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234 Stents, covered stents, stent–grafts

it until aer the stent is deployed. Perform a road

map with the patient having taken a half breath

in (not a deep sea diver breath that can change all

the positions and the landmarks). Advance the

stent into the lesion, have the patient take the exact

same half breath in, and hold it as he/she had done

during the angiographic run. During the breath

hold, the road map should match up and the stent

is deployed. Aer the stent is in place across the

lesion, but before it is deployed, if there is any doubt

about correct placement, pu contrast through the

sheath to reconrm the position or do another

road map. Aer the stent is in the lesion, additional

contrast runs may be performed, but the ow of

contrast around the stent and through the lesion

may be limited. e trailing end of the stent will

be visualized, and this is oen the most important

part of the stent, especially in aortic branch origin

lesions (e.g., innominate, subclavian, visceral, and

renal arteries). Sometimes, this process is repeated

a couple of times until the operator is satised with

the position for stent placement. Have a contin-

gency plan for what to do if the stent is placed too

far one way or the other with respect to the lesion.

Guidewire control must be maintained across

the stent until the reconstruction is complete. e

operator must be aware of and manage guidewire

bias. In the case of branch artery origin lesions, tra-

versal of the wire from the aorta into the branch

is accompanied by wire bias, which will direct the

wire toward one side of the lumen of the artery.

Anything that is passed over the wire, such as a

subsequent balloon or the next stent, will tend to

catch on the initial stent because of this wire bias.

If additional stents are required, the sheath is

advanced into the appropriate position. is can

sometimes be done over the wire alone and some-

times it is necessary to advance the wire over the

dilator. If the latter maneuver is selected, the opera-

tor must be careful to avoid damaging or dislodging

anything with the dilator tip. If numerous overlap-

ping stents are required, the distal stent is placed

rst and built proximally to create a “telescope”

eect (Figure19.4). If dilation to a larger diameter

is required, the deployment balloon is exchanged.

Aballoon-expandable stent does not taper well but

it can be dilated to a slightly larger size on one end if

necessary to are the end of the stent and attempt to

match vessel size and taper. is is especially true of

the newer balloon-expandable stents that are con-

structed of lighter and less rigid metal than the ear-

lier generation of stainless steel stents.

A completion arteriogram is obtained by plac-

ing the tip of the sheath at the distal end of the stent

and injecting contrast so that it reuxes through

the area of stent placement. Another option is to

place a 4-Fr or 5-Fr straight catheter through the

sheath, over the guidewire, and position the tip

of the catheter at a location proximal to the stent.

A 4-Fr or 5-Fr ush catheter may also be placed

in the same manner and positioned upstream from

the stent site.

A B C

Fig. 19.4 Telescope effect using balloon-expandable stents. (A) A long iliac artery stenosis requires

more than one stent for coverage. (B) The distal stent is placed ﬁrst. (C) The second stent overlaps

the ﬁrst and ﬁts inside to create a telescope effect. This technique avoids a prominent metal edge

protruding into the ﬂow stream. The proximal end of the proximal or second stent may also be ﬂared

slightly with secondary balloon dilation.

https://t.me/med1917

Placement technique for self-expanding stents 235

PLACEMENT TECHNIQUE FOR

SELF-EXPANDING STENTS

Standard self-expanding nitinol stents must be

oversized by 1–2 mm so that they exert continu-

ous outward radial force at the site of deployment.

Placing a stent that is too small in diameter must be

avoided since these stents cannot be dilated beyond

their nominal diameter in the same manner that

a balloon-expandable stent can be overexpanded.

If there is doubt about the appropriate diameter

stent to use, consider balloon angioplasty rst with

an evaluation of the inated balloon prole. If still

in doubt, use a stent that is a bit bigger in diam-

eter. is is the opposite of balloon-expandable

stents. Placement of a self-expanding stent is per-

formed by withdrawing the covering catheter layer

that encloses the stent on a prepackaged delivery

catheter. e prepackaged stent delivery catheter is

placed through a 5-Fr or 6-Fr sheath in most cases

for peripheral arterial usage, as recommended

by the manufacturer. e largest self-expanding

stents used for aortic or venous applications may

require an 8-Fr or 10-Fr sheath. Stent length choice

varies signicantly from one stent type to another.

Self-expanding stents are manufactured in mul-

tiple lengths, from 20 to 250 mm in fully expanded

form. Self-expanding nitinol stents, which are

commonly used in the noncoronary arteries, usu-

ally do not shorten much on placement, although

there are dierent designs. It makes sense to get

used to a couple of products that you will routinely

use in your practice and really understand the

extent to which the trailing end of the stent tends

to foreshorten. Self-expanding stents are generally

simple to place and they adapt to tortuosity and

manage longer lesions well.

Woven nitinol stents (Supera

and Wallstent

)

experience signicant changes in length with

deployment. e current application for the

Supera

is in the femoropopliteal vessel segment,

whereas the Wallstent

may be used in multiple

arterial and venous vascular beds. e Supera

stent is deployed by pushing it out of its delivery

catheter. e artery must be well prepared for the

stent to reach its nominal diameter. e Supera

stent is highly crush resistant but exerts no chronic

outward force. It is very eective at its nominal

diameter, but is quite ineective if it is deployed in

a crimped manner. e ultimate length of the stent

when deployed depends on the degree to which

the operator packs the stent into the lesion dur-

ing deployment. e Wallstent

has quite a bit of

chronic outward force and the nal length of the

stent depends on the nal overall resting diameter.

e constrained length of the Wallstent

(in the

package) is longer than the deployed length and,

aer placement, is constrained by the artery. If the

Wallstent

is opened on a tabletop and is completely

unconstrained, it is even shorter. For example,

a 10×42 Wallstent

(10-mm diameter × 42-mm

length) placed in a 9-mm iliac artery is 50–52 mm

long aer deployment. e Wallstent

in practice

is not intended to be completely expanded, since

it is oversized for the artery into which it is placed.

e self-expanding stent catheter is removed

from its package, ushed, wiped with heparin–

saline solution and advanced over the guidewire

(Figure 19.5). Because the delivery catheter and

the stent are somewhat exible, it can usually be

passed over the aortic bifurcation or into branches

without diculty. Standard self-expanding niti-

nol stents are marked by radiopaque markers on

their proximal and distal ends, which are observed

using uoroscopy. Woven nitinol stents typically

do not have markers. To deploy a standard nitinol

stent or a Wallstent

, the metal pushing rod is held

steady and the valve body is withdrawn, which

removes the covering membrane and permits the

stent to expand on its own. e view on uoros-

copy is magnied and continuous because it is

easy to move the stent with minimal force and it

makes sense to carefully adjust the stent location

asit begins to open. As the metal pushing rod is

held stationary and the valve body is withdrawn,

the proximal end of the stent begins to expand.

Asthe nitinol warms up, it becomes more rm.

e position of the stent is continually assessed

as it is being deployed. A road map can be used

to assist in placement. Self-expanding stents are

more likely to be used for lesions in conduit arter-

ies (e.g.,iliac artery, SFA), which may be longer

and have some degree of tortuosity (e.g., carotid

artery, iliac artery). Self-expanding stents have

the disadvantage that only the leading end of the

stent, usually the end toward the tip of the cath-

eter, can be placed with a high degree of accuracy.

e back end, trailing end, or end of the stent

that is closer to the hub end of the catheter will

land with much less placement accuracy than

the leading end of the stent. Somewhere in the

course of self-expanding stent deployment, but

https://t.me/med1917

236 Stents, covered stents, stent–grafts

Fig. 19.5 Placement technique for self-expanding stents. (A) The guidewire is placed across the

lesion. (B) The stent delivery catheter is placed over the guidewire so that the proximal marker on the

stent delivery catheter is proximal to the lesion. The metal push rod is held stationary while the valve

body is slowly withdrawn. (C) The position of the stent is continuously monitored during deployment.

A magniﬁed view may help perfectly place the proximal end of the stent. As the stent is about to

open, it can be withdrawn slightly to reposition it, but not advanced. As the valve body is withdrawn

along the length of the pushing rod, the covering sheath or membrane that constrains the stent is

removed and the stent spontaneously expands. (D) After stent deployment, the delivery catheter is

removed. Poststent placement balloon angioplasty isperformed.

https://t.me/med1917

Placement technique for covered stents 237

before there is full engagement of the stent with

the artery wall, the stent can be moved and its

position readjusted. When the leading end of the

stent starts to open it “blossoms”. Once that blos-

som becomes big enough to touch the wall of the

artery, the stent cannot be advanced, but usually

can still be withdrawn. Most self-expanding niti-

nol stents can deploy about 15% to 20% of their

length, or 1 cm (whichever is less), and it still be

possible to withdraw the whole stent to readjust

its position. Ifthere is too much adherence of the

stent to the wall already in play, when the catheter

is withdrawn, the stent just hugs and hangs on to

the wall and the stent deploys. If the stent is moved

aer there is a lot of contact between the artery

wall and the stent, there is a risk that the end of the

stent will be mangled.

ere is a reconstrainable Wallstent

that can

be covered up again by its covering membrane,

provided the release process has stopped short

of a certain point that is marked on the delivery

catheter. e stent can then be moved to a dier-

ent place and deployed. e Wallstent

is a closed

cell structure. is permits a relatively smooth

outer surface without any “V”-shaped stent joints

extruding beyond the prole of the open or par-

tially open stent. is facilitates recovery of the

outer surface of the stent if desired. is recaptur-

ability will probably not be possible with open cell

nitinol self-expanding stents in the near future.

e design allows the stent to spring all the way

open when one end is deployed and one end is

still constrained in the delivery catheter. In other

words, the open cell stents contour well and they

are able to go from a very small diameter to a large

diameter over a very short longitudinal distance.

is property is needed for the management of tor-

tuous or tapered arteries, but it also creates rough

edges where stent joints are under stress and pro-

trude into the lumen.

Most of the self-expanding stents deploy in a

similar manner to each other: holding a pushing

rod in a stationary position while withdrawing

the covering membrane and allowing the stent to

expand. Some have ratcheted handles or turnwheel

knobs to activate for better control, possibly accu-

racy, but it is the same underlying mechanism.

Take the slack out of the guidewire and cath-

eter. Be aware that any withdrawal of the catheter

for placement accuracy will also tend to pull the

sheath out. Built-up energy in the stent delivery

catheter, when released, tends to make the stent

pop forward a bit (toward the tip end) during

deployment. Aer stent deployment, the delivery

catheter is removed and balloon angioplasty of the

length of the stent is performed, especially in sec-

tions where there is residual crimping of the stent

by the lesion. It is sometimes dicult to assess

whether the stent is fully expanded. Keep the

balloon within the stent if injury is to be avoided

to neighboring artery segments. When balloon

angioplasty is to be used within the Wallstent

, the

central part of the stent is dilated rst. e ends of

the stent are dilated last because the tines of the

stent may rupture the balloon.

e guidewire is maintained across the stented

segment until aer satisfactory completion stud-

ies are performed. Completion arteriography is

performed in the same manner as with balloon-

expandable stents. If guidewire control of the stent

is relinquished prematurely, advance a J-tip or very

oppy-tip guidewire back through the stent using

a small eld of view for magnication. is is done

to avoid passing the guidewire through the struts

of the stent. is is easy to do, especially prior to

postdeployment balloon angioplasty. If you have

to cross a fresh stent and you are not sure if you

are under its tines, pass a straight or simple curve

catheter over the guidewire. If the guidewire goes

under one of the stent struts, the catheter will hang

up instead of passing freely.

PLACEMENT TECHNIQUE FOR

COVERED STENTS

Choosing the appropriate stent diameter is impor-

tant no matter what kind of stent is planned, but

with self-expanding covered stents the diameter

choice is even more important. is is because

signicant oversizing of the stent results in place-

ment of a larger amount of material, which may

overwhelm the available lumen. In addition, when

treating longer segments with self-expanding

stents, there may be some overlap between dier-

ent stents. In the overlapped segment the amount

of material is even larger. When there is a change

in diameter or tapering of the artery, typically

the smallest diameter covered stents are placed

rst and the larger diameter self-expanding cov-

ered stents are placed subsequently. is permits

the development of a friction seal. When treating

occlusive disease, consider minimal overlap of the

https://t.me/med1917

238 Stents, covered stents, stent–grafts

covered stents in order to prevent build-up of mate-

rial. When treating aneurysmal disease, such as in

the popliteal artery, more overlap will be required

to prevent the stents from becoming dislodged or

disjointed. When selecting a balloon-expandable

covered stent, the stent is sized to the artery. In that

setting the operator has the luxury of a slight over-

expansion of the balloon if additional diameter is

required.

ere is typically a larger sheath required for

covered stents than for bare metal stents. In order

to make more room for delivery through the

sheath, many covered stents are delivered over

smaller diameter guidewires, such as 0.018-inch

diameter wires. e deliverability is partly

diminished with covered stents due to the larger

amount of material that usually ts very tightly

within the sheath. Aer the constrained covered

stent has passed through the sheath, the outside

surface of the covered stent is typically irregular,

and the device itself on the catheter is usually

slightly bulkier than a bare metal stent. All these

aspects aect the ability to deliver the covered

stent to its desired location. If the covered stent is

being delivered into a tortuous area, such as when

being used as a renal or visceral snorkel, it will

likely not pass bareback. In this case, the sheath

is placed where the covered stent is desired, the

stent is advanced into location, and then the

sheath is withdrawn.

Once the device is in the appropriate location,

the placement depends to some extent on the type

of covered stent. For balloon-expandable cov-

ered stents, the delivery is very similar to other

balloon-expandable stents. e device is placed

exactly where desired and the balloon is inated.

ere is typically minimal foreshortening. With

self-expanding covered stents, there may be some

adjustment of position during deployment of the

leading edge of the stent, and there is usually mini-

mal foreshortening.

Aer placement of self-expanding covered

stents, the operator performs aggressive balloon

angioplasty of the stent to make sure it is fully

expanded. e outward radial force is typically low

and the potential for the lumen to be compromised

is increased. With balloon-expandable covered

stands, additional balloon dilation is usually not

required, but sometimes, depending on the loca-

tion, the operator decides to dilate the end of the

stent to are it slightly.

Strategy: What to consider when

selecting a stent

1. Can you visualize the stent in this position?

2. What are the length and diameter require-

ments of the diseased segment?

3. What is the location of the lesion and what

type of lesion is it?

4. Are there delivery restrictions posed by dis-

eased access arteries, sheath size, vessel tortu-

osity, working room, or distance to the lesion?

5. Can the number of required stents be

minimized?

6. Is the stent in your inventory?

WHICH STENT FOR WHICH

LESION?

Table 19.3 oers a practical comparison of the

working properties of dierent stent categories. In

general, orice lesions and those that are heavily

calcied are best treated with balloon-expandable

stents. Lesions located in exible or tortuous arter-

ies, or that are more than several centimeters in

length, are usually treated with self-expanding

stents. Either balloon-expanding or self- expanding

stents may be used in the aorta (Table19.4). Short

focal lesions may be treated with balloon-expand-

able stents. Placement is precise and the single stent

is less expensive. Self-expanding stents are well

suited to longer aortic lesions (longer than 2–3cm).

Placement of a single longer self-expanding stent

is usually simpler, faster, and less expensive than

placing multiple balloon-expandable stents. Just be

careful to ensure that the trailing end of the stent

clears the aortic bifurcation and opens fully within

the aorta. e other advantage of self-expanding

stents in the aorta is when there is a heavily calci-

ed, shelf-like, or iceberg-like lesion, the stent can

be laid in and the lumen gradually enlarged with

successively enlarging angioplasty balloons. is is

done to avoid rupture.

Lesions in the aortic bifurcation are treated

by “raising” the aortic ow divider with balloon-

expandable stents. Precise, “kissing,” and side-

to-side placement is possible with self-expanding

stents, but is more challenging and may not be

adequate to manage heavily calcied plaque at the

aortic bifurcation. Aortic bifurcation plaque usu-

ally extends into the common iliac artery orices.

Self-expanding stents do not have as much hoop

https://t.me/med1917

Which stent for which lesion? 239

Table 19.3 Practical stent comparison: working qualities of balloon-expandable, self-expanding, and woven nitinol stents

Working

quality

Balloon-

expandable

Self-expanding

(nitinol)

Woven nitinol

(Wallstent

)

Woven nitinol

(Supera

) Advice

Method of

expansion

Balloon-

expandable

Self-expanding Self-expanding Self-expanding Requirement for balloon expansion to

deploy makes balloon-expandable

stent placement a little more

complicated, but self-expanding

stents always require postexpansion

balloon dilation

Maximum

length

>5 cm 25 cm >9.4 cm Approximately 15

Balloon-expandable stent length

limited; lesions more than 3 or 4 cm

need more than one stent; adds

complexity, time, and cost to the

case. Self-expanding stents provide

longer length

Length changes

during

placement

Shortens by 5% to

25%, depending

on ﬁnal diameter

Less than 8%, does

not depend on

ﬁnal diameter

Shortens by more

than 30% of

constrained length

Signiﬁcant; depends

on how tightly the

stent is packed

Final resting Wallstent

length can be

difﬁcult to predict; nitinol stents

have minimal shortening

Hoop strength High Low to medium Low High Balloon-expandable stent is a better

choice for oriﬁce lesions and heavily

calciﬁed arteries

Flexibility None High Moderate High Self-expanding stents are better

choices for tortuous or tapered

arteries

Contourability None High Moderate Poor; does not

contour to

diameter changes

(Continued)

https://t.me/med1917

240 Stents, covered stents, stent–grafts

Table 19.3 (Continued) Practical stent comparison: working qualities of balloon-expandable, self-expanding, and woven nitinol stents

Working

quality

Balloon-

expandable

Self-expanding

(nitinol)

Woven nitinol

(Wallstent

)

Woven nitinol

(Supera

) Advice

Maximum

diameter

>24 mm 14 mm 24 mm 7 mm Self-expanding stents a better choice

for vessels >12 mm in diameter;

balloon-expandable stents can be

pushed to larger sizes, but with

severe foreshortening

Precision of

placement

Precise Precise on one

end

Precise only on one

end

Only somewhat

precise and only

on one end

Proximal end (ﬁrst end to be

deployed) of self-expanding stent

can be placed precisely and moved

a bit prior to full deployment;

location of second/distal end of

stent is not precise

Delivery sheath 6–9 Fr 6–8 Fr 6–9 Fr 6-Fr or 7-Fr Balloon-expandable stent requires a

long sheath to be placed through

the lesion, which adds risk of

instrumenting lesion and creates

problems for remote delivery.

Self-expanding stents are on

delivery catheters

Biohazard Sharp edges;

cannot be

clamped; can

tear balloon

No sharp edges;

can be clamped

in emergency

Loose wire ends are

sharp; can be

clamped in

emergency

Will not expand to

nominal diameter

if lumen is not

adequate

In an emergency, self-expanding

stents can be clamped with a

shodded clamp

https://t.me/med1917

How to select the best stent for the job 241

strength, which is desirable for the aortic bifurca-

tion and other orice lesions.

Routine common and external iliac artery

lesions may be treated with either self-expanding

or balloon-expandable stents. Focal lesions are

treated with balloon-expandable stents and self-

expanding stents are used for longer lesions and

those located in tortuous arteries or arteries with

signicant taper. Distal iliac artery lesions that

are close to the groin should be treated with self-

expanding stents to maintain exibility.

Self-expanding stents are better for stenting in

exible arteries, such as the supercial femoral,

popliteal, and distal subclavian arteries. Lesions

in an aortic branch orice, such as the proximal

innominate, common carotid, subclavian, vis-

ceral, or renal artery, are best treated with balloon-

expandable stents. e combination of placement

accuracy and hoop strength is better in this setting.

HOW TO SELECT THE BEST STENT

FOR THE JOB

Although there are multiple considerations when

selecting a stent for a given case, there is substantial

overlap in the capabil ities of the various stents . Most

specialists develop a short list of a couple of favor-

ites in each stent category, balloon- expandable and

self-expanding, in each vascularbed. Onetrend of

note is that self-expanding stents are being used

more widely than before. ey are becoming more

versatile, better engineered, provide more choices,

and there is better data on results. What follows is

a discussion of some of the issues that drive stent

preferences in clinical practice.

Most practices have at least some restriction

on the variety of stents stocked and the number

of dierent stent diameters and lengths avail-

able. Specialists with a limited inventory will ask

the question sooner, but everyone must face the

availability issue at some point. Work with what

is available or plan ahead well enough so that spe-

cic items are anticipated and ordered. e devel-

opment of various sizes, lengths, designs, proles,

and qualities of stents has been signicant over the

past few years.

e single most important thing to do when

selecting a stent is to visualize the stent in the

intended location. Will it expand to oppose the

wall of the artery? Can it handle the tortuosity

and/or diameter changes? Does it have the hoop

strength to stand up to the amount of calcication

present in the lesion? Will one end of the stent be

oating free in a segment of poststenotic dilation?

Will it cover the segment of artery most in need

of treatment? Can the stent be passed safely to the

target site? Will it cover or impinge on an impor-

tant branch and, if so, is that acceptable? Can the

Table 19.4 Some examples of which stent to use

Angioplasty site Lesion type Stent to use

Reason

Aorta Focal lesion Balloon-expandable Length match

Bulky lesion Self-expanding Gradual expansion, avoid rupture

Long (>2–3 cm) Self-expanding Fewer stents required

Aortic bifurcation Iliac origin Balloon-expandable Hoop strength

Iliac Focal Balloon-expandable Length match; simple

Tortuous Self-expanding Flexible

Long (especially

external iliac)

Self-expanding Fewer stents required; handles

tortuosity well

Superior femoral/

popliteal

Long Self-expanding Fewer stents required

Across joint Self-expanding Flexible

Focal, short Self-expanding Better patency

Heavily calciﬁed Woven nitinol Supera

hoop strength

Renal Oriﬁce Balloon-expandable Hoop strength, rigid

Body of artery Either

Subclavian Tortuous Self-expanding Flexible

Oriﬁce Balloon-expandable Hoop strength

https://t.me/med1917

242 Stents, covered stents, stent–graf ts

lesion be treated with a single stent or will multiple

implants be required?

e length and diameter requirements of the

lesion must be taken together with the type and

location of the lesion in order to come up with a

stent choice. Lesion type and location were dis-

cussed in an earlier section. It is not always appar-

ent how long a length of artery should be stented if

there is mild or even moderate disease juxtaposed

to the lesion. e operator must make an arbi-

trary decision in many cases. e diameter may

be sized the same way as for balloon angioplasty,

but the consequences of a bad guess are greater. If a

balloon-expandable stent is undersized, it may not

be securely adherent to the artery. If it is oversized

too much, the artery may be injured. One method

of dealing with this dilemma is to undersize the

balloon-expandable stent just slightly. Deploy the

stent so that it is held in place by the newly dilated

lesion. en dilate the stent again to the desired

size using a larger balloon if necessary. e diam-

eter choices for self-expanding stents provide more

leeway since the stents are oversized from 1 to 3

mm. Nevertheless, if too small a stent is used, it

may become free-oating. Required stent lengths

can be challenging. All external marking methods

have some degree of parallax.

Finally, delivery restrictions may be posed by

diseased access arteries, the sheath size of the

selected stent, vessel tortuosity, adequacy of work-

ing room, a long distance to the lesion, or branch

points between the access point and the lesion. e

risk of puncture site thrombosis increases when a

large sheath is passed through a diseased common

femoral artery. Sheath size may inuence the choice

of stent, since relatively larger diameter sel f-expand-

ing stents may be placed through 6-Fr sheaths.

Vessel tortuosity or a branch point on the way to

the lesion can be overcome with a guiding access

sheath of the appropriate length. Occasionally, a

more exible stent is required to make these turns

(e.g., over a very narrowly angled aortic bifurca-

tion) and a self-expanding stent is used instead of a

balloon-expandable stent. e distance to the lesion

is an important variable. Balloon-expandable stents

must be mounted on a balloon with an adequate

sha length, and self-expanding stents must be

delivered on a delivery catheter of adequate length.

Both balloon-expandable and self-expanding stents

are generally available on two dierent lengths of

catheter, either 80cm or 120 cm. If an 80-cm sha

is opened when a longer sha is required, it will

have to be discarded. ese challenges can usu-

ally be solved by using the balloon sha length to

estimate distance if the lesion was dilated prior to

stent placement. If not, a standard arteriographic

catheter with a bright tip may be placed over the

guidewire and advanced close to the lesion and

used to estimate the length from the access to the

lesion. Ifthe distance from the access to the lesion

is farther, there are some devices up to 150 cm in

length, but care must be taken to ensure that these

are available. If not, or if the longest devices are

inadequate, the operator must make a plan for an

alternative access closer to the treatment site.

TRICKS OF THE TRADE

Raising the ﬂow divider with kissing

stents

A bifurcation can be reconstructed by modifying

the ow divider with kissing stents. Two stents

are placed simultaneously with the leading edge

of each stent abutting the other at a point proxi-

mal to the location of the native ow divider. e

need for kissing stents arises most commonly at

the aortic bifurcation (see Chapter 23 for a detailed

discussion of this technique). e atherosclerotic

disease that occurs at the aortic bifurcation tends

to be extensive and circumferential. With kissing

stents, the aortic bifurcation can be reconstructed.

ere is also a technique for reconstruction of

the aortic bifurcation in which a covered stent is

placed in the infrarenal aorta and covered balloon-

expandable stents are placed at the aortic bifurca-

tion in the fashion of kissing stents. is provides

a completely covered reconstruction of the aortic

bifurcation. Aer any of these techniques for rais-

ing the ow divider are performed, it is usually not

possible to deliver endovascular devices up-and-

over the aortic bifurcation.

Tapering a stent

e various self-expanding stents tend to taper

naturally with diminishing distal arterial diameter.

Standard open cell nitinol stents should be dilated

with the appropriately sized balloon. All of the self-

expanding nitinol stents exhibit variable degrees

of foreshortening. Because of this, balloon dilation

should be performed rst at the location along the

https://t.me/med1917

Tricks of the trade 243

stent where some shortening would be least desir-

able (Figure 19.6). Once the nal diameter of the

stent is xed in this location, dilation of other seg-

ments of the stent with the appropriately sized bal-

loon is performed. e Wallstent

tends to shorten

quite a bit with expansion. e very end is dilated

last since it may lead to rupture of the balloon.

Woven nitinol stents (Supera

) cannot taper and

cannot be manipulated much with balloon dilation.

e shorter, more rigid balloon-expanding

stents can also be tapered, but to a much lesser

degree (1–2 mm maximum). One end of the stent

is selectively dilated using only the shoulder of

the balloon (Figure 19.7). e operator may also

consider aring the proximal end of a balloon-

expandable stent at the origin of a renal or visceral

artery. In this case, only a very short segment of

balloon shoulder is placed in the stent.

Moving a self-expanding stent

To varying degrees, self-expanding stents can be

moved a bit to adjust deployment position. e

delivery catheter can be withdrawn or pulled back

but not advanced forward aer beginning partial

deployment. e entire deployment catheter appa-

ratus must be withdrawn in a retracted position to

move the stent (Figure 19.8). Most standard niti-

nol stents tend to move a little during initiation of

deployment. Moving the stent can be helpful in

achieving very precise placement of its proximal

end. It is not possible to move a stent aer it has

been deployed. Under magnied uoroscopy, the

stent delivery catheter tip is carefully observed.

When the proximal end of the stent begins to

expand and change shape, this is the opportunity

to adjust its position. If too much of the stent is

C D E

Fig. 19.6 Tapering a self-expanding stent. (A) The guidewire is passed through an iliac artery stenosis.

(B) The self-expanding stent is deployed across the lesion. (C) The self-expanding stent tends to taper

naturally with decreasing distal arterial diameter. (D) The distal end of the stent is ballooned to the

diameter appropriate for the external iliac artery. (E) Angioplasty is performed in the larger proximal

end of the stent, which lies in the common iliac artery, using a slightly larger balloon.

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