Keywords
endoleak - Ovation - endovascular aneurysm repair - Amplatz - occluding plug
Introduction
The Ovation trimodular endograft is based on a pair of polymer-filled sealing rings
to ensure optimal sealing on the infrarenal neck of abdominal aortic aneurysms (AAAs),
accommodating even to challenging neck anatomies.[1] Yet, absence of integrated radiopaque markers onto the limb gates of this endograft
makes their visualization difficult, rendering sometimes the catheterization of the
contralateral limb challenging, especially in cases of anteroposterior limb orientation.[2] Therefore, our case presented below illustrates a relevant problem, the diagnostic
pitfalls, and the successful management. Informed consent was obtained from the patient
for presentation of the case and relevant images.
Case Presentation
A 62-year-old male presented with an infrarenal AAA of 51 mm. The treatment chosen
for the patient was endovascular repair with the use of the Ovation endograft (Endologix,
Irvine, CA) and a main-body 29 mm with iliac limbs of 14 × 16 mm and 14 × 14 mm for
the right and left side, respectively. After deployment of the endograft and during
polymer filling of the inflated rings, the impression of inadvertent anteroposterior
position of the limb gates was given. Under left anterior oblique view, the contralateral
limb catheterization was assumed to take place uneventfully, confirmed with the classic
tests to ensure proper position.[3] In completion angiography the impression of either a Type-Ia or -II endoleak was
mistakenly given. The patient was released on the second postoperative day but admitted
urgently to the hospital after 1 month due to acute ischemia of the left lower limb.
A computed tomography angiography (CTA) was conducted showing placement of both iliac
limbs within the same limb gate on the right accompanied by collapse and thrombosis
of the left iliac limb ([Fig. 1A], white arrow). While pooling of the contrast agent confirming the endoleak was prominent
([Fig. 1A], arrowhead), careful inspection revealed a gray halo encircling the second dye sequestration
on the right ([Fig. 1A], yellow arrow), corresponding to the radiopaque solidified polymer within the lowest
sealing ring of the left limb gate seen open. Therefore, the endoleak was now identified
as Type-III, attributed to inadvertent bilateral iliac limb insertion into the same
(right) gate without cannulation of the contralateral gate.
Fig. 1 (A) Computed tomographic angiography conducted during the emergent readmission of the
patient due to acute ischemia of the left limb. Occlusion and collapse of the left
iliac limb of the endograft is shown (white arrow) while buildup of the contrast agent
(arrowhead) reveals an endoleak. Careful inspection of the opacification on the left
reveals (yellow arrow) a rim encircling the former, corresponding to the radiopaque
filling polymer within the Ovation sealing ring, thus identifying the endoleak as
Type-III. (B) Τhe brachial angiographic catheter advanced and placed on the right (arrow) of the
endograft shows both iliac limbs normally perfused. No endoleak is visualized. (C) Withdrawal and placement of the catheter on the left of the main body (arrow) unveils
the Type-III endoleak, perfusing exclusively the aneurysm sac; note the lumbar arteries
network.
To restore directly perfusion of the left limb, the patient was subjected immediately
to successful open thrombectomy of the left limb, followed by placement of balloon-expandable
stents (9 × 36 mm, Valeo, BARD, Peripheral Vascular, Tempe, AZ) at the top end of
both iliac limbs with restoration of distal palpable pulses on the left. Accordingly,
a 16-mm nitinol-meshed occlusion plug (Amplatzer device; St. Jude Medical, Plymouth,
MI) was ordered to treat the endoleak.
After a few days, open vascular access was achieved through the left brachial approach.
An angiographic catheter was advanced to the endograft's main body and placed within
the right limb gate ([Fig. 1B], arrow) perfusing sufficiently both iliac limbs, without revealing any endoleak.
On the contrary, slight withdrawal of the catheter and selective placement via the
open left limb gate ([Fig. 1C], arrow) enables protrusion in the AAA sac and exclusive visualization of the lumbar
arteries, documenting the Type-III endoleak. Accordingly, releasing the occluding
plug in the proper position led to complete elimination of the endoleak ([Fig. 2A, B]). The 12-month follow-up CTA confirmed complete sealing of the endoleak and patency
of both iliac limbs ([Fig. 2C]).
Fig. 2 (A) Accurate placement of the Amplatzer plug within the open left iliac limb. The arrows
correspond to the markers of the plug. Note the anteroposterior position of both iliac
limbs. (B) Successful occlusion of the left iliac limb (asterisk). (C) Follow-up computed tomography angiography at 6 months confirms patency of both iliac
limbs. The arrow depicts the occluding plug (no contrast).
Discussion
Our article presents a challenging case of identifying correctly and catheterizing
the contralateral limb gate of an endograft for treatment of AAA. Moreover, it underscores
the diagnostic difficulty and uncertainty that a nonexperienced radiologist or interventionist
may encounter to identify the proper type of the emerging endoleak.
Since both iliac limbs in our case were adequately perfused at the end of the implantation,
the retrograde angiographic control via the iliac route proved inappropriate to identify
the intrasac leak, due to the anteroposterior position of the endograft allowing no
splay of the limb gates. Another important feature for identifying properly the endoleak
type was the awareness of the radio-opacity of the filling polymer within the sealing
rings of Ovation ([Fig. 1A]). Apart from the opacity of the sealing rings, another unique feature of the Ovation
endograft is the lack of nitinol endoskeleton in its main body which can be often
perceived as disengagement between the modular parts of the endograft.[4]
Notably, the continuous education of radiologists should keep up with the advent of
new endografts, especially those involving radiopaque polymer agents associated with
consequent findings that could be missed or misinterpreted.[4]
[5] In doubtful cases, anterograde angiography via the brachial route is recommended,
because this maneuver provides ease and accuracy to selective placement of the angiographic
catheter to inspect potential sites of endoleaks and delineate diagnostic dilemmas.[6] Furthermore, the anterograde route can facilitate and support the fast advancement,
positioning, and very accurate deployment of the occluding plug; the Amplatzer plug
is an ideal agent to occlude large endoleaks and can be advanced from the brachial
route via an 8 F × 65 cm guiding catheter.[7]
[8]
It should be mentioned that the aforementioned difficulty presented with the particular
endograft has been properly addressed recently with the incorporation of a crossover
lumen in the endograft, facilitating reliable contralateral gate access in the current
Ovation iX design, which should be used in any case of questionable limb cannulation.
Yet, such intraoperative challenges with respect to visualization and catheterization
of the contralateral limb can be encountered with all other endografts. Therefore,
in such cases we strongly advocate anterograde selective angiography and catheterization
via the brachial access without delay, as well as multiple oblique projections of
the C-arm to ensure the optimal visualization during catheterization.
In cases of ambiguous catheterization of the endograft's contralateral limb gate during
endovascular treatment of AAA, high level of suspicion, multiple projections, and
anterograde selective angiography via the brachial route should spare intraoperative
time and avoid inadvertent failures. Availability of proper embolization materials
render the management of endoleaks Type-III quick and effective, while the acknowledgment
of each new endograft's special, unique features precludes misdiagnosis and dictates
proper management.
The educational value of this report underscores the comparative advantage of the
anterograde angiography via the brachial route in ambiguous diagnostic cases and marks
the need for continuous education of physicians on the unique, specific features and
structure of new endografts to avoid delay in detection and misdiagnosis of associated
complications.
