# Presentation: 522966

## Failure modes of endovascular grafts that maybe simulated through preclinical testing
AND
Clinical characteristics that need additional consideration in these tests 

Michael Lawrence-Brown

**AND**
**Clinical characteristics that need additional consideration in these tests**
**Michael Lawrence-Brown**

## Proximal FixationSeal to prevent perigraft flowDistal landing zone attachment and sealAccessGraft / limb occlusionDeployment failureDevice defect ( short / long term )Physician Induced.......Inappropriate usage.......Technique defect ( education / human ).......Inadequate infrastructure esp. IMAGINGInadequate Support  ‘ TOOL KIT & PLANNING’                                      

**Prevalence of AAA (65+yrs):    30+mm - 7.4 %    50+mm - 0.7%**** **

**         **

**CESAR GIANTURCO et al**
**RADIOLOGIST**
**HOUSTON, TEXAS**
**“ ****PERCUTANEOUS ENDOVASCULAR GRAFT “**
**1986 RSNA**

## Which Materials Can/Should be Used for Device Construction?	

**Which Materials Can/Should be Used for Device Construction?****	**

**Dacron****(polyester)**
**PTFE**
**Stainless steel**
**Nitinol alloy**
**Polyurethane**
**Polypropylene**
**polyester**
**Nylon**
**Metal markers****	****	**** **
**	****     ****	****	****	**

**Notes:**
If the deployment at the end of the procedure was satisfactory; including the use of adjuvant balloons, stents and minor surgical procedures; and the aneurysms apparently excluded on completion angiography, the procedure was deemed successful.  Three patients were converted to open repair (see Figure 5).  The definitions for endoleak and retroleak are provided in the next figure.

**         **

**ROYAL PERTH HOSPITALENDOVASCULAR UNIT**
**DEPARTMENTS OF :-**
**MEDICAL IMAGING AND VASCULAR SURGERY**

**         **

**ROYAL PERTH HOSPITALENDOVASCULAR UNIT**
**DEPARTMENTS OF :-**
**MEDICAL IMAGING AND VASCULAR SURGERY**

## IDEAL

**Stress Fracture**

## Anchor Stent Modification

**         **

**FRICTION ONLY  < 10n****.**
**FRICTION + ATTACHMENT HOOKS >50n.**

**         **

**DETACHMENT FORCE**
**newtons ( n.)**

## Proximal Attachment--Displacement Forces and the use of Hooks

**Pull out force in ****cadaver aorta without hooks is 6-8 N**** **
**Drag force with computer modelling is 7-9 N for bifurcated grafts**** **** **

## Anticipating Difficulties

**Anticipating Difficulties**

**Position of the renal arteries in**
**relation to the di****rection**** of**** the**** angle**

## The Effect of Angle and Potential Endoleak

**The Effect of Angle ****and**** ****Potential Endoleak**

**	****     ****	****	****	**

**28mm**

**28mm**

**45o**

**X**

**X = 28 x sin45o**
**    ****=  19.8mm**

**Notes:**
If the deployment at the end of the procedure was satisfactory; including the use of adjuvant balloons, stents and minor surgical procedures; and the aneurysms apparently excluded on completion angiography, the procedure was deemed successful.  Three patients were converted to open repair (see Figure 5).  The definitions for endoleak and retroleak are provided in the next figure.

## Design Features

**For the same inflow pressure the mean pressure in the contained cavity is higher than the lumen with run-off**
**A full pressure endoleak increases the risk of rupture**

## Reasons for Crossing the Renal Arteries

**Reasons for Crossing the Renal Arteries**

**The region of the mesenteric and renal vessels is the strongest part of the aorta**
**Durability demands secure fixation without migration**
**Migration may repressurise aneurysm**
**Closed endoleaks increase the risk of rupture ****	****	****	****	****	****	****	****	****	****	**** **
**	****     ****	****	****	**

**Notes:**
If the deployment at the end of the procedure was satisfactory; including the use of adjuvant balloons, stents and minor surgical procedures; and the aneurysms apparently excluded on completion angiography, the procedure was deemed successful.  Three patients were converted to open repair (see Figure 5).  The definitions for endoleak and retroleak are provided in the next figure.

## The Effect on Blood Flow of a Wire Crossing an Artery 

**The Effect on Blood Flow of a Wire Crossing an Artery **

**	****	**_**	**__**Model**__**	**__**	**__**	**_
**7mm tube  & 0.5mm wire****	****         ****(3.0% decrease)**
** ****3mm tube & 0.5mm wire****	****         ****(5.3% decrease)**
**      ****(Both had the same flow **
**       ****velocity (1.8 m/s): chosen **
**       ****as typical blood flow rate)****   ****	****	****	****	****	****	****	****	****	****	**
**	****     ****	****	****	**

**Notes:**
If the deployment at the end of the procedure was satisfactory; including the use of adjuvant balloons, stents and minor surgical procedures; and the aneurysms apparently excluded on completion angiography, the procedure was deemed successful.  Three patients were converted to open repair (see Figure 5).  The definitions for endoleak and retroleak are provided in the next figure.

## The Effect of Age on Creatinine Levels in Males and Females

**         **

**DEVELOPMENT**
**problem**
**TORTUOUS     VESSELS **
** ****AND**
**POST      DEPLOYMENT KINKING**

**         **

**POST DEPLOYMENT KINKING**

**         **

**POST DEPLOYMENT KINKING ****solution****                             ADDITIONAL FLEXIBILITY**

## Set the Gaps to Fit the Curves

**Set the Gaps to Fit the Curves**

## Deviation from the Guidelines

**Outside**

**Within**

**Outside**

**Within**

## Order of increased risk of endoleak of neck criteria

**1.****	****Contour (flare) > 3mm**
**2.****	****Length < 20mm**
**3. ****	****Diameter > 28mm**
**4.****	****Angle**
**5. ****	****Filling defect**

## Neck Contour

**Straight**

**Flare**

**Inverted**
**Flare**

## Risk Combinations for the Neck

**Contour change / diameter ****	****p = 0.0004**
**Contour change / length ****	****  ****	****p = 0.006**
**Neck diameter / length ****	****	****p = 0.01**
**Contour change / angle****	****	****p = 0.03****:**** **

##    good workmen work with good tools

## Forces 1

## Forces 3

## Forces 5

## Complex Pulsating Forces Apply Over                  TIME 

## Perceptions & Anticipating Difficulties

**Perceptions & ****Anticipating Difficulties**

**?****  ****Chose straight line - right side determined by the neck (Racing curves)**

**Maybe right side - determined by the iliac vessels.  Observe relationship of aortic bifurcation to entry position of neck**

## Graft Types and Modules

**Tortuous Infra-renal neck**

**Composite **
**Design**

## Composite Grafts  

**Composite Grafts**
** ****Better stability if graft bifurcation seated on the aortic bifurcation**
**Allows orientation of the bifurcated module independently from the deployment of the anchor module in the tortuous neck**

## Slide 50

## Time Development of Artificial AAA

- Thrombus

- Lumen

- 15 minutes

- 30 minutes

- t = 0

## “Blowing Up” a Balloon

**“****Blowing Up” a Balloon**

- Difficult at first, but then gets easier.
- Consider a “patch”on a balloon

- Tension

- Tangential Components

- Radial
-  Components

- Pressure

**Notes:**
If the deployment at the end of the procedure was satisfactory; including the use of adjuvant balloons, stents and minor surgical procedures; and the aneurysms apparently excluded on completion angiography, the procedure was deemed successful.  Three patients were converted to open repair (see Figure 5).  The definitions for endoleak and retroleak are provided in the next figure.