Immediate and Long-Term Results of a Modified Simultaneous Kissing Stenting for Percutaneous Coronary Intervention of Coronary Artery Bifurcation Lesions

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Abstract: Objectives. We propose a modified simultaneous kissing stenting technique (MSKS) based on systematic implantation of a protective stent in the proximal main vessel (PMV) proximally to the bifurcation before simultaneous kissing stenting (SKS). Background. SKS has been proposed in large-size coronary vessel bifurcation lesions (BLs) when the PMV can accommodate two stents. SKS implies, however, low-pressure simultaneous final balloon inflations to avoid retrograde PMV dissection or rupture and therefore may not ensure optimal final stent apposition. Methods. From January 2005 to May 2008, a total of 97 patients with 100 BLs (true bifurcation in 92%) who underwent MSKS were enrolled in a prospective registry. Drug-eluting stents were used for distal main vessel and side branch. Drug-eluting or large-size bare-metal stents were used as proximal protective stents. Results. Immediate procedural success rate was 100%. Global restenosis rate was 10% (5% in the main vessel and 8% in the side branch) at follow-up angiogram performed at 7 months in all patients (100%). No patient had early or late stent thrombosis. Two cases of non-fatal very late stent thrombosis occurred at 46 and 64 months. Over a mean 4.5-year follow-up period, target lesion revascularization rate was 11%, with only 3% driven by clinical ischemia. Conclusion. Protective stent systematic implantation in the PMV represents a newly modified SKS technique that allows safe finalization of the procedure by high-pressure kissing balloon final inflation, ensuring optimal stent apposition with high immediate procedural success and low rates of long-term events.

J INVASIVE CARDIOL 2013;25(3):126-131

Key words: bifurcation lesions, restenosis, sirolimus-eluting stents, zotarolimus-eluting stents, paclitaxel-eluting stents

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Percutaneous coronary intervention (PCI) of coronary bifurcation lesions (BLs) remains a challenge for the interventionalist, with high restenosis rates, especially of the side branch (SB), despite the use of drug-eluting stents (DESs).^1,2 Although the strategy of stenting the main vessel with SB provisional stenting has become the favored approach for PCI of bifurcation lesions in recent years, all bifurcation lesions cannot be treated by provisional stenting and there is still a need for complex double-stent techniques in some cases. Various approaches of bifurcation double-stent techniques have been proposed, including T-, Y-, V-, reverse-T, culotte, and crush techniques.^3-12 Most of these previously described techniques result in stent distortion that may contribute to restenosis. Sharma et al^13,14 have proposed a modified V-stenting technique, the simultaneous kissing stent technique (SKS), which involves two stents, one in the distal main vessel (DMV) and one in the SB, with overlapping stents in the proximal main vessel (PMV) creating a new carina. This latter technique allows complete coverage of the SB ostium, relatively maintains the geometry of the bifurcation, and avoids excessive deformation of the stents, but can be proposed only in large-size vessel bifurcations with a PMV that can accommodate two stents with a size at least two-thirds of the aggregate diameter of the 2 stents.^13,14 To avoid retrograde dissection or rupture of the PMV, SKS implies, however, low-pressure simultaneous final inflation of the balloons,^13,14 which may not ensure optimal final stent apposition. In addition, the long-term results and restenosis rate of SKS, which creates a new metal carina, have not been fully investigated. In the present study, we propose a modified technique using the systematic implantation of a protective stent in the PMV proximal to the bifurcation stenosis before SKS, allowing the performance of the SKS even when the PMV angiographically appears not to accommodate two stents and to finalize the procedure by high-pressure kissing balloon inflation that may ensure better final stent apposition. We report the immediate and long-term clinical results of this new technique, as well as the restenosis rate evaluated by systematic control angiogram in a cohort of 97 patients with 100 BLs who were treated at our single institution and prospectively enrolled in a registry.

Methods

Study population. From January 2005 to May 2008, a total of 100 de novo BLs in 97 consecutive patients  (67 men; mean age, 65 ± 11 years) were treated at our institution with PCI using a modified SKS technique. BLs were classified using the Medina classification,¹⁵ which has been adopted by the European Bifurcation Club.¹⁶ All patients provided written informed consent before all procedures. 

PCI technique. All patients were given 300 mg of clopidogrel and 250 mg of aspirin the day before the procedure. Bolus injection of unfractionated heparin (5000 to 10,000 U) with 250 mg aspirin was administrated at the beginning of the procedure. Glycoprotein IIb/IIIa inhibitors were given at the discretion of the operator in patients with unstable angina and non-ST segment elevation myocardial infarction (NSTEMI). A 7 or 8 Fr guiding catheter was used in all patients. A first guidewire was advanced in the DMV. An appropriately sized stent (1:1 stent-to-artery ratio) was first implanted in the PMV proximal to the bifurcation lesion. Length of the PMV protective stent was selected to cover a segment of totally healthy artery proximal to the bifurcation lesion. As only the DMV was first wired, care was taken to implant the protective stent proximal to the PMV stenosis to cover only a totally healthy artery segment or, at most, the beginning of the lesion but not the stenotic segment. This was done in order to avoid anterograde dissection of the SB that could be subsequently hardly wired in case of first stent deployment inside the PMV stenosis (Figure 1). For PMV protective stenting, sirolimus-eluting stents (SES; Cypher, Cordis Corporation) of 3.0 and 3.5 mm diameters were used and zotarolimus-eluting stents (Endeavor, Medtronic), paclitaxel-eluting stents (Taxus, Boston Scientific Corporation), or bare-metal stents (Driver, Medtronic) were used for larger diameters. Inflation pressure was applied to obtain adequate expansion of the PMV stent. After protective stent implantation in the PMV, a second guidewire was advanced in the SB. In patients with tight stenosis, predilation was performed  prior to stent positioning in the DMV and in the SB. Two SESs were then advanced, one in the DMV and one in the SB. Stent lengths was selected in order to cover the lesions completely as well as creating a new carina inside the proximal protective stent. Care was taken to keep the proximal markers of both stents overlapped at the same level and downstream the proximal marker of the PMV stent (Figure 1). After confirmation of stent positions, they were dilated sequentially at 10 to 12 atm and then at 10 to 12 atm simultaneously. After these 2 first low-pressure inflations, deflated stent balloons were slightly withdrawn simultaneously with proximal markers positioned at the same site inside the PMV protective stent. Care was taken to keep the proximal markers of the 2 balloons well inside the PMV stent. The 2 balloons were then sequentially inflated at high pressure (15 to 20 atm) and finally inflated simultaneously also at the same level of high pressure (15 to 20 atm). In cases of non-satisfactory results, additional simultaneous kissing inflations were performed with 2 non-compliant balloons (Quantum Maverick balloon, Boston Scientific Corporation) at 20 to 25 atm. Finally, if results were not considered to be angiographically optimal, additional in-stent kissing stenting was performed using 1 or 2 bare-metal Driver stents or 1 or 2 SESs with simultaneous balloon inflation at 20 atm. Femoral sheaths were removed immediately after the procedure and closure of the arterial puncture was performed using a closure device (Angio-Seal, St Jude Medical). After PCI, clopidogrel 75 mg/day  and 100 mg aspirin were administrated indefinitely. 

Angiographic and clinical follow-up. All patients (100%) underwent a systematic follow-up coronary angiogram at a mean of 7 months (range, 6 to 11 months). Quantitative coronary angiographic data were analyzed by an operator blinded to patient identities and sequence for the films, and binary angiographic restenosis was defined as >50% diameter stenosis. Clinical follow-up was obtained in all patients every 6 months by direct contact with the patients and their relatives, interview of their referring physicians, and reviewing the medical reports when patients had been hospitalized during follow-up. The following major events occurring after hospital discharge were searched and recorded: death (cardiac and non-cardiac), non-fatal stroke, stent thrombosis, non-fatal myocardial infarction, repeat PCI or surgical revascularization, hospitalization for cardiac failure or unstable angina. 

Statistical analysis. Continuous variables are expressed as mean ± standard deviation. A 2-tailed student’s t-test was used to test differences among continuous variables. Differences between categorical variables were analyzed with a Chi-square test or Fisher’s exact test. A P-value of <.05 was considered significant. Statistical tests were performed with package software SPSS 7/0 (SPSS Inc). 

Results

Table 1 summarizes the baseline clinical characteristics of our population and procedural characteristics are presented in Table 2. Immediate procedural success rate was 100%. No proximal edge dissection or perforation were observed during the procedures. One patient who underwent PCI both on a circumflex (CX) bifurcation lesion and the distal segment of the left anterior descending (LAD)  artery underwent an acute myocardial infarction due to subacute stent thrombosis of the LAD 4 days after the procedure without any abnormality on the bifurcation lesion on the emergency coronary angiogram; stent thrombosis was treated successfully by repeat PCI. 

Follow-up coronary angiogram was completed at a mean of 7 months in all patients (100% angiographic follow-up). At follow-up angiogram, restenosis was observed in 10 cases (10%). The rate of global restenosis was higher in the patients with type [1, 1, 1] of the Medina classification than in the other patients (13.2% vs 6.4%) as well as in diabetics than in non-diabetics (17.7% vs 7.2%), but the differences were not statistically significant. Restenosis rate was 5% in the main vessel and 8% in the SB. Table 3 shows the distribution of the restenosis sites according to the Medina classification. According to the Medina classification, restenosis occurred in 15 of the 245 lesion sites (6.1%). Among the 10 restenotic patients, only 1 complained with stress chest pain at the time of control angiogram and was referred to bypass surgery due to worsening of an ostial lesion of the LAD associated with in-stent restenosis. The clinically ischemia-driven lesion repeat revascularization rate was therefore 1% during the first year. Another patient with in-stent restenosis on the SB received medical treatment. The 8 remaining patients with angiographic restenosis at control were all successfully treated by repeat PCI.

Late long-term follow-up data were obtained in all patients (100%) between August 2011 and September 2011. The mean clinical follow-up for the entire study population was therefore 54 ± 13 months, with a range of 11 to 81 months. All patients but 5 (95%) were under dual antiplatelet therapy during the entire follow-up period. No patient presented with early or late stent thrombosis during the first 45 months of follow-up. The first cases of stent thrombosis occurred very late during follow-up in 2 patients, at 46 and 64 months, respectively. None of these very late stent thrombosis cases were associated with ST-elevation myocardial infarction. The total rate of target lesion revascularization over a mean follow-up of 54 months was 11%, with only 3% driven by clinical ischemia.  

There were 8 deaths during follow-up, 4 of which were caused by cardiovascular events. Three patients with initial low ejection fraction (19%, 36%, and 32%, respectively) died from progressive terminal heart failure. One death occurred at 23 months in an 89-year-old female patient 72 hours after onset of a massive stroke; no investigation was done due to the severity of the clinical status and the advanced age of the patient, so it was not possible to state whether the stroke was of ischemic or hemorrhagic cause. Four additional deaths were due to cancer. Clinical follow-up data are summarized in Table 4.

Discussion

This study demonstrates that systematic implantation of a protective stent in the PMV proximal to the bifurcation lesion allows performance of simultaneous kissing stenting with high-pressure simultaneous final inflations leading to high procedural success without immediate procedural complication and relatively low rates of both angiographic restenosis and major clinical events during a long-term follow-up. In addition, this study suggests that the rate of stent thrombosis is relatively low despite the use of a complex stenting technique that creates a new metal carina.

When compared with the data previously published in the literature on double-stent techniques for bifurcation lesions, the global rate of restenosis observed in our population appears to be relatively low, with 5% and 8% rates of restenosis on the main vessel and the SB, respectively. Indeed, despite the various stenting technical approaches that have been proposed for the treatment of bifurcation lesions^3-14 and the use of DESs, the overall rate of restenosis ranges from 17% to 26% in the studies previously reported by other investigators.^17-24 In addition, the restenosis rates previously reported in the literature may underestimate the actual rates since the angiographic follow-up rate is less than 100% in the majority of the studies^13,14,18-23 and is very low, less than 45% of the patients, in studies on SKS.^13,14 By contrast, our results are obtained from a cohort of 100 patients who all (100%) underwent a follow-up coronary angiogram. 

Further comparisons with other studies regarding the restenosis rate remain difficult, in particular because the distribution of the various bifurcation lesion types are often not mentioned.^13,14,17-21 In our study, 92% of the lesions were true bifurcation lesions involving both the main vessel and the SB, which may represent the most unfavorable lesion type. 

In our modified SKS technique, final simultaneous inflation of the 2 stents was performed at high pressure, whereas it was done at low pressure in the previous works on SKS.^13,14,22 Indeed, as two stents have to overlap in the proximal main vessel, Sharma et al,^13,14 in their original works, strongly advised only low-pressure final simultaneous inflations (ie, 10 to 12 atm) to reduce the chances of proximal coronary edge dissection as well as to apply this technique only when the proximal main vessel is able to accommodate the 2 stents with its size approximately equal to 66% of the aggregate diameter of the 2 stents. Despite these precautions, Sharma et al^13,14 reported a 0.5% rate of proximal perforation and a 6% rate of proximal dissection with 1 case of subacute stent thrombosis in 1 patient with type II proximal dissection. In addition, low-pressure final simultaneous inflations may not result in optimal stent apposition in a complex bifurcation lesion. By contrast, our modified technique allows simultaneous expansion of the 2 stents at high pressure without any risk of proximal dissection and reduced risk of perforation since the 2 stents are deployed inside a protective third stent, which absorbs the force of deployment of the 2 other stents. Indeed, no case of proximal perforation or dissection was observed in our work despite a kissing-balloon final inflation at a mean pressure of 20 atm with inflation pressure ≥20 atm in 84%. We believe that such high-pressure final simultaneous inflations provide optimal stent deployment and apposition, ensuring better long-term results. Also, the systematic implantation of a protective proximal stent allows the application of this technique even in cases where the proximal main vessel angiographically appears not to accommodate two stents. Indeed, in our patients, the mean ratio of the PMV stent diameter to the sum of the DMV and SB stent diameters was less than 0.66 in 45% of cases and less than 0.60 in 11% of cases. 

Implantation of a stent first deployed proximally on the PMV before SKS has been previously reported in a few cases of true bifurcation lesions with involvement of a long segment of the PMV.^14,25 By contrast, the concept of our technique is based on the systematic implantation of a protective stent proximal to the bifurcation stenosis at a site of totally healthy arterial segment. In our study, there was no stenosis on the PMV in 22% of the cases. In our cases of bifurcation with involvement of the PMV (78%), the protective stent was implanted proximal to the PMV stenosis. This is in opposition to the technique described by Helqvist et al,²⁵ which deployed the stent proximal to the bifurcation as close as possible to the origin of the SB to cover the PMV stenosis. We believe that this latter approach as proposed by Helqvist et al²⁵ may, however, lead to anterograde dissection by the distal part of the large PMV stent during its deployment with the risk of difficulties to rewire the distal leg of the bifurcation not wired initially. In our study, as the PMV stent was not implanted close to the bifurcation in the large majority of cases, the new metal carina was not especially short, with a mean length of 10 mm (range, 5 to 22 mm). Despite a long metal carina in several cases of our study population, a low rate of stent thrombosis was observed during the long-term follow-up. 

Also, by contrast with the original studies by Sharma et al,^13,14 who included only bifurcations with large SBs ≥2.5 mm diameter, we included patients with smaller SBs, since a 2.25 mm diameter stent was used in 17% of our cases without greater restenosis rates. This suggests that bifurcations involving relatively small-size vessels and not only large-size vessels can be treated using our technique. 

Interestingly, in our study, among the 8 patients who underwent repeat angioplasty for restenosis, repeat control coronary angiogram at 6 months in 6 of these patients showed no restenosis and the 2 remaining patients who denied control angiogram were both asymptomatic at 24 months. This suggests that a net good final angiographic result may be obtained using this technique even in patients with a first angiographic restenosis. 

The rate of major cardiovascular events was relatively low in our patients during a mean clinical follow-up of 54 months without any lost patient. In our cohort, no patient died from early or late PCI complications. Bifurcation stenting has been suggested to be a significant predictor of stent thrombosis,^26,27 with stent thrombosis rates ranging from 0.6% to 4.3% over relatively short follow-up ranging from 6 to 14 months.^18,19,26-28 and one might expect even higher rates of stent thrombosis with SKS due to the metal neo-carina. In our study, there was no acute, subacute, or late stent thrombosis (0%). In particular, there was no stent thrombosis for nearly the first 4 years in our study since the first case in our cohort occurred at 46 months and the second case occurred at 64 months. In addition, if we exclude the revascularizations triggered by the protocol-mandated angiographic follow-up findings (“occulo-stenotic reflex”), the rate of target lesion revascularization driven by clinical ischemia appears to be relatively low in our cohort since it was 1% during the first year of follow-up and 3% over the entire 54-month follow-up period. 

Study limitations. Although results obtained in our study appear to be promising when compared with current data in the literature, a randomized study would be mandatory to demonstrate the superiority of our modified SKS technique over classic SKS as well as over other double-stent techniques.

Our technique is a double-stent approach for bifurcation coronary lesions. During the recent past years, the strategy of stenting the main vessel with SB provisional stenting has become the current favored approach for PCIs of bifurcation lesions.³¹ All bifurcation coronary lesions cannot, however, be treated by provisional stenting and there is still a need in some cases for more complex techniques including double-stent implantation. In particular, results of SB simple ballooning are quite variable in the provisional stenting approach and may require a switch from single-stent into a double-stent strategy in up to 31% of cases.³²

Conclusion

SKS using protective systematic stent implantation in the proximal main vessel represents a modified technique of SKS that can be applied to many types of bifurcation lesions with high immediate procedural success, relatively low restenosis rate, and low cardiovascular event rates at long-term follow-up. 

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From the Division of Cardiology, University of Saint Etienne, Saint Etienne, France. 

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted July 18, 2012, provisional acceptance given August 8, 2012, final version accepted October 1, 2012.

Address for correspondence: Pr Karl Isaaz, Service de cardiologie, Hôpital Nord, Centre Hospitalo-Universitaire de Saint Etienne, 42055 Saint Etienne Cedex 2, France.  Email: isaaz@univ-st-etienne.fr