Iris, another General sizing idea is that in general the proximal LED is about 3.5 millimeters, the proximal left circumflex is about 3 to 3.5 millimeters, and the left main, which based on the fractal law is two-thirds of the summation of the LED plus love circumflex, is usually around 4.5 to 5 millimeters.

Now regarding sheath size and Radial versus femoral access, I often use radial access for left main interventions. Sixth French is often okay, but if the radial artery is large, it is easier to use seven French, and I prefer seven French. It's possible; it's easier to fit simultaneous stand balloon in seven French then six French. In top and in Nano crush and in SK or DK Crush, you need at one point to position simultaneously stand and a balloon. Six French can fit simultaneous stand balloon as long as both the stent and the balloon are three millimeter or less. Six fresh can also fit a stent that is a 3.5 millimeter with a short balloon that is a three millimeter, but it is tight the space. So consider seven French radial if radial size allows, but you can use six French if you use those sizes. LV support is rarely needed in left main intervention unlike what fellows think. LV support was using five percent of patients in Excel left main trial, three percent in provisional and ten percent on the plan to send strategy. If support is needed, you can still use radial access for your left main intervention. I would use radial for the left main typically if I can, seven French radial, and I would use femoral access for the support or in patients who are relatively short. You can use single access femoral impeller and through the 14 French impeller sheets you put your guiding catheter. Now, how do you decide if LV support is needed? Review my prior talk regarding LV support, and the decision is based on two major factors and six other factors. The two major factors being hemodynamics and the complexity of your PCI. Both those factors are modifiable. You can simplify the complexity of your PCI by using a simpler bifurcation technique, provisional and tap or perfect T, and you can improve the hemodynamic by diariesing the patients before the complex procedure. And these are slots from EBC Main and DK crash 5. In both radial access was used in 70 plus percent of the cases, and six French guiding catheter was used in 53 to 61 percent whereas seven French was used in less than 50 percent of the cases.