BIOFLEX-COF Study
- Does chronic outward force
trigger restenosis?
Martin Funovics
Cardiovascular and Interventional Radiology
Medical University of Vienna
Disclosure
Speaker name:
Martin Funovics
I have the following potential conflicts of interest to report:
Research Grants
Travel Support
BIOFLEX-COF
(chronic outward force)
investigator initiated
blinded
prospective randomised (2 groups)
de-novo SFA lesions
primary nitinol stenting
high vs. low COF
Background – what is COF?
COF is:
Force exerted by a nitinol stent on the
vessel wall
Chronic: after pre- and postdilatation
Background – how big is COF?
COF depends on:
• Oversizing (stent size vs.vessel size)
• (operator dependent, every mm)
• Stent Material
• „stiffness“ of the stent (a.k.a. „spring constant)
• Irregularities in the lesion
• After pre and postdilatation
COF differs in lesions
Nominal Stent
Diameter
COF
Lesion
Stent placement
After balloon post-dilatation
Lesion
6
Study Hypothesis:
Oversizing/stiffer stents 
high COF 
neointimal hyperplasia 
early restenosis
Oversizing – Restenosis in porcine model
Example: 8 mm stent
Optimal Oversizing
Medium Oversizing
High Oversizing
7.3 – 6.2 mm
6.2 – 5.0 mm
5.0 – 4.2 mm
Stent
Stent
Stent
Preclinical animal model.
Zhao HQ et. al. Cardiovasc Intervent Radiol. 2009 Jul;32(4):720-6.
8
VIPER – lessons learned
6 mm
2 groups:
• Low-COF stent: Biotronic Pulsar
– minimal oversizing, „soft“ expansion curve
• High-COF Stent: (Bard Life Stent)
– 1-2mm oversizing, „stiff“ expansion curve
The candidates…
BIOTRONIK Pulsar 7/150
Abbott Absolute Pro (LL) 7/150
BARD Lifestent FlexStar (XL) 7/150
Cordis Smarter(er) CONTROL 7/150
0.12 N/mm
eV3 EverFlex Plus 7/150
Terumo Misago 7/150
0.04 N/mm
Stent size selection table
Vessel
Diameter
4 - 4.5 mm
4.6 - 5.5 mm
5.6-6.5 mm
6.6 – 7.0 mm
PRE Dil
3
4
5
6
POST Dil
4
5
6
7
Life Stent size
(high COF)
6
6
7
8
Pulsar Stent
size
(low COF)
4
5
6
7
Study workflow
Lesion transversal
Randomization
Pre-dilatation
Stent placement
Post-dilatation
Completion angio
Measure stent dimater with ruler
Calculate COF along stent axis
Schedule and Follow-up Testing
Pre Procedure: Clinical, lab, ABI, WIQ
Procedure:
Randomization and stent deployment, recording of AEs
Discharge:
Clinical, lab, ABI,CDUS
2 Follow-ups
 12 months:
Clinical, lab, ABI, WIQ, CTA
 24 months:
Clinical, lab, ABI, WIQ, CTA
Outcome Variable
 % of restenosis measured at CT-Angiography
 NOT: binary restenosis (too insensitive)
 NOT: doppler US (operator-dependent)
 NOT: TLR (patient-dependent & insensitive)
Discrete variable, 15-100 values per patient
Measurement of lumen diameter
Measurement of stent diameter
Length
COF
Study status:
Start of Recruitment: Oct 2015
13/80 Patients included
Est. recruitment time: 12 Months
BIOFLEX-COF Study
- Does chronic outward force
trigger restenosis?
Martin Funovics
Cardiovascular and Interventional Radiology
Medical University of Vienna