Journal Of Indian College Of Cardiology

REVIEW ARTICLE
Year
: 2020  |  Volume : 10  |  Issue : 3  |  Page : 105--110

Double kissing crush and nano crush stenting in left main coronary bifurcation lesions: Besting the rival techniques!


Debabrata Dash 
 Department of Cardiology, Aster Hospital, Dubai, UAE

Correspondence Address:
Dr. Debabrata Dash
Zulekha Hospital, Al Zahra Street Al Nasserya, P.O. Box: 457, Sharjah
UAE

Abstract

Percutaneous coronary intervention of left main (LM) bifurcation can be technically demanding and is often associated with significant in-stent restenosis in contemporary practice. The heterogeneity of these lesions makes it difficult to establish a consensus as to the best interventional strategy. The provisional one-stent approach has shown a more favorable outcome than two-stent technique in terms of both efficacy and safety. In complex LM bifurcation lesions, double kissing has demonstrated its superiority over culotte and provisional-T in terms of restenosis making it one of the most performed techniques. On the other hand, the nano-crush technique has recently become part of the repertoire of two-stent techniques, providing evidence that the use of ultrathin-strut stents and very minimal crush would be beneficial for both the physiological and rheological properties of the complex LM bifurcations, leading to a lower rate of thrombosis and restenosis at both side branch and true carina. Finally, the newest generation of ultrathin-strut stents is gaining a reputation for its safe and effective use in this scenario thanks to an improved design with increased expansion rate capable of LM treatment up to 5–6 mm diameter. The modern crush techniques, such as double-kiss-crush and nano-crush, are providing excellent results on mid- and long-term follow-up, suggesting that minimal crushing obtained using ultra-thin stents is an excellent way to obtain surgical-like outcomes in the treatment of complex LM bifurcation disease.



How to cite this article:
Dash D. Double kissing crush and nano crush stenting in left main coronary bifurcation lesions: Besting the rival techniques!.J Indian coll cardiol 2020;10:105-110


How to cite this URL:
Dash D. Double kissing crush and nano crush stenting in left main coronary bifurcation lesions: Besting the rival techniques!. J Indian coll cardiol [serial online] 2020 [cited 2021 Feb 24 ];10:105-110
Available from: https://www.joicc.org/text.asp?2020/10/3/105/304374


Full Text



 Introduction



Significant unprotected left main (LM) disease constitutes approximately 5%–7% of patients undergoing coronary angiography,[1] with 80% of the lesions involving bifurcation. Randomized clinical trials (RCTs) have demonstrated a higher rate of repeat revascularization after the percutaneous coronary intervention (PCI) compared with coronary artery bypass grafting (CABG), but a lower incidence of cerebrovascular events; no differences were reported in overall major adverse cardiovascular events (MACEs).[2] Marked technical innovations in PCI and stent technology have emboldened the interventionists to expand the feasibility of the LM PCI. The treatment of ostial and mid-shaft has shown more favorable outcomes with minimal mortality and long-term complications compared with distal LM bifurcations.[3] Despite there are several RCTs evaluating the optimal stenting strategy in non-LM bifurcations, there is a paucity of data on optimal stenting strategy of LM bifurcation. Although the provisional stent (PS) technique has been the default strategy, two-stent techniques are opted more frequently for the complex LM bifurcation.[4],[5] The amount of metal layers at both the carina and bifurcation angle after two-stent techniques appear to be an important issue to achieve favorable short- and long-term outcomes.[6],[7] Recently, double-kiss (DK)-crush has demonstrated its superiority over rival stent techniques. Even more recently, the nano-crush technique has become part of the repertoire of two-stent techniques, providing evidence that the use of ultrathin-strut stents and very minimal crush is beneficial for both the physiological and rheological properties of the complex LM bifurcations, leading to a lower rate of thrombosis and restenosis at both side branch (SB) and true carina.[8],[9]

 Anatomy and Rheology



The LM tends to have a high plaque volume because of its large caliber. It also is prone to calcification. The plaque and carina shift and incomplete stent expansion are critical to technical considerations in stenting of the LM.[4]

The elastic recoil and high restenosis following balloon angioplasty is explained by the greater elastic content of this artery.[5],[6],[7],[8],[9],[10] Representing the largest coronary bifurcation, LM PCI techniques are driven by potential complications to the SB, usually the left circumflex (LCX) coronary artery such as acute occlusion and long-term adverse outcomes of target vessel failure and target lesion revascularization (TLR). In LM bifurcation, atherosclerotic process is accelerated primarily in the area of low wall shear stress (WSS) along the lateral wall extending distally on the myocardial walls of the left anterior descending (LAD) and LCX arteries.[11] The carina is minimally involved or spared. There is interaction between flow dynamics, rheology, and geometry. The local hemodynamic factors play an important role in the genesis of atherogenesis, atherosclerosis, and thrombosis. A long LM (≥10 mm) is more prone to pressure drop and lower WSS contributing to plaque formation.[12] Three-dimensional computational fluid dynamics model demonstrates the development of atherosclerotic plaque at sites of bifurcation where low WSS, oscillating WSS, flow division, and stasis appear.[13] Medina 1.0.0 has the greatest risk of plaque proliferation. Medina 1.1.0, 1.1.1, and 1.0.1 increase average WSS and hence resists atherogenesis better.[13] The current strategy to treat distal LM bifurcation by extending the main branch (MB) stent into the proximal LAD is supported by continuous extension of plaque from LM to the proximal LAD artery in 90% of cases.[14] The LM typically has a diameter ranging between 4.5–6 mm in a majority of cases, while the LAD and LCX have diameters ranging from 3.5–4.5 mm to 3.0–4.5 mm, respectively. This propels the interventionists to be acquainted with large diameter stents with expansion properties.[15]

 Crafting a Stent Strategy



The LM bifurcation PCI significantly differs from non-LM bifurcation in that there is the larger area of myocardium at jeopardy; there is less room for error during the procedure; the vessels are larger; the SB is as important as the MB with regard to the size and territory of the distribution, and the interventionist is less likely to accept a suboptimal result in the SB.[16]

The choice of strategy depends on vessel and lesion characteristics (plaque distribution, the diameter of the branches, the angle between them, and anatomy of the SB). The PS is a one-stent strategy allowing the deployment of a second stent if required (T, T, and protrusion [TAP], culotte technique). More complex lesions may require two-stent strategy (T-stenting, TAP, Nano-crush, DK crush, culotte, V-stenting) at the outset.[17] To stratify the best stenting strategy, the LM bifurcation is classified as simple or complex on the basis of the DEFINITION (Definitions and Impact of Complex Bifurcation Lesions on Clinical Outcomes After PCI Using Drug-Eluting Stents study) criteria.[18] The LM bifurcation is designated as simple if SB diameter stenosis is <70% and lesion length <10 mm. This is observed in 75% of cases, and a single PS approach is the treatment of choice. A complex LM bifurcation lesion has the SB diameter stenosis and lesion length of >70% and >10 mm, respectively. A simple lesion may become complex with the presence of two of the following 6 minor criteria[17] (1) moderate-to-severe calcification; (2) multiple lesions; (3) LAD-LCX bifurcation angle >70; (4) the MB reference vessel diameter <2.5 mm; (5) thrombus-containing lesion; and (6) the MB lesion length >25 mm. A complex bifurcation lesion generally requires a two-stent strategy even if PS is easier and more effective in the long term.[19] The decision for specific types of complex two-stent strategy depends on the basis of the vessel size, bifurcation angle and severity, and length of the lesion of the major SB. Even if there is a lack of consensus, and a few data, on the optimal complex two-stent technique, DK-crush stenting can be applied in almost all types of complex LM bifurcation effectively [Figure 1].[15] The take-off angle of the LCX is >90° in >70% of the patients. The size discrepancy and take-off angle of LCX has great ramifications for LM bifurcation stenting.[20] A pre-PCI wide bifurcation angle has predicted the worse outcomes after the culotte and classic crush techniques.[21],[22],[23] However, in the DK-CRUSH-III (Double Kissing Crush Versus Culotte Stenting for the Treatment of Unprotected Distal LM Bifurcation Lesions III) study, DK crush was associated with lower rates of MACEs even if the bifurcation angle between the LAD and LCX was >70° compared with the culotte stenting technique.[24]{Figure 1}

 Need for Double-Kiss-Crush and Nano-Crush Technique



Whereas a PS technique enables excellent stent strut apposition and warrants preservation of the MB patency, the technique often fails to protect the SB ostium with the risk of late focal restenosis. On the other hand, complex techniques such as crush, culotte, or V techniques have been designed to provide continuity in the stent coverage between the SB and the MB. Gaps in-stent scaffolding and focal ostial restenosis remain major drawbacks of the T-stenting technique (particularly for angles <50 degrees).[25] The culotte and crush techniques are usually employed for a large SB with a relatively low bifurcation angle (<70°). In the culotte technique, a first stent is deployed in one of the branches, usually across the SB to the MB, and the MB is then rewired through the strut of the first stent and dilated with a noncompliant balloon. The second stent is implanted in the MB, followed by final kissing balloon inflation (KBI).In the crush technique, a stent is first positioned in the SB and retracted to protrude 1–2 mm into the MB. The protruding portion of the SB stent is then crushed against the wall by the deployment of the MB stent. The procedure is completed with the rewiring of the SB and final KBI. Both the SB and MB stents are deployed either simultaneously or sequentially to form a double-barrel stent with a neocarina in the MB in the V stenting technique. This technique does not require recrossing of the stent but raises concerns over the potential risk of stent thrombosis (ST) induced by the double neocarina in the MB.[5],[17] In the TAP technique, the MB is stented jailing the SB guidewire. The KBI is performed after rewiring the SB. The proximal edge of the SB stent is positioned 1–2 mm inside the MB stent and deployed at high pressure with a deflated balloon kept in the MB stent. Then, the SB balloon is slightly retrieved and aligned to the MB balloon, followed by the final KBI. The technique poses the risk of misplacing the SB stent and producing a neocarina, extensively protruding into the MB lumen.[5],[17]

Complex techniques are, however, limited by the significantly higher rate of malapposition of struts.[26],[27] A final KBI is necessary to completely expand the stents and to prevent stent distortion in both the MB and SB. Unfortunately, the final KBI immediately after the classic crush technique is difficult or sometimes impossible to do, resulting in worse outcomes during follow-up. An unsatisfactory and incomplete final KBI (20%–25% after classic crush) is associated with a high rate of ST and in-stent restenosis (ISR). The bench test attributes this kissing failure to stent platform, irregular and small stent cell, severe distortion of the MB stent, and the irregular overlapping of three layers of stent struts.[28] DK-crush technique [Figure 2] introduced by Chen et al. employs the KBI twice to overcome limitations of the classical crush technique.[29] It includes the following steps: the SB stenting with 2–3 mm protrusion into the MB, balloon-crush of the SB stent, first SB rewiring through proximal stent cell, first KBI, the MB stenting followed by the proximal optimization technique (POT), second rewiring of the SB through the proximal stent cell, final KBI and the re-POT [[Figure 3] (Parts I and II)]. It is important to rewire the SB from the proximal stent cell to prevent abluminal wiring and the SB ostial gap.{Figure 2}{Figure 3}

Different from DK-Crush, in which the ostial circumference is completely covered by the SB stent, in the nano-crush, the ostium is covered at the carina by the SB stent strut and at the opposite site of the carina by the MB struts opened by the POT into the SB ostium, providing complete circumferential coverage, especially in the case of tight angles, in which the ostial coverage might be incomplete at the carina. Among these two stenting techniques, one significant difference is represented by the most appropriate stent to the implant. In DK-crush, virtually every kind of stent can be used, while the nano-crush has been created to fit with the concept of less metal in the carina, and hence, the ideal stent should have the thinnest struts possible, at least 60–80 μ.[8]

 Will Double-Kiss-crush and Nano-Crush Supplant the Rival Stent Techniques?



In clinical practice, however, complex LM bifurcation stratified by DEFINITION criteria, are unlikely to be successfully addressed because of the SB ostial restenosis (PS), superposition of two layers (culotte) or three layers (crush) of the stent struts in the MB. The rates of malapposition are increased by the superposition of two layers (culotte) or three layers (crush) of the stent struts in the MB [le 1].[6] Multiple layers of stent struts at the carina and in the proximal MB may be the nidus for ST.[30] Neocarina after TAP and V stenting cause juxtaposition of a large number of struts, which increase the risk of ST [Table 1]. The shortcomings of the crush technique have been overcome by the introduction of double kissing. After the balloon crush of the implanted SB stent, there are two layers of the stent struts from the SB ostium to the MB. Thus, first, KBI can optimize the distorted SB stent and leave only one layer of stent struts at the SB ostium, which facilitates the second kissing after the MB stenting. Another advantage of DK-crush over classical crush is that the first KBI rebuilds the shape of bifurcation anatomy by minimizing repeated distortion of the SB ostial stent. This technique theoretically gives the largest amount of laminar flow both in the MB and the SB. This innovative DK-crush technique compared to classical crush is shown to have a significantly shorter procedural time, lower contrast usage, and a higher final KBI rate (100% vs. 70%; P < 0.01), leading to an improved angiographic result with residual stenosis.[31] The technique has been compared to other two stent techniques as well as to provisional stenting and has been reliably shown to be superior in all studies.[32] DK-CRUSH-I study demonstrates a significant reduction of ST, ISR, and MACEs in patients with true bifurcation lesions compared to the classical crush.[33] TLR is significantly lower after DK crush for complex bifurcation lesions at 5-year follow-up, compared to provisional T stenting in DK-CRUSH-II trail.[34] There are several important factors in this trial that need to be highlighted. (1) All the lesions are complex true bifurcational; (2) The SB is significantly diseased with a mean length of 15 mm (much longer than in other randomized trials where the majority are <10 mm; (3) Final KBI has been archived in 100% of cases treated with DK-crush. Therefore, it can be stated without hesitation that DK-crush is a superior strategy in complex LM bifurcation lesions and should be considered in preference to PS. DK-CRUSH V trial demonstrates the best evidence so far on the treatment of LM bifurcation, showing that DK-crush is superior to PS.[35] The absolute benefit for the DK-crush is greatest in roughly 30% of the patients with complex LM bifurcation. The target lesion failure is 5.0% in patients treated assigned to DK-crush and 10.7% with provisional stenting. Compared with PS, DK-crush also results in lower rates of target vessel myocardial infarction, definite or probable ST, clinically driven TLR and angiographic ISR.[35] The author strongly feels that higher use of DK-crush technique would have been significantly more favorable for the PCI arm in NOBLE (CABG versus Drug Eluting Stent Percutaneous Coronary Angioplasty in the Treatment of Unprotected LM Stenosis)[36] and EXCEL (Evaluation of XIENCE Everolimus-Eluting Stent versus CABG Surgery for Effectiveness of LM Revascularization) study.[37] DK crush bested the culotte method in patients with high-risk LM bifurcation in the DKCRUSH-III randomized trial.[23] This is a high quality, well-powered study with 100% follow-up. More than twice as many patients in the culotte group experienced MACE at 1 year compared with the DK-crush group (16.3% vs. 6.2%, P < 0.05). Even 3 years, clinical outcomes were in favor of DK-crush compared to culotte stenting.[24],[38]{Table 1}

Significantly high rates of TVR are the main drivers of the high MACE rate in the culotte technique. A bench study reports that a “napkin” or a gap is usually exits at SB ostium after culotte stenting, leading to failure to fully scaffold the ostial SB and resulting in increased ISR, TLR, and ST.[39] Compared to the culotte technique with two stent layers in the proximal part of the MB, the DK-crush has a single stent layer in the MB. Furthermore, the subsequent deployment of the stent in the MB is not restricted by cell-opening as in culotte, where a cigar-belt effect may increase the malapposition risk and inadequate vessel expansion in both the ostium of the MB and SB.[40] In the DK-crush technique, only the SB may be affected by suboptimal recrossing, whereas in culotte, there remains the risk of rewiring through a stent strut cell opposite the carina during wiring of both the MB and SB. The DK-crush strategy is straightforward to be employed by all interventionists, reliable and seems to be effective for all bifurcation angles. Furthermore, the data from the DK crush trials are uniformly positive. The currently ongoing EBC MAIN (European Bifurcation Club LM Study) trial would shed light on further information comparing provisional stenting with culotte, DK-crush, TAP techniques with a Medina 1,1,1 or 0,1,1 LM lesions (NCT02497014). DEFINITION II study (NCT02284750) is a prospective, multinational, randomized, endpoint-driven trial to compare the benefits of the two-stent technique with PS for complex coronary bifurcation lesions.[41]

As suggested by Rigatelli et al., using computed fluid dynamics, the culotte and other techniques that leave large amounts of metal at the carina unfavorably impacts the bifurcation rheology, causing lower WSS in the SB. Indeed, low WSS is a potential substrate for restenosis and thrombosis.[8],[9] To achieve a more physiological flow profile, there should ideally be less metal coverage in the carina side and full metal coverage in the area opposite of the carina and the ostium of the SB. DK-Crush and Nano-crush are likely to work differently in terms of lowering WSS areas depending on the LM bifurcation. The distribution of metal and the coverage of the carina by the struts strictly depend on the angles. Sharp angles tend to increase the amount of metal at the carina, especially when a generous portion of the SB stent is protruding and should be crushed, whereas if the portion of the stent to be crushed is shorter and the angle is wider, the amount of the metal would be less and coverage might be even incomplete. Hence, the use of ultrathin stent struts in DK-crush or other techniques is likely to improve both safety and long-term outcomes.[8],[9] However, this needs to be confirmed in RCTs. The day is not far when the DK-crush and Nano-crush technique supplant all other rival stenting techniques in LM bifurcation lesions.

 Conclusion



Although LM PCI gains respect as an alternative to CABG, the treatment of complex LM bifurcation lesions continue to pose considerable challenges and require expertise to achieve optimal results. In such cases, the complex strategy of two-stent technique would provide a more reliable strategy as evidenced by both clinical and virtual studies. The modern crush techniques such as DK-crush and nano-crush are promising techniques for producing better mid- and long-term clinical outcomes, suggesting that minimal crush resulting from the use of ultra-thin stents is an excellent way to obtain CABG like outcomes in the treatment of complex LM bifurcation lesions. The author personally acknowledges that these techniques require training, experience, and attention to procedure detail, including careful rewiring of the SB. The interventionists should have done > 300 PCIs for the previous 5 years under their belts, including at least 20 LM PCIs per year. Nonetheless, the procedure is highly successful when it can be accomplished.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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