Zenith® Fenestrated AAA Endovascular Graft – General Steps for Planning and Sizing
General Steps for Planning and Sizing the
Zenith® Fenestrated AAA Endovascular Graft
1. Plan the seal/fenestration Zone
•
Choose the lowest aortic segment that will provide an adequate seal – both designing and
deploying a graft increase in difficulty with the number of fenestrations
•
Go higher only as needed to find the straightest segment of aorta (at least 50% of segment
should be straight)
•
Avoid being too aggressive with first cases
Choose one or two internal stents
• In general two internal stents is preferred because it:
– Maximizes the available sealing potential
– Allows greater range of fenestration placement
•
Note that choosing two internal stents does:
– Increase the proximal graft length by 8 or 10mm, depending on diameter
– Reduce parallel overlap with the distal graft piece (Note the minimum overlap is 2
stents/ 36mm long)
The number of internal stents chosen should be reviewed and confirmed later when selecting
graft lengths.
2. Select Side for Graft Body Introduction
•
Assess potential access vessels with reference to:
Tortuosity
Diameter
Stenosis
Calcification
Length, etc.
•
Generally choose the side that has the best access vessels, as this facilitates advancement
and manipulation of the graft (e.g., rotation) to position the fenestrations where they will be
easier to cannulate.
•
EXCEPTION: Unusual anatomy may dictate that the body be placed through the less
desirable access vessels (e.g., because the graft delivery system will straighten access
vessels more than wires and catheters will — anticipated difficulty in graft cannulation may
justify graft delivery through more tortuous side.
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Zenith® Fenestrated AAA Endovascular Graft – General Steps for Planning and Sizing
•
The diameter of the access vessel to be used should be checked throughout its full length to
ensure that it is large enough.
Graft Diameters
Minimum Access
Vessel Diameter
22-36mm Proximal Body (20Fr)
7.5 mm
Distal Body (20Fr)
7.5 mm
8-16mm TFLE Leg extension (14Fr)
5 mm
18-24mm TFLE Leg extension (16Fr)
6 mm
3. Choose fenestration Configuration
Determine the Clock Position of Vessel(s):
•
This is established from the AP MIP CT angiography – The 2mm images at right angles to
the centre line axis of the neck must NOT be used; these images will falsely represent the
vessel clock positions and will likely cause misalignment of the fenestrations.
•
Clock positions are determined by first noting the middle of the aorta, then:
12 o’clock is on the anterior margin
6 o’clock is on the posterior margin
3 o’clock is 90 degrees away from 12 o’clock on the anatomical left
12:00
3:00
9:00
6:00
NOTE: a vessel falling between two clock positions is recorded to the quarter hour (e.g.,
2:15, 2:30, 2:45 etc.)
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Zenith® Fenestrated AAA Endovascular Graft – General Steps for Planning and Sizing
•
A sagittal plane drawing can be used to record the clock positions of the vessels – accurate
clock and distance information is needed to determine where the fenestrations should be
placed during graft construction.
NOTE: any aortic angulation
should also be taken into account
Coeliac
CT Table position _______
Clock position_________
SMA
CT Table position _______
Clock position_________
Left Renal
CT Table position _______
Clock position_________
Right Renal
CT Table position _______
Clock position_________
Accessory Vessel
CT Table position _______
Clock position_________
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Zenith® Fenestrated AAA Endovascular Graft – General Steps for Planning and Sizing
•
Complete form with fenestration dimensions and heights
(heights are difference between table position targeted for top of graft material, and table
position of corresponding vessel)
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Zenith® Fenestrated AAA Endovascular Graft – General Steps for Planning and Sizing
EXAMPLES OF FENESTRATION CONFIGURATIONS:
 Example 1 – Single scallop
When one renal is lower than the other, distance from lower limit of upper renal and
mid line of lower renal is 3-9 mm, and distance from lower edge of upper renal and
lower limit of infra-renal neck is 20 mm or more
Steps
Choose depth of scallop: 6, 8, 10, or 12 mm
Choose angle (clock position) of scallop
Limitations
None (other than general principles)
 Example 2 – Two scallops
When infra-renal neck is 8-15 mm, renal arteries are within 3 mm of same level and
distance from mid-line of lower renal and lower limit of SMA is greater than 9mm
Steps
Choose depth of 1st scallop (6, 8, 10, or 12 mm)
Choose clock position of 1st scallop
Choose depth of 2nd scallop (6, 8, 10, or 12 mm)
Choose clock position of 2nd scallop
Limitations
Angles of scallops must be two hours or more apart
 Example 3 – One scallop and one small fenestration
When one renal artery is lower than the other, the infra-renal neck is < 10 mm, and
distance from mid line of lower renal and lower limit of SMA is > 12mm
Steps
Choose size of small fenestration (6 mm or 6x8 mm)
Choose distance of small fenestration from top edge (>15mm)
Choose angle of small fenestration
Choose depth of scallop
Choose angle of scallop
Limitations
Fenestration and scallop must be more than 1hr 30min apart in angle if they
are at the same stent level
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Zenith® Fenestrated AAA Endovascular Graft – General Steps for Planning and Sizing
 Example 4 – Two small fenestrations
When infra-renal neck < 10 mm, and distance from mid line of upper renal and lower
limit of SMA is > 12 mm
Steps
Choose size of 1st small fenestration (6 or 6x8 mm)
Choose distance of 1st small fenestration from top (>15mm)
Choose angle of 1st small fenestration
Choose size of 2nd small fenestration
Choose distance of 2nd small fenestration from top
Choose angle of 2nd small fenestration
Limitations
Small fenestrations must be > 2 hrs apart in angle
 Example 5 – Two small fenestrations and a scallop
When infrarenal neck < 10 mm, and distance from mid line of upper renal and lower
limit of SMA is > 5mm (distance of the celiac artery above the SMA should be
checked to ensure that it is clear of the upper edge of the graft)
Steps
Choose depth and angle of scallop
Choose size, distance, and angle of 1st small fenestration
Repeat steps for 2nd small fenestration
Limitations
Small fenestrations must be > 1hr 30min apart in angle from scallop, and > 2 hr apart
from each other
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Zenith® Fenestrated AAA Endovascular Graft – General Steps for Planning and Sizing
 Example 6 – Two small fenestrations and one large fenestration
When infra-renal neck < 10 mm, and distance from mid line of upper renal and lower
limit of SMA is less than 5 mm (distance of celiac above SMA should be checked to
ensure that it is clear of the upper edge of the graft)
Steps
Choose diameter of large fenestration (8, 10, or 12 mm)
Choose distance of large fenestration below top edge of graft (>10 mm)
Choose angle of large fenestration
Choose size. distance below the top, and angle of 1st small fenestration
Repeat for 2nd small fenestration
Limitations
Small fenestrations must be > 1hr 30min apart from large fenestration, and > 2 hr
apart from each other if they are at the same stent level.
4. Choose Proximal Body Diameter (D1)
•
•
•
•
•
Measure aortic diameter over a length of approximately 20-30 mm, or the length of the
sealing stent(s).
Measure at the external diameter of the vessel, including the vessel wall thickness when it
can be seen.
Add an appropriate amount of over-sizing to ensure that the graft has an ‘interference fit’
within the vessel.
When the landing zone has varying diameters throughout its length, the graft should be
oversized to ensure good contact with the largest diameter of the landing zone.
Over-sizing can vary from 15-25%, depending upon anatomy and physician preference.
Aortic Diameter
Proximal Body
Diameter (D1)
% Oversize
19-21 mm
24 mm
26.3% - 14.3%
Introducer
Sheath
20Fr
21-22 mm
26 mm
23.8% - 18.2%
20Fr
23-24 mm
28 mm
21.7% - 16.7%
20Fr
24-26 mm
30 mm
25.0% - 15.4%
20Fr
26-28 mm
32 mm
23.1% - 14.3%
20Fr
28-29 mm
34 mm
21.4% - 17.2%
20Fr
29-31 mm
36 mm
24.1% - 16.1%
20Fr
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Zenith® Fenestrated AAA Endovascular Graft – General Steps for Planning and Sizing
Considerations
• With an oblique axial CT slice, the true diameter is usually the longest distance measured
across the short axis of the vessel seen on the axial slice
• Consider that the ellipse or elongated shape may be due to vessel irregularities rather than
imaging angle
• Calibrated angiography may be helpful in confirming the vessel size and nature, but be
mindful that angiography generally shows only lumen size without atheroma, thrombus or
vessel wall thickness
NOTE: Angiography should not be used exclusively to determine vessel diameters, as it can
be misleading.
5. Determine Inner Aortic Vessel Diameter
•
The inner aortic vessel diameter is taken at the level of the fenestrations — this
measurement will determine the lateral placement of the fenestrations in graft construction
•
If there is any thrombus present, do not measure the lumen size — measure the inner vessel
size.
6. Choose proximal graft length (L1)
•
•
•
In general, choose a proximal graft length that will place the distal end of the graft between
20-35 mm above the aortic bifurcation
Review of CT angiography can be used to check that the choice of graft length would be
suitable
Angiography using a vessel-sizing catheter is helpful in considering suitable graft length
7. Choose Distal Body Length (L2)
When choosing the distal body length:
• The minimum overlap that must be planned is two stents (36mm)
• It is usual to plan more overlap, e.g., 3-4 stents
• The length chosen should place the contralateral limb position 5-10 mm above the aortic
bifurcation
• You must ensure that the proximal edge of the distal body is well below the lowest renal
artery/lowest fenestration
• The use of calibrated angiography, CT angiography, the anatomy sketch or a combination of
these tools, are useful to confirm that aspects of the selected distal body are suitable
Considerations
• The graft component lengths should be chosen so that adequate overlap will be maintained if
the completed graft takes a curved path out into the aneurysm sac
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Zenith® Fenestrated AAA Endovascular Graft – General Steps for Planning and Sizing
8. Choose Distal Body Ipsilateral Leg Diameter (D3)
•
•
The integral ipsilateral leg distal diameter is determined by the sealing zone iliac vessel
diameter from axial CT images:
– Measure the vessel diameter at the landing zone of the sealing stent
– Note the diameters over the length of the vessel
– Measure at the external diameter of the vessel, including the vessel wall thickness
when it can be seen
Oversize from 15-25% to ensure an interference fit within the vessel, depending upon
anatomy and personal choice
Vessel Diameter
9-11 mm
Graft Diameter (D3)
12 mm
12-15 mm
16 mm
15-18 mm
20 mm
18-21 mm
24 mm
Considerations
•
•
•
In the presence of thrombus or atheroma, diameter should be determined from the outer
vessel wall diameter and not from the lumen diameter
Care should be taken with the amount of oversizing in small vessels – with larger vessels, a
greater degree of oversizing can be applied, without the risk of compromising an adequate
lumen
The incidence of complications and secondary procedures is increased in iliac vessels that
have:
– Length less than 17mm
– Diameters greater than 20mm
– Tapering
– Irregularities
– Tortuosity
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Zenith® Fenestrated AAA Endovascular Graft – General Steps for Planning and Sizing
9. Choose Distal Body Ipsilateral Leg Length (L3)
•
•
Plan the integral ipsilateral leg length to land just above the common iliac bifurcation – this
increases stability and lowers risk of endoleak
Choose a limb length that will span the distance from the contralateral limb (5-10 mm above
the aortic bifurcation) to the desired landing zone
NOTE: Because tortuous iliac arteries are angled posterior to the pelvis, the measured distance
from the aortic bifurcation to the landing zone around the greater curvature will be greater than
that measured using a 2D frontal image.
During deployment, the stiff wireguide and introducing systems will straighten and foreshorten
the vessel – a leg extension chosen from true length of a vessel (as determined by calibrated
angiography or mid-lumen CT) may be too long
In general if the ipsilateral limb length is chosen from the length measured on a twodimensional frontal image using CT reconstruction, the undersizing that arises will be
compensated by the vessel shortening during graft introduction
Considerations
•
•
When the ipsilateral internal iliac is to be sacrificed, a standard TFLE leg graft may be
required to reach the desired landing zone in the external iliac – this can be achieved by
planning a 12 mm diameter ipsilateral leg on the distal body, long enough to maximise
overlap with a standard TFLE leg graft (at least two stents should land in the external iliac
artery)
If endoluminal treatment might require sacrificing one or both of the internal iliac arteries,
possible consequences of this approach should be considered and discussed with the patient
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Zenith® Fenestrated AAA Endovascular Graft – General Steps for Planning and Sizing
10. Choose Controlateral Leg Diameter
NOTE: The contralateral leg graft is a standard Zenith
TFLE-XX-XX
•
•
•
From axial CT images, measure the vessel diameter over the
length of the landing zone of the sealing stent
Measure at the external diameter of the vessel, including the
vessel wall thickness when it can be seen
Oversize from 15-25%, depending on anatomy and personal
choice to ensure an interference fit within the vessel
Vessel
Diameter
7 mm
8-9 mm
10-11 mm
12-13 mm
13-15 mm
15-17 mm
16-18 mm
18-19 mm
20-21 mm
Graft
Diameter
(D4)
8 mm
10 mm
12 mm
14 mm
16 mm
18 mm
20 mm
22 mm
24 mm
Considerations (same as for ipsilateral leg)
•
•
•
In the presence of thrombus or atheroma, diameter should be determined from the outer
vessel wall diameter and not from the lumen diameter
Care should be taken with the amount of oversizing in small
vessels – with larger vessels, a greater degree of oversizing
can be applied, without the risk of compromising an adequate
lumen
The incidence of complications and secondary procedures is
increased in iliac vessels that have:
– Length less than 17mm
– Diameters greater than 20mm
– Tapering
– Irregularities
– Tortuosity
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Zenith® Fenestrated AAA Endovascular Graft – General Steps for Planning and Sizing
11.Choose Contralateral Leg Length (L4)
•
•
•
Estimate the position that the contralateral limb of the distal graft body is expected to take
after deployment
Determine the length from the distal edge of the limb (of the distal body) to the chosen
landing zone in the iliac artery
Choose a limb length that would satisfactorily span this distance
Note the following:
• The contralateral leg graft is a standard Zenith TFLE-XX-XX
• TFLE leg grafts are 22mm longer than the nominal length to allow a 1 to 1¾ stent overlap
into the contralateral limb
• The overlap must never be less than one stent
Considerations
• It is usually desirable to plan the contralateral leg to land just above the common iliac
bifurcation for greater stability and reduced likelihood of endoleak
• When an internal iliac is to be sacrificed, it is suggested that at least two stents (34mm) land
in the external iliac artery
• If endoluminal treatment might require sacrificing one or both of the internal iliac arteries,
possible consequences of this approach should be considered and discussed with the patient
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