Impact of Acute Coronary Syndrome Classification and Procedural Technique on Clinical Outcomes in Patients With Coronary Bifurcation Lesions Treated With Drug-Eluting Stents

Authors

  • Pil Sang Song MD,

    1. Division of Cardiology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul
    2. Division of Cardiology, Department of Internal Medicine, Inje University Haeundae Paik Hospital, Busan
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  • Dong Ryeol Ryu MD,

    1. Department of Cardiology, Kangwon National University Hospital, Kangwon National University School of Medicine, Chuncheon
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  • Seung-Hyuk Choi MD, PhD,

    Corresponding author
    1. Division of Cardiology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul
    • Seung-Hyuk Choi, MD, PhD Division of Cardiology, Cardiac and Vascular Center, Samsung Medical Center Sungkyunkwan University School of Medicine No. 50, Irwon-dong, Gangnam-gu Seoul, 135-710, South Korea
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  • Jeong Hoon Yang MD,

    1. Division of Cardiology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul
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  • Young Bin Song MD, PhD,

    1. Division of Cardiology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul
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  • Joo-Yong Hahn MD, PhD,

    1. Division of Cardiology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul
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  • Jin-Ho Choi MD, PhD,

    1. Division of Cardiology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul
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  • Ki Bae Seung MD, PhD,

    1. Cardiovascular Center and Cardiology Division, Seoul St Mary's Hospital, The Catholic University of Korea, Seoul
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  • Seung-Jung Park MD, PhD,

    1. Division of Cardiology, Asan Medical Center, College of Medicine, University of Ulsan, Seoul, South Korea
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  • Hyeon-Cheol Gwon MD, PhD

    1. Division of Cardiology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul
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Abstract

Background:

We examined the impact of non–ST-segment elevation acute coronary syndrome (NSTE-ACS) on clinical outcomes in patients with bifurcation lesions treated with drug-eluting stents.

Hypothesis:

We hypothesized that NSTE-ACS would be attributable to the increased risk of major adverse cardiac events (MACE) in bifurcation percutaneous coronary intervention.

Methods:

We enrolled 1668 patients, using data from a multicenter real-world bifurcation registry. The primary objective was to compare the 2-year cumulative risk of MACE in patients with NSTE-ACS to those with stable angina. Major adverse cardiac events were defined as the composite endpoint of cardiac death, myocardial infarction (MI), and target-lesion revascularization.

Results:

Non–ST-segment elevation acute coronary syndrome was seen in 969 (58.1%) patients and stable angina in 699. Major adverse cardiac events occurred in 7.3% of NSTE-ACS patients and in 5.2% with stable angina (P = 0.042). However, cardiac death, MI, and target-lesion revascularization were similar between the 2 groups. We stratified patients with NSTE-ACS into those with non–ST-segment elevation MI and those with unstable angina. Cumulative risks of 2-year MACEs were 7.0% in non–ST-segment elevation MI patients and 7.5% in unstable angina patients (P = 0.87). In the NSTE-ACS cohort, the baseline lesion length in the side branch (adjusted hazard ratio [HR]: 1.04, 95% confidence interval [CI]: 1.01-1.07, P = 0.022), paclitaxel-eluting stents in the main vessel (adjusted HR: 2.02, 95% CI: 1.21-3.40, P = 0.008), and final kissing ballooning (adjusted HR: 1.88, 95% CI: 1.10-3.21, P = 0.021) were independent predictors of MACE.

Conclusions:

Compared with stable angina patients, the NSTE-ACS patients who underwent bifurcation percutaneous coronary intervention had an increased risk of MACE during the 2-year follow-up. Clin. Cardiol. 2012 doi: 10.1002/clc.22020

Drs Pil Sang Song and Dong Ryeol Ryu contributed equally to this work. Coronary Bifurcation Stenting (COBIS) Registry in South Korea, US Department of Health and Human Services, US National Institutes of Health, ClinicalTrials.gov no. NCT00851526.

This work was supported by the Korean Society of Interventional Cardiology, Seoul, South Korea. The authors have no other funding, financial relationships, or conflicts of interest to disclose.

Introduction

Many studies have issued bifurcation lesions previously, but no study has addressed the impact of clinical presentation on outcomes in patients with bifurcation lesions treated with drug-eluting stents. Therefore, we examined the independent prognostic value of non–ST-segment elevation acute coronary syndrome (NSTE-ACS), using data from the large, dedicated, multicenter real-world Coronary Bifurcation Stenting (COBIS) registry. Furthermore, we stratified patients with NSTE-ACS into those with non–ST-segment elevation myocardial infarction (NSTEMI) and those with unstable angina (UA), and also compared clinical outcomes between these 2 subgroups.

Methods

Study Population and Percutaneous Coronary Intervention

We used data from a multicenter real-world registry dedicated to bifurcation lesions in Korea. The population and percutaneous coronary intervention (PCI) in the COBIS registry have been described previously.1

Data Collection and Angiographic Analysis

Bifurcation lesions were classified according to the Medina classification.2 Medina classification (1, 1, 1), (1, 0, 1), or (0, 1, 1) lesions were categorized as true bifurcation lesions. Angiographic success was defined as achievement of Thrombolysis in Myocardial Infarction (TIMI) 3 flow with a final residual stenosis <30% for the main vessel or <50% for the side branch.

Definitions and Study Endpoints

Non–ST-segment elevation acute coronary syndrome was defined as the occurrence of NSTEMI or UA. Intraprocedural complications were defined as cardiac death, emergency bypass surgery, coronary perforation, or cardiac tamponade. Procedural success was defined as angiographic success without major adverse cardiac events (MACE) during the hospital stay. The primary objective of the study was to compare the 2-year cumulative risk of MACE in patients with NSTE-ACS to those with stable angina. The MACE were defined as the composite endpoints: cardiac death, myocardial infarction (MI), and target-lesion revascularization (TLR). Clinical events were defined based on the recommendations of the Academic Research Consortium.3

Statistical Analysis

The occurrence of adverse events was analyzed by the Kaplan-Meier method. Differences between event curves were compared by the log-rank test. The Cox proportional hazards model was used to identify independent predictors of MACE. Covariates statistically significant on univariate analysis and/or those that were clinically relevant were considered candidate variables in the multivariate models. A second multivariable analysis was performed using propensity score as a covariate. Propensity score was determined by use of a logistic regression model from which the probability of having an NSTE-ACS rather than stable angina was calculated. Model discrimination was assessed with the C statistic and model calibration with the Hosmer-Lemeshow statistic. Statistical significance was accepted for a 2-sided value of P < 0.05. All analyses were performed SPSS version 17.0 (SPSS Inc., Chicago, IL).

Results

Baseline Characteristics and Procedural Data

A total of 1691 bifurcation lesions in 1668 patients were included in this study. Non–ST-segment elevation acute coronary syndrome occurred in 969 patients and stable angina in 699 patients. Baseline characteristics of the 2 groups are in Table 1. Patients with NSTE-ACS presented with higher cardiac risk profiles in clinical characteristics. The prevalence of true bifurcation was higher in NSTE-ACS patients, and baseline minimal luminal diameter in the distal main vessel and side branch distal vessel were smaller in the NSTE-ACS patients. Paclitaxel-eluting stent on the main vessel was more frequently used in NSTE-ACS patients than in stable angina patients. Final kissing ballooning (FKB) was performed less frequently in NSTE-ACS patients (34.7%) compared with 44.1% of stable angina patients (P < 0.001).

Table 1. Baseline Characteristics
Overall Cohort (N = 1668) Clinical CharacteristicsNSTE-ACS (n = 969)Stable Angina (n = 699)P Value
  1. Abbreviations: DM, diabetes mellitus; FKB, final kissing ballooning; IVUS, intravascular ultrasound; LAD, left anterior descending coronary artery; LCX, left circumflex coronary artery; LVEF, left ventricular ejection fraction; MI, myocardial infarction; MLD, minimal luminal diameter; NSTE-ACS: non–ST-segment elevation acute coronary syndrome; RCA, right coronary artery.

  2. Values are mean ± SD or n (%). Dyslipidemia was defined as a total cholesterol >200 mg/dL.

Age, y62 ± 1162 ± 100.32
Female sex326 (33.6)226 (32.3)0.57
Current smoking254 (26.2)151 (21.6)0.03
DM304 (31.4)209 (29.9)0.52
Hypertension551 (56.9)436 (62.4)0.024
Dyslipidemia328 (33.8)193 (27.6)0.007
Creatinine >2.0 mg/dL34 (3.5)22 (3.1)0.69
Prior MI80 (8.3)59 (8.4)0.89
LVEF (%)58 ± 1261 ± 10<0.001
Glycoprotein IIb/IIIa receptor inhibitor38 (3.9)20 (2.9)0.24
Dual antiplatelet therapy ≥6 mo859 (89.0)604 (86.5)0.13
Overall Lesions (N = 1691) Angiographic and Procedural CharacteristicsNSTE-ACS (n = 979)Stable Angina (n = 712)P Value
Location  0.85
 RCA52 (5.3)40 (5.6) 
 LAD741 (75.7)544 (76.4) 
 LCX186 (19.0)128 (18.0) 
Bifurcation type  0.16
 0, 0, 115 (1.5)13 (1.8) 
 0, 1, 089 (9.1)79 (11.1) 
 0, 1, 1119 (12.2)92 (12.9) 
 1, 0, 060 (6.1)59 (8.3) 
 1, 0, 158 (5.9)50 (7.0) 
 1, 1, 0114 (11.6)85 (12.0) 
 1, 1, 1524 (53.5)333 (46.8) 
True bifurcation701 (71.6)475 (66.8)0.034
Bifurcation angle (°)52 ± 1952 ± 170.86
Baseline MLD (mm)
 Main vessel, distal1.51 ± 0.691.66 ± 0.73<0.001
 Side branch, distal1.50 ± 0.571.59 ± 0.550.002
Thrombi in
 Main vessel49 (5.0)20 (2.8)0.024
 Side branch16 (1.6)4 (0.6)0.07
Multivessel coronary disease481 (49.2)343 (48.3)0.72
Transradial approach273 (27.9)245 (34.4)0.004
IVUS273 (27.9)266 (37.4)<0.001
Predilatation of side branch193 (22.9)132 (20.7)0.31
Stent, implanted  0.003
 Sirolimus-eluting stent591 (60.4)479 (67.3) 
 Paclitaxel-eluting stent364 (37.2)209 (29.4) 
 Others24 (2.5)24 (3.4) 
Paclitaxel-eluting stent in
 Main vessel364 (38.1)209 (30.4)0.001
 Side branch68 (37.8)47 (35.3)0.66
Stent techniques  0.10
 Main vessel stenting only813 (83.0)586 (82.3) 
 T technique71 (7.3)71 (10.0) 
 Crush technique67 (6.8)32 (4.5) 
 Culottes technique4 (0.4)4 (0.6) 
 Kissing technique24 (2.5)19 (2.7) 
2-stent technique166 (17.0)126 (17.7)0.69
FKB340 (34.7)314 (44.1)<0.001
Procedural success
 Main vessel966 (98.7)707 (99.3)0.22
 Side branch640 (65.4)461 (64.7)0.79

Of patients with NSTE-ACS, 299 had NSTEMI and 670 had UA. Baseline characteristics of these 2 subgroups are in Table 2. The NSTEMI subgroup had more complex cardiac risk profiles. The procedural success rate was similar between the 2 subgroups (98.7% in NSTEMI vs 98.7% in UA, P < 0.99 on main vessel, and 61.9% in NSTEMI vs 67.3% in UA, P = 0.10 on side branch).

Table 2. Clinical, Angiographic, and Procedural Characteristics of Patients Stratified Into NSTEMI and UA Subgroups
NSTE-ACS Cohort (N = 969)NSTEMI Subgroup (n = 299)UA Subgroup (n = 670)P Value
  1. Abbreviations: DM, diabetes mellitus; FKB, final kissing ballooning; IVUS, intravascular ultrasound; LAD, left anterior descending coronary artery; LCX, left circumflex coronary artery; LVEF, left ventricular ejection fraction; MI, myocardial infarction; MLD, minimal luminal diameter; NSTE-ACS: non–ST-segment elevation acute coronary syndrome; NSTEMI, non–ST-segment elevation myocardial infarction; RCA, right coronary artery; UA, unstable angina.

  2. Values are mean ± SD or n (%). Dyslipidemia was defined as a total cholesterol >200 mg/dL.

Age, y62 ± 1162 ± 100.51
Female sex81 (27.1)245 (36.6)0.004
Current smoking99 (33.1)155 (23.1)0.001
DM88 (29.4)216 (32.2)0.38
Hypertension157 (52.5)394 (58.8)0.07
Dyslipidemia100 (33.4)228 (34.0)0.86
Creatinine >2.0 mg/dL11 (3.7)23 (3.4)0.85
Prior MI23 (7.7)57 (8.5)0.67
LVEF (%)53 ± 1261 ± 11<0.001
Location  0.07
 RCA18 (6.0)33 (4.9) 
 LAD211 (70.6)525 (78.4) 
 LCX70 (23.4)112 (16.7) 
Bifurcation type  0.91
 0, 0, 15 (1.7)10 (1.5) 
 0, 1, 022 (7.4)64 (9.6) 
 0, 1, 138 (12.7)80 (11.9) 
 1, 0, 018 (6.0)40 (6.0) 
 1, 0, 123 (7.7)35 (5.2) 
 1, 1, 033 (11.0)81 (12.1) 
 1, 1, 1160 (53.5)360 (53.7) 
True bifurcation221 (73.9)475 (70.9)0.34
Baseline MLD (mm)
 Main vessel, proximal1.35 ± 0.841.53 ± 0.870.005
 Main vessel, distal1.42 ± 0.761.55 ± 0.660.021
 Side branch1.46 ± 0.591.51 ± 0.560.24
Baseline lesion length (mm) in main vessel20 ± 1118 ± 110.016
Thrombi in
 Main vessel31 (10.4)18 (2.7)<0.001
 Side branch10 (3.3)6 (0.9)0.006
Multivessel coronary disease168 (56.2)304 (45.4)0.002
Transradial approach85 (28.4)181 (27.0)0.65
IVUS70 (23.4)203 (30.3)0.028
Glycoprotein IIb/IIIa receptor inhibitor19 (6.4)19 (2.8)0.009
Stent, implanted  0.74
 Sirolimus-eluting stent184 (61.5)407 (60.7) 
 Paclitaxel-eluting stent112 (37.5)252 (37.6) 
 Others3 (1.0)11 (1.6) 
Paclitaxel-eluting stent in
 Main vessel112 (37.7)252 (38.1)0.90
 Side branch14 (31.8)54 (40.0)0.33
Stent techniques  0.13
 Main vessel stenting only255 (85.3)548 (81.8) 
 T technique24 (8.0)47 (7.0) 
 Crush technique15 (5.0)52 (7.8) 
 Culottes technique3 (1.0)1 (0.1) 
 Kissing technique2 (0.7)22 (3.3) 
2-stent technique44 (14.7)122 (18.2)0.18
FKB93 (31.1)247 (36.9)0.08
Procedural success
 Main vessel295 (98.7)661 (98.7)>0.99
 Side branch185 (61.9)451 (67.3)0.10
Dual antiplatelet therapy ≥6 months256 (86.2)603 (90.3)0.06

Clinical Outcomes

Intraprocedural complications occurred in very few patients, specifically in 1.1% of the NSTE-ACS patients vs in 0.9% of stable angina patients (P = 0.58), and in 0.7% of the NSTEMI patients vs in 1.3% of unstable angina patients (P = 0.52).

Complete clinical follow-up data were obtained for 97.8% of the overall cohort. Two-year MACE were 7.3% in patients with NSTE-ACS and 5.2% in stable angina patients (P = 0.042), mainly driven by higher TLR rate (5.5% in patients with NSTE-ACS vs 3.9% in stable angina patients; P = 0.08). However, cardiac death occurred in 1.1%, MI in 1.4%, and stent thrombosis in 0.6% in NSTE-ACS patients, and these rates were 0.6%, 1.0%, and 0.7% in stable angina patients, respectively (Figure 1). A typical example of cases is demonstrated in Figure 2.

Figure 1.

Kaplan-Meier curves of 2-year cumulative clinical outcomes. (A) Cumulative rate of MACE. (B) Cumulative rate of cardiac death. (C) Cumulative rate of MI. (D) Cumulative rate of TLR. Abbreviations: MACE, major adverse cardiac event; MI, myocardial infarction; NSTE-ACS, non–ST-segment elevation acute coronary syndrome; NSTEMI, non–ST-segment elevation myocardial infarction; SA, stable angina; TLR, target-lesion revascularization; UA, unstable angina.

Figure 2.

An example of target lesion revascularization. (A) A 63-year-old male with a type (0, 1, 1) lesion located at the left anterior descending artery and the first diagonal branch presented with unstable angina. (B) Provisional main vessel stenting and final kissing ballooning. (C) A final result. (D) Symptom-driven follow-up coronary angiography at 6 months showing TLR at side branch ostium. Abbreviations: TLR, target-lesion revascularization.

The cumulative risks of 2-year MACE were 7.0% in patients with NSTEMI and 7.5% in UA patients (P = 0.87). Moreover, in NSTEMI patients cardiac death occurred in 1.3%, MI in 2.0%, TLR in 4.7%, and stent thrombosis in 1.0%, and these rates were 1.0%, 1.2%, 5.8%, and 0.4% in patients with UA (Figure 1).

Independent Predictors of Major Adverse Cardiac Events

Table 3 shows the independent predictors of MACE in each cohort. Non–ST-segment elevation acute coronary syndrome had borderline significance (adjusted hazard ratio [HR]: 1.49, 95% confidence interval [CI]: 0.99-2.25, P = 0.06), and FKB (adjusted HR: 2.01, 95% CI: 1.29-3.13, P = 0.002) was an independent predictor of MACE in the overall cohort.1 In the NSTE-ACS patients cohort, baseline lesion length in the side branch, paclitaxel-eluting stent in the main vessel, and FKB were independent predictors of MACE. And also, peripheral artery occlusive disease, creatinine >2.0 mg/dL, dyslipidemia, paclitaxel-eluting stent in main vessel, and FKB were independent predictors of MACE in the stable angina patients cohort. A second multivariable analysis was performed using propensity score as a covariate. The C statistic of the regression model for the propensity score was 0.674. After adjusting for propensity score, the HR for risk of 2-year MACE in patients with NSTE-ACS compared with stable patients was 1.47 (95% CI: 0.90-2.29, P = 0.13).

Table 3. Multivariate Analysis for Predictors of MACE in Each Cohort
CohortAdjusted HR95% CIP Value
  • Abbreviations: BUN, blood urea nitrogen; CI, confidence interval; DM, diabetes mellitus; FKB, final kissing ballooning; HR, hazard ratio; IVUS, intravascular ultrasound; MACE, major adverse cardiac events; MLD, minimal luminal diameter; NSTE-ACS: non–ST-segment elevation acute coronary syndrome.

  • a

    The following variables were selected for the analysis with the Cox model in overall cohort: age, sex, NSTE-ACS, DM, true bifurcation, 1-stent vs 2-stent technique, FKB, IVUS guidance, stent type, procedural success in side branch, stent diameter in main vessel, total stent length in main vessel, and dual antiplatelet therapy for >6 mo.

Overall cohort (N = 1668)a
NSTE-ACS1.490.99–2.250.06
Stent diameter, implanted in main vessel (mm)0.570.31–1.080.08
Total stent length, implanted in main vessel (mm)1.021.001–1.030.03
Paclitaxel-eluting stent in main vessel1.981.34–2.920.001
FKB2.011.29–3.130.002
NSTE-ACS cohort (n = 969)
BUN (mg/dL)1.010.99–1.040.35
Creatinine >2.0 mg/dL1.410.37–5.300.61
Baseline MLD in distal main vessel (mm)0.790.54–1.160.23
Baseline lesion length in side branch (mm)1.041.01–1.070.022
Paclitaxel-eluting stent in main vessel2.021.21–3.400.008
Total stent length, implanted in main vessel (mm)1.010.99–1.020.58
FKB1.881.10–3.210.021
Dual antiplatelet therapy ≥6 mo0.630.31–1.300.21
Stable angina cohort (n = 699)
Peripheral artery occlusive disease5.601.30–24.220.021
Creatinine >2.0 mg/dL4.531.34–15.260.015
Dyslipidemia2.261.17–4.380.016
True bifurcation1.990.85–4.640.11
Paclitaxel-eluting stent in main vessel2.211.14–4.300.019
FKB2.711.32–5.560.007
Overall cohort with propensity score (n = 1282)
Creatinine >2.0 mg/dL3.501.38–8.890.008
Baseline MLD in distal main vessel (mm)0.870.59–1.290.49
Stent diameter, implanted in main vessel (mm)0.400.20–0.820.012
Stent diameter, implanted in side branch (mm)0.250.038–1.680.15
Paclitaxel-eluting stent in main vessel2.531.59–4.02<0.001
FKB2.561.58–4.15<0.001
Propensity score0.980.10–7.910.93
NSTE-ACS1.470.90–2.290.13

Subgroup Analysis

We compared the unadjusted hazard ratio of FKB for MACE in the various subgroups (Figure 3). The rate of MACE was consistently higher in the FKB group than in the non-FKB group across various subgroups.

Discussion

This is the first study assessing the impact of NSTE-ACS on clinical outcomes in a large sample of patients with coronary bifurcation lesions treated with drug-eluting stents. Our study demonstrated that NSTE-ACS was associated with an increased risk of MACE during a 2-year follow-up. Of patients with NSTE-ACS, however, those with NSTEMI had similar risks of MACE, cardiac death, MI, TLR, and stent thrombosis as did patients with UA. In addition, the rate of MACE was consistently higher in the FKB group than in the non-FKB group among several subgroups.

Figure 3.

Subgroups analysis on FKB. Abbreviations: CI, confidence interval; FKB, final kissing ballooning; HR, hazard ratio; NSTE-ACS, non–ST-segment elevation acute coronary syndrome; NSTEMI, non–ST-segment elevation myocardial infarction.

The increased risk of MACE in patients with NSTE-ACS is attributable in part to the coexistence of serious comorbidities and NSTE-ACS itself. Results of our study correspond with the results of earlier studies.4–6 In our study, the NSTE-ACS patients had a higher proportion of current smokers, a higher probability of dyslipidemia, and a lower left ventricular ejection fraction than did patients with stable angina. As a result, patients with NSTE-ACS had a significantly increased risk of adverse events, with 7.3% MACE. In contrast, stable angina patients had a relatively favorable clinical outcome, with 5.2% MACE.

We stratified patients with NSTE-ACS into those with NSTEMI and those with UA and analyzed clinical outcomes among the 2 subgroups. Against expectations, no differences were seen in 2-year MACE, including cardiac death, MI, TLR, and stent thrombosis between the patients with NSTEMI and the UA patients. Acute coronary syndrome is a heterogeneous condition that may be divided into UA, NSTEMI, and ST-segment elevation myocardial infarction. All forms of ACS, however, share a similar underlying pathophysiology, primarily the rupture of an atherosclerotic plaque resulting in an intracoronary thrombus.7 Thus, clinical prognosis might be similar between NSTEMI and UA patients. Moreover, improvements in revascularization techniques as well as new agents to address factors of the acute thrombotic process underlying ACS have resulted in considerable reductions in mortality and adverse clinical outcomes.

Interestingly, we found the rate of MACE was significantly higher in both the NSTE-ACS and stable angina groups by the time of FKB and no significant interaction between the NSTE-ACS or stable angina patient groups and MACE. And also, the FKB group had consistently worse outcomes across various subgroups. Final kissing ballooning was reported to be associated with a lower incidence of clinical events.8–10 These associations, however, have been studied mostly in 2-stent techniques, including mainly crush stenting techniques, so data on FKB in 1-stent techniques are limited. Considering that most lesions were treated with 1-stent techniques in our study (85.3% in NSTE-ACS patients and 81.8% in stable angina patients), the implications of FKB in our registry could be different from previous studies. Our COBIS investigation showed that FKB increased the long-term risk of TLR, most of which occurred in the main vessel, even after propensity score matching.11 In the present study, the rate of MACE was consistently higher in the FKB group among several subgroups. We propose that distortion of the main vessel stent might occur after opening a stent though the ostium of the side branch, but this distortion might not be corrected by FKB. In a previous intravascular ultrasound study on changes in the geometry of the main vessel stent following side branch ballooning and FKB, a reduction was observed in the cross-sectional area of the main vessel stent immediately distal to the side branch origin after side branch ballooning. However, the area did not return to its initial value after FKB.12 Decreased main vessel stent area, main vessel stent deformation, or polymer disruption of drug-eluting stent associated with side branch intervention may translate into increased restenosis and TLR in the main vessel. The Nordic-Baltic Bifurcation Study III also reported that a simple main vessel stenting technique without FKB provides excellent clinical results that are similar to those of the more complex strategy of main vessel stenting with FKB in patients with bifurcation lesions.13 However, as our study used post hoc analysis, the results should be interpreted carefully, and a well-powered, randomized trial is required to evaluate the role of FKB in the simple, 1-stent strategy.

Study Limitations

We used a retrospective multicenter registry; therefore, our results were affected by limitations inherent to this type of study. First, it is a nonrandomized and observational study, so uncounted confounders may have influenced study outcomes. Second, the selection of treatment strategies, including FKB, was at the discretion of the operators. Even though rigorous statistical adjustments were made to adjust for potential confounding factors, we were not able to control all variables. Third, in the present study, it is clear that NSTE-ACS patients presented higher risk profiles and more complicated angiographic pictures than stable angina patients. Thus, the study populations may not be well matched to draw definitive conclusions. Fourth, systemic angiographic follow-up was not performed, and coronary angiography was analyzed qualitatively, not quantitatively. Detailed quantitative analysis of the angiographic data would be helpful for interpreting our findings. Another limitation is that patients with ST-segment elevation myocardial infarction were excluded in this registry, so we cannot offer a more comprehensive view of the ACS patients and elucidate differences in outcomes between patients with various types of ACS. Finally, our sample was not large enough to evaluate the incidence of MACE, especially in the NSTE-ACS cohort. This limitation might be the reason that no significant differences were seen in clinical outcomes between the NSTEMI and UA patient subgroups.

Conclusion

The NSTE-ACS patients treated with drug-eluting stents for bifurcation lesions had an increased risk of MACE during the 2-year follow-up after percutaneous coronary intervention compared with stable angina patients. Also, the rate of MACE was significantly higher in the various subgroups by the time of FKB.

Ancillary