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State-of-the-Art Technique for Treatment of Bifurcation Lesions in the Drug Eluting Stent Era ("Crush Technique") : Characteristic Intravascular Ultrasound Findings for Optimal Stenting

Background

Percutaneous intervention (PCI) of coronary bifurcation lesion has been regarded as a challenging field in the stent era with technical difficulty to preserve side-branch (SB) and high angiographic restenosis rate (RR) more than 30-40%. In the era of bare-metal stents, double-stenting for both branches was used to ensure SB patency, but elective stenting of the SB has not improved the results over simple balloon dilatation.1-2 The introduction of drug-eluting stents (DES) have dramatically reduced the RR in simple coronary lesions, but data on treatment of bifurcation lesions are still double digits, mainly due to SB restenosis.3-4 This fact suggested incomplete coverage of SB ostium as main cause of restenosis. Therefore, when treating bifurcation with DES, complex approach (stenting of both branch) has been frequently used to guarantee a complete coverage of the SB ostium more than bare stents. The recent studies comparing a complex strategy (double-stenting) to a simple strategy (main vessel stenting and balloon dilation of the SB) showed that both strategies are equally effectve in terms of RR of 10-30% and major adverse cardiac events (MACE) of 15-20%.3-5 Although the DES implantation for bifurcation lesions showed more favorable results than bare-metal stents, double-digits figures of RR and MACE still may impose a considerable burden to the interventional physician. At this time, crush technique was newly invented and proposed as most appropriate approach to treat bifurcation lesion with DES if both branches need to be stented.6 Recently, intravascular ultrasound (IVUS) has been established as a valuable tool for assessment of accuracy of PCI, including the implantation of DES. Furthermore, IVUS may be particular useful for the treatments of complex lesions such as bifurcation and ostial lesions. At treating bifurcation lesions in DES era, the best technique to completely cover the side branch will be the name of game, for which IVUS is essential guide tool. In this section, we will elaborate the caveat of crush technique and advise the best ways for optimal stent deployment by using IVUS.

The Technique

Dr. Colombo recently reported new crush technique to treat bifurcation lesions using DES.6 The crush stenting technique, considered to be evolution of modified T stenting, was designed to overcome the incomplete coverage of the side-branch ostium. At first, two guidewires pass into both branches of the bifurcation, which then are dilated alternatively. After pre-inflation of both branches, a first stent is advanced to the side-branch, and a second stent is advanced to the main-branch. At positioning stents, the proximal marker of the side-branch stent should be positioned at least 3-4mm inside the main branch proximal to the carina of the bifurcation (Figure 1-A). Ensuring the appropriate position of the main-branch and side-branch stent, the side branch is stented first (Figure 1-B) and then balloon and guidewire in the side branch vessel are removed. After the side-branch stent deployment, the proximal part of this stent will protrude in the main-branch. The second stent is then deployed in the main branch, crushing the proximal part of first stent into the vessel wall (Figure 1-C). It is important to make sure that the proximal part of the main-branch stent should be located more proximal to the side-branch stent. If necessary, the final kissing technique can also be conducted additionally. For final kissing balloon dilatation, the side branch is rewired and balloon dilatation should be performed to reopen of the side branch. After final kissing, balloon and guidewire are removed from the both branches (Figure 1-D).6-7

Figure 1. Modified T stenting with crushing. A first stent is advanced into the side branch but not expanded, and a second stent is advanced into the main branch to cover fully the bifurcation (A). At this time, the proximal marker of this stent in the main vessel is always more proximal in the coronary tree than the proximal marker of the stent for the side branch. When the side-branch stent is appropriately positioned, the balloon is inflated and the stent is deployed (B). After stent implantation in the side branch, the delivery balloon and the wire are removed from the side branch. Then, the stent in the main branch is then expanded and the protruding struts of the stent implanted in the side branch are crushed against the wall of the main vessel (C). After final kissing if needed, guide-wires and balloons are removed from both branches (D).

The Caveat of crush technique

There are some important matters to consider for performing crush technique properly. First of all, at the time crush technique was first introduced, the final kissing balloon was provisional technique. After completion of this technique, immediate angiographic results were mostly acceptable and recrossing of the guidewire into side-branch seemed to be complex. That is the reason why final kissing technique was optional at first and is contributed to simplicity of this technique. But, recent in vitro and in vivo data showed that poor stent apposition and underexpansion of struts at the ostium of side-branch occurred, unless final kissing appropriately conducted.7-8 After all, final kissing balloon has become indispensable process to perform crush technique adequately. Also, recent clinical experience demonstrated that final kissing inflation was a crucial step in the crush technique with influence on clinical outcomes (Target vessel revascularization; 5.8% with final kissing vs 23.3% without final kissing in 86 patients with crush technique).9 Second, before final kissing, it is very important to make sure that protruded portion of side-branch stent within the main branch is completely crushed against the wall of the main vessel, as the name of this technique. Because suboptimal crush of side-branch stent will leave angiographically invisible dead space, if recrossing guidewire is introduced into gaps between the three layers of floating stents proximal to the bifurcation or gap between partially crushed stents and stent-uncovered vessel wall, it may cause stent distortion and catastrophic results that can give rise to acute or subacute thrombosis. Finally, to prevent underexpansion of the side-branch stent and distortion of the main-branch stent, application of different strategies for final balloon inflation according to different angles of bifurcation and selection of appropriate sized balloon are requisite for completeness of this procedure. Stent underexpansion is well-known cause of in-stent restenosis after DES implantation. As the angle of bifurcation is steeper, the degree of underexpansion of the stent at the ostium of the side branch will be larger after crush technique. This may not be corrected easily by simple final kissing technique. In experimental test using bifurcation phantom, Ormiston et al suggested that sequential side-branch and then main-branch postdilatation would be effective to solve this problem and finally to reduce the restenosis of side-branch ostium.7 Also, at final kissing, if smaller sized balloon than first used delivery balloon is applied to postdilate main-branch, it will cause distortion of the main-branch stent. This will be predisposing factor of in-stent restenosis or stent thrombosis of main-branch. It can be corrected by using proper sized main-branch balloon that is larger or at least the same diameter than the deployment balloon.

IVUS findings for optimal stenting with crush technique

Various studies have shown that IVUS guidance during stenting is an independent predictor of less abrupt stent closure, less periprocedural complication and less major adverse cardiac events, including a lower rate of repeat revascularization. It is no doubt that the IVUS guidance is particularly valuable in complex lesions, such as bifurcation lesions, ostial lesions, small vessel leisions, diffuse long lesions, calcified lesions, and coronary lesions in diabetic patients. In bare metal stents, even though ISR is mostly the result of intimal hyperplasia (IH), mechanical problems related to stent deployment procedures contributed to a significant minority of ISR lesions.10 Because DES dramatically reduced neointimal hyperplasia, mechanical problem regarding stent implantation (eg, lesion missing, gap, stent disconfiguration, and stent underexpansion) will be cause of majority of ISR in DES era. In this current situation, IVUS guidance to reduce mechanical problems is essential part to improve outcome of DES implantation. This can be equally applicable to crush technique to treat bifurcation lesions. IVUS can be helpful to confirm optimal stenting at each step and pay attention to previously mentioned caveats at the time of stenting with crush technique. At first, before rewiring into side-branch to expand the ostium of side-branch fully, it is necessary to ensure that there is no dead space proximal to the carina. IVUS may be useful to confirm it and decide to conduct additional postdilation of main-branch for complete crush (Figure 2).

Figure 2. IVUS findings before rewiring to side-branch. Proximal to the bifurcation, incomplete crush leave dead space, which can cause misleading of rewiring into side-branch (A). To identify crushed three layers of struts is key point before proceeding the next step (B).

Second, before final kissing, IVUS can judge that the opening of side-branch ostium is enough and determine whether additive side-branch dilation is needed or direct final kissing is possible. Lastly, after final kissing, IVUS may be mostly useful in verifying possible mechanical problems which can be underexpansion of main- or side-branch stents, dislodgement of main- or side-branch stents, stent-uncovered gap at the carina, incomplete coverage of side-branch ostium, distortion of main-branch stent caused by undersized main-vessel postdilation and inappropriate stent crush. Conclusively, IVUS will facilitate recognition of these mechanical problem and lead to proper reparative measures to counter it. Representative of multiple cross-sections of IVUS findings following successful crushing can be shown in Figure 3.

Figure 3. Final IVUS following successful stenting with crush technique. A; Proximal to the bifurcation, crushed three layers of struts can be visualized. B; In the initial portion of bifurcation, a double line of struts (each from main-branch and side-branch) is shown. C; In the midportion of bifurcation, wide-opened side-branch ostium can be detected. D; At the carina, fully expanded main- and side-branch stents are shown. E; Distal to the bifurcation, well-apposed and fully expanded main-branch stent can be founded.

Conclusion

Up to recently, crush technique is thought to be invincible at the treatment of bifurcation lesions in the DES era because of theoretical completeness and practical simplicity to cover the ostium of side-branch certainly. But there is no invention as perfect as originally suggested without amelioration in the real world. At stenting with crush technique, the optimization of this procedure is difficult to appreciate only on the angiogram, whereas IVUS can provides detailed, high-quality information about vessel wall and stent structs which permits accurate the assessment of stent expansion and apposition. In conclusion, exact insight into vessel and stent geometry provided by IVUS has been fundamental in developing and reforming this technique, by which we will anticipate single-digit restenosis rate in the bifurcation lesions.

Reference

  1. Al Suwaidi J, Berger PB, Rihal CS, Garratt KN, Bell MR, Ting HH, Bresnahan JF, Grill DE, Holmes DR Jr. Immediate and long-term outcome of intracoronary stent implantation for true bifurcation lesions. J Am Coll Cardiol. 2000;35(4):929-36
  2. Yamashita T, Nishida T, Adamian MG, Briguori C, Vaghetti M, Corvaja N, Albiero R, Finci L, Di Mario C, Tobis JM, Colombo A. Bifurcation lesions: two stents versus one stent-immediate and follow-up results. J Am Coll Cardiol. 2000;35(5):1145-51
  3. Colombo A, Moses JW, Morice MC, Ludwig J, Holmes DR Jr, Spanos V, Louvard Y, Desmedt B, Di Mario C, Leon MB. Randomized study to evaluate sirolimus-eluting stents implanted at coronary bifurcation lesions. Circulation. 2004;109(10):1244-9
  4. Tanabe K, Hoye A, Lemos PA, Aoki J, Arampatzis CA, Saia F, Lee CH, Degertekin M, Hofma SH, Sianos G, McFadden E, Smits PC, van der Giessen WJ, de Feyter P, van Domburg RT, Serruys PW. Restenosis rates following bifurcation stenting with sirolimus-eluting stents for de novo narrowings. Am J Cardiol. 2004;94(1):115-8.
  5. Pan M, de Lezo JS, Medina A, Romero M, Segura J, Pavlovic D, Delgado A, Ojeda S, Melian F, Herrador J, Urena I, Burgos L. Rapamycin-eluting stents for the treatment of bifurcated coronary lesions: a randomized comparison of a simple versus complex strategy. Am Heart J. 2004;148(5):857-64
  6. Colombo A, Stankovic G, Orlic D, Corvaja N, Liistro F, Airoldi F, Chieffo A, Spanos V, Montorfano M, Di Mario C. Modified T-stenting technique with crushing for bifurcation lesions: immediate results and 30-day outcome. Catheter Cardiovasc Interv. 2003;60(2):145-51
  7. Ormiston JA, Currie E, Webster MW, Kay P, Ruygrok PN, Stewart JT, Padgett RC, Panther MJ. Drug-eluting stents for coronary bifurcations: insights into the crush technique. Catheter Cardiovasc Interv. 2004;63(3):332-6
  8. Colombo A. Bifurcational lesions and the "crush" technique: understanding why it works and why it doesn't-a kiss is not just a kiss. Catheter Cardiovasc Interv. 2004;63(3):337-8
  9. Airoldi F, Stankovic D, Orlic D, Chieffo A, Calino M, Montorfano M, Mikhail G, Michev I, Vitrella G, Di Mario C, Colombo A. The “crushing” technique for bifurcation lesions: immediate and mid-term clinical outcome. Abstract from ACC 2004
  10. Castagna MT, Mintz GS, Leiboff BO, Ahmed JM, Mehran R, Satler LF, Kent KM, Pichard AD, Weissman NJ. The contribution of "mechanical" problems to in-stent restenosis: An intravascular ultrasonographic analysis of 1090 consecutive in-stent restenosis lesions. Am Heart J. 2001;142(6):970-4.

Fuente: Angioplasty SummitM.D Focus review

Ultima actualizacion:16 de Diciembre de 2006

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