A New Proposed Simplified Classification of Coronary Artery Bifurcation Lesions and Bifurcation Interventional Techniques

Coronary artery bifurcation lesions remain a significant challenge for interventional cardiologists. Percutaneous coronary intervention (PCI) involving bifurcation lesions is associated with an increased risk of procedure-related myocardial infarction, chest pain, cardiac enzyme elevation and restenosis.¹ In the era of bare metal stents, the use of two stents in a bifurcation lesion was associated with an increased risk of restenosis as compared to stenting of the parent vessel with balloon dilatation only for the side branch.^2–4 With the advent of drug-eluting stents, however, PCI involving complex bifurcation lesions has become widespread, with improved long-term outcomes despite the use of multiple stents.^5–7 It is now common practice to use two stents for bifurcation lesions to prevent side branch occlusion, but there are currently no established guidelines to address the use of particular interventional techniques with regard to the specific anatomy of the bifurcation lesion. There are multiple coronary artery bifurcation lesion classification systems described in the literature,^8–11 but these systems are confusing, very difficult to remember and are not clinically oriented. Therefore, a simplified classification system that is clinically oriented and can be easily remembered is proposed in this manuscript. Bifurcation lesions are summarized by a simple combination of letters and numbers which provide a description of the lesion in the context of currently-used PCI techniques. Proposed Classification of Coronary Artery Bifurcation Lesions The lesion classification system begins with the prefix B (for Bifurcation lesion) to which four different suffixes are added to obtain the final description of the lesion (Table 1). Assigning the first suffix. I) Proximity to the bifurcation carina: Lesions that are further away from the bifurcation carina are less likely to lead to complications such as side branch compromise or occlusion. Lesions that are in the vicinity of a bifurcation, but in which the distance from the carina is more than the width of the nearest plaque edge which protrudes into the vessel lumen, are assigned the first suffix of C (for Close to the bifurcation). While such lesions are not true bifurcation lesions, assigning this connotation brings attention to the fact that intervention of such lesions can potentially lead to the need for further intervention involving the bifurcation itself if edge dissection or other complications arise. This class of bifurcation lesion does not need any further subgroup division and therefore is simply referred to as a BC lesion. II) Size of the branch vessels: When describing a bifurcation lesion it is important to take into account the diameter of both branch vessels. If one branch is less than 2 mm in diameter, it is generally considered to be small and not suitable for PCI. In such situations, the small branch can be ignored and stenting is performed in the larger vessel only. Although occlusion of these small vessels can occasionally lead to clinically important events such as prolonged chest pain, ECG changes, myocardial infarction or hemodynamic instability (if such occlusion leads to right ventricular infarction or papillary muscle dysfunction), most manifestations are not clinically severe. Bifurcation lesions in which one branch is less than 2 mm are referred to in the classification system as BN lesions (N = Nonsignificant), since they do not need to be treated from an interventional standpoint as true bifurcation lesions. These bifurcation lesions do not need further subgroup division due to low clinical importance. III) Size of the Proximal Segment: If both branch vessels are > 2 mm, and the lesion is closer than the width of the nearest plaque edge which protrudes into the vessel lumen, the lesion is considered to be a true bifurcation lesion for the purposes of PCI and requires further subdivision for clinical decision making. In such cases, the first suffix is used to denote the size of the proximal segment. From an interventional standpoint, the kissing stent technique may need to be used for optimal results. Use of the kissing stent technique, however, is limited to the treatment of bifurcation lesions that have a large proximal segment which is at least two-thirds of the sum of the diameters of both branch vessels.⁷ Therefore, the size of the proximal nondiseased segment provides important information for PCI decision making. If the proximal segment is large (defined as more than two-thirds of the sum of the diameters of both branch vessels), it is assigned the first suffix of L (for Large proximal segment), whereas if the proximal segment is small (less than two-thirds of the sum of the diameters of both branch vessels), it is assigned the first suffix of S (for Small proximal segment). Therefore, BL lesions are suitable for the kissing stent technique, while BS lesions are not. This important clinical distinction in the classification of bifurcation lesions is not addressed in any of the existing available classification systems. Assigning the second suffix. The second suffix describes the number of ostia that are diseased. When considering PCI of a bifurcation lesion it is important to recognize whether one or both ostia are involved. Disease of just one ostium may preclude the need to intervene on both vessels, but if both ostia are diseased, the interventional approach is different. Bifurcation lesions in which only one ostium is diseased allow for easier access to the other branch vessel after stenting. If both ostia are involved, however, a technique that would maintain access to both branch vessels during PCI would be the preferred technique if feasible (such as the kissing stent technique). If only one ostium is involved, however, it is important to denote whether it is the ostium of the parent/main vessel or the daughter/side branch vessel, since this will influence the approach to PCI. Lesions in which only the main vessel ostium is diseased are denoted by the second suffix of 1M (for 1 ostium involved which is the Main branch), while lesions in which only the side branch ostium is involved are designated as 1S. Lesions in which both ostia are involved are denoted by the second suffix of 2 (for 2 ostia involved). This classification is very simple, is clinically oriented and emphasizes the importance of ostial involvement which makes intervention involving bifurcation lesions more risky. For example, a BL2 lesion is a true bifurcation lesion with a large proximal vessel size suitable for kissing stenting and involvement of both ostia at the bifurcation. Assigning the third suffix. Another important consideration in the clinical classification of bifurcation lesions is the angle between the two bifurcating vessels. If the angle between the two vessels is > 70º, advancement of a stent can be difficult and the interventionalist needs to consider modifying the stenting technique in such a case. For example, two stents can often not be advanced simultaneously across a bifurcation lesion when the angle is > 70º, making the kissing stent technique difficult or impractical in such lesions. Lesions in which the angle between the two vessels is > 70º are designated by the third suffix of T (since they most resemble a “T”), and lesions in which the angle between the vessels is Assigning the fourth suffix. The fourth suffix is optional and is added to denote important clinical subsets of bifurcation lesions, such as those that are heavily calcified or involve the left main. The fourth suffix is added to the end of the existing conglomerate of suffixes after a hyphen. Calcification is a major risk for any intervention, and if a bifurcation lesion contains significant calcification, the fourth suffix of CA is added (for CAlcium). Lesions which involve the left main are denoted by the fourth suffix of LM (for Left Main). A BL2V-LM, for example, is a true bifurcation lesion with a large proximal vessel diameter, involvement of both ostia at the bifurcation, an angle between both vessels Bifurcational PCI techniques. With the introduction of drug-eluting stents, more complex lesions such as high-risk bifurcations are now being treated routinely by PCI. Multiple techniques for bifurcation intervention have been described elsewhere.^8–15 The current classification of bifurcational techniques is not standardized and can often be confusing. For example, the kissing stent technique is also known as “V” stenting.^7,12 Sometimes depending on the treatment order of the parent or side branch, the terminology of “reverse” is added to the technique which can cause more confusion.^16,17 Here, a simplified classification system for bifurcational PCI techniques is proposed which takes into account the specific bifurcation subset present. Such a system can serve as a method for easier communication amongst physicians and for the standardization of PCI-related research. This manuscript proposes the division of existing bifurcational PCI techniques into six simple categories. The optional prefix R can be added to an applicable PCI technique to designate that the technique was performed in a reverse fashion to improve communication between interventionalists. For example, R-CRT would describe a reverse crush stenting technique. The choice of any specific interventional technique, however, should be utilized at the discretion of the individual operator. Classification of Existing Bifurcational PCI Techniques I) OST = One Stent Technique: This is probably the simplest approach to BC and BN lesions. It is simple and can be changed to another technique if needed in the case of edge dissection or other complications occurring near the bifurcation. II) SBT = Stent with Balloon Technique: This technique uses a stent in the main branch and balloon angioplasty of the side branch. This technique is also very simple, but can be associated with a higher risk of side branch occlusion. BL1M or BS1M lesions are well suited for this technique. The side branch can be difficult to rewire, particularly in lesions where both ostia are diseased or in lesions with an angle between branches > 70º (such as BL2T or BS2T lesions). III) KST = Kissing Stent Technique: This technique involves simultaneous advancement of two stents which are positioned side by side into each vessel spanning the bifurcation, which creates a new carina proximal to the bifurcation. Other names have been used for this technique such is ‘V’ stenting,^7,18,19 This technique is advocated by some operators,⁷ but criticized by others. The major advantage of this technique appears to be the ability to maintain access to both branches at all times. However, an edge dissection could be very difficult to treat and the additional stent struts in the main vessel poses a theoretical risk of thrombosis, and could make rewiring of the bifurcation lesion difficult if restenosis in the bifurcation or a new distal lesion occurs. A very important anatomical requirement of this technique is the presence of a large proximal segment sufficient to accommodate the proximal ends of both stents. It is recommended that the proximal healthy segment should be at least two-thirds of the sum of the diameters of both branch vessels. Large angulations can also cause difficulty in advancing two stents simultaneously. BL2V lesions are better suited for the KST technique in comparison to BS2V, BS2T, and BL2T lesions. The other limitation of the kissing stent technique is the length of proximal disease involvement. The safety of creating an excessively long carina is not well established. IV) TST = T Stenting Technique: This technique involves the placement of two stents in a “T” fashion. This technique is referred to by various names in the literature such as “modified T technique” or “classic T technique”^12,14,15,20 and there are many variations. A recently described approach is the pullback, where a stent is placed in the smaller branch vessel and a balloon is placed in the larger branch vessel and inflated to low pressure. The stent is then pulled back to the ostium with protection of the larger branch vessel afforded by the low pressure-inflated balloon. After the stent is deployed, stenting of the larger branch vessel is then performed. It is also possible to stent the larger branch vessel first and then stent the smaller branch through the stent struts, but advancement of the stent into the smaller branch vessel can be difficult. There are several drawbacks to this technique. The ostium of the smaller branch vessel is “jailed” and can be difficult to rewire should final kissing balloon inflation be necessary or further interventions be needed to the smaller branch vessel in the future. In addition, the ostium of the smaller branch vessel can be incompletely covered by the stent which can predispose to restenosis. This technique can be used in bifurcation lesions where both ostia are involved, the proximal vessel is too small for the kissing stent technique such as BS2T or BS2V, or per operator expertise and preference based on the clinical scenario. Alternatively, the crushing stent technique can be used which is more complicated, but offers improved coverage of the smaller branch vessel ostium. V) CRT = CRush stenting Technique: The “crush technique,” pioneered by Colombo et al.,¹⁴ consists of advancing two stents simultaneously into both branch vessels but with nonsimultaneous deployment, such that a portion of one stent is crushed inside the proximal segment. A modification of this technique is described as the “reverse crushing technique.^16,17 At the conclusion, the branch vessel that received the crushed stent is rewired and a simultaneous kissing balloon inflation is then performed. This technique can be used to treat most bifurcation lesions. Steep angulations, however, such as in all “T” lesions (BS2T, BL2T, BS1MT, BS1ST, BL1MT, or BL1ST) could cause a problem when attempting to recross the side branch. In addition, the long-term consequences of having three layers of drug-eluting stent present in the proximal vessel are not well known. VI) CUT = CUlotte stenting Technique: The Culotte technique is also known as “trouser legs” or “Y” stenting.^12,20,21 This technique that was almost abandoned due to high restenosis rates is again gaining in popularity, as preliminary results with drug-eluting stents have been encouraging with low restenosis rates.²² This technique is useful as a bailout technique similar to the crush stent technique when a branch vessel is compromised unexpectedly after stenting the first branch vessel. With this technique, the operator usually stents the less angulated of the two branch vessels first, wires the other branch vessel through the stent struts next, and then stents the second branch vessel all the way back to the proximal edge of the previously deployed stent. The originally stented branch vessel is then rewired, and a simultaneous kissing balloon inflation is necessary in order to open up the stent struts covering the originally stented branch vessel. This technique can be useful in T or V lesions. If both ostia of the bifurcation are involved, this technique can pose a risk for branch vessel occlusion, making rewiring of the compromised branch vessel difficult or impossible. The goal of this classification is to simplify and foster a better understanding of the existing bifurcation lesion techniques in order to assist the clinician in decision making. Each of the techniques has individual characteristics which require the interventionalist to exercise clinical judgment and expertise before choosing a specific method. This description is not intended to recommend one particular technique over another, but rather to give examples of how the proposed classification system can be used to assist in the planning of a particular technique. For example, a BL2V lesion is suitable for PCI using the kissing stent technique (based on operator preference and experience), but if the proximal segment of the vessel has a very long lesion or is small (BS lesions), the use of the kissing stent technique (KST) could be risky regardless of operator preference. This classification system serves as a guide for operators engaging in bifurcation lesion intervention and does not address other nonbifurcational lesions which may coexist in the same vessel. In such circumstances, the interventional cardiologist must use his or her own experience to tackle each lesion based on anatomical complexity. Regardless of the other lesions present, however, the specific classification of the lesion involving the bifurcation portion of the vessel remains valid. A comparison of the coronary bifurcation classification system presented here with the four currently known classifications is shown in Table 3. A summary of some examples of interventional techniques for each of these lesion classifications is shown in Figure 2. Figure 3 shows a flow chart for suggested clinical decision making in the context of the coronary artery classification presented here. Figures 4 through 8 are some examples from our own experience in using the new classification of bifurcation lesions in combination with several different PCI bifurcation techniques. Figure 4 is a typical example of a BN (nonsignificant bifurcation) lesion which was successfully treated using the OST (one stent technique). Figure 5 is an example of a BS2V lesion (significant bifurcation lesion with a small proximal segment, involvement of both ostia, and an angle between the branch vessels 70º) and Figure 7 is an example of a BL2V lesion (significant bifurcation lesion with large proximal segment, involvement of both ostia, and an angle between branch vessels 8–11,20 Some of the classifications describe every detail of a bifurcation lesion with marginal clinical importance which leads to redundancy. In the classification system described by Sanborn,⁹ for example, there is no distinction in clinical decision making between Type II and Type IV lesions that both involve only one ostium. The same ambiguity in clinical decision making applies for Type I and Type III lesions which involve both ostia. The Duke classification system⁸ is similar to the Sanborn classification in that technical decision making is not significantly different between Type B and Type E lesions that involve one ostium, or Type C or Type F lesions. Similarly, Safian¹¹ Type IIIB and Type IV lesions and Lefevre¹⁰ Type 4a and Type 4b lesions are similar and should be classified as a single type of bifurcation lesion for clinical reasons. Technical decision making is also similar between Safian Type IA or IIIA lesions and Lefevre Type 1, Type 2 and Type 4 lesions. The nomenclature in these classifications is difficult to remember and does not classify lesions in the clinical context of currently employed PCI techniques. Conclusion This manuscript proposes a simplified classification system that is clinically oriented and can be easily remembered. This classification system is derived from the anatomic features of a bifurcation lesion and incorporates this information directly into the nomenclature. The system is composed of a single prefix to which up to four different suffixes are added. The nomenclature for true bifurcation lesions is straightforward and involves only two subgroups for each of the four suffixes. Each subgroup is distinguished based on clinically relevant features of the lesion in the context of currently employed PCI techniques. This manuscript does not attempt to recommend any specific technique or provide outcome data in this regard, but rather attempts to create a systematic simplified approach to the classification of bifurcation lesions which can be easily remembered and takes into account currently employed PCI techniques. Hopefully, adoption of this simple classification will facilitate memorization, assist in the selection of interventional techniques, and improve communication between clinicians and researchers. Acknowledgment. This manuscript is dedicated to my beloved father, Asgary Movahed Shariat Panahi, who has been my mentor and inspiration throughout my life.

1. Al Suwaidi J, Yeh W, Cohen HA, et al. Immediate and one-year outcome in patients with coronary bifurcation lesions in the modern era (NHLBI dynamic registry). Am J Cardiol 2001;87:1139–1144. 2. Al Suwaidi J, Berger PB, Rihal CS, et al. Immediate and long-term outcome of intracoronary stent implantation for true bifurcation lesions. J Am Coll Cardiol 2000;35:929–936. 3. Cervinka P, Stasek J, Pleskot M, Maly J. Treatment of coronary bifurcation lesions by stent implantation only in parent vessel and angioplasty in sidebranch: Immediate and long-term outcome. J Invasive Cardiol 2002;14:735–740. 4. Assali AR, Teplitsky I, Hasdai D, et al. Coronary bifurcation lesions: To stent one branch or both? J Invasive Cardiol 2004;16:447–450. 5. Colombo A, Moses JW, Morice MC, et al. Randomized study to evaluate sirolimus-eluting stents implanted at coronary bifurcation lesions. Circulation 2004;109:1244–1249. 6. Pan M, de Lezo JS, Medina A, et al. Rapamycin-eluting stents for the treatment of bifurcated coronary lesions: A randomized comparison of a simple versus complex strategy. Am Heart J 2004;148:857–864. 7. Sharma SK, Choudhury A, Lee J, et al. Simultaneous kissing stents (SKS) technique for treating bifurcation lesions in medium-to-large size coronary arteries. Am J Cardiol 2004;94:913–917. 8. Popma JJ, Leon MB, Ej T. Atlas of Interventional Cardiology. 1994. 9. Spokojny AM, Tm S. Strategic Approaches in Coronary Intervention. Philadelphia: Williams and Wilkins. 1996: p. 288. 10. Lefevre T, Louvard Y, Morice MC, et al. Stenting of bifurcation lesions: Classification, treatments, and results. Catheter Cardiovasc Interv 2000;49:274–283. 11. Safian RD. Bifurcation lesions. The Manual of Interventional Cardiology. 2001: p. 222. 12. Melikian N, Di Mario C. Treatment of bifurcation coronary lesions: A review of current techniques and outcome. J Interv Cardiol 2003;16:507–513. 13. Lefevre T, Louvard Y, Morice MC, et al. Stenting of bifurcation lesions: A rational approach. J Interv Cardiol 2001;14:573–585. 14. Colombo A, Stankovic G, Orlic D, et al. Modified T-stenting technique with crushing for bifurcation lesions: Immediate results and 30-day outcome. Catheter Cardiovasc Interv 2003;60:145–151. 15. Ge L, Iakovou I, Cosgrave J, et al. Treatment of bifurcation lesions with two stents: One year angiographic and clinical follow up of crush versus T stenting. Heart 2006;92:371–376. 16. Ormiston JA, Webster MW, El Jack S, et al. Drug-eluting stents for coronary bifurcations: Bench testing of provisional side-branch strategies. Catheter Cardiovasc Interv 2006;67:49–55. 17. Ormiston JA, Currie E, Webster MW, et al. Drug-eluting stents for coronary bifurcations: Insights into the crush technique. Catheter Cardiovasc Interv 2004;63:332–336. 18. Melikian N, Airoldi F, Di Mario C. Coronary bifurcation stenting. Current techniques, outcome and possible future developments. Minerva Cardioangiol 2004;52:365–378. 19. Gobeil F, Lefevre T, Guyon P, et al. Stenting of bifurcation lesions using the Bestent: A prospective dual-center study. Catheter Cardiovasc Interv 2002;55:427–433. 20. Louvard Y, Lefevre T, Morice MC. Percutaneous coronary intervention for bifurcation coronary disease. Heart 2004;90:713–722. 21. Chevalier B, Glatt B, Royer T, Guyon P. Placement of coronary stents in bifurcation lesions by the “culotte” technique. Am J Cardiol 1998;82:943–949. 22. Hoye A, van Mieghem CA, Ong AT, et al. Percutaneous therapy of bifurcation lesions with drug-eluting stent implantation: The Culotte technique revisited. Int J Cardiovasc Intervent 2005;7:36–40.