Effect of Side Branch Predilation in Coronary Bifurcation Stenting With the Provisional Approach　― Results From the COBIS (Coronary Bifurcation Stenting) II Registry ―

Abstract

Background: Whether side branch (SB) predilation before main vessel (MV) stenting is beneficial is uncertain, so we investigated the effects of SB predilation on procedural and long-term outcomes in coronary bifurcation lesions treated using the provisional approach.

Methods and Results: A total of 1,083 patients with true bifurcation lesions undergoing percutaneous coronary intervention were evaluated. The primary outcome was a major adverse cardiovascular event (MACE): cardiac death, myocardial infarction, or target lesion revascularization. SB predilation was performed in 437 (40.4%) patients. Abrupt (10.5% vs. 11.3%; P=0.76) or final SB occlusion (2.7% vs. 3.9%; P=0.41) showed no differences between the predilation and non-predilation groups. The rates of angiographic success (69.1% vs. 52.9%, P<0.001) and SB stent implantation (69.1% vs. 52.9%, P<0.001) were significantly higher in the predilation group. During a median follow-up of 36 months, we found no significant difference between the groups in the rate of MACE (9.4% vs. 11.5%; P=0.67) in a propensity score-matched population. In subgroup analysis, patients with minimal luminal diameter of the parent vessel ≤1 mm benefited from SB predilation in terms of preventing abrupt SB occlusion (P for interaction=0.04).

Conclusions: For the treatment of true bifurcation lesions, SB predilation improved acute angiographic and procedural outcomes, but could not improve long-term clinical outcomes. It may benefit patients with severe stenosis in the parent vessel.

Coronary bifurcation lesions are relatively common, found in up to one of every 5 percutaneous coronary interventions (PCI).¹ Based on the results of numerous randomized trials, the provisional approach is now regarded as the standard treatment for coronary bifurcation lesions.^2–4 However, bifurcation lesions may suffer from side branch (SB) compromise after dilation of the balloon or implantation of the stent in the main vessel (MV). Although predilation of the SB may be performed to prevent SB occlusion and to simplify the procedure, the advantage of this strategy remains debatable. In addition, few data are available about the effects of SB predilation on procedural and long-term clinical outcomes.^5–7 Therefore, we used a large dedicated bifurcation registry to compare the procedural and clinical outcomes of patients receiving or not receiving SB predilation for true bifurcation lesions.

Methods

Study Population and Data Collection

The COBIS (COronary BIfurcation Stenting) II registry is a retrospective multicenter registry of patients with coronary bifurcation lesions undergoing PCI with drug-eluting stents (DES). From January 2003 through October 2010, a total of 2,897 consecutive patients from 18 major coronary intervention centers in South Korea were enrolled. Inclusion criteria were: (1) coronary bifurcation lesions treated with DES only; and (2) MV diameter ≥2.5 mm and SB diameter ≥2.3 mm confirmed by core laboratory quantitative coronary analysis. Exclusion criteria were: (1) cardiogenic shock or requiring cardiopulmonary resuscitation; and (2) protected left main trunk (LMT) disease. The decision to perform SB predilation before MV stenting or not was made by the respective operators.

To assess the effects of SB predilation before MV stenting on procedural and clinical outcomes, we excluded 1,395 patients with non-true bifurcation according to the Medina classification.⁸ Additionally, we excluded 96 patients because of total SB occlusion before PCI and 323 patients because of the use of the systematic 2-stent technique. Finally, we included 1,083 patients in this study (Figure 1). The local institutional review board at each hospital approved this study.

Figure 1.

Schematic of the study. COBIS II, COronary BIfurcation Stenting II registry; PCI, percutaneous coronary intervention; SB, side branch.

Treatment Strategy

All interventions and procedural anticoagulation were performed according to current standard guidelines.⁹ All patients received loading doses of aspirin (300 mg) and clopidogrel (300–600 mg) before PCI unless they had previously received these antiplatelet medications. Aspirin treatment was continued indefinitely, and the duration of clopidogrel treatment was left to the discretion of the physician. The choices of treatment strategy and stenting technique were left to the discretion of the interventional cardiologists.

Data Collection and Angiographic Analysis

Data were collected using a Web-based reporting system. Additional information was obtained from the medical records or by telephone contact, if necessary. All outcome data reported from the participating center were reviewed by an independent clinical event adjudicating committee. Coronary angiograms were reviewed and analyzed quantitatively by an independent core laboratory at Samsung Medical Center. Angiographic and procedural characteristics of all cine-angiograms were reviewed and analyzed at the angiographic core laboratory (Heart, Stroke and Vascular Institute, Samsung Medical Center, Seoul, South Korea) using an automated edge-detection system (Centricity CA1000, GE; Waukesha, WI, USA) using standard definitions.¹⁰ Medina classification (1,1,1), (1,0,1) or (0,1,1) lesions were categorized as true bifurcation lesions. For the MV, the reference diameter was defined as the average of the proximal and distal reference lumen diameters. For the SB, the reference diameter was the distal reference lumen diameter.

Study Outcomes and Definitions

The primary outcome was major adverse cardiac events (MACE), which was defined as a composite of cardiac death, myocardial infarction (MI) and target lesion revascularization (TLR) during follow-up. TLR was defined as revascularization of the MV or SB. Parent vessel (PV) was defined as the proximal vessel of the bifurcation lesion. MV was defined as the distal main branch of the PV. We defined the bifurcation angle as that between the axis of the MV and the axis of the SB at its origin. The diameter of the stenosis in the SB ostium was calculated by the following equation: 100×(reference diameter of distal SB−minimum lumen diameter of SB ostium)/reference diameter of distal SB. We identified calcifications as apparent radiopacities within the vascular wall at the site of the stenosis and classified them as moderate (radiopacities noted only during the cardiac cycle before the contrast injection) or severe (radiopacities noted without cardiac motion before the contrast injection and generally compromising both sides of the arterial lumen).¹¹ We assessed the occurrence of periprocedural MI using the SCAI definition of a clinically relevant MI.¹² SB compromise was defined as Thrombolysis in Myocardial Infarction (TIMI) flow grade <3 during the procedure. The definition of angiographic success was final TIMI 3 flow and <30% residual stenosis in the MV and <50% residual stenosis in the SB. Procedural success was defined as angiographic success plus no cardiac death, ST-segment elevation MI, or emergency coronary artery bypass graft surgery during the hospital stay.

Statistical Analysis

For continuous variables we used the t-test or Wilcoxon rank-sum test when applicable, and we present the results as mean±standard deviation or median with interquartile range (IQR). Differences among groups were evaluated using the Chi-square or Fisher’s exact test for categorical data. Variables associated with abrupt SB occlusion (left main bifurcation, usage of a non-compliant balloon, final kissing balloon, SB lesion length ≥5 mm, calcification of the MV and SB, bifurcation angle, and minimal luminal diameter (MLD) of the PV and SB ≤1.0 mm) were included in multiple logistic-regression analyses to search for independent predictors. Model calibration was assessed using the Hosmer-Lemeshow statistics. Odds ratios are reported with 95% confidence intervals (CI). Survival curves were constructed using Kaplan-Meier estimates and compared with the log-rank test. We compared the adjusted hazard ratio (HR) using Cox regressions based on diabetes, acute coronary syndrome, final kissing balloon, the total length of the PV, the MLD of the PV and SB, and the lesion length of the SB, which were statistically significant and/or clinically relevant. To reduce treatment-selection bias for predilation of the SB and potential confounding factors, we performed rigorous adjustments for patients’ baseline and angiographic characteristics using their propensity scores, which we estimated using multiple logistic-regression analyses. Model discrimination was assessed with c-statistics, and model calibration was assessed with Hosmer-Lemeshow statistics. An absolute standardized difference <10% for the measured covariate suggested an appropriate balance between the groups. We compared the continuous variables with paired Student t-tests or the Mann-Whitney test as appropriate, and categorical variables with McNemar’s or Bhapkar’s tests of symmetry, as appropriate. In the propensity score-matched population, we compared the HR for outcomes using a stratified Cox regression model. We performed statistical analyses using SAS 9.2 (SAS Institute Inc., Cary, NC, USA). All tests were 2-tailed, and P<0.05 was considered statistically significant.

Results

Clinical, Angiographic, and Procedural Characteristics

SB predilation before MV stenting was performed in 437 (40.4%) of the 1,083 patients with a true bifurcation lesion undergoing PCI using the provisional approach. The clinical, angiographic, and procedural characteristics of the 2 groups are shown in Table 1 and Table 2. We found no significant differences between the groups in terms of clinical characteristics. The rates of using SB protection wire, final kissing balloon and 2 stents were higher in the predilation group than in the non-predilation group. The predilation group had shorter total stent length and larger stent diameter than the non-predilation group. We created 392 matched pairs of patients by performing propensity score-matching for the total population. We found no significant imbalances in the baseline variables of the matched population between the non-predilation and predilation groups (Tables 1,2).

Table 1. Baseline Clinical Characteristics in the Total and Propensity Score-Matched Populations

	Total population				Propensity score-matched population
	Non-predilation (n=646)	Predilation (n=437)	P value	Standardized mean difference	Non-predilation (n=392)	Predilation (n=392)	Standardized mean difference
Age	64.0 (57.0–70.0)	63.0 (55.0–70.0)	0.22	−7.55	63.0 (56.0–69.0)	63.0 (55.0–70.0)	−2.71
Male	455 (70.4)	321 (73.5)	0.31	−6.84	374 (73.4)	376 (73.0)	−1.15
ACS	405 (62.7)	262 (60.0)	0.40	−5.58	235 (59.9)	235 (59.9)	0
Smoking	161 (24.9)	116 (26.5)	0.60	3.67	98 (25.0)	104 (26.5)	3.46
Diabetes	190 (29.4)	117 (26.8)	0.38	−5.95	112 (28.6)	107 (27.3)	−2.88
Hypertension	393 (60.8)	255 (58.4)	0.45	−5.03	232 (59.2)	234 (59.7)	1.03
Dyslipidemia	217 (33.6)	143 (32.7)	0.82	−1.85	126 (32.1)	131 (33.4)	2.72
CKD	20 (3.1)	9 (2.1)	0.40	−7.29	8 (2.0)	9 (2.3)	1.79
History of MI	35 (5.4)	23 (5.3)	0.99	−0.69	21 (5.4)	23 (5.9)	2.28
History of PCI	81 (12.5)	60 (13.7)	0.63	3.46	53 (13.5)	56 (14.3)	2.22
LVEF <50%	96 (14.9)	50 (11.4)	0.11	−7.35	60 (15.3)	59 (15.1)	−0.72

Values are median (interquartile range) or n (%). ACS, acute coronary syndrome; CKD, chronic kidney disease; MI, myocardial infarction; PCI, percutaneous coronary intervention; LVEF, left ventricular ejection fraction.

Table 2. Angiographic and Procedural Characteristics in the Total and Propensity Score-Matched Populations

	Total population				Propensity score-matched population
	Non- predilation (n=646)	Predilation (n=437)	P value	Standardized mean difference	Non- predilation (n=392)	Predilation (n=392)	Standardized mean difference
Medina class			0.002
(1, 1, 1)	377 (58.4)	297 (68.0)		20.56	256 (65.3)	261 (66.6)	2.70
(1, 0, 1)	101 (15.6)	64 (14.6)		−2.80	60 (15.3)	57 (14.5)	−2.16
(0, 1, 1)	168 (26.0)	76 (17.4)		−22.70	76 (19.4)	74 (18.9)	−1.34
LMT bifurcation	122 (18.9)	89 (20.4)	0.55	3.67	79 (20.2)	77 (19.6)	0.00
MV calcification	159 (24.6)	94 (21.5)	0.24	−7.54	88 (22.4)	87 (22.2)	−0.62
SB calcification	53 (8.2)	30 (6.9)	0.42	−5.29	24 (6.1)	28 (7.1)	4.03
SB protection wire	415 (64.2)	390 (89.2)	0.001	80.61	337 (86.0)	345 (88.0)	6.58
Newer-generation stent	96 (14.9)	50 (11.4)	0.11	−10.73	49 (12.5)	48 (12.2)	−0.80
Multilesion intervention	327 (50.6)	232 (53.1)	0.46	4.94	197 (50.3)	203 (51.8)	3.06
IVUS	236 (36.5)	136 (31.1)	0.07	−11.67	142 (36.2)	127 (32.4)	−8.26
Non-compliant balloon	147 (22.8)	111 (25.4)	0.32	6.07	91 (23.2)	97 (24.7)	3.51
Total stent length of PV, mm	28.0 (23.0–33.0)	24.0 (20.0–33.0)	<0.001	−14.99	28.0 (23.0–33.0)	24.0 (20.0–33.0)	−3.62
Stent diameter of PV, mm	3.00 (2.75–3.50)	3.00 (3.00–3.50)	0.01	13.86	3.0 (3.0–3.5)	3.0 (3.0–3.5)	2.05
Total stent length of SB, mm	18.0 (16.0–28.0)	18.0 (15.0–24.0)	0.62		18.0 (15.0–24.0)	18.0 (15.0–24.8)
Stent diameter of SB, mm	2.75 (2.50–3.00)	3.00 (2.75–3.00)	0.08		2.8 (2.5–3.0)	3.0 (2.8–3.5)

Values are median (interquartile range) or n (%). IVUS, intravascular ultrasound; LMT, left main trunk; MV, main vessel; PV, parent vessel; SB, side branch.

Quantitative Coronary Angiography (QCA) Data

The QCA data are described in Table 3. The predilation group showed smaller MLD of the PV and SB, and longer length of SB plaque than the non-predilation group. After propensity matching, we found no significant difference in the QCA data of the 2 groups (Table 3).

Table 3. Baseline Quantitative Coronary Angiographic Data in the Total and Propensity Score-Matched Populations

	Total population				Propensity score-matched population
	Non-predilation (n=646)	Predilation (n=437)	P value	Standardized mean difference	Non-predilation (n=392)	Predilation (n=392)	Standardized mean difference
Bifurcation angle, degrees	57.3 (44.8–74.1)	58.1 (44.3–75.8)	0.69	1.57	57.4 (45.0–75.0)	58.5 (44.3–75.0)	−0.19
Preprocedural RD
PV	3.3 (2.9–3.7)	3.3 (3.0–3.8)	0.10	9.12	3.32 (2.92–3.72)	3.30 (2.93–3.76)	0.13
MV	2.6 (2.4–2.9)	2.6 (2.4–3.0)	0.42	6.94	2.64 (2.41–2.97)	2.64 (2.40–2.97)	0.29
SB	2.4 (2.3–2.6)	2.4 (2.3–2.6)	0.52	7.09	2.37 (2.30–2.57)	2.37 (2.30–2.64)	2.34
Preprocedural MLD
PV	1.5 (1.1–2.0)	1.3 (0.8–1.9)	<0.001	−18.76	1.42 (1.01–1.93)	1.32 (0.76–1.92)	−6.73
MV	1.1 (0.7–1.4)	1.1 (0.8–1.4)	0.39	6.06	1.06 (0.77–1.42)	1.06 (0.75–1.42)	−1.28
SB	1.0 (0.8–1.2)	0.9 (0.6–1.1)	<0.001	−33.67	1.00 (0.78–1.21)	0.96 (0.69–1.19)	−9.81
Lesion length of MV	17.7 (11.5–26.8)	16.6 (10.4–25.0)	0.098	−11.66	16.91 (11.50–26.48)	17.17 (10.37–25.95)	−1.85
Lesion length of SB	5.5 (2.7–10.5)	6.2 (3.4–10.7)	0.013	10.65	5.89 (3.35–10.80)	5.98 (3.26–10.55)	3.92

Values are median (interquartile range) or n (%). MLD, minimal luminal diameter; RD, reference diameter. Other abbreviations as in Table 2.

Procedural Outcomes

The incidence of both SB dissection (1.8% vs. 1.5%; P=0.91) and SB closure during PCI (10.5% vs. 11.3%; P=0.76) was similar between the predilation and non-predilation groups. SB stent implantation was more frequently performed in the predilation group than in the non-predilation group (28.4% vs. 14.7%, P<0.001). The angiographic success rates, overall (68.4% vs. 51.9%; P<0.001) and of the SB (69.1% vs. 52.9%; P<0.001), were higher in the predilation group than in the non-predilation group (Table 4). The rate of procedural success was also significantly higher in the predilation group than in the non-predilation group (68.4% vs. 51.7%; P<0.001). In the propensity score-matched population, SB predilation was associated with a higher rate of overall (69.1% vs. 57.1%; P=0.001) and SB (69.9% vs. 58.4%; P=0.001) angiographic success, and procedural success (69.1% vs. 56.9%; P<0.001). In addition, in-hospital MACE was lower in the predilation group (2.6% vs. 0.5%; P=0.02).

Table 4. Acute Angiographic and Procedural Outcomes in the Total and Propensity Score-Matched Populations

	Total population			Propensity score-matched population
	Non-predilation (n=646)	Predilation (n=437)	P value	Non-predilation (n=392)	Predilation (n=392)	P value
Postprocedural MLD
PV	3.0 (2.7–3.4)	3.1 (2.7–3.6)	0.006	3.03 (2.69–3.41)	3.10 (2.67–3.57)	0.22
MV	2.6 (2.3–2.9)	2.7 (2.4–3.0)	0.11	2.63 (2.35–3.01)	2.65 (2.33–2.98)	0.63
SB	1.2 (0.9–1.9)	1.6 (1.1–2.2)	<0.001	1.32 (0.89–2.01)	1.65 (1.12–2.25)	<0.001
SB stent implantation	95 (14.7)	124 (28.4)	<0.001	74 (18.9)	112 (28.6)	0.001
Final kissing balloon	293 (45.4)	246 (56.3)	<0.001	208 (53.1)	219 (55.9)	0.43
Intraprocedural event
SB dissection	10 (1.5)	8 (1.8)	0.91	2 (0.5)	5 (1.2)	0.26
SB closure during PCI	73 (11.3)	46 (10.5)	0.76	55 (14.0)	40 (10.2)	0.10
Final TIMI flow <3	29 (4.5)	12 (2.7)	0.14	18 (4.6)	10 (2.6)	0.13
Angiographic success
In MV	633 (98.0)	430 (98.4)	0.79	384 (98.0)	385 (98.2)	0.80
In SB	342 (52.9)	302 (69.1)	<0.001	229 (58.4)	274 (69.9)	0.001
Overall	335 (51.9)	299 (68.4)	<0.001	224 (57.1)	271 (69.1)	0.001
In-hospital MACE	13 (2.0)	5 (1.1)	0.27	10 (2.6)	2 (0.5)	0.02
Procedural success†	334 (51.7)	299 (68.4)	<0.001	223 (56.9)	271 (69.1)	<0.001
Periprocedural MI‡	118 (19.6)	69 (17.5)	0.40	70 (19.2)	64 (17.8)	0.63

Values are n (%). *Angiographic success defined as final TIMI 3 flow, <30% residual stenosis in the MV and <50% residual stenosis in the SB. ^†Procedural success defined as angiographic success plus no in-hospital MACE. ^‡Periprocedural CK-MB was checked in a total of 997 patients and in 724 patients in the propensity score-matched population. CABG, coronary artery bypass graft surgery; CK-MB, creatine kinase, myocardial bound; MACE, major adverse cardiac event; TIMI, Thrombolysis in Myocardial Infarction. Other abbreviations as in Tables 1–3.

Clinical Outcomes

The median follow-up duration was 34 months (IQR 21–51) in the non-predilation group and 38 months (IQR 28–50) in the predilation group (P<0.001). The risk of MACE (9.1% vs. 11.7%; adjusted HR, 1.18; 95% CI, 0.79–1.75; P=0.43) was not different between the 2 groups in the multivariate analysis (Table 5, Figure 2A). In addition, we found no significant difference in the rate of cardiac death, MI, TLR or stent thrombosis. The propensity score-matched analysis showed the same results (Table 5, Figure 2B).

Table 5. Clinical Outcomes During the Follow-up Period in the Total and Propensity Score-Matched Populations

	Non- predilation (n=646)	Predilation (n=437)	Unadjusted HR (95% CI)	P value	Multivariate analysis*		Propensity score-matched population
					Adjusted HR (95% CI)	P value	Non- predilation (n=392)	Predilation (n=392)	Adjusted HR (95% CI)	P value
MACE	59 (9.1)	51 (11.7)	1.18 (0.81–1.72)	0.38	1.18 (0.79–1.75)	0.43	37 (9.4)	45 (11.5)	1.10 (0.72–1.68)	0.67
Cardiac death	9 (1.4)	9 (2.1)	1.41 (0.56–3.54)	0.47	1.36 (0.50–3.70)	0.46	5 (1.3)	7 (1.8)	1.32 (0.41–4.16)	0.64
MI	9 (1.4)	9 (2.1)	1.36 (0.54–3.42)	0.52	1.61 (0.60–4.36)	0.35	6 (1.5)	8 (2.0)	1.23 (0.43–3.56)	0.70
TLR	46 (7.1)	35 (8.0)	1.00 (0.64–1.55)	0.99	0.97 (0.61–1.54)	0.89	31 (7.9)	32 (8.2)	0.91 (0.56–1.48)	0.70
ST†	6 (0.9)	4 (0.9)	0.93 (0.26–3.28)	0.90	1.01 (0.26–3.92)	0.99	3 (0.8)	4 (1.0)	1.23 (0.28–5.42)	0.79

Values are n (%). *Covariates are diabetes, ACS, SB protection wire, final kissing balloon, total length and stent diameter of parent vessel, MLD of parent vessel and SB, and length of SB.^†Defined as definite or probable ST. CI, confidence interval; HR, hazard ratio; ST, stent thrombosis; TLR, target lesion revascularization. Other abbreviations as in Tables 1–4.

Figure 2.

Kaplan-Meier curves for major adverse cardiac events in the side branch predilation group vs. the non-predilation group. (A) Total population. (B) Propensity score-matched population.

Subgroup Analysis

To determine whether abrupt SB occlusion was consistent in the total population or varied with SB predilation, we calculated the odds ratio for abrupt SB occlusion in various complex subgroups (Figure 3). Patients with an MLD of the PV ≤1.0 mm by QCA benefited from SB predilation (P for interaction=0.04). Other variables showed no interaction for abrupt SB occlusion.

Figure 3.

Comparison of abrupt side branch occlusion in the subgroups. CI, confidence interval; HR, hazard ratio; SB, side branch.

Analysis of the Patients With LMT Bifurcation

We additionally analyzed the acute angiographic and procedural outcomes, and long-term clinical outcomes in patients with LMT bifurcation. Baseline, angiographic and QCA data showed that the rate of using SB protection wire was higher in the predilation group. In addition, the MLD of the SB was smaller and the SB lesion length was longer in the predilation group (Tables S1–S3). In a total of 211 patients with LMT bifurcation, acute angiographic and procedural outcomes were not statistically different between the predilatation and non-predilation groups (Table S4). Moreover, there were no significant differences in the rate of MACE, cardiac death, MI, TLR or stent thrombosis between the 2 groups in either the total or propensity score-matched population (Table S5).

Discussion

The main findings of this study were as follows: (1) predilation of the SB might not reduce abrupt SB occlusion in a bifurcation intervention using the provisional approach; (2) predilation of the SB showed better acute angiographic and procedural outcomes compared with non-predilation; (3) long-term outcomes showed no differences between the predilation and non-predilation groups; and (4) SB predilation may, however, prevent abrupt SB occlusion during stent implantation in patients with an MLD of the PV ≤1.0 mm.

Effect of SB Predilation in the Provisional Strategy

Predilation of the SB before MV stenting in a coronary bifurcation intervention is generally performed to maintain TIMI flow and facilitate the rewiring of the SB.⁷ Therefore, SB predilation could improve the angiographic and procedural success rates of the bifurcation intervention by decreasing the rate of SB compromise. In addition, predilation could help prevent rewiring and post-dilation of the SB after implantation of the MV stent.¹³ The positive effect of SB predilation is enabling the MV stent to maintain its original shape without strut disruption, preventing additional SB intervention. On the other hand, the risk of SB dissection could increase with SB predilation. In a previous study, SB predilation was associated with a higher rate of crossover to SB stenting during the provisional approach, which corresponds well with our results here.^4,5 Additionally, if the dilated SB ostium is not covered by the MV stent, the risk of restenosis could be increased.¹³ Although using protection wire for the SB was frequently performed to prevent SB occlusion in both groups, it could not prevent abrupt SB occlusion during the procedure. However, protection wire in the SB was helpful for recovery of the occluded SB.¹

Current Status of SB Predilation in Coronary Bifurcation Stenting With the Provisional Approach

To date, only a few studies of the effects of SB predilation have been done. Pan et al showed improved TIMI flow after MB stenting and decreased additional SB treatment in patients who were treated with SB predilation, but the overall clinical outcomes were comparable with those who did not receive SB predilation.⁶ However, although it was a randomized trial, that study analyzed a small population; hence it could not effectively compare clinical outcomes. Moreover, it focused on immediate angiographic results, and the follow-up duration was only 9 months. In contrast, our present study used a large study population and found no differences between the predilation and non-predilation groups with regard to acute closure or clinical outcome. One observational study found that predilation before MV stent implantation using the kissing balloon technique safely prevented SB compromise and showed improved clinical outcomes.¹⁴ That study performed SB predilation only via the kissing balloon technique, and it had a small population. On the other hand, some studies have presented worse outcomes of the patients who were treated with SB predilation. A prior analysis of the COBIS registry found unfavorable results, such as increments of target vessel failure, among patients who underwent SB predilation.⁵ We can consider several explanations for this different result. First, the diameter of the SB may affect the clinical outcome. In the current study, we excluded patients with SB diameter <2.3 mm and included patients with LMT bifurcation. The ballooning of a small coronary artery is associated with coronary artery dissection.^15,16 In addition, the use of newer-generation stents could promote favorable clinical outcomes. Generally, newer-generation stents show a better results than 1st-generation stents such as the Cypher and Taxus stents.^17–19 Moreover, the use of 2nd-generation DES when treating of bifurcation lesions is associated with clinical outcomes better than those with 1st-generation DES.²⁰ The use of newer-generation stents was higher in this study than in prior studies, and implanting newer-generation DES in the SB in the predilation group may have affected the clinical outcomes. Recently, a small randomized trial also reported that SB predilation was associated with worse outcomes, such as more common dissections in the SB ostium and impairment of flow, but the number of participants in that study was small, and it excluded patients with LMT bifurcation or extensive SB disease.²¹

Patients Who Benefit From SB Predilation

Routine SB predilation is not recommended in bifurcation interventions, but if SB compromise is anticipated after MV stenting, it should be considered. Factors favoring SB predilation include the presence of severe SB ostial stenosis, suboptimal SB flow after wiring, extensive calcification and extensive SB disease extending beyond the ostium.¹³ Nevertheless, SB predilation had no beneficial effect on patients with an MLD of the SB ≤1.0 mm, SB calcification, or SB lesion length >5 mm in the subgroup analysis of the present study. On the other hand, patients with an MLD of the PV ≤1.0 mm did benefit from SB predilation in respect to abrupt SB occlusion. PV stenosis independently predicts SB occlusion after MV stenting.¹ Intravascular ultrasound studies have postulated that the key mechanism of SB occlusion is carina or plaque shifting.^22,23 In addition, although carina shift was the most common mechanism for anatomic SB compromise, plaque shift appeared to play an important role in a subset of patients with functional SB compromise.²⁴ Hence, PV stenosis plays a major role in SB compromise because it contributes to plaque shifting during procedures.¹ Consequently, rearranging PV plaque via SB predilation may prevent abrupt occlusion of SB during a MV intervention. Based on our results, SB dilation might be effective in patients with a large plaque burden in the PV.

Study Limitations

Our results should be appraised with consideration of the following limitations. This study was based on a retrospective registry and was not randomized, and therefore selection bias and potential confounding factors might have significantly affected the results. There is a possibility that SB predilation was performed in patients with severe SB disease because of the operator’s choice and actually, the SB predilation group showed a higher rate of some variables that were assumed as risk factors of SB occlusion such as longer lesion length of the SB and smaller MLDs of the PV and SB. In order to correct these differences, we conducted propensity score-matching, and standardized mean differences of all covariates after matching were between −10% and 10%, which equates to well balanced. Although we performed rigorous propensity score-matching, there is possibility that the SB predilation group had unmeasured variables that made operators to perform predilation and it is difficult to predict how residual confounding would affect clinical outcomes. Neither treatment strategy nor stenting technique was prespecified. The reason for SB stenting was unclear. There was a lack of data regarding predilation, such as balloon size, pressure, time, and ratio between balloon and SB diameters. Advances in devices, techniques, and operator experience during the study period are not reflected in the results. The implantation rate of newer-generation stents was relatively low, so our results might not reflect contemporary practice of PCI. Finally, our QCA data were measured using conventional 2D QCA analysis, which is less accurate, less precise, and less reproducible in bifurcation lesions than 3D QCA analysis. Despite these limitations, the present study provided useful data about SB predilation from a large multicenter registry with rigorous propensity score-matching, so it can be used to inform the current practice of coronary bifurcation interventions.

Conclusions

In the treatment of true bifurcation lesions with the provisional approach, SB predilation improved acute angiographic and procedural outcomes, but could not improve long-term clinical outcomes. It may benefit patients with severe stenosis in the PV.

Conflict of Interest Statement

The authors have no conflicts of interest to declare.

Supplementary Files

Supplementary File 1

Table S1. Baseline clinical characteristics in the total and propensity score-matched populations with LMT bifurcation

Table S2. Angiographic and procedural characteristics in total and propensity score-matched populations with LMT bifurcation

Table S3. Baseline quantitative coronary angiographic data in the total and propensity score-matched populations with LMT bifurcation

Table S4. Acute angiographic and procedural outcomes in total and propensity score-matched populations with LMT bifurcation

Table S5. Clinical outcomes during the follow-up period in the total and propensity score-matched populations with LMT bifurcation

Please find supplementary file(s);

http://dx.doi.org/10.1253/circj.CJ-17-0921

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