Keywords
tortuous vessels - neuro intervention - difficult access
Introduction
The field of neurointervention has grown enormously over the last two decades. We
have better microcatheters, coils, balloons, and wires than ever before. However,
none of these devices have any use until we are able to reach the target site. Often,
complex vascular anatomy can pose a problem to navigate microcatheters and balloons
to the actual site of pathology. This article attempts to help a beginner overcome
some of the challenges one can face during endovascular treatment of vascular pathology
in a patient with tortuous vascular anatomy.[1]
[2]
[3]
Tortuous Iliac Arteries
Vessel tortuosity results in lack of pushability of catheters and also the loss of
torque on the guidewires that are necessary to cannulate vessels. Further, tortuous
vessels can prevent transmission of energy over the catheter, and these catheters
may suddenly move forward resulting in a dissection or perforation. This can result
in longer procedure times and thus complications.
The simplest way to cross a tortuous iliac artery is to use a combination of a simple
angled catheter (Berenstein's) along with a Terumo angled Glidewire ([Fig. 1]). These are nitinol wires, which have a good 1:1 torque. Further, if the procedure
is done under road map, the chances of dissection become extremely low. Once the catheter
is in the aorta, it is recommended that the catheter is exchanged for a 40- or a 70-cm-long
sheath to ensure that all the tortuosity in the iliac artery segment is overcome ([Fig. 2]).
Fig. 1 Combination of a simple angle catheter and angled Glidewire helps cross-tortuous
vessels.
Fig. 2 A long sheath can correct tortuosity.
Overcoming a Tortuous Dilated Arch
Overcoming a Tortuous Dilated Arch
Once the aorta elongates, the arch vessels become difficult to cannulate as it becomes
angulated and rotates in the anterior-posterior direction. Based on this angulation,
the arch is divided into three types: types 1, 2, and 3, which is based on whether
all three vessels arise at the same transverse plane at the convexity of the arch
or whether the innominate and the left carotids go way below the apex of the arch.
The best view to profile the arch is the left anterior oblique and one of the best
catheters used to engage the vessels in an unfolded arch is the Simmons 1 or 2 ([Fig. 3]). There are many ways to make the curve in the Simmons 1. The most common way is
to first take the catheter up to the proximal descending aorta over a J wire. The
wire is then pulled back by approximately 10 cm, and the catheter tip is pushed against
the outer curve of the arch to enable it to form a loop and then a clockwise rotation
is given, following which a clockwise torque is given to the catheter with the guidewire
in the artery in the same position. At times, the catheter forms a tighter loop rather
than actually forming the Simmons 1 shape. In such a situation, the guidewire is gently
pushed distally to enable the loop to open up.[4] Sometimes these techniques will not work, especially when the aorta is grossly dilated
and a Simmons 2 has to be used. In this situation the Simmons catheter is taken to
the root of the aorta and the guidewire pulled back by 10 cm, following which this
catheter tip is pushed against the annulus to form the loop and the catheter is torqued
to stabilize the shape. Once the ostium is engaged, a road map is taken and an exchange
length angled Terumo wire is navigated deep into a branch of the external carotid
artery. The Simmons 1 is then exchanged for a catheter with a simple curve like the
Berenstein, and the angled Terumo wire is then replaced with an exchange length Amplatz
extra stiff straight wire. A long sheath or the diagnostic catheter of choice is then
tracked over the extra stiff wire. The long sheath is positioned at the ostium of
the common carotid artery. Once the long sheath is in position, changing of catheters
become easy and it also gives stability to the guiding catheter for neuro-interventions.
If one has a biplane digital subtracted angiography (DSA), one can make use of the
lateral plane to see the distal end of the wire and the frontal plane to see the arch
by overcoming the default isocenter position and positioning the lateral plane distal
to the frontal plane. Your application expert will be able to tell you how this can
be achieved in your cath laboratory.
Fig. 3 Simmons catheter can be used to cannulate vessels from an unfolded arch.
Separating the Right Subclavian and the Right Carotid Artery
Separating the Right Subclavian and the Right Carotid Artery
The best view to separate the right carotid and the right subclavian artery is the
right anterior oblique of approximately 30 degrees, following which the same technique
that was used in the previous paragraph can be used ([Fig. 4]).
Fig. 4 Right anterior oblique (RAO) helps separate the right carotid from the right subclavian.
AP, anteroposterior.
Managing Multiple Internal Carotid Artery Loops
Managing Multiple Internal Carotid Artery Loops
Once the long sheath is in position, we may often find multiple loops in the internal
carotid artery making it difficult to access the intra-cranial vessels. The way to
overcome this is to take an access catheter such as the Neuron (Penumbra Devices),
Fargo (Balt Devices) or any other distal access catheter with a minimum internal diameter
of 0.07 in. Before placing these catheters, it is mandatory that the internal carotid
artery is primed with 1 mg of nimodipine (5 mL), which is diluted in 50 mL of saline
and injected over 10 minutes. Although intra-arterial nimodipine has been practiced
in the treatment of intracranial vasospasm,[5] it is mandatory that an intra-arterial pressure monitoring line is available during
nimodipine infusion and the infusion is stopped when the mean arterial pressure drops
below 50 mm Hg. The anesthetist is also informed before the nimodipine infusion is
initiated to ensure management of drop in blood pressure (BP) during this step. The
long sheath is normally kept close to the origin of the common carotid artery. Following
this, the distal access catheter is then navigated over a 125-cm 4F catheter and Terumo
Glidewire combination ([Fig. 5]). This step is important to prevent a dissection when the distal access catheter
is pushed across tortuous loops. The distal access catheter is navigated to a point
close to the carotid siphon. It is extremely important that the long sheath is kept
in view as you push the distal access catheter because the long sheath tends to be
pushed back out of the carotid artery.
Fig. 5 Taking a distal access catheter through a long sheath placed in the distal CCA can
help overcome problems in the internal carotid artery.
Direct Carotid Access
At times, the arch may be so difficult that it is impossible to access a carotid artery.[3] For example, in a patient who has got chronic type A dissection or an extremely
unfolded aortic arch, the only way out is the direct carotid puncture.
The carotid artery is accessed using radial puncture or a pediatric puncture set under
ultrasound guidance at the lowest possible point in the neck. A road map is then taken
through the sheath or needle, and a guidewire is then navigated into the external
carotid artery ([Fig. 6]). This is exchanged for a 5 or 6F sheath depending on whether a single microcatheter
or two devices are going to be used. The sheath is then positioned at the origin of
the internal carotid artery, and the internal carotid artery is primed with nimodipine.
Following this, the guiding catheter is navigated to a position, which is comfortable,
and then the sheath along with the guiding catheter is either sutured to the skin
or stuck using Tegaderm (3M). This step is extremely crucial because there is a very
high risk of the sheath slipping out of the skin during the procedure with massive
hematoma in the neck. The rest of the procedure can be performed through the guiding
catheter, which will be now near the groin.
Fig. 6 Accessing the carotid artery directly is possible by using a pediatric puncture set
and with a guidewire navigated into the external carotid artery.
While removing the sheath, all you need is compression for approximately 30 minutes.
However, ensure that an ultrasound is done to make sure that there is no pseudoaneurysm.
Also, carotid compression is ideal after reversal of heparin.
Crossing a Large Aneurysm into the Distal Vessel
Crossing a Large Aneurysm into the Distal Vessel
Crossing into the distal vessel can be a challenge whenever a stent-assisted coiling
or a flow diverter is to be placed across the neck of a large aneurysm. To achieve
this, the wire is allowed to loop inside the aneurysm and then go distally ([Fig. 7]). The microcatheter is then tracked over the wire, and this combination is taken
to a point as distal as possible. Once this is achieved, the wire is removed and a
blank road map taken. Then, the microcatheter is filled with contrast for visibility.
Now, the loop inside the aneurysm can be straightened by gently pulling on the catheter
until the loop is completely straightened ([Fig. 8]). Thus, it is important that the microcatheter tip is as distal as possible so that
it does not fall back into the aneurysm sac.[6]
Fig. 7 A loop is created with the wire and the microcatheter navigated over it.
Fig. 8 The wire is withdrawn, and then the catheter is generally pulled until the loop is
straightened.
Conclusion
It is often said that difficult vascular anatomy can pose a challenge to even a most
experienced interventional radiologist. However, a combination of good techniques,
proper wires, long sheaths, guiding catheters, and other similar hardware can help
us overcome this problem. It is also prudent to remember that at times when nothing
works, it would be wiser to stop the procedure and think of an alternative way to
treat the patient.
