A Review of Double Kissing Crush Stenting in Coronary Bifurcation Lesions : Cardiology Discovery

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Special Issue for Coronary Bifurcation Lesions, Guest Editor, Shaoliang Chen: Hot Topics

A Review of Double Kissing Crush Stenting in Coronary Bifurcation Lesions

Kwan, Tak W.1,*; Lin, Patricia2

Author Information
doi: 10.1097/CD9.0000000000000058
  • Open

Abstract

Introduction

Many studies have reported that coronary bifurcation lesions account for up to 20% of all lesions in percutaneous coronary intervention (PCI).[1,2] For bifurcation lesions of the distal left main (LM) artery, it may be as high as 70% in patients referred for bypass surgery or other interventions.[3] Percutaneous intervention of bifurcation lesions remains one of the most challenging procedures in interventional cardiology, as it is associated with higher rates of adverse cardiac outcomes. Based on the COronary BIfurcation Stenting (COBIS) II study, the side branch (SB) occlusion rate from bifurcation PCI was reportedly 8.4%.[4] In patients with SB occlusion, the rate of major adverse cardiac events (MACEs) was 12.3%, with a peri-procedural myocardial infarction (MI) rate of 2.1%, and a cardiac death rate of 3.7%.[5] Therefore, different interventional techniques have been investigated in an attempt to decrease the complication rate. Many reports have supported provisional stenting (PS) as the most optimal approach of percutaneous intervention in bifurcation lesions.[6,7] This approach is done by using a single stent in the main branch (MB) across the SB. If the SB is compromised, an extra stent is placed in the SB using either the T-stenting or the T-stent at protrusion (TAP) technique. However, T-stenting is associated with inadequate SB ostial coverage, while TAP may have excess protrusion into the MB, which therefore causes excessive turbulent flow. Nonetheless, in most bifurcation lesions, PS has been shown to be superior to the 2-stent technique and is currently the most favored approach by most interventionists worldwide.[7–9] Although there are many studies that have demonstrated PS in bifurcation coronary lesions as the preferred technique over the systemic 2-stent technique, PS is still associated with about 30% of crossover to the 2-stent technique.[10] In certain circumstances, complex lesions with large SB may benefit from a planned 2-stent strategy from the beginning of bifurcation stenting.

To provide an acceptable amount of stent coverage of the bifurcation, the aim of any bifurcation stenting technique is to accomplish a satisfactory final minimum stent area in the MB and SB, which translates into appropriate and reliable long-term clinical outcomes. Thus, Colombo et al[11] developed a classic crush technique in the early 2000s, which uses an SB stent followed by an MB stent crush. This crush technique was designed to combat the most common limitations of T-stenting, which include occlusion and restenosis of the ostial SB that can occur because of incomplete stent coverage of the ostial SB. However, a final kissing balloon inflation (KBI) must be performed to decrease the cardiac event rate, by fully apposite the SB stent and achieve an adequate stent area which subsequently lowers the stent thrombosis and restenosis rates in this technique.[12] This crush technique evolved over time with the aim to improve the final KBI success rate and limit the amount of metal struts in the MB. To optimize the PCI crush technique for bifurcation lesions, Chen et al[13,14] first described the double kissing crush (DK crush) stenting technique, which has been shown to provide a more reliable final KBI than the classic crush stenting technique. In recent times, an abundance of scientific and clinical evidence has been obtained to demonstrate the effectiveness and safety of this specific 2-stent technique.[14–27]

How does DK crush differ from the classic crush stenting techniques?

A significant downside of the classic crush stenting technique is the failure to recross the SB crushed stent strut to perform the final KBI.[12] Even for an experienced operator, re-access of the SB for the final KBI after a crush stent is not straightforward. As in the classic crush, the wire needs to navigate through 3 layers of stent struts with one of the MB stent layers and 2 of the crushed SB stent layers. The DK crush stent technique was invented to improve the success rates of the final KBI by requiring an additional first KBI. The additional first KBI is performed after the balloon crush of the SB stent. This is done to clear the crushed stent struts away from the SB ostium to increase the likelihood of successful recross after MB stenting for the final KBI. As the name suggests, the 2 steps of KBI and crushing of stents function to achieve better clinical outcomes for coronary bifurcation lesions than classic crush stenting.

Contemporary DK crush stenting techniques

Many operators do not experience good clinical results from the DK crush technique, because the necessary steps for optimal performance are not completed. To attain a superior clinical advantage over classic crush, all the steps of DK crush stenting must be followed meticulously. These include: (1) adequate preparation of MB and SB, especially calcium in the ostial SB, is essential to fully expand the stents. (2) Protrusion of SB stent should be limited to 2 mm. The less triple metal is better. (3) Aim to fully apposite the SB stent to the ostium; proximal SB optimization[28] occurs by pulling back the SB stent balloon or by using a non-compliant balloon inflating the SB stent to high pressure. This technique can prevent the wire from going underneath the stent strut during re-wiring the SB stent for KBI. (4) First complete crush of the SB stent using a short but large MB balloon with high pressure. The SB balloon and wire are then removed. (5) Re-wire the SB through the proximal stent strut and avoid the wire passage at the distal margin of the crushed SB stent. If the kissing inflation is performed with the wire under the stent strut, the SB stent will be deformed. (6) First KBI using a 1:1 non-compliant balloon. The first KBI is the most important step in DK crush to ensure full expansion of the SB ostium and reduce 2 layers of stent struts to 1 layer at the SB. (7) MB stenting. (8) Proximal optimization technique (POT) facilitates the re-wiring of SB and balloon recross. (9) Re-wiring of SB in the proximal-to-mid stent portion. (10) Final KBI corrects MB and SB stents distortion. (11) Final POT corrects the MB stent distortion from an elliptical deformation shape into a round shape, which thus reduces the MB stent malapposition. Examples of these steps are summarized in an in vitro model [Figure 1].

F1
Figure 1::
In vitro model of represented steps in DK crush stenting. DK: Double kissing; KBI: Kissing balloon inflation; MV: Main vessel; POT: Proximal optimization technique; SB: Side branch.

Lately, several clinical studies have examined the nanocrush technique and expanded into the space of DK crush stenting.[29–31] This nanocrush technique aims for minimum protrusion of SB stent ranging from 0.2 to 2.7 mm, depending on the bifurcation angle, and it hypothesizes a complete SB stent coverage without excessive metals in the MB. However, these studies are limited by the small non-randomized sample size without long-term clinical data. Presently, it is still unclear how this nanocrush technique will become a main component of DK crush stenting.

Clinical trials and randomized studies

Based on a significant study by Ge et al,[12] the final KBI was only successful in 116 patients out of the 181 consecutive patients who underwent classic crush stenting (64%). As an important strategy to improve the final KBI success rate, in 2005, Chen et al[13] first investigated 20 patients with bifurcated coronary lesions who were treated with DK crush stenting and compared this technique to another 20 patients who were treated with classic crush stenting. The re-crossing success rate of the SB and final KBI was 100% in the DK crush arm versus 80% in the classic crush arm.

Since then, the DK crush trials have investigated complex bifurcations coronary lesions in both the LM and non-LM arteries. Thus far, 4 completed randomized controlled trials that focus on all bifurcations including LM and non-LM lesion have been performed, namely DK-Crush I, DK-Crush II, DK-Crush III, and DK-Crush V.[14,16–18] Additionally, 3 DK crush follow-up studies have also been conducted: DK-Crush II: 5 years, DK-Crush III: 3 years, and DK-Crush V: 3 years.[19–21] Three physiologic or intravascular ultrasound (IVUS) studies for assessment during bifurcation stenting (DK-Crush IV, DK-Crush VI, and DK-Crush VII) have also been performed.[32–34] DEFINITION II, a randomized controlled study, enrolled complex patients and compared the 2-stent strategy with majority DK crush stenting and provisional stenting.[35] Several other meta-analyses were conducted recently[22–25]; the details of all these studies have been summarized below.

DK-CRUSH I

DK-Crush I (study comparing the DK crush with classical crush for the treatment of coronary bifurcation lesions) is the first randomized study that compares the DK crush (n = 155) and classic crush (n = 156) techniques, and has demonstrated the significant benefit of treating LM and non-LM bifurcations with DK crush over classic crush with true bifurcation lesions.[14] The composite primary end point of MACE including cardiac death, MI, and target lesion revascularization (TLR) at 8 months was significantly lower in the DK-crush group (11.4%) than the classic crush group (24.4%) (P = 0.02). The TLR-free survival rate was greater in the DK-crush group (89.5%) than the classic crush group (75.4%) (P = 0.002). Interestingly, the final KBI was remarkably successful in 100% of the DK crush group and in only 75% with the classic crush group.

DK-CRUSH II

The DK-Crush II (a randomized clinical study comparing DK crush with PS for treatment of coronary bifurcation lesions) study randomized 370 patients with non-LM bifurcations.[16] The primary end point of MACE (cardiac death, MI, TLR) at 12 months showed no difference between these 2 groups. However, DK-crush stenting demonstrated a significantly lower revascularization rate than PS with TLR of 6.5% and 14.6%, respectively (P = 0.017).

After 5 years, the trend of the DK crush stenting group for MACE was better than that for the PS group (15.5% vs. 23.8%), but this difference was not significantly different (P = 0.051). Moreover, the rates of TLR between the DK crush stenting group and PS group was significantly different through the 5-year follow-up period (8.6% vs. 16.2%, respectively) (P = 0.027). The rate of definite and probable stent thrombosis was 2.7% in each group (P = 1.0).

DR-CRUSH III

The DK-Crush III (comparison of DK crush vs. culotte stenting for unprotected distal LM bifurcation lesions) study randomized 419 patients with distal LM disease when treated with DK crush stenting (n = 210).[17] The results demonstrated a significantly lower MACE rate in those treated with DK crush stenting than those treated with culotte stenting (n = 209). The primary endpoint of MACE (cardiac death, MI, target vessel revascularization (TVR)), which was driven by TVR rates after 1 year, occurred more significantly in the culotte stenting group (16.3%) than in the DK-crush group (11.0%) (P < 0.05). Overall, in-stent restenosis in the SB ostium was more prevalent in the culotte group (12.6%) versus the DK-crush group (6.8%) (P = 0.037). Interestingly, the bifurcation angle of >70° showed DK crush stenting to be more superior than culotte stenting.

In this cohort of patients, the rate of MACE in the culotte stenting group and the DK crush stenting group was 23.7% and 8.2%, respectively (P < 0.001), which was associated with increased MI (8.2% vs. 3.4%, respectively; P = 0.037) and TVR (18.8% vs. 5.8%, respectively; P < 0.001) at the 3-year follow-up.[20] Therefore, there was a definite stent thrombosis rate of 3.4% in the culotte group and 0 in the DK crush group (P = 0.007).

DR-CRUSH IV

DK-Crush IV (hemodynamic changes of fractional flow reserve after DK crush and provisional stenting technique for true bifurcation lesions) studied hemodynamic changes in bifurcation stenting lesions.[32] Post intervention fractional flow reserve (FFR) was obtained in 38 DK crush patients and 37 PS patients. DK crush stenting was associated with superior improvement of FFR when compared with PS.

DK-CRUSH V

DK-Crush V (DK crush vs. PS for LM distal bifurcation lesions), a significant study that examines the LM bifurcation lesion, randomized over 482 patients with true distal LM bifurcation lesions to DK crush (n = 240) or provisional stenting (n = 242).[18] At 1 year, this study showed that the composite endpoint of target lesion failure (TLF) was significantly lower in the DK crush group (5.0%) versus the PS group (10.7%) (P = 0.02). DK crush also resulted in lower rates of target vessel myocardial infarction (TVMI) than PS (0.4% vs. 2.9%, respectively, P = 0.03), and lower definite or probable stent thrombosis (0.4% vs. 3.3%, respectively, P = 0.02). Clinically driven TLR tended to be less frequent with DK crush than with PS (3.8% vs. 7.9%, respectively, P > 0.05). The absolute benefit of DK crush versus PS was seen in both complex and simple bifurcation lesions, but it was relatively greater in complex lesions.

At 3 years, TLF occurred significantly less in patients in the DK crush stenting group (8.3%) than in those in the PS group (16.9%) (P = 0.005), mainly driven by increased TVMI (1.7% vs. 5.8%, respectively; P = 0.017) and TLR (5.0% vs. 10.3%, respectively; P = 0.029).[21] The definite or probable stent thrombosis rate was significantly lower in the DK crush stenting group than the PS group (0.4% vs. 4.1%; P = 0.006). Furthermore, there was a significant reduction of the primary and secondary endpoints for patients with complex lesions.

DK-CRUSH VI

DK-CRUSH VI (randomized comparison of FFR-guided and angiography-guided PS of true coronary bifurcation lesions) randomized 320 patients with provisional stenting strategy in bifurcation lesions to angiographic-guided or fractional flow reserve (FFR)-guided SB intervention.[33] There was no significant difference in the 1-year clinical outcome when performing PS using angiographic guidance or FFR guidance for SB intervention. However, the angiographic-guided group was associated with increased intervention of the SB when compared to the FFR-guided group (63.1% vs. 56.3%, respectively; P = 0.07). The 1-year composite MACE rate was 18.1% in both groups (P = 1.00). The 1-year TVR and stent thrombosis rates were 6.9% and 5.6% (P = 0.82) and 1.3% and 0.6% (P = 0.56) in the angiographic and FFR-guided groups, respectively.

DEFINITION II

In the DEFINITION II study, 653 patients with pre-defined complex bifurcation lesions were randomized to pre-systemic 2-stent strategy (77.8% patients with DK crush stenting) or PS.[35] This study concluded that a planned 2-stent strategy in patients with pre-defined complex bifurcation lesions significantly reduced the incidence of 1-year TLF as compared to PS. At the 1-year follow-up, TLF was significantly better in the 2-stent group versus the PS group (6.1% vs. 11.4%, respectively; P = 0.019). It was largely driven by more TVMI (P = 0.025) and clinically driven TLR (P = 0.049) in the PS group.

Meta-analysis

Several meta-analyses consistently demonstrated that DK crush was associated with fewer coronary events and complications than bifurcation techniques.[22–25] In a recent network meta-analysis, Di Gioia et al[23] analyzed 21 randomized studies of 5711 patients, which showed that the DK-crush stenting technique was associated with less occurrence of MACE than those treated using PS mainly driven by a reduction in TLR. More specifically, no significant differences among techniques were observed in cardiac death, MI, and stent thrombosis. In non-LM bifurcations, DK crush stenting also reduced MACE. A clinical benefit of the 2-stent techniques was observed over PS in bifurcation with SB lesion length >10 mm. In another network meta-analysis by Chiabrando et al,[24] who studied 4285 patients in 14 studies, DK crush stenting and mini-crush stenting were shown to be associated with less MACE or complications when compared to other techniques including PS. Chen et al[22] published a recent meta-analysis which also suggested the clinical benefits of lower MACE from DK crush stenting than the other 2-stent strategies.

The most important results from the meta-analysis are described below. The 2-stent techniques, compared to PS, significantly reduced the primary endpoint, in addition to rates of TVMI, TVR, and TLR. Moreover, the DK crush stenting technique significantly decreased the primary endpoint and TLR when compared to other 2-stent techniques. Among all bifurcation stenting techniques, there were no significant differences of all-cause mortality, cardiovascular death, and stent thrombosis.

Limitations of the DK-crush stenting technique

Because the final KBI can improve clinical outcomes in bifurcation lesions that underwent 2-stent techniques, the failure to perform a final KBI should be reflected as an unsuccessful procedure. The DK crush stenting technique not only has a better SB ostium stent coverage and apposition but it also can guarantee a 100% final KBI success rate when compared to other bifurcation stenting techniques. With its strong randomized data favoring better clinical outcomes, the DK crush stenting technique ends up being the best technique to treat complex coronary bifurcation lesions. However, not every surgeon can achieve the same impressive results as those in the randomized studies. Operators using the DK crush stenting technique must be fully familiar with every step of the procedure, and they must recognize the associated limitations and challenges. Undoubtedly, it is more laborious with multiple steps, but it is necessary to ensure good quality outcomes for reaching the first and final KBI. The DK crush stenting technique requires a much steeper learning curve than provisional stenting and is nowadays considered to be an Achilles’ heel for conquering bifurcation stenting worldwide.

Trouble shooting of common clinical scenarios

How are vessels prepared for DK crush stenting?

In cases of significant calcium in the MB and/or SB, we prefer imaging in both vessels, then deciding upon the preparation with non-compliant balloon, cutting balloon, atherectomy, or intravascular lithotripsy. If the vessel fails to be fully dilated, it should not be placed with a stent [Figure 2].

F2
Figure 2::
Inadequate preparation of vessels. (A) Arrow shows inadequate preparation of SB resulting in an unexpanded SB stent; (B) Rotational atherectomy of the left main artery to left anterior descending artery and left circumflex artery for severe calcification. SB: Side branch.

How is the SB wired for KBI?

Distal wiring of the SB crush stent may deform the stent. If distal wiring is suspected, the guide wire must be withdrawn. We recommend POT and re-wiring to the proximal cell of the SB crush stent complex. In rare occasions, we might need a special microcatheter, like an angulated microcatheter or twin-pass catheter, to wire the SB crush stent [Figure 3].

F3
Figure 3::
Wiring into the SB using different techniques. (A) Wiring to the SB using an angulated microcatheter; (B) Wiring to the SB using a double lumen microcatheter; (C) Wiring of the SB crushed stent, avoiding distal stent wiring. SB: Side branch.

What are the techniques to advance a balloon through the crushed SB stent if it cannot cross from the beginning?

First, it is imperative to ensure the SB wire is not under the stent strut. Then, by using anchoring balloon technique and inflating a balloon in the MB, it will help to advance the balloon to the crushed SB stent. If it still cannot be advanced, a smaller balloon with step-up to a 1:1 appropriate vessel size can be attempted [Figure 4].

F4
Figure 4::
The white arrow shows the balloon inflated in the main vessel. The black arrow shows the balloon advancing to the crushed side branch stent.

Should we perform DK crush stenting in a small vessel SB?

We do not recommend any SB vessel diameter <2.5 mm, as the rate of occlusion is high. From the DK Crush II, III, and V trials, the SB diameter must be >2.5 mm [Figure 5].

F5
Figure 5::
The black arrow shows a small side branch vessel occluded after double kissing crush stenting.

What must be done if the SB stent is deformed?

This happens when the guidewire passes distally under the distal crushed SB stent complex and then the balloon is inflated. Once it is deformed, it is almost impossible to repair it [Figure 6].

F6
Figure 6::
After wiring to the crushed side branch stent distally, a balloon was inflated and caused side branch deformation. (A) Left circumflex artery stent was deformed (black arrow). (B) Stent boost image with deformed stent of left circumflex artery (black arrow).

Is an acute angle a problem for DK crush?

There is no exclusion of all the DK crush trials from bifurcation angle. In fact, for a bifurcation angle > 70°, the DK crush stenting performed better than the culotte stenting as shown in the DK-Crush III study [Figure 7].

F7
Figure 7::
Double kissing crush stenting in a 90° bifurcation angle. (A) Left main distal bifurcation lesion with a bifurcation angle of 90°; (B) Final result after double kissing crush stenting in a 90° bifurcation angle distal to the left main lesion.

Future directions

There are several promising tools that can enhance these technological and clinical outcomes. Specifically, IVUS and optical coherence tomography (OCT) have shown an established benefit in stent optimization including the assessment of stent malposition, stent under-expansion, and stent-edge dissection. These have an additional benefit of assessing the guidewire position when re-crossing the SB.[36] The ULTIMATE (Intravascular Ultrasound Versus Angiography-Guided Drug-Eluting Stent Implantation) trial has already demonstrated the benefit of IVUS in clinical outcomes by optimizing coronary interventions.[37] During IVUS/OCT evaluation in DK crush stenting, MB and/or SB stents under-expansion remains one of the significant predictors for stent failure that should be identified by IVUS and subsequently, this should be corrected by high-pressure balloon inflation. In addition, this can give invaluable information about adequate balloons, stents sizing, and position of guidewire crossing. DK-CRUSH VIII is an ongoing randomized controlled trial for DK crush stenting using IVUS or angiographic guidance in 556 patients with complex bifurcation coronary lesions.[38] The results of this trial are eagerly awaited, as they have the potential to address critical questions regarding optimal DK crush stenting.

Notably, all of these DK crush clinical trials were performed at high-volume centers by operators who are highly experienced with the DK crush stenting technique. It is important for all operators to be familiar with the different steps to achieve good outcomes. There is a need to shorten the learning curve. We believe regional training courses collaborated by different societies and meetings may be the first step. In addition, bifurcation stenting simulation and hands-on training by experienced proctors should be followed. Furthermore, DK crush stenting is rapidly evolving ever since its introduction in 2005. To evaluate the outcomes, data regarding the latest DK crush technique should be collected.

Conclusions

Despite being a more complex technique, DK crush has become popular worldwide for the treatment of coronary bifurcation lesions owing to the large amount of data from randomized controlled trials, increasing favorable scientific information, and widespread clinical experience since its introduction in 2005. Based on all the available evidence, the DK crush technique is superior when compared to the PS technique for complex bifurcation lesions, with a significant reduction in MACE, TVMI, and rates of revascularization. The DK crush stenting provides the best evidence-based approach to complex bifurcation lesions especially LM bifurcation lesions. Thus, the DK crush stenting technique has attained a class IIb recommendation in the 2018 European clinical guidelines for revascularization of LM coronary artery true bifurcation lesions after documenting its efficacy.[39] Further research should explore the role in improving the operators’ experiences and clinical outcomes by using IVUS, OCT guidance, as well as shortening the learning curve. Particularly, operators should follow all of these crucial steps as this complex procedure continues to be an area of unprecedented challenges.

Acknowledgments

We thank Dr. Shaoliang Chen and Dr. Junjie Zhang for their design of the in vitro model of Figure 1.

Funding

None.

Conflicts of interest

None.

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Keywords:

Coronary artery disease; Double kissing crush; Provisional stenting; Bifurcation

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