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Multilayer Endografts are still
an ongoing project but with a
grounded scientific rationale
Prof. Domenico Palombo
Vascular and Endovascular Unit
IRCCS San Martino – IST
University of Genova - Italy
introduction
• It’s a tubular, radiopaque, self-expandible bare
stent.
• It consists of multilayer (3-5) braided wires made of
a chrome and cobalt alloy
• Cobalt  resistance to corrosion, compatible with MRI
• The wires are curved at each point of intersection  prevent
friction and preserve the shape
• The two interconnected layers increase the anular resistance
and the radial elasticity
• The best result is achieved at a 65% porosity
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
introduction
• Longitudinal flexibility and low profile
• allows the penetration through tortuous/winding vessels
• 20 Fr aortic
• 8-12Fr peripheral
• Multilayer 3D structure
• Tougher/more resistant
• Prevent myointimal hyperplasia
• Great expansion rate  self fixing on arterial wall  no migration
• Design
•
•
•
•
Consists in a radiopaque guiding catheter.
For peripheral use the delivery system can accommodate a 0,025 inch guide-wire
The stent can be removed or repositioned when <80% of its length has been extruded
Access preferentially from the femoral artery
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
introduction
key point is to change the flow
Turbulent
Flow
Laminar
Flow
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
introduction
• Turbulence increases, significantly, Local
pressure and fluid shear stress in the
aneurysm: this results in an enlargement and
rupture of the vessel
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
introduction
• Turbulent Flows Are
Naturally Laminated
When the Volume of
Porosity Reaches 50-65%
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
introduction
Advantages & Effects of The Lamination
MFM®
1
2
3
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
1_Converting Turbulence to Lamination
• Multilayer Technology Converts Turbulence to
Lamination
• With Three-Dimensional Porosity Range of
60-65%
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
1_Converting Turbulence to Lamination
Peak of Wall Shear Stress is an indicator
of rupture -PWSS-
Streamline: velocity field
Surface: von Mises stress
Weak Area (rupture)
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
1_Converting Turbulence to Lamination
Applied Fluid _ Structure_ Interaction
Flow Velocity Pre & Post
3D Reconstruction
High PWSS at the
area of rupture
Reduction of
Stress
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
1_Converting Turbulence to Lamination
Applied Fluid _ Structure_ Interaction
Flow Velocity Pre & Post
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
1_Converting Turbulence to Lamination
Applied Fluid _ Structure_ Interaction
Flow Velocity
Lamination
pre MFM
post MFM
Vorticity
Without MFM
With MFM
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
2_Branches
Perfusion
by
Lamination
Applied Fluid _Structure _ Interaction –FSIFlow Velocity Pre & Post
Flow Velocity Pattern Post
–MFM®-
23%
25% Perfusion Improvement
24%
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
post MFM
pre MFM
Flow Velocity Pattern PRE
–MFM®-
2_Branches Perfusion by Lamination
Kidney Perfusion Improvement of 23 %
25% of Increased Blood
Flow rate
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
3_Endothelialization while keeping branches
perfused
Lamination Effects
MFM®
Integration
Endothelialization
while keeping
branches perfused
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
3_Endothelialization while keeping branches
perfused
Explantation
36 months
(3 years)
Histolgy by NAMSA
Antoine Alves
Reinforcement of the wall
(3*) which regulates the
vascular tonus and strength
as a normal wall
Elastic lamina
lysis
Avoids any rupture
First In Man (Dec 2006) - Dr M. Henry & Dr A. Polydorou, Athens
(Greece)
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
Laminar Flow
Clinical data
Converting
Turbulence
to
Lamination
Branches Perfusion
by
Lamination
Endothelialization
while keeping
branches perfused
No
aneurysm
rupture risk
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
Clinical data
Unfortunately
MFM is not for all patients
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
Clinical data
MFM different complications type
Aortic arch rupture after multiple multilayer stent treatment
of a thoracoabdominal aneurysm
Ferrero E, Gibello L, Ferri M, Viazzo A, Nessi F.
J Vasc Surg. 2013 Nov 4.
Aortic Arch
Rupture
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
Clinical data
MFM different complications type
Severe
visceral
ischemia
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
Clinical data
MFM different complications type
Aneurysm
rupture
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
Clinical data
•
•
•
•
Prospective
Non randomized
Multicenter
Approved by the French Health Authority
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
Clinical data
30 day and 1 year follow-up:
No aneurysm-related mortality
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
Clinical data
Comparison with volume analisys:
STRATO Trial 3 year follow-up (preliminary data)
Courtesy C. Vaislic
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
Clinical data
Natural History of thoracoabdominal aneurysms
Elefteriades JA(1), Farkas EA. Thoracic aortic aneurysm clinically pertinent controversies and uncertainties.
J Am Coll Cardiol. 2010 Mar 2;55(9):841-57
Italian experience and STRATO Trial
No mortality related to TAAA and Juxtarenal aortic aneurysm rupture
during follow-up
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
conclusion
 Organized Laminar Thrombi of the aneurysm over time
 Improves flow up to 20% into vital branches.
 Endothelization of multilayered mesh occurs over time
allowing the aneurysm to shrink.
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
conclusion
@Short and mid-term results seem to be encouraging even
compared with the results of branched and fenestrated
endograft
@Preoperative accurate planning and Follow-up is important as
it is for the treatment with branched or fenestrated endograft
@Some patients cannot be treated with MFM because of
unfavorable anatomy
@However, prospective studies are needed with larger series
and longer follow-up
@Finally, coupling between experimental and clinical data
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
conclusion
University of Pavia
Computational Mechanics
&
Advanced Materials Group
Team :
Ferdinando Auricchio , Michele Conti,
Elena Faggiano, Simone Morganti,
Marco Fedele
University of Genova
Laboratory of Clinical and
Experimental Vascular
Biology
Team :
Domenico Palombo, Giovanni Spinella,
Bianca Pane
Vascular and Endovascular Surgery
IRCCS San Martino IST - Genova
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
conclusion
Experimental
data
Clinical data
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
conclusion
AIM 1)
Specific analysis of
patients CT scans:
Total volume, thrombus
volume, flow volume
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
conclusion
AIM 2)
Hemodynamic analysis trough
numerical simulations on
geometries patient-specific.
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
conclusion
AIM 3)
In vitro analysis (patients specific
model) of MFM porosity trough
pressure value up-stream and downstream and collateral vessels
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy
Technology makes some surgeons
better, some others only braver!
Prof. Domenico Palombo
Vascular and Endovascular Unit
IRCCS San Martino – IST
University of Genova - Italy
Vascular and Endovascular IRCCS San Martino – IST University of Genova - Italy