J Cardiol 2003 May; 41（5）: 215 – 224

Evaluation of Restenosis in Major
Vessels and Side Branches
Teruo

OKABE, MD

YasushiASAKURA, MD

KeikoASAKURA, MD

Akiko

YAMANE, MD

KeishuRI, MD

Akio
Satoshi

KAWAMURA, MD
OGAWA, MD,

Abstract ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Objectives. The indications for concurrent intervention for stenosis of a side branch during the treatment
for stenosis of the main vessel were investigated using quantitative coronary angiography.
Methods. The retrospective study included 451 patients treated for a stenotic main vessel incorporating aside branch, who underwent follow-up angiography within 6 months. Patients were divided into Group Ⅰwith the side branch treated by coronary angioplasty, and Group Ⅱ with the side branch left untreated.
Quantitative coronary angiography was used to measure the minimum luminal diameter（MLD）and percentage diameter stenosis（%DS）of the main vessel and the side branch.
Results. The MLD of the side branch after treatment was larger in Group Ⅰ（1.4 ± 0.1 mm）than inGroup Ⅱ（0.7 ± 0.1 mm）, and the %DS of the side branch after treatment was smaller in Group Ⅰ（34 ±3%）than in Group Ⅱ（63 ± 2%）. These differences decreased at follow-up to 1.1 ± 0.1 mm, 48 ± 2% inGroup Ⅰ ; 0.9 ± 0.04 mm, 46 ± 2% in Group Ⅱ, respectively. The MLD and %DS of the side branch atfollow-up in Groups Ⅰ and Ⅱ were affected by the presence of main vessel restenosis［Restenosis（＋）:
0.9 ± 0.1 mm, 57 ± 4% ; restenosis（−）: 1.2 ± 0.1 mm（p ＜ 0.05）, 43 ± 3%（p ＜ 0.05）in Group Ⅰ ;Restenosis（ ＋）: 0.9 ± 0.1 mm, 51 ± 8% ; restenosis（ −）: 1.0 ± 0.1 mm, 44 ± 3% in Group Ⅱ］.
Multivariate analysis showed that %DS of the main vessel at follow-up was the only powerful predictor ofrestenosis of the side branch（p ＝ 0.0249, odds ratio ＝ 1.031, confidence interval ＝ 1.004−1.059）inGroups Ⅰ and Ⅱ.
Conclusions. Restenosis of the main vessel rather than the initial outcome of the side branch is the
major influence on restenosis of the side branch.
────────────────────────────────────────────────────────────────────────────────────────────────────────────────────J Cardiol 2003 May ; 41
（5）
: 215−224

Key Words
Coronary artery disease
Interventional cardiology

Angiography

INTRODUCTION
Stenotic lesions which incorporate side branches
are often difficult to treat by coronary angioplasty,
and the results are frequently suboptimal, as dilation of the main lesions may damage the ostium of
the side branch as a result of plaque movement or

Angioplasty

Restenosis

dissection1）. Coronary angioplasty also carries ahigh risk of side branch occlusion 2−5）, so side
branch protection by wire placement and a kissing balloon technique are required6,7）. In addition,
the ostium of the side branch frequently undergoes
marked elastic recoil after angioplasty1,8）, so themedium-term outcome is less satisfactory com-──────────────────────────────────────────────
慶應義塾大学医学部 呼吸循環器内科 : 〒 160−8582 東京都新宿区信濃町 35
Cardiopulmonary Division, Department of Medicine, Keio University School of Medicine, Tokyo
Address for correspondence : OKABE T, MD, Cardiopulmonary Division, Department of Medicine, Keio University School of
Medicine, Shinano-machi 35, Shinjuku-ku, Tokyo 160−8582
Manuscript received October 31, 2002 ; revised January 30, 2003 ; accepted March 7, 2003

215

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Okabe, Asakura, Asakura et al

pared to that of stenotic lesions without side
branches2,6,8）.
Treatment of major stenoses associated withstenosis of a side branch by directional atherectomy
improves the immediate outcome compared to only
balloon dilation, but the incidence of restenosis
remains high 9）. The use of coronary stents also
improves the outcome of such lesions, but this procedure is technically challenging and carries a highrisk of compromising the branch 10）. Therefore,
treatment planning for a stenosis of a major vessel
must also consider the effect on the side branch.
Treatment of a side branch imposes limitations
on the procedures used for the main lesion. Various
techniques6,7）and new devices have been tried9−20）,
but none have achieved optimal initial and lateeffects, and the influence of the immediate effects
on the late effects in the side branch remain
unknown.
The present retrospective study examined theearly and late outcomes in patients with stenotic
lesions in a major vessel associated with a side
branch treated by coronary angioplasty to evaluate
whether concurrent intervention for side branchlesions during the procedure for the main lesion iseffective using quantitative coronary angiography（QCA）.
SUBJECTS AND METHODSPatients
This retrospective study included 451 consecutive patients admitted to our institution for percutaneous coronary intervention because of stable angina pectoris, unstable angina pectoris or acute
myocardial infarction.
The patients were treated by coronary angioplasty, using plain old balloon angioplasty, stentimplantation, or directional coronary angioplasty.
The main lesion was contiguous to the side branch,
and was located in the angle of the bifurcation in all
patients. All patients underwent QCA evaluation
before and after angioplasty and at follow-up examination within 6 months was performed at the Keio
University School of Medicine between August
1995 and January 1999.
A significant lesion was defined as a stenosis
greater than 75% according to the American
College of Cardiology/American Heart Association（ACC/AHA）classification. Group Ⅰ consisted of
85 patients who underwent coronary angioplasty
for significant lesions in the ostium of a side branch

before treatment of the main lesion, or had newly
developed significant lesions during the procedure.
Group Ⅱ consisted of 142 patients who received notreatment for significant lesions in the ostium of aside branch regardless of whether the lesions were
present before treatment or were newly developed
during the procedure. Group Ⅲ consisted of patients
who had no significant side branch lesions beforeor throughout the procedures, and had QCA parameters of the main lesion before the procedure
matching those of the other two groups. Group Ⅱ
acted as a control.
Angioplasty procedure
Coronary angioplasty was performed according
to the standard technique via the femoral approach.
All patients received aspirin（81 mg daily）
from theday before the procedure and continued for 6
months. Patients who underwent stent implantation
received ticlopidine（100 mg twice daily）
continued
for 1 month after the procedure. During the procedure, all patients received a bolus of heparin（10,000 IU）, followed by an additional bolus if
necessary. The double wire technique was used totreat the bifurcation lesion, and either the kissing
balloon technique or sequential balloon technique
was performed in Group Ⅰ. Patients who underwent stent implantation for side branch lesions
were excluded. Cases in which the side branch was
finally occluded without hemodynamic abnormality
were included in this study.
Angiographic analysis
Quantitative coronary angiography analysis of
the main lesion was performed by an experienced
angiographer not involved in the treatment, using
an automated edge detection algorithm（QCA-CMS
system version 3.0, MEDIS ; Leiden）and a contrast-filled catheter as the calibration standard. The
reference diameter and the minimum lumen diameter（MLD）of the main lesion were measured, andthe percentage diameter stenosis（%DS）
was calculated at each evaluation point. Two angiographers
performed QCA analysis of the side branch, toavoid measurement bias. The same indices for theside branch as mentioned above were measured andcalculated by each angiographer, and the mean values were used. The reference diameter of the side
branch was measured at a site ＜ 10 mm from theostium which was considered not to be involved in
the stenotic lesion.
J Cardiol 2003 May; 41（5）: 215 – 224

Restenosis of Side Branches

217

Table 1 Clinical characteristics of the patients
GroupⅠ（n＝85）

GroupⅡ（n＝142）

GroupⅢ（n＝224）Sex（male/female）

75/10

125/17193/31Age（yr, mean±SE）

64±1

63±1

61±1

Risk factor
Hypertension

31（36）

58（41）

76（34）

Hyperlipidemia

23（27）＊
54（38）

62（28）

Diabetes mellitus

17（20）

23（16）

32（14）

Smoking

33（39）

54（38）

71（32）Left anterior descending artery

60（71）

86（61）

141（63）

Left circumflex artery

18（21）

17（12）

37（17）

Right coronary artery

7（8）＃39（27）＃
46（20）

Target vessel

（ ）
: %.
GroupⅠ : With side branch treated by coronary angioplasty. GroupⅡ : With side branch left untreated.
GroupⅢ : No significant side branch lesions.
＊p＜0.05 vs GroupⅢ, ＃p＜0.05 vs GroupⅠ.

Coronary angiography was repeated within 6months of the treatment to evaluate the occurrenceof restenosis of the main lesion. If the patient
became symptomatic, coronary angiography was
performed at less than 6 months, and the measurements were included in this analysis. Restenosis of
the main vessel was defined as ＞ 50%DS in thetreated segment at follow-up angiography.
Restenosis of the side branch was defined as＞ 60%DS in the treated segment at follow-up
angiography, because the differences in QCA measurements by the two angiographers were minimized by this definition.
Statistical analysis
The chi-squared test and Fischer s exact test
were used for analysis of categorical variables if
appropriate, and one-way ANOVA and post hoc
tests were used for analysis of continuous variables
between the three groups. The unpaired t-test wasused to compare the quantitative data between two
groups. Differences were considered statisticallysignificant if p ＜ 0.05. Univariate and multivariate
logistic regression analyses were used to determine
predictors of side branch restenosis. Univariate predictors with p ＜ 0.2 were entered into the multivariate model. Independent predictors of side
branch restenosis and 95% confidence interval were
calculated. Baseline clinical characteristics, sex,age, target vessel and risk factors were included.
Reference diameter, MLD and %DS of the main
J Cardiol 2003 May; 41（5）: 215 – 224

vessel, and reference diameter, MLD and %DS of
the side branch, both before and after the procedure
and at follow-up examination, were included in themodel.
RESULTS
Characteristics of patients and lesions
The clinical characteristics of the patients areshown in Table 1. There were significantly morepatients with hyperlipidemia in Group Ⅱ comparedto Groups Ⅰ and Ⅲ. The main lesion was locatedmore often in the right coronary artery in Groups Ⅱ
and Ⅲ.
Baseline angiographic characteristics
The baseline angiographic characteristics of themain lesion were similar in all groups（Table 2）.
The reference diameter of the side branch was significantly larger in Group Ⅰ than in Groups Ⅱ and
Ⅲ. Predictably, MLD was significantly smaller inGroups Ⅰ and Ⅱ than in Group Ⅲ. Similarly, %DS
was significantly larger in Groups Ⅰ and Ⅱ than inGroup Ⅲ.
Quantitative coronary angiography of side
branches
The MLD of the side branch was similar before
treatment in Groups Ⅰ and Ⅱ, but became significantly greater after treatment（1.4 ± 0.1 mm）in
Group Ⅰ compared to Group Ⅱ（0.7 ± 0.1 mm）（p ＜ 0.05）. However, although MLD at follow-up

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Okabe, Asakura, Asakura et al

Table 2 Baseline angiographic characteristics
GroupⅠ（n＝85）

GroupⅡ（n＝142）

GroupⅢ（n＝224）

Reference diameter（mm）

2.6±0.1

2.6±0.1

2.6±0.1

Minimum luminal diameter（mm）

0.5±0.1

0.5±0.03

0.5±0.03

Percentage diameter stenosis（%）

79±2

80±1

81±1

2.1±0.1＊

1.7±0.1

1.7±0.04

Main lesion

Side branch
Reference diameter（mm）
Minimum luminal diameter（mm）

0.8±0.1

0.9±0.03

1.4±0.1＃

Percentage diameter stenosis（%）

58±3＊

44±2＊＊

18±1

Values are mean±SE.
p＜0.05 vs GroupsⅡandⅢ, ＃p＜0.05 vs GroupsⅠandⅢ, ＊＊p＜0.05 vs GroupⅢ.
Explanation of the groups as in Table 1.

＊＊

Fig. 1 Comparison of minimum luminal
diameter of the side branch before
and after treatment, and at follow-up（left）and comparison of the percentage diameter stenosis of the side
branch before and after treatment,
and at follow-up（right）＊＊＊

was still larger in Group Ⅰ（1.1 ± 0.1 mm）than inGroup Ⅱ（0.9 ± 0.04 mm）（p ＜ 0.05）, there was asignificant late loss in Group Ⅰ, so the difference
between the two groups clearly decreased（Fig. 1−
left）
. The %DS of the side branch before treatment
was significantly greater in Group Ⅰ（58 ± 3%）
compared to Group Ⅱ（44 ± 2%）（p ＜ 0.05）, andbut became significantly smaller after treatment inGroup Ⅰ（34 ± 3%）compared to Group Ⅱ（63 ±2%）（p ＜ 0.05）. However, the difference in %DS
between Groups Ⅰ（48 ± 2%）and Ⅱ（46 ± 2%）
had disappeared at follow-up angiography（Fig. 1−right）.
Relationship between outcomes of the main vessel and side branch
The MLD of the side branch after the procedure
had significantly increased compared to the MLD
before the procedure in Group Ⅰ, regardless ofrestenosis of the main lesion（without restenosis,＊＊
p ＜ 0.05 vs Groups Ⅰ and Ⅱ, † p ＜ 0.05
vs Group Ⅱ, ‡ p ＜ 0.05 vs Group Ⅰ.
MLD ＝ minimum luminal diameter ;%DS ＝ percentage diameter stenosis ;Pre ＝ before procedure ; Post ＝ after procedure. Explanation of the groups as in Table
1.

before : 0.8 ± 0.1 mm, after : 1.4 ± 0.1 mm ; withrestenosis, before : 0.9 ± 0.1 mm, after : 1.4 ±0.1 mm）（both p ＜ 0.05）. However, the MLD ofthe side branch was significantly greater at followup angiography in the absence of restenosis of themain lesion（ without restenosis, 1.2 ± 0.1 mm ;with restenosis, 0.9 ± 0.1 mm）（ p ＜ 0.05）.
Moreover, there was no difference in MLD of theside branch between before the procedure and at
follow-up angiography in the presence of restenosis（Fig. 2−left）.
The %DS of the side branch similarly increased
after the procedure（ without restenosis, before :58 ± 4%, after : 33 ± 4% ; with restenosis, before :59 ± 4%, after : 35 ± 5%）（ both p ＜ 0.05）. The%DS of the side branch at follow-up angiography
was greater in the presence of restenosis of themain vessel（57 ± 4%）, compared to absence ofrestenosis（43 ± 3%）（p ＜ 0.05）. The %DS of theside branch did not differ between before the proceJ Cardiol 2003 May; 41（5）: 215 – 224

Restenosis of Side Branches

219

Fig. 2 Relationship between restenosis of themain vessel and the side branch, andthe minimum luminal diameter inGroup Ⅰ（ left）and relationshipbetween restenosis of the main vessel
and the side branch, and the percentage diameter stenosis in Group Ⅰ（right）§

p ＜ 0.05 vs main lesion restenosis.
Explanation of the group and abbreviations
as in Table 1, Fig. 1.

Fig. 3 Relationship between restenosis of themain vessel and the side branch, andthe minimum luminal diameter inGroup Ⅱ（ left）and relationshipbetween restenosis of the main vessel
and the side branch, and the percentage diameter stenosis in Group Ⅱ（right）§

p ＜ 0.05 vs main vessel restenosis.
Explanation of the group and abbreviations
as in Table 1, Fig. 1.

dure and at follow-up angiography in the presence.
of restenosis（Fig. 2−right）
The MLD of the side branch was greater after theprocedure in the absence of restenosis than in thepresence of restenosis（ without stenosis, after :0.8 ± 0.1 mm ; with restenosis, after : 0.5 ±0.1 mm）（p ＜ 0.05）. The difference was not significant at follow-up angiography（without restenosis,
1.0 ± 0.1 mm ; with restenosis, 0.9 ± 0.1 mm ; Fig.
3−left）. The %DS of the side branch was smallerin the absence of restenosis（without restenosis,
after : 59 ± 3% ; with restenosis, after : 69 ± 4%）.
The difference was not significant at follow-up
angiography（without restenosis, 44 ± 3% ; withrestenosis, 51 ± 4% ; Fig. 3−right）.
Effect of main vessel variables on restenosis of
the side branch
The baseline characteristics were not significantJ Cardiol 2003 May; 41（5）: 215 – 224

ly different in Groups Ⅰ and Ⅱ between populations with and without side branch restenosis（datanot shown）. Univariate analysis showed that both
the MLD and %DS of the main vessel at follow-up
angiography were significantly correlated withrestenosis of the side branch（p ＜ 0.05 ; Table 3）.
Effect of side branch variables on restenosis
Statistical analysis showed that both the MLD
and %DS of the side branch after the procedure inGroups Ⅰ and Ⅱ significantly differed between
populations with and without side branch restenosis（p ＜ 0.05）. The reference diameter of the side
branch after the procedure also tended to differ
between populations with and without side branchrestenosis, although the difference was not significant（Table 4）.

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Okabe, Asakura, Asakura et al

Table 3 Univariate analysis of predictive factors for restenosis of the side branch（1）

Restenosis of side branchGroupsⅠandⅡ

Original lesion

New lesion（＋）（−）
p value（ n＝101）（n＝126）（＋）（−）
p value（n＝62）（n＝74）（＋）（−）
p value（n＝36） （n＝55）0.384

2.3±0.1

2.8±0.1

0.007

3.1±0.2

2.6±0.1

0.048

Parameters of main lesion
Pre RD（mm）

2.6±0.1

2.7±0.1

Post RD（mm）

3.1±0.1

3.0±0.10.600

2.9±0.1

3.1±0.1

0.621

3.3±0.2

2.9±0.1

0.116

Follow-up RD（mm）

2.7±0.1

2.8±0.1

0.637

2.6±0.1

2.8±0.1

0.354

2.8±0.2

2.7±0.1

0.650

Pre MLD（mm）

0.6±0.1

0.6±0.1

0.970

0.6±0.1

0.5±0.1

0.675

0.5±0.1

0.6±0.1

0.518

Post MLD（mm）

2.7±0.1

2.9±0.20.616

2.5±0.2

2.7±0.1

0.287

3.1±0.3

3.0±0.4

0.085

Follow-up MLD（mm） 1.4±0.2

1.8±0.1

0.028

1.4±0.2

1.8±0.1

0.072

1.4±0.3

1.8±0.1

0.214

Pre %DS
（%）

78±3

80±2

0.481

76±3

81±2

0.156

82±4

77±2

0.316

Post %DS
（%）

13±3

11±2

0.530

15±4

11±2

0.295

9±4

12±3

0.608

Follow-up %DS
（%）

48±4

35±3

0.007

47±5

36±3

0.066

51±8

33±4

0.042

Values are mean±SE.
RD＝reference diameter. Explanation of the groups and other abbreviations as in Table 1, Fig. 1.

Table 4 Univariate analysis of predictive factors for restenosis of the side branch（2）

Restenosis of side branchGroupsⅠandⅡ

Original lesion

New lesion（＋）（−）
p value（ n＝101）（n＝126）（＋）（−）
p value（n＝62）（n＝74）（＋）（−）
p value（n＝36） （n＝55）

Parameters of side branch
PCI

52/49

54/72

0.157

32/30

32/42

0.271

15/21

22/33

0.929

Pre RD（mm）

2.1±0.1

2.1±0.1

0.594

2.1±0.1

2.3±0.1

0.476

2.0±0.1

2.0±0.1

0.670

Post RD（mm）

1.9±0.1

2.1±0.1

0.142

2.0±0.1

2.1±0.10.285

1.9±0.1

2.0±0.1

0.264

Pre MLD（mm）

0.9±0.1

0.9±0.1

0.739

0.7±0.1

0.6±0.10.425

1.4±0.1

1.4±0.1

0.943

Post MLD（mm）

0.9±0.1

1.3±0.1

0.011

0.9±0.1

1.4±0.1

0.002

1.0±0.2

1.0±0.1

0.942

Pre %DS
（%）

56±3

56±2

0.987

68±2

70±2

0.453

32±4

28±3

0.434

Post %DS
（%）

53±4

41±3

0.024

55±5

34±3

0.001

48±9

55±4

0.488

Continuous values are mean±SE.
PCI＝percutaneous coronary intervention. Explanation of the groups and other abbreviations as in Tables 1, 3, Fig. 1.

Multivariate analysis
Multivariate analysis of the significant univariate
variables showed that follow-up %DS of the main
lesion was the only independent factor affecting therestenosis of the side branch in all groups, with the
cut-off value of side branch restenosis set at 60%（p ＝ 0.0249, odds ratio ＝ 1.031, confidence interval ＝ 1.004−1.059 ; Table 5）.
Subgroup analysis
The patients were sub-divided into two groups
according to the timing of side branch lesion development. Patients in the original lesion group had
preexisting lesions in the ostium of the side branch
before the treatment of the main lesion. Patients inthe new lesion group had newly developed lesions
in the side branch during the procedure for the main
lesion. Both univariate and multivariate analyses
were performed to examine the effect on restenosisof the side branch. The baseline characteristics inthese groups did not differ between populations
with and without side branch restenosis（data notshown）. Univariate analysis showed that reference
diameter of the main lesion before the procedure,and MLD and %DS of the side branch were significantly associated with restenosis of the side branchin the original lesion group（p ＜ 0.05）. Reference
diameter before the procedure and %DS at followup angiography of the main lesion were significantly associated with restenosis in the new lesion
J Cardiol 2003 May; 41（5）: 215 – 224

Restenosis of Side Branches

221

Table 5 Multivariate logistic regression analysis of predictive factors for restenosis of the side
branchGroupsⅠandⅡ
Odds ratio

Confidence interval

p value

Follow-up %DS of main lesion

1.031

1.004−1.059

0.0249PCI

0.475

0.223−1.012

0.0538

Post RD of main lesion

1.775

0.939−3.356

0.0773

Post MLD of side branch

0.678

0.241−1.911

0.4623

Follow-up MLD of main lesion

1.295

0.558−3.007

0.5471

Post %DS of side branch

1.005

0.981−1.030

0.6814

Follow-up %DS of main lesion

4.315

2.738−7.49

0.0058

Post RD of main lesion

1.739

0.982−2.258

0.1871

Post %DS of main lesion

1.013

0.027−0.028

0.3480Pre MLD of side branch

2.494

2.087−12.794

0.3484

Pre RD of side branch

1.442

0.635−1.133

0.6558

Post MLD of side branch

0.736

0.508−1.64

0.7874

Follow-up RD of main lesion

1.205

0.659−1.452

0.8957

Post %DS of side branch

1.019

0.028−0.029

0.8957

Follow-up %DS of main lesion

2.947

1.832−4.841

0.0381

Post %DS of main lesion

0.977

0.025−0.026

0.3162

Pre %DS of side branch

1.015

0.025−0.026

0.5372

Original lesion

New lesion

Explanation of the groups and abbreviations as in Tables 1, 3, 4, Fig. 1.

group（p ＜ 0.05）. However, multivariate analysis
showed that %DS at follow-up angiography of themain lesion was the only independent factor affecting the restenosis of the side branch in Groups Ⅰ
and Ⅱ.
DISCUSSION
The present study showed that the MLD of theside branch was significantly larger after the procedure and at follow-up in Group Ⅰ, in which theside branch was treated by coronary angioplasty,
compared to Group Ⅱ, in which the side branch
was not treated. However, the difference in MLD
between the two groups was clearly decreased atfollow-up. Moreover, there was no difference in%DS between the two groups at follow-up. Thesefindings indicate that the initial outcome for theside branch does not reflect the possibility of late
restenosis. The late outcome of the side branch is
not affected by the perfusion status or the presenceof an ostial stenosis immediately after the procedure21）.
This study also found that restenosis of the main
vessel was associated with unfavorable outcome for
J Cardiol 2003 May; 41（5）: 215 – 224

the side branch. This finding suggests the possibility of restenosis in the main vessel directly affects
the likelihood of restenosis in the side branch, especially if the side branch was treated during the procedure for the main lesion. Univariate analysis
showed that %DS of the main vessel at follow-up,
and both MLD and %DS of the side branch after
the procedure were significant predictors ofrestenosis of the side branch. However, the multivariate model indicated that %DS of the main
lesion at follow-up, and not %DS of the side branch
immediately after the procedure, was the only powerful predictor of late results of the side branch.
Accordingly, the restenosis of the side branchdepends on the occurrence of restenosis of the main
vessel. The analysis of the two subgroups, containing original lesions existing at the ostium of theside branch prior to procedures for the main vessel,
and newly developed side branch lesions during theprocedures, also showed that %DS of the main
lesion at follow-up was the only powerful predictorof restenosis of the side branch in both groups.
A previous study found that despite the association between restenosis of the main lesion and the

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Okabe, Asakura, Asakura et alside branch, reference diameter of the side branch
before the procedure was the only predictor ofrestenosis of the side branch21）. This finding is notconsistent with our results. There are some possible
reasons for this inconsistency, such as differencesin the study population, reference diameter of theside branch before the procedure, treatment for themain vessel, and absence of treatment for the side
branch in the previous study.
The exact mechanisms governing the flow in theside branches after treatment for stenosis of themain vessel remain unknown, but plausible explanations include the following : Remodeling of theplaque geometry at the ostium of the side branch by
the increased flow in the main vessel, and reversalof acute coronary spasm of the side branch.
Therefore, the patency of the side branch should bemaintained in most cases even in the presence ofany stenosis of the side branch after the treatment.
This study indicated that the initial results ofcoronary angioplasty for side branch lesions did notreflect the possibility of restenosis, so a different
approach or strategy from that for the main vessel
should not be chosen for the simultaneous treatment of side branch lesions. Adequate therapy forthe main vessel should avoid restenosis of both themain vessel and the side branch.
CONCLUSIONS
We conclude that if intervention for stenosis of aside branch is considered during a procedure totreat stenosis in a main vessel, whether the side
branch stenosis was previously present or newly
developed, treatment for the main vessel mustreceive priority for optimal prevention of restenosis.
Study limitations
This study was non-randomized, retrospective
and included a small population, so extension of要

the present findings to the general clinical population requires caution. The study was non-randomized, so there was bias in selecting cases and thedevices used to treat side branches and main vessels. In addition, this study has several other limitations.
Firstly, the reference diameter of the side branch
before the procedure tended to be small comparedto that of the main vessel. However, the present
study focused not on true bifurcation lesions, but
on main vessels with side branches. Multivariate
logistic regression analysis showed that restenosisof the side branch was more strongly affected by
the %DS of the main vessel at follow-up, comparedto the reference diameter of the side branch before
the procedure.
Secondly, the reference diameter of the side
branch at baseline differed between the threegroups. Accordingly, the side branch restenoses
that were not dilated could have been smaller, so
the surgeon did not attempt dilation. Although we
could not completely exclude this bias, multivariate
logistic regression analysis suggested that the reference diameter of the side branch before the procedure did not influence the restenosis of the side
branch.
Thirdly, we did not perform analysis according
to the device used to treat the side branch and themain lesion. Treatment of the main vessel with astent generally resulted in worse initial and late outcomes for the side branch compared to other procedures for the main lesion. Debulking of the main
lesion seemed to give a superior outcome for theside branch. Although the results are not presented
here, we confirmed that the same relationship held
between the main vessel and the side branch in only
patients who underwent stent implantation forstenosis of the main vessel.
A larger, prospective, randomized study isrequired to provide more accurate information.
約

本幹主病変部と側枝における再狭窄の評価
岡部

輝雄
李

目

朝 倉
慧 崇

靖

朝倉

恵子

山根

川村

朗夫

小 川

聡

明子

的 : 本幹主病変部分に一致して側枝が存在すると，側枝起始部に病変が存在する場合や，主病変治療中にプラークシフトなどにより狭窄が出現した場合には，主病変とともに治療を行うことが多い．しかし，側枝への加療は手技を複雑にするうえ，その遠隔期成績もいまだ満足できるもの
J Cardiol 2003 May; 41（5）: 215 – 224

Restenosis of Side Branches

223

ではない．本幹主病変治療に際し，側枝病変への加療が有効か否かを定量的冠動脈造影法を使用して評価した．
方

法 : 対象症例は，本幹主病変部分に一致して側枝が存在した症例で，6 ヵ月以内に確認造影を施行しえた 451 症例である．側枝への加療の有無により，加療群と非加療群とした．定量的冠動脈造影法により，主病変および側枝起始部の最小血管径，狭窄率を計測した．
結果 : 術後側枝起始部の最小血管径と狭窄率は，側枝へ加療をしなかった非加療群（0.7 ±0.1 mm，63 ± 2%）に比べて，側枝へ加療を施した加療群（1.4 ± 0.1 mm，34 ± 3%）で良好であった．
しかし，この差は遠隔期には失われた（加療群では 1.1 ± 0.1 mm，48 ± 2%，非加療群では 0.9 ±0.04 mm，46 ± 2%）．側枝起始部の遠隔期最小血管径と狭窄率は，両群とも本幹主病変が再狭窄した場合に，より増悪していた［加療群では，再狭窄（＋）: 0.9 ± 0.1 mm，57 ± 4% ; 再狭窄（−）:
1.2 ± 0.1 mm（p ＜ 0.05），43 ± 3%（p ＜ 0.05）．非加療群では，再狭窄（＋）: 0.9 ± 0.1 mm，51 ± 8% ;再狭窄（−）: 1.0 ± 0.1 mm，44 ± 3%］．多変量解析の結果，両群において，本幹主病変の遠隔期 %DS が，側枝狭窄の遠隔期成績に対する独立規定因子であった（p ＝ 0.0249，オッズ比＝ 1.031，
信頼区間＝ 1.004−1.059）．
結論 : 側枝狭窄の遠隔期成績は，側枝への加療の有無および側枝狭窄の程度とは関係なく，むしろ本幹主病変の遠隔期成績の影響を強く受けていることが示唆された．

J Cardiol 2003 May; 41（5）: 215−224

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