Provisional Approach Is the Default Strategy

There are now seven randomized studies available comparing a provisional approach of implanting one DES (1S) in the MB only versus a two-DES (2S) approach of implanting a DES on both the MB and SB of the bifurcation, the results of which are summarized in Table 10-1 and Figure 10-2 . It is apparent from these data that routine stenting of both branches offers no clear advantage over a provisional strategy of stenting the MB only with balloon angioplasty of the SB, with regard to restenosis in the main or side branches or in repeat bifurcation revascularization. A 2S approach is associated with procedures that are longer, with more fluoroscopy time and contrast volumes and a higher rate of procedure-related biomarker release. Importantly, none of these studies showed that elective double stenting of the bifurcation is associated with higher revascularization, follow-up MI, or stent thrombosis rates. Interestingly, the most recent of these studies (DKCRUSH-II) is the first and only randomized trial to suggest that double stenting may be superior to provisional stenting and associated with a lower rate of restenosis and repeat revascularization. In this study, 370 true bifurcations were randomly assigned to treatment with either provisional stenting or a modification of the crush technique, the DK (double-kissing) crush. The DK crush was associated with a reduction in restenosis, especially of the SB (4.9% vs. 22.2%, p < 0.001) and TLR (4.3% vs. 13%, p = 0.005) but not in MACE (10.3% vs. 17.3%, p = 0.07). How do we reconcile the contradictory findings of the DKCRUSH-II study with those of the other six bifurcation studies? In our opinion, this study reconfirms the importance of the bifurcation technique, and optimization of the final result (in this case, a refinement of the standard crush technique) with a 2S approach is directly related to long-term outcomes. Nevertheless, we see no rationale to make a procedure more complex when similar immediate and medium-term follow-up results can be obtained with a simpler approach.

Clinical outcomes in the seven randomized trials comparing one- versus two-stent strategy, utilizing drug-eluting stents. 1S , Single stent; 2S , two stents; MACE , major adverse cardiac events; TLR , target lesion revascularization.

These randomized bifurcation studies provide us with the evidence that the provisional approach should be the default strategy in most bifurcations. However, we should not incorrectly interpret them as stating that all bifurcations must be treated with a provisional approach, as complex or high-risk bifurcations were not well represented in these trials. As seen in Table 10-1 , patients included in these RCTs had moderately sized SBs with focal ostial lesions of moderate severity, and patients with long and/or severe SB stenoses or large SBs were largely excluded. Also, other important anatomic features, such as the myocardial territory supplied by the SB, the angle of the SB, and the presence or absence of distal SB disease, were not provided in these trials. In an attempt to resolve these shortcomings, there are two other randomized trials about to be published or near completion. In the Nordic-Baltic Bifurcation Study IV, Kumsars randomized true bifurcations with large SBs (≥2.75 mm) to provisional SB stenting or a 2S approach. A 2S approach was associated with a longer procedure and a nonsignificantly lower rate of MACE (1.8% vs. 4.6%, p = 0.09) and TLR (1.3% vs. 3.2%) as compared to the provisional approach. However, once again these data may not be applicable to more complex bifurcations, as SBs with lesions >15 mm were excluded. Hopefully, the European Bifurcation Club Two (EBC-TWO) trial that has randomized true bifurcations (with SBs of >2.5 mm and lesion length >5 mm) to provisional or culotte stenting will provide us better data in regard to more complex bifurcations (ClinicalTrials.gov Identifier: NCT01560455).

Thus, although the default strategy for most bifurcations should be the provisional approach, we should continue to individualize decision making based on the patient’s individual anatomy, as there are bifurcation lesions where two stents (main and side branch stenting) need to be implanted as intention to treat due to the characteristics of the lesion and the distribution of the SB. Not all bifurcations can be treated with one technique, but rather the technique should be matched to the individual bifurcation anatomy, guided by the available data as well as by personal experience.

Two Stents Can Be Selectively Implanted As Intention to Treat or Crossover from Provisional

The distinction between a provisional approach and electively implanting two stents is that, in the 1S approach, the operator may be willing to accept a suboptimal result in the SB, provided TIMI (thrombolysis in myocardial infarction) flow is normal and the SB has limited clinical relevance regarding territory of distribution. However, how do we define a suboptimal result in the SB? It is important to note that a major difference among the eight randomized trials in Table 10-1 was the definition of a suboptimal result in the SB. This definition has a major impact on both the crossover rate from a 1S to 2S strategy and the restenosis rate in SBs treated with a provisional strategy. In the Sirius Bifurcation study, a residual stenosis of >50% in the SB was considered unacceptable, which explains the very high crossover rate of 51.2%. In contrast, in the Nordic study, the residual SB stenosis was irrelevant and the SB had to remain open with TIMI >0 flow. This clarifies why the highest (19.2%) SB restenosis rate with a 1S approach was observed in this study. Although it may be satisfactory to accept a suboptimal result with TIMI 1 flow in a small obtuse marginal branch, such a result is not acceptable when treating a distal left main bifurcation or a bifurcation involving a large diagonal branch. In examining the recent CACTUS, Bad Krozingen, and DKCRUSH-II bifurcation studies, a more realistic figure is that in about 20% of bifurcations treated with a provisional strategy, a second stent will have to be implanted on the SB.

The major difference between an elective 2S approach and crossover to 2S from a 1S approach is that in the former, the SB is stented first. This may be appropriate in complex bifurcations where the risk of SB occlusion with MB stenting is high, such as those with more severe disease, longer lesions, wider angles that are difficult to rewire or that have a dissection after predilatation. Although the presence of a large plaque burden at the bifurcation can be associated with SB ostial deterioration or occlusion after MB stent implantation, even in the absence of baseline SB ostial disease, the presence of SB disease increases this risk. A number of studies have shown that the risk of SB occlusion increases with the severity of SB disease. Aliabadi et al. showed that the risk of SB occlusion was 14% to 27% for SBs with ostial stenosis >50% as compared to 1% to 4% in SBs with minimal or no disease. Furukawa et al. showed that the risk of SB deterioration (final TIMI ≤2) was more common in SBs with ostial disease ≥50% (20.8% vs. 6.1%, p = 0.049) and in longer lesions. Similarly, Chaudhry et al. demonstrated that the risk of SB compromise increased with increased SB ostial stenosis severity (for every 10% increase in SB stenosis severity, the risk of SB compromise increased by 23%) and calcification (46% vs. 26%, p = 0.06). A criticism of these studies is that they are old and may not reflect current advances in techniques and devices. However, Hahn et al. recently studied the predictors of SB occlusion that occurred in 187 (8.4%) of 2227 bifurcation lesions. On multivariable analysis, independent predictors of SB occlusion were preprocedural percentage diameter stenosis of the SB ≥50% and proximal MV >50%, SB lesion length, and acute coronary syndromes. Of 187 occluded SBs, flow was restored spontaneously in 26 (13.9%) and by SB intervention in 103 (55.1%) but not in 58 (31.0%).

However, an important change that has occurred in clinical practice is the understanding that in SBs without high-risk features, the operator could cross over to 2S if necessary (i.e., significant residual stenosis or flow-limiting dissection). The reasons for crossover depend on the size, the severity of residual disease, and the myocardial territory of the SB. All of these features are best assessed by a physiological evaluation as discussed in the next section. There are a number of bifurcation techniques that can be performed as crossover as discussed later in the chapter, but we prefer the T-stenting and small protrusion (TAP) technique because of its simplicity and that it is associated with excellent long-term outcomes. We evaluated the long-term outcomes of this technique in 95 patients who underwent SB stenting with the TAP as a crossover from the provisional approach. TAP stenting was successful in all patients and was associated with a TLR rate of 5.1% and no stent thrombosis at 3-year follow-up.

Residual SB Stenosis After the Provisional Approach Is Often Not Significant

As the provisional approach has now become the gold standard, important questions are the cause, significance, and management of a residual stenosis at the ostium of the SB. There has been considerable debate as to whether the appearance of a new stenosis or aggravation of an existing stenosis at the SB ostium after MB stenting is due to plaque shift or carina shift. Historically, it has been suggested that SB compromise during PCI is the result of snowplowing of plaque over the SB ostium, that is, plaque shift, especially in bifurcations with a shallow SB angle. However, pathologic evaluation and IVUS studies have shown that although atherosclerosis develops frequently at the bifurcation, it is often located opposite to the flow divider, that is, opposite to the origin of the SB. This led to the hypothesis that has subsequently been demonstrated on IVUS that SB compromise after MB stenting may be due to carina shift rather than plaque shift (see Figure 10-3 for an example of carina shift).

Example of carina shift. Angiographic and IVUS images of an LMCA bifurcation showing an unobstructed circumflex ostium (A) before stenting and an ostial narrowing (B) after stent implantation from the LMCA to the LAD. The IVUS images (C) demonstrate there is an alteration in the location and geometry of the carina (arrow) . The carina is shifted toward the side branch, and this shift results in an eccentric luminal narrowing of the SB ostium (D); a three-dimensional image such as with optical coherence tomography will probably show that this narrowing occurs only in one single plane while the total lumen dimensions remain functionally adequate.

A recent study by Koo et al. of IVUS evaluation after MB stent implantation showed the following: (1) a significant increase in the vessel and lumen volume index in both the proximal and distal segments of the MB, (2) a significant decrease in the plaque volume index in the proximal segment of the MB, and (3) no change in the plaque volume index in the distal segment of the MB after stenting. These results suggest that the lumen increase in the distal MB is primarily due to enlargement of the vessel and not plaque shift, supporting the concept that part of the luminal narrowing of an SB after stenting the MB is explained by carina shift. However, in the proximal MB, the plaque area changed significantly after stent implantation, particularly in the region closest to the ostium of the SB. Although plaque shift to the SB ostium was not observed directly, these data provide indirect evidence of plaque shift from the proximal segment of the MB into the SB ostium after main vessel stent implantation. Thus both plaque shift from the MB and carina shift contribute to the creation and aggravation of an SB ostial lesion after main vessel stent implantation. Carina shift will occur if the bifurcation angle is less than 90° when full MB dilatation is performed. Although carina shift may be prevented by selecting the MB stent diameter according to the distal MB diameter, the operator should not compromise optimal MB dilatation to avoid carina shift.

Additionally, there appears to be increasing evidence that trying to get an optimal angiographic result with minimal residual stenosis in the SB may not be physiologically important. This concept is especially important in smaller SBs, where the majority of angiographically significant SB lesions have been demonstrated to be not functionally significant by fractional flow reserve (FFR) analysis. Koo et al. performed FFR measurements on 94 jailed SB lesions after stent implantation on the MB. No lesion with a ≥50% and <75% stenosis had an FFR <0.75. Among 73 lesions with >75% stenosis, only 20 lesions were functionally significant, and among those with >95% stenosis, only 14 out of 25 had FFR values <0.75. Furthermore, smaller SBs are less likely to result in angina if a residual stenosis is left untreated or if restenosis occurs. Indeed, FFR may be the most physiological and evidence-based method to guide the decision as to whether a jailed SB with a residual stenosis should be treated. Koo et al. evaluated the FFR in 91 jailed SBs (RVD: 2.3 ± 0.3) after MB stenting and if treatment based on whether the FFR was functionally significant would impact clinical outcomes. Only 30% of all jailed SB lesions had an FFR <0.75, with 96% of all SBs successfully accessed with pressure wire. The functionally significant SB lesions were treated with kissing balloon inflation, which resulted in 92% (23/25) of these lesions having an FFR >0.75. At 6-month follow-up, 48% of SB lesions had a stenosis >75% but only 8% had a functionally significant FFR. However, this approach is more time consuming, costly, at times technically challenging (rewiring the jailed SB with a pressure wire), and not associated with better clinical outcomes than an angiography-guided approach (MACE: 4.6% vs. 3.7%, p = 0.7). Nevertheless, this study does confirm that kissing inflation is effective in treating functionally significant SB stenoses caused by carina or plaque shift and that many moderately sized jailed SBs with a residual stenosis may be treated conservatively or only with kissing inflation rather than stenting.

Kissing Balloon Inflation or High-Pressure Individual (SB & MB) Postdilatation Should Always Be Used When Implanting Two Stents and Optionally When Implanting One Stent

Final kissing balloon inflation (FKBI) allows SB ostium treatment and apposition of the MB stent struts on the SB ostium. It also enables correction of stent distortion and inadequate apposition in the MB. However, FKBI increases procedural complexity and may result in stent ovalization, proximal dissection when balloons are inadequately positioned, and even suboptimal deployment of the proximal stent segment. There is uncertainty as to whether FKBI is mandatory when a provisional approach is used. Theoretically, and from benchmark studies, FKBI has the advantage of opening stent struts that potentially can scaffold the SB ostium, correcting MB stent distortion and proximal expansion caused by SB balloon dilatation through the MB struts, and facilitate future access to the SB. There is also concern that stenting across a bifurcation without opening the stent struts into the SB results in “malapposed” struts across the SB ostium that are not endothelialized. There are now two clinical studies that address whether FKBI should be routinely performed after the provisional approach. In the Nordic-Baltic Bifurcation Study III, 477 patients with bifurcation lesions undergoing main vessel stenting were randomized to FKBI (n = 238) or no FKBI (n = 239). The 6-month MACE rates were 2.1% and 2.5% (p = 1.0) in the final kissing and no-final kissing groups, respectively. At 8 months, the rate of angiographic restenosis of the entire bifurcation lesion was 11.0% versus 17.3% (p = 0.11), 3.1% versus 2.5% in the MB (p = 0.68), and 7.9% versus 15.4% in the SB (p = 0.039), in the final kissing versus no-final kissing groups, respectively. The lower restenosis rate in the SB was due to the efficacy of FKBI in reducing angiographic restenosis in true bifurcation lesions, where the SB restenosis rate was 7.6% versus 20.0% (p = 0.024) in the final kissing and no-final kissing groups, respectively. Similar results were obtained in the CORPAL-KISS study that compared the incidence of 1-year clinical events in patients with bifurcation lesions that had been treated with a simple approach who were randomized to either a simultaneous FKBI or an isolated SB balloon postdilation. The angiographic data and immediate results were also similar in both groups. Target lesion revascularization was required in 7 patients (3%): 5 from the FKBI group and 2 from the non-FKBI group. The incidence of MACE at 1 year (death, TLR, or acute myocardial infarction) was similar in both groups: 11 (9%) from the FKBI group and 7 (6%) from the non-FKBI group (p = NS). These studies support the simple approach of only MB stenting without routine FKBI in nontrue bifurcation lesions. However, in true bifurcation lesions that are treated with the provisional approach, FKBI should be considered, as it is associated with improved angiographic outcomes in the SB. Also, as previously mentioned, FKBI is very effective in improving the FFR in functionally significant SB lesions. Finally, it should be remembered that FKBI should only be performed in bifurcations in which the SB is suitable for stenting should dissection occur. Indeed, to reduce the risk of SB injury, compliant balloons should be avoided, as they may result in underexpansion of the MB stent and significant overexpansion of the SB ostium. Indeed, in a study by Mylotte et al., systematic kissing balloon postdilatation with noncompliant balloons was associated with favorable procedural results, a low (6%) rate of crossover to SB stenting, and a promising 12-month MACE rate of 4%.

In contrast to the provisional approach, FKBI has been repeatedly demonstrated to reduce late loss and restenosis, especially at the SB ostium, and it has now become standard in the performance of all double stenting techniques. FKBI is not only important in correcting stent distortion and expansion but is especially significant in fully expanding the proximal stent, in particular when treating the LMCA bifurcation where the diameter of the distal LMCA is usually much larger than the diameters of the LAD and LCX. The initial data supporting the importance of FKBI with a 2S approach come from bench-testing by Ormiston with three different stent platforms (BX Velocity, Cordis, a Johnson & Johnson Company, Miami Lakes, Florida; Express II, Boston Scientific, Natick, Massachusetts; and Driver, Medtronic, Minneapolis, Minnesota) utilizing the crush technique. FKBI with appropriately sized SB and MB postdilatation was needed to fully expand the stent at the SB ostium, to widen gaps between stent struts overlying the SB (facilitating subsequent access), and to minimize stent distortion. The importance of FKBI with the crush technique has also been confirmed in a clinical study that demonstrated significant reductions in restenosis (11.1% vs. 37.9%) and late loss (0.32 mm vs. 0.52 mm) of the SB in the group treated with FKBI. Similarly, a subanalysis of the CACTUS trial showed that FKBI was associated with better angiographic results and lower MACE rates when complex stenting was performed, and similar results were observed when using a simpler provisional SB stenting technique.

However, it is imperative that FKBI with a 2S approach be performed with an optimal technique for it to be effective, including the use of adequately sized noncompliant balloons (i.e., a diameter equal to greater than the implanted stent), high pressure inflation, two-step kissing inflation, and correction of proximal distortion by the overlapping balloons with a short, noncompliant balloon. The two-step kissing inflation consists of high-pressure balloon inflation in the SB before performing the true FKBI at medium pressures and is particularly important when performing the crush technique. Ormiston et al. recently demonstrated through imaging of bench deployments that (1) recrossing the crushed stent for kissing postdilation, the most difficult part of the procedure, is technically easier with minicrush than with classical crush; (2) traditional one-step FKBI leaves considerable residual metallic stenosis that may not be visible on angiography and may predispose to thrombosis because of eddy currents, stasis, altered shear stress, and foreign body presence; and (3) SB ostial coverage and residual stenosis by metal struts are significantly reduced by two-step FKBI ( Figure 10-4 ).

Bench-top imaging of the ostium of the SB after the crush technique with no FKBI (A), classical one-step FKBI (B), and the recommended two-step FKBI (C) that results in the best opening of struts toward the SB.

(Images provided courtesy Dr. John Ormiston.)

Optimal Technique Is a Must, Especially When Two Stents Have Been Implanted

The requirement for double stenting is dependent on the complexity of the bifurcation that the interventional cardiologist is willing to treat, the importance of the bifurcation to that patient, and the willingness to accept a suboptimal angiographic result in the SB. Thus, in treating simple bifurcations with small to moderately sized SBs, the rate of double stenting may be as low as 5% to 10%. In more complex bifurcations with large and extensively diseased SBs, this may be as high as 15% to 20%, with the highest rate of double stenting in the LMCA bifurcation (up to 30%). Thus, there will still be situations where the operator needs to implant a stent in both branches of the bifurcation electively or as a crossover from the provisional approach. If properly performed, there appears to be no evidence of harm to the patient and there may even be an advantage over the provisional approach in certain situations. However, when implanting two stents, the operator takes on the responsibility to ensure optimal performance of the technique, as a 2S approach is less forgiving to a suboptimal result, which may result in restenosis or stent thrombosis. In this regard, there are a number of important technical factors that may contribute to optimizing outcomes when performing 2S techniques such as high-pressure SB inflation, the use of noncompliant balloons, selection of the correct balloon size for FKBI, the double-kissing crush technique, and the use of intravascular imaging. Despite the absence of a dedicated IVUS study, we strongly favor utilizing IVUS to evaluate and improve the final result when implanting two stents. An exception to this approach is present when the TAP technique is utilized. This approach may make IVUS evaluation difficult to perform.

Stent Thrombosis After Bifurcation PCI

Stenting bifurcation lesions with DES have been identified as a risk factor for stent thrombosis (ST). However, data from the individual randomized trials discussed above have not demonstrated an increased risk when utilizing two stents versus one stent. Similarly, two metaanalyses of the randomized trials performed have not demonstrated an increased risk of ST with double stenting techniques. Finally, long-term data from the Nordic Bifurcation Study have shown similar rates of definite ST with provisional and double stenting (3% vs. 1.5%, p = 0.31) at 5 years. However, the usage of two stents may be associated with an increased risk of ST in the setting of acute myocardial infarction. Furthermore, it would appear that ST at coronary bifurcations is associated with a higher in-hospital and long-term mortality rate than ST at nonbifurcation lesions. This higher mortality rate is at least partly explained by a larger area of myocardium at risk among subjects with bifurcation ST. There is currently no convincing evidence to suggest that we should refrain from using DES in bifurcations or that a 2S strategy is associated with a greater risk of ST. However, we should make every attempt to prevent ST when DESs are implanted in bifurcations. This requires attention to the technical aspects of the procedure, optimization of stent implantation, and dual antiplatelet therapy for at least 12 months. Despite these statements, we should take into consideration the fact that implanting two stents always demands more attention and expertise to obtain the best result in both the MB and SB.

General Aspects

Wiring Both Branches of the Bifurcation and Jailed Guidewires

Two wires should be placed in most bifurcations and the SB wire should be “jailed” in the majority, following deployment of the stent on the MB. This approach of wiring both branches during bifurcation stenting is important in protecting the SB from closure due to plaque shift, carina shift, and/or stent struts during MB stenting. Even SBs with minimal disease may occlude during MB stenting ( Figure 10-6A-B ,Videos 10-1 and10-2 ). There has been some debate as to whether placing a wire in the SB can protect it from closure after MB stenting. A recent study has finally confirmed that the jailed wire in the SB is associated with flow recovery of SBs that occlude after MB stenting (74.8% vs. 57.8%, p = 0.02). Protecting SBs with guidewires to prevent their closure is important, as SB compromise may not be inconsequential. Occlusion of SBs >1 mm can be associated with a 14% incidence of myocardial infarction, and SB (≥2 mm) compromise during a provisional approach can be associated with a large periprocedural myocardial infarct. The jailed SB wire not only protects it from closure but also facilitates rewiring of the SB (if SB postdilatation-stenting or final kissing inflation is needed or if the side branch occludes) by widening the angle between the MB and SB, acting as a marker for the SB ostium, and changing the angle of SB takeoff. Finally, in the case of SB occlusion, the jailed wire can be used to reopen the SB by pushing a small balloon between the stent and the wall of the vessel. There is no need to remove the jailed wire during high-pressure stent dilatation in the MB. It is preferable to avoid jailing hydrophilic guidewires, as there is a risk of removing the polymer coating. Accurate handling of the guide catheter to prevent migration into the ostium of the coronary vessel will allow removal of the jailed wire.

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