# Presentation: 692928

## Workshop on Pre-Clinical Testing

**Workshop on Pre-Clinical Testing**
**for Endovascular Grafts**
**July 30- August 1, 2001**

**Hugh G. Beebe, MD**
**Jobst Vascular Center**
**University of Michigan**

## Physiologic, Anatomic and Morphologic

**Workshop on Pre-Clinical Testing**
**for Endovascular Grafts**

**FDA   CDRH**

**Physiologic, Anatomic and Morphologic**
**Characteristics of AAA **

## Morphology Assessment 

**is Important**

**Patient selection**
**Device selection**
**Outcome assessment**

**All**
**depend on**
**morphology**

**Pre-clinical testing will depend on it**

## Assessment methods affect 

**Assessment methods affect **
**precision and accuracy**

**Many artifacts, errors and limitations**

## Aneurysms exist in many shapes

**Aneurysms exist in many shapes**

**Angulation**

## 1997 AAA Classification

**Grade I**

**Grade IIa**

**Grade IIb**

**Grade III**

**Grade IV**

**1997 AAA Classification**

**Ahn SS, et al, JVS, 1997**

## 1997 AAA Classification

**1997 AAA Classification**

**Ahn SS, et al, JVS, 1997**

## Aneurysms exist in many shapes

**Aneurysms exist in many shapes**

**Iliac tortuosity**

## Aneurysms exist in many shapes

**Aneurysms exist in many shapes**

**Lumen size**

## The “Empty” Aneurysm

**70 mm**

**The “Empty” Aneurysm**

## The “full” aneurysm

**The “full” aneurysm**

## Anatomical Factors in Patient Selection

**Anatomical Factors in Patient Selection**

**AAA size**
**Attachment zones**
**	****Proximal neck**
**	****Distal neck**
**	****Iliac arteries**
**Transit vessels**
**Aortic lumen**

**Are these OK for pre-clinical testing?**

## Anatomy for endografts:

** ****The big, bad and ugly factors **

**Proximal Neck**
**	****Size, length, angle, shape, lumen**
**Common iliac arteries**
**	****Size, tortuosity, lumen**
**Access vessels**
**	****Lumen, angle, calcium**

## .

**Most important factor**
**in late results**

**Diameter**
**Length**
**Angle**
**Shape**
**Filling defect, calcium **
**Accessory renal artery**

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## Normal aortic diameter variance

**JVS 1992**

**Normal aortic diameter variance**
**by gender and age**

## The “cone shaped” neck

**The “cone shaped” neck**

## Cone shaped neck

**22 mm**

**25 mm**

**Cone shaped neck**
**within protocol limits**

## Migration at one year

**20 mm**

**12 mos**

**Migration at one year**

## Axial Slice Artifact

- Tortuosity makes
- neck appear
- elliptical

**Axial Slice Artifact**

## Assuming the aortic neck is round

**Ouriel K, Green RM, et al, JVS 1992**

**Assuming the aortic neck is round**
**can lead to “axial slice” error**

## Reformatted Slice

- Reformatted slice
- shows accurate
- neck shape

**Reformatted Slice**
**Perpendicular to vessel axis**

**Axial Slice**

**Reformatted Slice**

## Axial

**Axial**

**Reformatted**

- FF

## Axial

**Axial**

**Reformatted**

**28 mm**

**33 mm**

**27 mm**

- FF

## Grading calcification by estimating

**Grading calcification by estimating**
**circumference is nuts!**

## No useful grading system exists

**No useful grading system exists**
**for aortoiliac vessel calcification**

## Dense calcium at

**Dense calcium at**
**aortic bifurcation**

**SS**

## Neck filling defects

**Neck filling defects**

## Neck filling defects

- Thrombus in the neck

**Neck filling defects**

## Neck filling defects

**Neck filling defects**

## Neck filling defects

- Thrombus in the neck

**Neck filling defects**

## Patent aortic branches and

**Patent aortic branches and**
**Type II endoleak**

## Enough about anatomy!

**What about physiology?**

## Windkessel

**Ernst Weber, 1834 Otto Frank, 1899 **

## Elastic recoil and reflected pressure

**Elastic recoil and reflected pressure**
**waves summate in infrarenal aorta**

## Exercise infrarenal blood flow increase 2-6X

**Schalet BJ, Taylor EJ, et al, Surgical Forum, 1997**

**Exercise MRA in human**

**In vitro model simulation**

**Ku DN, Glagov S, et al, JVS, 1989**

**Exercise infrarenal blood flow increase 2-6X**
**Aorta change > cardiac output change**

## Aortic flow rate and shear stress

**Rest**

**Light**

**Moderate**

**Aortic flow rate and shear stress**
**exercise increase**

**Taylor CA, Zarins CK, et al, JVS, 1999**

## Complex stress strain curve

**Complex stress strain curve**
**influenced by:**

**Arterial wall compliance**
**Peripheral resistance**
**Cardiac stroke volume**
**Heart rate**
**Endograft impedance**

**What’s important?**

## .

**Many characteristics of aortoiliac**
**morphology and physiology can be**
**Measured.**

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**Existing classifications are limited and**
**may not suit pre-clinical testing well.**

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## .

**limitations make 3D methods**
**important for pre-clinical testing**

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**Conclusions**

**Pre-clinical testing methods must**
**select and include anatomical and**
**physiological factors influencing**
**failure mode inducers and promoters.**

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