EVAR Instructions for Use (IFU): What They Mean ... - VascularWeb

EVAR Instructions for Use (IFU):
What They Mean,
How They are Derived,
Outcomes When Ignored
Andres Schanzer, MD
Department of Vascular and Endovascular Surgery
UMass Medical School
June 6, 2012
SVS Postgraduate Course

Disclosures
None

Baseline aortic anatomy is a
key determinant of EVAR
appropriateness and long
term clinical success.

Endovascular
Candidacy
Anatomic criteria:
Ideal
15-20 mm
18-32 mm
Neck angulation
7-8 mm
30 o
Patent IIA
Minimum Ca+ and tortuosity

Endovascular
Candidacy
32 mm diam
Neck angulation
>45 0
Anatomic Criteria:
deviations from ideal
= chances for failure
CIA 22 mm diam
< 7 mm
Moderate/severe Ca++ and tortuosity

27 of 626 Late AAA Rupture s/p EVAR
§
*Lancet, 2005; Annals of Surgery, 2010.

EVAR in 2004
Rupture 2/10/2012
Aortic neck angle 90 degrees

EVAR in 2007
Rupture 2/11/2012
Aortic neck 38 mm

In the United States, >70% of
elective repairs of AAA are
performed utilizing EVAR *
*Schwarze et al, JVS, 2009.

Instructions for Use (IFU)
Guidant
Ancure
Medtronic
AneuRX
Gore
Excluder
Cook
Zenith
Gore Excluder
Low
Permeability
Endologix
Powerlink
Cook
Zenith
Enlarged
Neck
Medtronic
Talent
Endologix
Enlarged
Neck
Gore
Excluder
Enlarged
Neck
Year of Release 1999 1999 2002 2003 2004 2004 2006 2008 2009 2009
Neck Diameter (mm) 18-26 18-25 19-26 18-28 19-26 18-26 18-32 18-32 18-32 19-29
Neck Length (mm) ≥15 ≥10* ≥15 ≥15 ≥15 ≥15 ≥15 ≥10 ≥15 ≥15
Neck Angle (degrees) NS ≤45 ≤60 ≤45 ≤60 ≤60 ≤60 ≤60 ≤60 ≤60
Iliac Fixation Length (mm) ≥20 NS ≥10 ≥15 ≥10 ≥15 ≥15 ≥15 ≥15 ≥10
Iliac Diameter (mm)

Instructions for Use (IFU)-Derivation
• Target IFU parameters
determined
• Prototype device designed
• Bench top testing
– Mock configurations in models
– Fatigue testing (10 year
simulation)
• Clinical testing
– Phase 1
– Phase 2

IFU-Implementation Post Approval
“Nothing…shall be construed to
limit or interfere with the authority
of a health-care practitioner to
prescribe or administer any legally
marketed device to a patient for any
condition or disease within a
legitimate health care practitionerpatient
relationship.
*Food and Drug Administration Act of 1997.

IFU-Implementation Post Approval

84 patients classified according
to neck IFU. Outside IFU
(30%): “Significantly higher
migration, device-related
complication, and secondary
intervention rates.”

565 patients classified
according to IFU. Outside
IFU (39%):
“…lower freedom from graftrelated
adverse event”
“…EVAR treatment outside
IFU should be performed
cautiously, and perhaps not at
all in…candidates for open.

238 patients classified
according to neck length (>15,
10-15,

258 patients classified
according to neck IFU. Outside
IFU (63%): “Significantly
higher rates of early type I
endoleak and intervention (9%
vs. 22%).”

44 open conversions:
“morbidity 55%, mortality 18%”
“…the number of OCs have
increased over the study period.
This trend is likely to continue
because of the rising number of
EVARs…that are performed outside
of instructions for use.”

Goals:
To analyze a large, multicenter,
prospectively acquired dataset,
representative of “real world”
EVAR practice, containing
extensive baseline and
postoperative anatomic
imaging data.
Schanzer et al, Circulation, 2011.

Goals:
1. Baseline anatomic characteristics
2. Changes in baseline anatomy
3. Incidence rates and predictors of
aortic sac enlargement after EVAR
Schanzer et al, Circulation, 2011.

Research Design and Methods
• Data Source
– M2S, Incorporated (West Lebanon, NH)*
• Line-item data on all patients who underwent a CT scan
prior to EVAR and minimum ≥1 post EVAR
• Inclusion Criteria
• January 1, 1999 to December 31, 2008
• AAA diameter >30 mm
• If either iliac diameter >20 mm, aortic diameter had to be
>40 mm
• N=10,228 patients
*M2S did not play any role in study design, analysis, or interpretation of the data provided

Instructions for Use (IFU)
Guidant
Ancure
Medtronic
AneuRX
Gore
Excluder
Cook
Zenith
Gore Excluder
Low
Permeability
Endologix
Powerlink
Cook
Zenith
Enlarged
Neck
Medtronic
Talent
Endologix
Enlarged
Neck
Gore
Excluder
Enlarged
Neck
Year of Release 1999 1999 2002 2003 2004 2004 2006 2008 2009 2009
Neck Diameter (mm) 18-26 18-25 19-26 18-28 19-26 18-26 18-32 18-32 18-32 19-29
Neck Length (mm) ≥15 ≥10* ≥15 ≥15 ≥15 ≥15 ≥15 ≥10 ≥15 ≥15
Neck Angle (degrees) NS ≤45 ≤60 ≤45 ≤60 ≤60 ≤60 ≤60 ≤60 ≤60
Iliac Fixation Length (mm) ≥20 NS ≥10 ≥15 ≥10 ≥15 ≥15 ≥15 ≥15 ≥10
Iliac Diameter (mm)

Instructions for Use (IFU)
• IFU Definitions as related to neck anatomy:
1. Conservative IFU (most restrictive):
• Neck length >15 mm
• Neck diameter

Research Design and Methods
Primary Outcome:
Aortic Sac Enlargement
(>5mm from baseline)
Schanzer et al, Circulation, 2011.

Results—Baseline Characteristics
Characteristics Number (%)
Patients 10,228
DEMOGRAPHICS
Age, years
Female Gender
AAA Max Diameter

Results—Baseline Characteristics
Characteristics Number (%)
PATIENTS 10,228
INSTRUCTIONS FOR USE
Outside of conservative IFU
5983 (58.5%)
Outside of liberal IFU
3178 (31.1%)
Schanzer et al, Circulation, 2011.

Results—Time Trends
Year 1999-2002 2003 2004 2005 2006 2007 2008
Time Dependent Significant Changes
Patients (n) 650 1024 1640 1883 1830 1650 1593
Characteristics 1999-2003 2008 P-value
Age >80 20.0% 26.3%

FREEDOM FROM SAC ENLARGEMENT
1 Year 3 Year 5 Year
Entire Cohort
(n=10,228)
97.2% 83.5% 59.1%

FREEDOM FROM SAC ENLARGEMENT
Outside
Conservative IFU
Within
Conservative IFU
1 Year 3 Year 5 Year
96.5% 81.5% 56.5%
97.8% 85.9% 61.0%

FREEDOM FROM SAC ENLARGEMENT
Outside Liberal
IFU
Within Liberal
IFU
1 Year 3 Year 5 Year
96.7% 81.5% 57.5%
97.3% 84.9% 59.1%

FREEDOM FROM SAC ENLARGEMENT
OP DATE 1 Year 3 Year 5 Year
1999-2003 98.7% 89.4% 74.3%
2004-2008 96.7% 81.0% 38.4%

Determinants of Sac Enlargement
COX REGRESSION MODEL FOR ANEURYSM SAC ENLARGEMENT
Covariates Hazard Ratio (95% CI) P-Value
Age (years)

Risk Factors:
•Aortic Neck Diameter >28 mm
•Aortic Neck Angle >60 degrees
•Common Iliac Diameter >20 mm
FREEDOM FROM SAC ENLARGEMENT
RISK FACTORS 1 Year 3 Year 5 Year
No Risk Factors 97.7% 86.5% 60.9%
One Risk Factor 99.4% 74.4% 52.9%
Two Risk Factors 92.5% 68.2% 37.1%
Three Risk Factors 81.8% 34.1% --

Discussion
• Even applying the most liberal IFU definition,
30% of treated patients do not meet aortic
neck criteria.
• Anatomy deemed acceptable for EVAR has
continued to liberalize and several of these
factors are independently associated with
aortic aneurysm sac enlargement.

Discussion
• Aortic sac enlargement post EVAR occurred in
40% of patients by 5 years.
• In >30% of patients demonstrating aortic sac
enlargement, this was not detected until >3
years postoperatively.

Discussion
• The incidence of aortic sac enlargement after EVAR
seems to be increasing, not decreasing—despite
increased surgeon experience and improved device
technology.

Conclusions
• Liberalization of the anatomic characteristics
deemed suitable for EVAR has occurred. This
is associated with a significant increase in the
incidence of aortic sac enlargement thereby
reducing durability of EVAR to protect against
AAA rupture.

Are current available
commercial devices
appropriate for the increasing
complex anatomy that they are
being applied to?

SVS Postgraduate Session
• Internal Iliac Preservation in the Setting of
Common Iliac Aneurysms
• Short Neck AAA
• Thoracic Aneurysms Extending Proximal to
the Left Subclavian
• Commercial Options on the US Horizon for
Patients Who Don't Meet IFU--Custom and
Off-The-Shelf Solutions

Thank You.