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64 Guidewire and catheter passage

Table 7.1 When to use ﬂuoroscopy during guidewire and catheter passage

Task When? Purpose?

How often is

it necessary?

Planning puncture Prior to arterial

puncture

Identify anatomy when there is no pulse

or poor pulse; locate proximal femoral

artery for antegrade puncture

Occasional

Guidewire passage

through entry

site

Guidewire will not

pass

Guidewire passes through needle but

will not advance into artery; check

guidewire position/direction with

ﬂuoroscopy

Occasional

Advancing

guidewire into

position

Soon after

guidewire enters

the artery

Observe guidewire progress; avoid

endoluminal injury; avoid passing the

guidewire into the wrong place

Always

Advancing

catheter through

entry site

Catheter will not

advance through

entry site

Check to see if catheter is coiling in the

subcutaneous tissue; check to see if

guidewire is bent

Rare

Advancing

catheter into

position

Soon after

catheter enters

the artery

Observe catheter progress; monitor

position; do not push catheter beyond

end of wire

Always

Removing

guidewire

After guidewire is

withdrawn from

catheter head

Observe appropriate formation and ﬁnal

position of catheter head

Always

T12

T12 T12

Fig. 7.1 Using landmarks to assist with catheter positioning. Bony landmarks are used to help place

the arteriographic catheter. (A) The renal arteries are usually located near the junction of the ﬁrst

and second lumbar vertebral bodies. The twelfth thoracic vertebral body is identiﬁed by its attached

ribs and the operator counts down. (B) The catheter head is placed near the L1–L2 junction so that a

high-pressure injection of contrast will reﬂux a few centimeters above that level. (C) The aortogram

demonstrates the origins of the renal arteries.

https://t.me/med1917

Where does the guidewire naturally want to go? 65

the head of the ush catheter assumes its proper

shape (Fig u re 7. 2). As the guidewire is removed

from the curved-head shape of the ush catheter,

the catheter head, which has been straightened

onto the guidewire, assumes its shape, which short-

ens the overall length of the catheter. erefore, the

catheter head position is usually adjusted slightly

within the artery, as appears necessary. Aer the

guidewire is removed, if there is any doubt about

its position or whether it is safe to administer con-

trast in this location, it is useful to twirl the cath-

eter to ensure its tip is free within the ow stream.

It is usually best to avoid unguided interactions

between the catheter and any lesions along the way.

e position and behavior of the catheter is help-

ful for determining if the catheter is in a safe posi-

tion. If there is any doubt, hand administration of

a small amount of contrast will solve the issue. In

general, intermittent uoroscopy can be performed

to provide adequate information to guide the case

but minimize the radiation required.

GUIDEWIRE AND CATHETER

COMBINATIONS

ere are many correct guidewire and catheter

choices; however, if the one you have chosen is

not working, move on. e goal of the procedure,

whether strategic or therapeutic, determines the

order and range of choices of guidewires and cath-

eters. e guidewire is chosen rst for routine arte-

riography. If a guiding sheath is needed to treat a

lesion, a stier guidewire is required for sheath

placement. If crossing lesions is required to set

up a therapeutic procedure, a dierent guidewire

may be required. If the initial guidewire choice is

not successful, a catheter may be placed over it to

alter the handling characteristics of the guidewire.

Acatheter may add stiness, steering, and pushing

strength to a guidewire. When the goal is selective

catheterization of a branch artery before the lesion

is encountered, the catheter is selected rst. When

a selective catheter is required, the usual guidewire

choice is one that is hydrophilic (low friction) and

steerable (directionality).

WHERE DOES THE GUIDEWIRE

NATURALLY WANT TO GO?

In passing the guidewire there are certain locations

that are inexplicably entered on a routine basis dur-

ing the casual placement of the wire in preparation

for catheter advancement. It is important that the

location of the wire placement is conrmed before a

larger catheter is advanced over it, especially if it is

a treatment catheter for balloon angioplasty, stent-

ing, or other types of treatment. Deployment of

these larger catheters can cause injury if the wire is

inadvertently placed in a collateral or small branch

vessel. When passing a guidewire up and over the

aortic bifurcation, it is common for the wire to

bounce o the outer wall of the contralateral com-

mon iliac artery and enter the internal iliac artery

instead of the external iliac artery. Oen, when

passing the wire from the external iliac artery into

the common femoral artery it passes directly, as

intended. However, a signicant minority of the

time, the guidewire enters into the medial or lat-

eral circumex iliac vessels and attempts to enter

the pelvis or the epigastric vessels. Passing the wire

into the lower extremity, as it advances through the

popliteal artery there are numerous perigenicu-

lar collaterals that fan away from the P2 segment

A B

Fig. 7.2 Evaluating the catheter head to ensure

that it has reached its appropriate shape and

location. (A) As the guidewire is removed, the

catheter head can be observed taking its pre-

formed shape. (B) The catheter may be twirled to

make certain that the catheter head is not stuck

against the wall of the artery.

https://t.me/med1917

66 Guidewire and catheter passage

of the popliteal artery and form an arborization.

Some of these collateral branches appear parallel

to the popliteal artery itself, and the guidewire can

easily enter and be mistaken for being in the popli-

teal artery. Another example as the wire progresses

distally in the leg is the recurrent collateral that

originates from the proximal anterior tibial artery.

is usually originates within a few centimeters of

the anterior tibial artery origin and at the location

where the artery turns inferiorly. is collateral

passes retrograde in a superior direction. is is

oen how the anterior tibial artery is collateralized

when its origin is occluded. During an antegrade

approach to the lower extremity and immediately

aer common femoral artery puncture, it is quite

common for the guidewire to progress posteri-

orly and directly into the profunda femoris artery,

rather than enter the supercial femoral artery.

In passing the guidewire into the carotid

artery, as it progresses from the common carotid

artery into the carotid bifurcation, it is quite com-

mon for the guidewire to select the superior thy-

roid artery. It must be redirected into either the

internal or external carotid artery, depending on

the intention of the operator. When cannulating

the subclavian artery, the guidewire frequently

enters into the thyrocervical trunk. Likewise,

if the artery selected is the internal mammary

artery and the patient has a le internal mam-

mary gra, this must be recognized prior to using

this as a location for an exchange guidewire to be

placed. As the guidewire is advanced from the

subclavian artery into the axillary artery, it fre-

quently selects the large collaterals at the head of

the humerus. ere are other examples, but these

demonstrate that the operator must be vigilant

and understandthe anatomy and have an index

of suspicion about the potential for the guidewire

to enter the wrong location.

PASSING THROUGH DISEASED

ARTERIES

As a general rule, lesions are only crossed just

prior to performing therapy, if at all possible (see

Chapters 15 and 16). Occasionally, arteries may

be so diusely diseased that there is no approach

through relatively healthy segments for arterio-

graphic catheter placement. In addition, a puncture

may be placed in an artery with a seemingly normal

pulse, and there may be a severe but unsuspected

stenosis just upstream or downstream from the

puncture site. ese factors indicate that uoros-

copy should be initiated early aer guidewire inser-

tion. e guidewire should be advanced steadily but

carefully through diseased segments. If the guide-

wire forms a leading elbow, continue to advance the

guidewire but do not force it. You do not want the

guidewire to become a loop stripper. Be particu-

larly careful with hydrophilic wires in this regard.

When the guidewire does not cross the desired arte-

rial segment, place a dilator overthe guidewire to

secure the access site and remove the initial choice

guidewire. If the guidewire has formed a loop, use

the catheter to pull the guidewire back to remove

the loop. Use a pu contrast to conrm the intra-

luminal position and obtain information about the

diseased segment. e catheter is used in this case

to guide and support the guidewire. A hydrophilic-

coated guidewire may cross the artery with greater

ease. Use a steerable guidewire and probe the lumen

of the artery gradually as the guidewire is advanced

(Fi g ure7.3). Aer the guidewire is placed, the cath-

eter is advanced over it and continuously observed

using uoroscopy.

If the arterial segment that has been crossed is

severely diseased, the passage of the guidewire and

catheter may stop ow or slow it down. Consider

anticoagulation to avoid generating thrombus

Fig. 7.3 Passing through severely diseased arterial segments can be challenging. A steerable

guidewire may be used to make multiple turns when attempting to cross a lengthy critical lesion.

Theguidewire tip may be used to probe the lesion. After the wire is across a long lesion, pass a

hydrophilic or lubricious exchange catheter; usually, a straight tip is easiest. Place a sturdier wire over

which to advance devices. An alternative is to place a low-proﬁle wire and follow it with a low-proﬁle

balloon and predilate the lesion to create space for the treatment devices that follow.

https://t.me/med1917

Negotiating tortuous arteries 67

along the catheter and also consider whether the

arterial segment should be treated right away.

Stoppage of ow will also aect the appearance

of ow in the artery during arteriography. As

wire passes through each lesion in a sequence

of diseased segments, the wire directionality is

decreased. is makes the subsequent lesions

more dicult to cross and if the wire is all the way

across the diseased segment, it makes the wire tip

less responsive. In addition, each wire has its own

sha stiness and trajectory based on the angle of

approach. is causes wire bias (Fi g ure 7.4). is

is important because it inuences the course of

everything that subsequently passes over that wire.

Technique: Catheter will not follow

guidewire

1. Use gentle catheter manipulations to assess the

exact location where the catheter fails to pass.

Where is the hang-up? Is it at a location of dis-

ease or tortuosity? Is the guidewire at that loca-

tion sti enough or is that segment too oppy?

2. Is the guidewire kinked? A seemingly minor

kink may be very dicult to pass with the cathe-

ter. Use a magnied view to study the guidewire.

Withdraw the guidewire a few centimeters and

pass the catheter again.

3. Is the guidewire subintimal? Does the guide-

wire itself move freely within the artery?

Usually, when the guidewire is in a dissection

plane, it will not advance beyond a certain

point and it will appear tethered at the point of

subintimal passage. Is the guidewire in a small

collateral or side branch?

4. Is the lesion so critical that the guidewire itself

has interrupted ow and there is not enough

residual lumen to pass a catheter? In this case,

heparin should be given. Immediate plans

should be made for treating the lesion.

5. In these situations, consider passing a smaller

(4-Fr) straight catheter with side holes. Aer

the tip of the straight catheter is passed just

beyond the point of obstruction, the guide-

wire may be withdrawn and a pu of contrast

should clarify the situation and an appropriate

guidewire may be placed.

6. Is there too much friction when passing

the catheter through an occlusion? Use an

exchange catheter with hydrophilic coating.

Place a small caliber wire and predilate with a

low caliber over-the-wire balloon.

NEGOTIATING TORTUOUS ARTERIES

ere are two issues: advancing the guidewire

through a tortuous passage and advancing the cath-

eter over the guidewire. In very tortuous arteries,

the guidewire and catheter must be advanced as a

team; one and then the other until enough ground

is gained to make it all the way across (Fig ure 7.5).

An access sheath is placed. A hydrophilic wire is

introduced and advanced until it slows to a crawl.

An angled catheter is passed over the guidewire

to support it and to point the way to the next turn.

Aer the guidewire is advanced, the catheter is

advanced in turn. Sometimes, the guidewire will go

but the catheter will not go over it. Sometimes, the

guidewire will not advance unless it is supported

by a sheath and also a catheter. Tortuous arteries

place constrictions on guidewires and catheters that

may not be immediately obvious under the two-

dimensional representation available with uoros-

copy. Anatomic segments, such as iliac vessels and

branches of the aorta, may exhibit tortuosity, kinks,

and loops. Despite a widely patent lumen, forces on

the guidewire–catheter apparatus may be such that

A B

Fig. 7.4 Wire bias. This is caused by the stiffness

of the shaft of the wire, the angle of approach

that the wire must take, and the impingement

on the wire by lesions along its course.

(A) In this example, the wire is usually biased

toward one wall of the renal artery. The pres-

ence of a lesion may also inﬂuence the wire bias.

(B) In this example of the aortic arch, wire bias

may be present and will depend on which arch

branch is cannulated.

https://t.me/med1917

68 Guidewire and catheter passage

they are prevented from advancing aer passing

through multiple turns. Each turn in a tortuous sys-

tem restricts the forward movement and the steer-

ability of the catheter as it approaches the next turn.

Oblique views of the tortuous segments are useful

to identify the true angles followed by the arteries.

A steerable, hydrophilic guidewire helps to negoti-

ate the turns. A straight or angle tip catheter may be

passed over the guidewire to help straighten some

of the initial curves and provide support for the

guidewire as it goes into its next turn. A sheath may

also be placed, not just at the entry site but into or

through the tortuous segment to decrease friction.

Aer the guidewire and catheter have been passed,

consider exchanging the guidewire for a stier one

before initiating therapy. When the forward motion

of the catheter stalls, the options are as follows:

place the guidewire further into the system; place a

stier guidewire; exchange for a longer access sheath

to support the guidewire–catheter apparatus and

straighten some of the initial tortuosity; and use a

soer, more hydrophilic catheter. In more dicult

cases, a body oss can be performed by externalizing

both ends of the guidewire and putting tension on

both ends. Anexample of this is a brachial-femoral

wire during complex aneurysm repair.

How to pass through a diseased

artery that is also tortuous

Passing through tortuous arteries depends on

the ability of the operator to be able to change the

curve of the vessels by passing devices through

them and causing them to “accordion” to some

extent. When the arteries are also heavily calci-

fied and have no flexibility, the diseased and tor-

tuous system will attempt to push the catheter

backward. If there is a calcific shelf at an angle

in the pathway, it can damage the catheter or

catch it so that the operator gets resistance when

attempting to remove the catheter. These are

situations where the patient’s anatomy will not

bend to the operator’s will. Use the techniques

described, especially the telescoping technique

in which the catheter and the wire are advanced

one-and-then-the-other. The guiding catheter or

a sheath may also be advanced this way so that

there are three parts to the system. Monitor the

patient carefully for pain or other symptoms or

signs. These are the situations where rupture or

dissection is more likely. If unsuccessful, it may

be better to choose a different approach than to

forge ahead.

Wire Wire is

advanced

Angled tip on

the catheter

Catheter tip

Access

sheath

Wire has

advanced further

A B C D

Fig. 7.5 Crossing tortuous arteries. (A) An access sheath is placed. (B) A Glidewire

is advanced.

(D)The wire is advanced and the process repeated.

https://t.me/med1917

Remote puncture site 69

REMOTE PUNCTURE SITE

A very remote puncture site may be required

in a variety of circumstances and the tools are

generally available for most of these occasions. An

example of this includes infrainguinal interven-

tion through a brachial approach when a femoral

approach is contraindicated by anatomy, infec-

tion, previous surgery, or other conditions. e

approach required for arteriography is dierent

from that required for treatment. Arteriography

requires catheter positioning upstream from the

lesion, whereas therapy requires guidewire and

catheter placement across the remote lesion at a

distance where guidewire control may be poor. e

operator must be prepared to undertake multiple

maneuvers to reach the intended destination sev-

eral vascular beds away from the entry site. In gen-

eral, the closer the tip of the sheath can be placed

to the target lesion, the more ecient and safe the

control of the intervention.

In the example mentioned above, selective arte-

riography would necessitate catheter placement

in the distal iliac or femoral arteries. e guide-

wire is introduced into the brachial artery and

advanced retrograde into the subclavian artery.

A catheter and a steerable tip guidewire are used

to advance into the aortic arch and avoid enter-

ing branches. e angle of take-o of the subcla-

vian artery from the aorta determines whether the

guidewire will preferentially enter the arch or the

descending aorta, but it usually enters the ascend-

ing aorta. A curved tip catheter, such as an Omni

Flush, is oen required to direct the guidewire

inferiorly into the descending aorta. e guide-

wire is advanced into the distal descending aorta,

and the catheter may be advanced over it. If a lon-

ger guidewire is required, it may be exchanged at

this point. Usually a 260-cm angle tip Glidewire

is a reasonable choice. e guidewire is advanced

into the femoral artery using the steerable tip and

using the catheter for support. Aer the catheter

has reached the infrainguinal area, the guidewire

is withdrawn and arteriography performed. Once

a wire is placed retrograde across the origin of the

subclavian artery, it is best to protect the artery

wall with a catheter so that the wire, when placed

under tension, does not injure the wall.

If endovascular therapy is appropriate, the

guidewire is replaced and a long (90 cm) 6-Fr or

7-Fr sheath is placed over the guidewire. e patient

is heparinized to protect the brachial access site

from thrombosis and prevent thrombus formation

along the sheath. e steerable Glidewire

advanced antegrade into the infrainguinal arteries.

Anticipate the respective lengths of guidewires,

catheters, sheaths, and therapeutic delivery cath-

eters that are required. e long sheath provides

extra support for the guidewire and helps to main-

tain its pushability and steerability. Consider pass-

ing an angletip catheter through the sheath to assist

in directing the guidewire across the lesion. e

more remote the approach, the more you need sup-

port with a long sheath or guiding catheter. ere is

more information on this technique in Chapter14,

which covers access for endovascular therapy. It is

oen helpful, aer the sheath is in place and in a

stable position, to switch to a low-prole wire and

small caliber platform to increase maneuverabil-

ity. e same process would be followed to treat a

visceral or renal lesion from a proximal approach.

An aortic branch is oen best treated with an

angle tip sheath or guiding catheter. e length

of the catheters and wires may be a limiting factor

depending on the distance between the access site

and the lesion intended for treatment.

Technique: Guidewire–catheter

buckling

A catheter–guidewire combination that buckles

when the catheter is advanced (F i g ure 7. 6) has lost

its pushability. is is usually because of distance,

tortuosity, or lack of an adequate rail. Very oen

in this situation, the catheter will not advance

smoothly over the wire and additional maneuvers

are required. A stier wire may be required, and

sometimes a telescoping system of access is useful.

1. Double-check that the guidewire–catheter

position is intraluminal and not subintimal.

2. Try a stier guidewire.

3. Use a long sheath to decrease friction over the

length of the catheter.

4. Try a stier catheter (e.g., nylon).

5. Try a dierent approach with a shorter or

straighter course, rather than force one that is

not going to work.

6. Prior to passing the catheter through a tortu-

ous area, take slack out of the wire (Figu r e 7.7 ).

https://t.me/med1917

70 Guidewire and catheter passage

A B C

Fig. 7.6 Guidewire–catheter buckling. (A) A contralateral approach is selected for treatment of a

superﬁcial femoral artery stenosis. (B) After initial access sheath placement, a catheter is advanced

with the intention of passing over the bifurcation. The wire is prolapsed into the infrarenal aorta.

Thiscreates slack in the system and encourages the possibility of the catheter prolapsing into the

infrarenal aorta rather than passing to the contralateral iliac artery. (C) In this setting, the slack must

be removed from the wire to offer smooth passage of the catheter.

A B C

Fig. 7.7 Situations where slack in the system promotes wire prolapse during catheter passage. After the

wire is in place, the catheter is advanced over the smoothest possible course. The principle of eliminat-

ing slack from the system applies to both angiographic catheters and treatment delivery catheters. Here

are some examples where slack may accumulate and prevent catheter passage. (A) After advancing a

wire into the carotid artery, the catheter may not follow in a tortuous arch. The wire tends to prolapse

back into the aortic arch. (B) When using a left brachial approach to the descending aorta, the turn from

the left subclavian artery into the aorta can be challenging and the wire tends toward prolapsing into

the arch and ascending aorta. (C) When a visceral or renal vessel is the target, there is limited distance

beyond the origin of the artery in which it is safe to pass the wire. When the catheter is advanced, rather

than follow the curve of the wire, it tends to drag the wire out of the vessel and prolapse into the aorta.

HOW TO CHANGE THE PLAN IF THE

CATHETER WILL NOT PASS AND YOU

HAVE TRIED EVERYTHING

Usually when this occurs, there is a fundamental

problem with your plan. Typically, you will have

already replaced any wire that is too oppy for

one that oers more support. More catheter sup-

port can also be gained by placing the sheath tip

very close to the area where the catheter must be

passed. In addition, sometimes the 0.035-inch plat-

form catheter is simply too large to pass through a

https://t.me/med1917

How do you decide if disease encountered on the pathway 71

heavily calcied or long occlusion. In this case you

can exchange it for a lower-prole wire and use a

hydrophilic catheter. Sometimes, a larger sheath

is required in order to support the force needed

to deliver the device. Lastly, consider the possibil-

ity that the wire passes through a place where the

catheter should not follow. An example would be if

it goes through the struts of a stent. If all of these

approaches fail, consider approaching the lesion

or artery segment from an alternative direction.

Change to an antegrade approach if the initial

approach was retrograde and change to a retro-

grade approach if it was antegrade.

HOW DO YOU DECIDE IF DISEASE

ENCOUNTERED ON THE PATHWAY

TO TREAT THE TARGET LESION

ALSO NEEDS TO BE TREATED?

When does treatment need to be initiated to

enhance wire or catheter passage or sheath pas-

sage? If there is a coincidental arterial lesion along

the way, how do you know when to go ahead and

treat it, or leave it alone? ere are a couple of

scenarios in which this will have a role. On the

way to treat a target lesion, if there is another

lesion in series with the target lesion as an inow

obstruction and it appears to be signicant, then

it usually should be considered for treatment.

An example of this would be a supercial femo-

ral or popliteal stenosis proximal to target tibial

disease. Another scenario is when the lesion is

coincidentally located in a pure access vessel and

does not diminish ow to the organ system that is

being treated. An example of this is when an up-

and-over approach encounters an iliac lesion on

the side of the puncture and contralateral to the

limb intended for treatment. If the lesion along

the access pathway is severe enough that the direc-

tionality in the passage of the catheter or sheath is

inhibited, then the lesion needs to be treated. If the

lesion alongthe access route is severe enough that

once the treatment sheath is passed through it that

ow is stopped, then it should be treated. Usually

it is best to perform angioplasty rst to create a

larger lumen. Pass the treatment sheath and treat

the target lesion. If the coincidental lesion requires

stent placement, that can be performed aerward.

Once a stent is placed it can create a point of fric-

tion or catch the edge of a sheath passing through

it. If there is doubt about the signicance of the

lesion, obtain oblique views to nd the greatest

degree of stenosis. Pressure across the lesion can

also be measured. However, the full pressure gra-

dient may not be accurate across an inow lesion

where there are lesions in series, since the more

distal lesion may cause outow obstruction.

Passing through dissected arteries

e most common situation in which an operator

is required to pass through a dissected artery is in

the case of aortic dissection (see “Passing through

aortic dissection”). However, there are also situa-

tions of dissection due to injury or spontaneous

dissection (carotid, renal, visceral). Another situa-

tion that every operator will face is when a dissec-

tion occurs during treatment, but the wire access

is inadvertently lost. Some examples of passing

through dissected arterial segments are shown in

Fi gure 7. 8 . Place a so tip, angled catheter, such

as a Glidecath

, close to the lesion. Do not per-

form a high-pressure injection, since this can lead

to additional propagation of a dissection. Allow

the dissected segment to ll with contrast and see

where it goes. If the dissection ap appears hazy

or there is no clear entrance, obtain oblique views.

Use a steerable, atraumatic 0.014-inch diameter

guidewire. Whichever wall of the artery appears

to have sustained the worst damage, steer the wire

toward the opposite side. Very oen, an entrance

to the dissection is visible. Advance the wire gently.

Allow the tip of the wire to oat and dance from

side to side to see if it can select the correctpathway.

A B C

Fig. 7.8 Passing through a dissected artery.

Inthis case guidewire access has been lost across

a partially treated lesion. (A) The wire is rein-

troduced using an angled catheter. (B) Oblique

views are obtained. Very often an entrance to the

dissection is identiﬁable. (C) A low-proﬁle wire

is advanced and allowed to probe gently and

dance freely through the lesion.

https://t.me/med1917

72 Guidewire and catheter passage

Carefullyobserve the wire tip to see if it is free or if

it is pinned in tissue. Steer away from areas where

the guidewire seems to get caught in the tissue.

Aer multiple attempts to cross from one direc-

tion, if it will not pass, attempt crossing from the

opposite direction. Do not form a loop of wire as

this will tend to go into the dissection plane and

propagate the dissection further.

Passing through stents

Stents may cause diculty for wire passage

(Fi g ure 7.9). Both balloon-expandable and self-

expanding stents can provide challenges and both

types of stents can be damaged with aggressive

attempts at device passage through them. Self-

expanding stents, especially if they are an open

cell design, may have a degree of luminal irregu-

larity or sh scaling, where stent struts and joints

protrude into the lumen at locations of curvature.

Every stent has struts with various sized apertures

in between the struts, and all may easily accept pas-

sage of a guidewire. When this occurs, the guide-

wire may appear to be constricted in its course as

it passes through a portion of the stent. It can also

be dicult to discover whether the guidewire has

passed in between stent struts. If there is any doubt

about this, pass a simple curve catheter over the

wire. If it repeatedly hangs up at the same location,

the likelihood is extremely high that the wire has

passed through the stent struts. e rst passage

through a stent is usually best with a loop of atrau-

matic guidewire tip, such as a Bentson or Rosen.

Guidewires passed through stents typically have a

certain degree of wire bias, with a specic trajec-

tory of the wire as it enters the stent and exits the

stent. When the next catheter or device is passed

over the wire it will tend to catch on whichever

edge of the stent is aected most by wire bias.

When stents have been placed at the aortic bifurca-

tion and the goal is to pass up-and-over the aortic

bifurcation, it is quite common for the tip of the

catheter to catch on the stent as it traverses to the

contralateral side.

Passing through aneurysms

e development of stent–gra treatment of

abdominal aortic aneurysms has resulted in

aggressive catheterization of aneurysms. Passing

catheters through aneurysms is associated with a

risk of embolization of the compacted thrombus

A B C D

Fig. 7.9 Passing through stents. (A) The guidewire is advanced in a very loose and easy manner and

allowed to pass through the stent, preferably leading with a loop of atraumatic wire. (B) After the

guidewire is passed, if there is doubt about its location with regard to the stent struts, a catheter is

passed over the wire to see if it catches on the stent. In this case, the wire has passed through the

edge of the stent, This is detected by advancing a standard angled catheter. (C) Fish-scaling occurs

when an open cell stent is placed in a tortuous artery. The metal is bunched up on the inner curve and

in a place where the wire can be caught. In this case, a catheter is used to steer around it. (D) Wire bias

occurs as a result of the inability of the wire to conform to the angulation of the pathway. Occasionally,

this leads to direct interaction with a stent, which must be negotiated carefully. In this example, there is

a previously placed stent in the proximal left common iliac artery. The wire bias is such that the wire is

eccentric and on the stent surface. Care must be taken as a sheath is advanced through the stent.

https://t.me/med1917

How do you decide if disease encountered on the pathway 73

in the aneurysm sac. Associated occlusive disease

that involves the neck of the aneurysm tends to be

friable, and embolization is a risk when this mate-

rial is present. It is surprising that embolization

does not occur more oen. e usual approach is

retrograde through the common femoral artery.

Passing through aneurysms involves crossing the

iliac arteries, which may also be aneurysmal and

are likely to be tortuous, and then getting through

the abdominal aortic aneurysm.

Tortuosity of the iliac arteries may make the

approach challenging, especially if there is associ-

ated occlusive disease. Because occlusive disease and

calcication cause an iliac segment to become stier

than adjoining segments, relatively xed in con-

guration, and less pliable, the angle of curvature

is more extreme in the more compliant, juxtaposed

segments. Unfortunately, this causes the occlusive

lesions to be present at either end of a tortuous seg-

ment. erefore, the operator must be prepared to

use steerable guidewires and selective catheters to

cross the aneurysm. Sometimes, tortuosity is severe

enough that the loops formed as the guidewire

crosses the tortuous segments create signicant ten-

sion. As the forward progress of the guidewire bogs

down, the back pressure by the vessel system on

the wire tries to “spit out” or force back the guide-

wire. When this happens, reconsider the approach.

If signicant tortuosity occurs in an aneurysmal

common iliac artery, the guidewire may want to

“pile up” inside the iliac aneurysm and the neck may

be dicult to nd since it is not a straight shot.

Passage of a guidewire through a large abdomi-

nal aortic aneurysm can be dicult if the neck is

hard to nd. e wire tends to get lost and pile up

in the wide open space of the aneurysm. High-

pressure contrast injection into the aneurysm

to dene anatomy is contraindicated. Pung

contrast in the iliac arteries may be useful but in

the aneurysm it is useless since there is tremen-

dous mixing with nonopacied blood. Multiple

attempts at passage are sometimes required. e

guidewire should not be placed so redundantly

into the aneurysm that it curls up within the sac.

It is a counterproductive maneuver and may result

in embolization of aneurysm contents or tangling

of the guidewire.

It is usually best to place a standard access

sheath and pass a starting guidewire from the

femoral artery using uoroscopy. Oen, the

guidewire will pass without specic direc-

tion, despite tortuosity and nearly blind sacs. If

it does not pass, or when the wire tip starts to

coil up, place an angle tip catheter over it, such

as an MPB, a Berenstein, or a TegT. Exchange

for a steerable guidewire and advance carefully.

Pu contrast into the iliac arteries if necessary.

If a CT scan or other imaging study is available,

refer to that for clues about what to expect. Aer

entering the aneurysm from below, advance the

angle tip catheter over the guidewire and use it

to point the wire toward the neck of the aneu-

rysm (Fig ure 7.10). Always use a oppy-tipped

guidewire.

Fig. 7.10 Crossing

an aneurysm.

(A)The guidewire

tends to pile up

in the aorta when

crossing an aneu-

rysm. (B) A multi-

purpose, simple

curve selective

catheter, such as an

MPB, may be used

to direct the guide-

wire past tortuous

iliac and aortic

segments.

A B

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