A New Proposed Simplified Classification of Coronary Artery Bifurcation Lesions and Bifurcation Interventional Techniques
- Volume 18 - Issue 5 - May, 2006
- Posted on: 8/1/08
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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 < 70º are designated by the third suffix of V (since they most resemble a “V”). T lesions can be particularly challenging during stenting since access to both branch vessels is not maintained throughout PCI. V lesions are most amenable to the kissing stent technique (if the proximal segment is large), while T lesions are often amenable to various “T” stenting techniques (which will be discussed later). As an example, a BL2V lesion is a true bifurcation lesion with a large proximal vessel suitable for kissing stenting, involvement of both ostia at the bifurcation, and an angle between the two branch vessels < 70º. This clinically relevant anatomical description of a bifurcation lesion is not part of any known currently available classification in the literature.
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 < 70º, and which involves the left main. A schematic diagram of the proposed classification system is shown in Figure 1.
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.