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Side Branch

Is There a Real Need for a

Dedicated Bifurcation Stent

Alan C. Yeung, MD

Li Ka Shing Professor of Medicine (Cardiology)

Director, Interventional Cardiology

Chief, Division of Cardiovascular Medicine

Stanford University Medical Center

Stanford


Bifurcation Restenosis Rate

• Lefevre et al. JACC 2005; 46

– Frontier (BMS) 44.8%

• Tannabe et al AJC 2004; 91

– Two Cyphers: Various techniques 22.7%

• Colombo et al Circ 2004;109

– 1 vs 2 Cyphers 25.7%


Technical Challenges with Bifurcations

Using Straight, Concentric Tubular Systems

Side Branch

Access

• Distort stent architecture

• Loss of access

• Stent protrusion

• Dissection

• Nidus for restenosis

Intersection

MV & SB

• Gaps

• Apposition incomplete

• Multiple Strut Layers

Injury

Scaffolding


Study Objectives

Define bifurcation anatomy and geometry

• Casts of human coronary tree to evaluate

intersection between Main Vessel (MV) & Side

Branch (SB)

• Qualitative assessments

– Shapes in intersections and SB take off

• Quantitative measures

– Specified Diameters (vessels > 1.6 mm)

– Various angles


LM

3 Dimensional Casts of Coronary Tree

(Aorta to terminal branches (


High Power Views of Anatomy & Disease

Multifaceted intersection without discrete angle

No disease

Minor stenosis;

minimal disease

Moderate ostial stenosis;

diffuse stenosis in SB and

proximal MV

Severe stenosis and

disease


Ostial Geometry:

Oval and Asymmetric Rather than Round

Example: Side Branch of RCA

Front view of ostium with

SB removed

Side view of ostium with

SB removed

Sketches of ostium

conical

taper

elliptical


Diameter Measurements

Side branch

diameter

Ostial diameter

Proximal diameter

Distal diameter

3 mm

3 mm

Center

point

3 mm

Note: Illustration not to scale


Diameters: Greater proximal to distal

Ostial SB diameter similar to distal MV

4.5

4.0

Main Vessel

1.70 - 4.18 mm

Side Branch

1.59 - 2.59 mm

mm

3.5

3.0

2.5

2.0

2.86

2.39

2.29

1.93

1.5

1.0

0.5

0.0

Proximal

vessel

diameter

Distal vessel

diameter

Ostial

Diameter

Side Branch

diameter


Ostial Geometry:

Transition Zone Taper Greater by 3-fold

Example of Diameter Measurements

Average Taper

0.7

0.6

Vessels with SB > 1.99 mm

6.58 mm

0.5

SB diameter

Ostial

diameter

mm

0.4

0.3

0.34

5.68 mm

Distal

diameter

Center

point

1.34 mm

At 3 mm

At 6 mm

Proximal diameter 3.14 3.15

Distal diameter 2.44 2.56

At ostium

At 3 mm

Side branch diameter 2.50 1.96

5.98 mm

Proximal diameter

At 6mm

2.03

0.2

0.1

0

0.10

Proximal to Distal

Taper

(Main Vessel)

Ostium to Side

Branch Taper

(Side Branch)

Main Vessel

Tapers 0.56 mm over 6.00 mm distance

Side Branch

Tapers 0.60 mm over 1.75 mm distance


Three Types of Angle Measurements

Proximal

transition angle

Distal

transition angle

Distal

Intersection angle

Proximal

Intersection angle

Intersection Angles: intersection of

centerline of

main vessel and side branch

(~measured by angiography)

Transition Zone Angles: actual

main vessel to side branch

progression as measured from the

main vessel

Note: Illustration not to scale


Transition Zone Angles*:

Differential smaller between proximal & distal angles

Transition Angle (degrees)

200

180

160

140

120

100

80

60

40

20

0

Proximal transition angles (107°-177°; mean 152°)

Distal transition angles (27°-163°; mean 109°)

Angle (Degrees)

200

180

160

140

120

100

80

60

40

20

0

152

Proximal transition

angle

Transition Angles:

Proximal

Distal

109

Distal transition

angle

0 20 40 60 80

Measurement Number

*Transition zone angles = actual

main vessel to side branch

progression as measured from the

main vessel


Summary

Bifurcation diameters ~ to previous findings

MV: Wide Range (1.7 to 4.2),

proximal mean= 2.86

distal mean= 2.39

SB: Wide Range (1.6 to 2.6), mean 2.28

Four types of Asymmetric Ostial Geometry:

• Multifaceted transition (high magnification detail)

• Oval rather than round ostium

• SB Taper 3-fold greater than MB

Side branch take off angles

– Proximal (obtuse)

– Distal (acute)


Conclusions

Distorted stent or Distorted anatomy

• Complex transition zone from the main vessel to the side

branch with many asymmetric features

• Anatomic distortion likely with symmetric (cylindrical)

designs

– Strut protrusion/injury

– Gaps

– Incomplete wall apposition

• Matching design to asymmetric ostial geometry may

minimize implant injury, enhance scaffolding and

improve outcomes


Dedicated Bifurcation Stents

Axxess BSC-AST Frontier Ymed Capella Tryton

DES Program Y Y

Y

N

N

N

FIM/Randomized Y/Y Y-P/P

Y/N

Y/N

Y/N

Y/N

Side Branch Angle Dep Indep

Dep

Dep

Dep

Indep

Overlap Struts (M/S) Main Side

Main

Main

Main

Main

New Carina Y N Y N

N

N

Marker Bands Align. Y Y

N

N

Y

Y

Accuracy Y Y




Y


TriReme Medical Inc.

Antares Sidebranch Adaptive System (SAS)

Stent geometry:

Material:

Positioning:

Antares stent with automatic sidebranch ostial

preservation structure

316L stainless steel

6F compatible, fully torqueable catheter

Strut thickness: 0.0035”

Crimped profile: 0.046”/0.038”

Available sizes:

Approval status:

3.0-4.5 mm

2.0-3.5 mm sidebranch compatibility

First in man completed; in clinical studies

27

Copyright TriReme Medical - Confidential


Antares Stent - 3D Imaging

No gaps or excessive metal protruding to main vessel

28

Copyright TriReme Medical - Confidential


Antares – Polymer Model

Automatic deployment of ostial crown upon expansion of main stent body

– single balloon is use

Ostial Locators:

improves alignment

provide structural support

improves apposition

minimize injury

2/12/08 Stanford, A. Yeung

Antares II, Cx

29

Copyright TriReme Medical - Confidential


FIM Experience

Pre-procedure

Deployment

Final result

Successful deployment of Antares stent in RCA case, Sao Paulo, Brazil

30 Copyright TriReme Medical - Confidential


True Bifurcation Continues to be a Problem

• Provisional stenting technique (stenting of

side branch if necessary) can be used to

treat a majority of the patients. Faster and

cheaper.

• Two stents technique is not perfect

• True bifurcation stent is needed for left main

and those lesions with “true” bifurcation

lesions.

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