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- ↵∗Reprint requests and correspondence:
Dr. Antonio Colombo, EMO-GV Centro Cuore Columbus, Via Buonarroti 48, 20145 Milan, Italy.
Ever since percutaneous coronary intervention (PCI) was first undertaken, bifurcation lesions, which account for up to 20% of all PCIs (1), have presented a technical challenge (2). The optimal strategy for the management of bifurcation lesions has been the subject of intense investigation, with single stent (or provisional) strategies being compared with side branch (SB) protection and 2-stent strategies (3). Leaving the 2-stent strategy aside, when a provisional strategy is opted for, an important decision that needs to be made is whether to place a wire in the SB to facilitate access in case of severe compromise or total occlusion. The 2 extreme options would be to perform wire protection of all SB or in only a select minority. Therefore, the ability to have a readily available angiographic tool to predict SB occlusion during bifurcation stenting is both attractive and very welcome. Ideally, this information should allow the operator to more accurately select the SB that needs protection, which would maximize resource and time utilization without compromising safety. An important concept that needs to be highlighted at the beginning is that SB protection can be performed either by preventative stenting or by wire protection alone. Depending on the appearances of the SB following main vessel (MV) stenting, with a wire in the SB, one could opt to: 1) do nothing at all; 2) perform SB balloon dilation; or 3) crossover to stent implantation.
In this issue of JACC: Cardiovascular Interventions, Dou et al. (4) established a novel score system, RESOLVE (Risk prEdiction of Side branch OccLusion in coronary bifurcation intervention), to evaluate the risk of SB occlusion in coronary artery bifurcation intervention. From a cohort of 7,007 consecutive patients that underwent PCI over a 6-month period, 1,545 patients with 1,601 bifurcation lesions were identified who were defined as having coronary artery narrowing adjacent to or involving the origin of a significant SB. Importantly, as the authors point out, the definition of an important SB was on the basis of the functional importance placed on the lesion rather than its reference diameter. Patients were excluded if they underwent elective SB stenting before MV stenting; 1,200 lesions were used in the construction of the risk model, and the remaining 401 lesions were used to test and validate the model.
The first observation we would like to highlight is that 290 patients (18.8%) presenting with bifurcations underwent elective SB stenting. The reasons for the choice of this strategy in this patient group have not been reported, and it is also unclear if intravascular imaging techniques were used to determine an initial provisional stenting strategy (5,6). However, it does demonstrate that, in certain instances, there are clear indications for SB stenting with no uncertainty with regards to the best interventional strategy. We will not consider these scenarios in our further discussion.
A number of findings of the study warrant further consideration. We assume, even if not stated, that wire protection of the SB was performed sparingly. SB occlusion occurred in 118 bifurcations of the 1,601 included in the initial analysis (7.37%) and resulted in permanent occlusion in 98 cases (83%) and, thus, myocardial injury. What would have been the outcome if a wire had protected the SB in these patients? In this patient cohort, 14 SBs would have required protecting to possibly prevent 1 SB occlusion. Fundamentally, the objective of this study is to reasonably lower the number of patients in whom SB protection is required by better selecting individuals at the highest risk of occlusion. Again, it is important to stress that protection of the side branch does not always equate to preventative stenting, but the presence of a wire in situ across the SB (even if jailed by the MV stent) in the setting of occlusion can facilitate recrossing and is usually feasible for subsequent stent implantation if required.
Although the risk score developed by the authors is interesting, we doubt that operators will try to calculate the specific score routinely prior to or during a procedure. However, further examination of the characteristics of the SB that occluded provides important information with regard to defining “high-risk” lesions and optimizing management strategy. The authors found that a high plaque burden (Medina classification 1, 1, 1), Thrombolysis In Myocardial Infarction flow grade before stenting, inadvertent dissection of the SB after pre-dilation of the MV, and a small SB diameter in relation to the MV (MV:SB >2) were all risk factors for occlusion. Interestingly, the severity of stenosis, and not lesion length, was important in determining risk of occlusion. It is important here to differentiate between the requirement to stent a long lesion in a large SB (which would have been excluded in this study) and a severe SB stenosis that may only require wire protection, pre-dilation, and occasional provisional stenting. Finally, contrary to intuition, an SB with an angle closer to 90° or larger had a higher risk of occlusion, which suggests mechanistically that SB occlusion may be caused more frequently by plaque shift as opposed to carina shift, which is likely to be more relevant in the setting of a narrow bifurcation angle.
In this study, the majority of the SBs that occluded did not have a protection wire placed at baseline and did not undergo pre-dilation prior to MV stenting. With regard to the latter point, although routine pre-dilation of an SB is not recommended and may lead to unnecessary dissection, when the SB has a severe ostial lesion, pre-dilation may be important and valuable in maintaining patency of the vessel (7).
In conclusion, there is no “one-size-fits-all” strategy for the optimal management of bifurcation lesions. The important message that this study provides is that all SBs do not require wire protection. Although provisional stenting is the preferred strategy if possible (8), in the presence of “high-risk” features as defined by this model, there should be a very low threshold to protect the SB prior to MV stent implantation. The risk of wire placement is easily offset by the knowledge that successful restoration of normal flow is unlikely after occlusion of the SB occurs, with resultant myocardial necrosis and worse patient outcomes.
↵∗ Editorials published in JACC: Cardiovascular Interventions reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Interventions or the American College of Cardiology.
Both authors have reported that they have no relationships relevant to the contents of this paper to disclose.
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