About fifteen to twenty percent of the coronary interventions are for the treatment of bifurcation lesions. Treatment of bifurcation lesions are more technically challenging, have lower success rates and worse clinical outcome than non bifurcation lesions. With the availability of drug eluting stents (DES), the results of bifurcation strategies are approaching that of non bifurcation lesions. Bare metal stent (BMS) is still indicated when there are contraindications to prolonged dual antiplatelet therapy. In the setting of acute myocardial infarction with primary PCI (percutaneous coronary intervention), BMS is preferred in bifurcation stenting because of potential risk of stent thrombosis. In short lesions of the main branch of non-true bifurcation lesions also, BMS may be preferred. There has long been a question of whether one stent or two stents should be used for bifurcation stenting. Now there is clear evidence that one stent strategy with provisional stenting of side branch in case of any problems is preferred to elective two stent strategy. That means stenting only the main branch with balloon angioplasty of the side branch has a better outcome in terms of restenosis of either the main branch or the side branch and the need for repeat revascularization. If a two DES approach is used, it makes the procedure more prolonged, with higher fluroscopy times, contrast volumes and more procedure-related release of cardiac biomarkers. Suboptimal result in the sided branch can be accepted if there is a TIMI III flow in the side branch and when the clinical relevance of the territory of distribution is limited. This strategy does not apply in the treatment of left main bifurcation lesions or in the case of a major diagonal. It applies very well to a small obtuse marginal branch.
T- vs Y- shaped coronary bifurcations
Coronary bifurcations with an angle of less than seventy degrees are known as Y-shaped bifurcations. Access to side branch is easier in Y-shaped bifurcations, though plaque shift while balloon dilating the main branch is much more likely in these lesions.When the angulation is more than seventy degrees, it is called a T-shaped lesions. Access to side branch is more difficult in T-shaped lesions, but plaque shift is minimal. The angulation between the branches is further modified when both branches are wired, due to the stiffness of the wires as compared to the vessels.
Medina classification of coronary bifurcation lesions
Medina classification of coronary bifurcation
Medina classification of coronary bifurcation lesions [Kaplan S, Barlis P, Dimopoulos K, et al. Culotte versus T-stenting in bifurcation lesions: immediate clinical and angiographic results and midterm clinical follow-up. Am Heart J 2007;154:336 – 43.] involves assigning a binary value (1,0) to each of the three components of a bifurcation (proximal region of main branch, distal region of main branch, and the side branch) according depending on whether have more than (1) or less than (0) fifty percent lesion. If only proximal segment of the main branch has a significant lesion, it becomes Medina 1,0,0. If distal segment of main branch alone is involved, it becomes 0,1,0. Sole involvement of side branch is designated 0,0,1 and involvement of all the three is designated 1,1,1 and so on.
Addressing coronary bifurcation lesions
Bifurcation lesions have wide range of variations in plaque burden, plaque location, site of the bifurcation, angle between the branches and diameter of the branches. Factors during treatment like plaque shift and dissection are also different with each lesion. The true bifurcation lesions are those belonging to the Medina classes 1.1.1, 1.0.1, and 0.1.1 where both the main branch and side branch are significantly narrowed. A single stent strategy is the rule for all non-true bifurcation lesions. While treating true bifurcation lesions, consideration should be given to the extend of disease in the side branch – whether the lesion is limited to the ostium or involving the vessel beyond the ostium, size of the side branch, angle of take off and the territory of distribution of the side branch. Earlier it was thought that all true bifurcation lesions need a two sent approach. At present, about one third of true bifurcation lesions will need two stents, except in left main coronary artery bifurcations which may need two stents in half of the cases. Stenting of the side branch is favoured if the side branch is an important vessel or sometimes as important as the main branch. Dedicated bifurcation stents may be another option in development in the treatment of bifurcation lesions. While treating bifurcation lesions, both vessels have to be wired initially. The side branch wire is jailed during stenting of the main branch. This is useful in protecting the side branch from closure by a plaque shift. This wire facilitates the rewiring of the side branch if needed as it widens the angle between the side branch and the main branch. Rewiring is needed if post-dilation or stenting of the side branch is needed or if a final kissing balloon dilatation is needed. Final kissing inflation is needed if the side branch has been dilated through the struts of the main branch stent. This is to correct the distortion of the main branch stent which was produced by the side branch dilatation. The side branch wire also acts as a maker for the side branch ostium if the side branch gets occluded. Jailing of hydrophilic guide wires should be avoided as there is a chance of removal of the polymer coating while pulling back. Care should be taken to prevent too much entry of guide catheter into the coronary ostium while removing the jailed wire from the side branch. Two stent strategy is preferred when the side branch is large (higher territory of distribution) and when the lesion in the side branch extends beyond the ostium. With the provisional side branch stenting strategy, side branch stenting is needed if there is plaque shift with more than 75% stenosis of side branch or there is a flow limiting side branch dissection. T-stenting is preferred when the bifurcation angle is close to 90 degrees as it will provide complete coverage of the side branch ostium. If the angle is more acute, culotte or crush techniques are preferred. When a side branch is insignificant or diffusely diseased and not suitable for stenting, it is not rewired or post dilated, though the initial wiring may be done.
V stenting for coronary bifurcation
This technique is useful when both vessels constituting the bifurcation are involved without much involvement proximal to the carina. Initially both branches are wired and balloon dilated. Then two stents are placed, one in each branch, without any significant overlap (overlap less than 5 mm) into the proximal segment. The stents are inflated alternately. Final kissing inflation is done using the same pressure in both balloons. This type of stenting is considered in left main bifurcation disease without significant involvement of the left main itself. The angle between the branches should be ideally less than ninety degrees for this approach. The important advantage of the V stenting technique is that future access to either side branch is not compromised. There is no need to re-cross any any while performing the final kissing inflation. Downside is the difficulty in placing a proximal stent accurately if needed. This is because the proximal stent cannot be easily aligned to both the components of the double barrel. The proximal stent tends to have a bias towards any one of the distal stent. If needed at all, either a small gap can be left or it can be converted to a crush technique with the stent in the main branch crushing the other stent. In this case, a short segment of the main branch has four layers of struts. Hence while selecting cases for V stenting, only those with a very low chance of requiring a proximal stent should be chosen.
Crush technique for coronary bifurcation lesion stenting
This technique is useful when the proximal segment of the bifurcation is also involved. This technique uses two stents, one in the main branch and another in the side branch, the the main branch stent a little proximal than the the side branch stent. Initially both branches are wired and dilated sequentially. Then the stents are placed as mentioned above. The side branch stent is dilated first. The balloon and wire are removed from the side branch and then the main branch stent is dilated. The side branch is then re wired and balloon dilated, followed by a kissing balloon dilatation. During the initial dilatation of the main branch without a wire across the side branch, a portion of the side branch stent protruding into the main main vessel gets crushed on to the proximal segment of the main vessel. Final kissing balloon inflation allows better strut contact against the side branch ostium and hence better delivery of the eluting drug. The maximum opening of the stent cell which can be achieved is different for different manufacturers. This should be kept in mind while choosing the stents for side branches of higher luminal diameter as there could be a miss match at the final side branch ostium. The up side of crush technique is immediate patency of both branches and good coverage of the side branch ostium. Down side is the need to cross multiple stent struts with a wire and balloon to dilate re dilate the side branch.
Mini crush technique for coronary bifurcation angioplasty
In mini crush technique for coronary bifurcation angioplasty, both branches are wired and balloon dilated initially. Then two stents are placed simultaneously in the main branch and the side branch. The side branch stent protrudes slightly into the main branch. Initial inflation of the side branch stent leaves a little overhang of the stent into the main branch. The side branch balloon is removed and the main branch stent inflated, crushing the overhanging region of the side branch stent to the side of the main branch. The side branch is rewired and balloon dilated to open up the side branch stent struts. This is followed by final kissing balloon dilatation with one balloon each in the side branch and the main branch.
Reverse crush technique of coronary bifurcation stenting
Reverse crush is performed mainly with provisional side branch stenting and sub optimal side branch result. A stent is deployed in the main branch followed by final kissing inflation towards side branch. This is achieved by wiring the side branch through the struts of the main branch stent and passing a balloon for dilating the struts and the side branch ostium. A second stent is passed into the side branch. A balloon is positioned in the main branch at the level of the bifurcation. Then the side branch stent is retracted two to three millimeters into the main branch and deployed. After removing the deploying balloon, check angio is taken to ensure a good result in the side branch and exclude the need for any additional stent in the side branch. After confirming this, the side branch wire is removed and the main branch balloon is inflated at high pressure to crush the proximal edge of the side branch balloon. Re-crossing of the side branch followed by side branch dilatation and final kissing dilatation is necessary. The procedure ensure immediate patency of both branches and can be done using a six French guide catheter. But this is more laborious than the standard crush technique.
Step crush technique for coronary bifurcation stenting
The difference between standard crush technique and step crush technique is that each stent is introduced into the vessel and deployed separately. Initially a side branch stent is introduced, protruding a few millimeters into the main branch. Next a balloon is advanced into the main branch and the side branch is deployed, keeping the main branch balloon across the bifurcation. Then the deploying balloon is removed and a check angio taken. If the result is good, the guide wire is also removed. Further the main branch balloon is inflated to crush the protruding portion of the side branch stent and then removed. Next step is to advance the main branch stent and deploy it at a pressure of 12 atmospheres or more. The side branch stent is then recrossed and dilated, followed by a kissing balloon dilatation as in crush technique. The advantage of the step crush is that a six French guiding catheter can be used and this could be specially attractive with the trans radial approach.
Simultaneous kissing stents (SKS)
Simultaneous kissing stents (SKS) are used in the treatment of coronary bifurcation lesions in situations where the need for a future side branch access is deemed unlikely. If future side branch access is needed, it is likely that a guide wire may pass through the struts of one wire and cross over to the other stent while negotiating the neo-carina. The difference between a V stenting and simultaneous kissing stent is basically that the protrusion into the proximal segment is typically more than 5 millimeters so that a new carina is formed within the parent vessel with a double barrel of stents. In the SKS technique, both branches are initially wired and dilated. Then two parallel stents are placed in both branches, extending into the proximal segment of the main branch. One stent is initially inflated, followed by the other stent. Finally a kissing balloon inflation is done in both stents together using same pressure for both stents.
T stenting and modified T stenting of coronary bifurcations
In both classic T stenting and modified T stenting for coronary bifurcations, both branches are initially wired and balloon dilated. Following this, in classic T stenting, side branch stent is placed avoiding protrusion into the main branch. A balloon may be kept in the main branch to guide the position of the main branch. After dilating the side branch stent and getting the check angio to confirm satisfactory deployment, the balloon and guide wire are removed from the side branch. The main branch is then stented. The side branch is re-wired through the struts of the main branch stent and dilated, followed by final kissing inflation. In modified T stenting, two stents are simultaneously positioned in both main branch and side branch. Side branch stent is dilated first. After check angio and confirming satisfactory dilatation, the guide wire and balloon are removed from the side branch and the main branch stent is dilated. The side branch is then re-wired and dilated, followed by a final kissing balloon dilatation simultaneously in the both main branch and side branch. An advantage of the T stenting compared to V stenting is that it can address a lesion in the proximal segment of the main branch. But the coverage of side branch ostium is likely to be incomplete with T stenting in most cases.
Culottes stenting technique for coronary bifurcation
Culottes stenting technique for coronary bifurcation gives good coverage of the bifurcation, but has more metal in the proximal segment. Initially both branches are wired and balloon dilated. Then a stent is placed in the most angulated branch (usually the side branch), jutting well into the proximal segment. The guide wire from the other branch is removed and the stent deployed in the more angulated branch. Wire is removed from the stented branch and the stent is crossed with the wire into the unstented branch and balloon dilated. A second stent is introduced into the unstented branch and expanded, with stent overlap in the proximal segment. The first stent is then recrossed and dilated followed by final kissing balloon inflation. The main advantage of the culottes technique is that it is suitable for bifurcations with all types of angles and provides good coverage of the side branch ostium. But the disadvantage is the double layer of metal at the carina and proximal vessel. The process of re-wiring through stent struts is time consuming and can be difficult.
T-stenting and small protrusion (TAP stenting) in coronary bifurcations
T-stenting and small protrusion technique (TAP-Stenting) is used to enhance side branch ostial coverage. It is an intentional protrusion of side branch stent within the main branch during coronary bifurcation stenting which ensures side branch ostial coverage and facilitates final kissing balloon inflation [Burzotta et al Catheterization and Cardiovascular Interventions. 2007; 70:75–82]. This technique has been introduced because the conventional T-stenting method is associated with the risk of incomplete side branch ostial coverage, especially when the angle between the main branch and the side branch is acute. The position of the side branch stent is
adjusted to fully cover the proximal (or upper) part of the side branch ostium. This causes a small protrusion of side branch stent in the lower part of the ostium. This is leveled off by the final kissing inflation.