Key-words:
Balloon occlusion - coiling - embolization - endovascular - technique
Introduction
Endovascular parent vessel occlusion is an established treatment option for a variety
of neurovascular pathologies, including vessel dissection,[[1]] carotid-cavernous fistula,[[2]] aneurysm,[[3]],[[4]] and tumor infiltration,[[5]] among others. Techniques for vessel occlusion vary depending on anatomy and operator,
with proximal flow arrest and coils being the main tenants of the procedure. Even
with proximal flow arrest during coiling, distal embolization can occur when the balloon
is deflated, particularly in high-flow vessels. Distal migration of coils is also
a concern during embolization, particularly when high packing density is desired,
large diameter coils are typically used, and the coiling catheter is immobile as a
result of proximal balloon inflation. The concern for distal migration is magnified
when preservation of a nearby branch vessel(s) is critical. In order to achieve a
more accurate parent vessel sacrifice with decreased risk of distal embolization,
we developed a balloon-assisted, dual microcatheter technique, used in five cases
thus far [[Table 1]].
Table 1: Patient characteristics
Case Report
There are several key steps to parent vessel occlusion using the balloon-assisted,
dual microcatheter technique [[Figure 1]]. Control angiography and working views are established to delineate the distal
most aspect of vessel occlusion, taking into consideration any branch vessels that
demand patency. Next, a guide catheter is introduced into the proximal vessel, such
as the vertebral artery or carotid artery. The guide catheter should be large enough
to accommodate two microcatheters and have residual lumen volume to perform control
angiography, if desired. The compatibility of a guide catheter to accommodate a balloon
microcatheter alongside another microcatheter varies depending on the manufacturer
and models selected. In general, a 6 French guide catheter or larger is required for
this method. Alternatively, a smaller guide catheter can be used and control angiography
can be performed via collateral circulation when available, such as the contralateral
vertebral artery. A dual-lumen balloon microcatheter (e.g., Scepter C or Scepter XC,
Microvention, Aliso Viejo, CA, USA) is then advanced through the guide catheter into
a position proximal to the site of desired occlusion. A coiling microcatheter (second
microcatheter) is then advanced past the balloon microcatheter to the distal most
desired site of vessel occlusion. After the balloon is inflated, a framing coil is
deployed through the second microcatheter to define the distal most aspect of the
vessel occlusion. This coil is not immediately detached. Then, further coils are deployed
through the balloon microcatheter to achieve a relatively high packing density in
the parent vessel. Of note, there are no coil delivery markers on the Scepter, so
care must be taken to deliver the coils under close fluoroscopic guidance. Because
there are no coil detachment markers, the operator needs to visually identify when
the coil is outside the distal tip of the catheter. For most coils, the coil itself
is more radiopaque than the pusher wire it is connected to, allowing for this distinction.
If preferred by the operator, other dual-lumen balloon microcatheters are available
that do have coil delivery markers, such as the Eclipse 2L dual-lumen balloon catheter
(BALT USA, Irvine, CA, USA).
Figure 1: Dual microcatheter balloon occlusion coiling technique. (a) Step 1: Placement of
dual-lumen balloon (balloon test occlusion can be completed, if desired). (b) Step
2: Placement of microcatheter at distal occlusion limit (balloon deflated). (c) Step
3: Placement of distal defining coil (not detached, balloon inflated). (d) Step 4:
Coiling proximally through dual-lumen balloon microcatheter (multiple coils detached).
(e) Step 5: Deflate balloon. If no movement of coil mass, then distal defining coil
is detached
During this time, the attached coil deployed from the second microcatheter serves
as a backstop and provides additional security against distal migration of the coils.
As the procedure progresses, control angiography can be performed with the balloon
deflated. In addition, the balloon microcatheter can be repositioned more proximal,
and further coil embolization can be performed to increase the length of the occluded
segment. With any balloon inflated, the feedback and natural flexibility of a catheter
as a response to coil delivery is altered. This can make it more difficult to “guide”
coils into different shapes and configurations. However, this is less of a concern
when performing parent vessel occlusion because the shape of the coils delivered does
not need to conform to a specific shape, as in the case of an aneurysm. After the
vessel is completely occluded, the balloon is deflated and the stability of the coil
construct is assessed. When there is no flow through the vessel and the coils are
stable, the first coil is detached and the microcatheters are removed under fluoroscopy.
Two illustrative cases utilizing this technique are presented [[Figure 2]], [[Figure 3]] and [Video 1].
Figure 2: Illustrative case, posterior circulation. A middle-aged female who presented with
high-grade subarachnoid hemorrhage. Angiography demonstrated a wide-necked aneurysm
located proximal to the origin of the posterior inferior cerebellar artery (a). Treatment
options possible for this patient include direct aneurysm clipping or aneurysm trapping.
Because the aneurysm was not at a branch point and the parent vessel was somewhat
irregular, the underlying pathology was believed to be a vessel dissection, favoring
vessel occlusion or sacrifice as a definitive treatment. As the patient had a robust
left vertebral artery and the aneurysmal segment was proximal to the posterior inferior
cerebellar artery, a right vertebral artery occlusion was planned. The operative technique
described above was utilized for this patient, with a working view of the posterior
inferior cerebellar artery origin selected (b). After following the steps listed previously,
the aneurysmal segment was not densely coiled initially and was still filling despite
dense coiling of the more proximal vertebral artery. With the balloon inflated, the
distal defining coil was detached, the coiling microcatheter was brought back a few
millimeters, and a few more soft coils were placed into the aneurysmal segment of
the vertebral artery. The balloon was deflated, and control angiography demonstrated
complete right vertebral artery occlusion, no filling of the aneurysm, and preservation
of the posterior inferior cerebellar artery (c). Postoperative magnetic resonance
imaging demonstrated no ischemia, and the patient went on to make an uncomplicated
recovery
Figure 3: Illustrative case, anterior circulation. A young female with a middle fossa tumor
causing invasion of petrous segment of the right internal carotid artery, who required
a balloon test occlusion followed by coil sacrifice. (a) Preoperative imaging demonstrating
the involved carotid artery. (b) Intraoperative imaging, showing vessel occlusion
with coil placement with the proximal balloon inflated. (c) Postoperative imaging
showing coils in place and complete parent vessel occlusion with removal of balloon
microcatheter and coiling microcatheter
[MULTIMEDIA:1]
Discussion
There are many techniques for endovascular parent vessel occlusion, with the overarching
principle being proximal flow arrest and coil embolization. The described balloon-assisted,
dual microcatheter technique is a novel iteration of this principle that is possible
as a result of the dual-lumen balloon microcatheters that are now available in clinical
practice. A major advantage of this technique is that large-lumen balloon guide catheters
are no longer needed to achieve proximal flow arrest, as it is readily achieved with
the balloon microcatheter. Further, the dual microcatheter approach also allows for
the procedure to be performed via radial artery access, if desired.
Although not described above as part of the procedural steps, the technique can seamlessly
integrate a balloon test occlusion into the workflow.[[6]] Because the balloon microcatheter results in flow arrest, a balloon test occlusion
can be performed prior to definitive parent vessel sacrifice. Once the patient has
“passed” the balloon test occlusion, there is no need for catheter exchanges or substitutions,
and the embolization procedure can proceed immediately.
Variations of this technique are also possible, and operators can choose to augment
their constructs with liquid embolic agents [[7]] or intravascular plug-type devices,[[8]] as both are compliant with the Scepter balloon microcatheter. As the embolization
procedure proceeds, there is also flexibility in repositioning the balloon microcatheter
to a more proximal location without the fear of distal embolization. The ability to
extend the length of the embolization construct in this manner prevents “pushing”
of previously detached coils distally or over packing of a fragile diseased vessel
segment, which can be possible with the traditional balloon guide catheter/microcatheter
approaches.
Limitations to this technique include the possibility of retrograde filling distal
to the occlusion through collateral flow. This is seen in the case illustrated above,
with retrograde filling of the distal segment of the aneurysm via the contralateral
vertebral artery. As seen in the illustrative case, this requires further coiling
via the distal microcatheter. This additional step may potentially increase the risk
of distal embolization or coil migration, although this was not seen in the case presented
here.
Conclusion
The balloon-assisted, dual microcatheter technique is a new tool for parent vessel
occlusion. Anecdotal experience suggests that there is improved protection against
distal embolization or migration of coils compared to traditional techniques. The
technique allows for a very precise parent vessel occlusion, which can be particularly
helpful when preservation of segments that give rise to a branch vessel mandates.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form the patient(s) has/have given his/her/their consent for his/her/their
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understand that their names and initials will not be published and due efforts will
be made to conceal their identity, but anonymity cannot be guaranteed.
