Catheterization and Cardiovascular Interventions 57:374 –386 (2002)
`
`Pediatric Curriculum
`
`Stents: What’s Available to the Pediatric
`Interventional Cardiologist?
`
`Frank Ing,* MD
`
`INTRODUCTION
`
`In 1988, Mullins et al. [1] first reported the use of
`stents in pulmonary arteries and veins. Since then, the
`use of stents to treat narrowed vessels and surgical grafts
`in congenital heart disease has expanded tremendously
`[2–23]. Many coronary and peripheral stents have been
`developed for adults, but none specifically for children.
`In fact, all stents used by pediatric cardiologists in chil-
`dren with congenital heart disease are adaptations from
`stents used in adults. As such, not all stents available for
`use in adults are appropriate for pediatric use. The pur-
`pose of this article is threefold: to discuss the desirable
`features of stents as applied to the pediatric population;
`the various stents available for pediatric use as related to
`the vascular site of the intended implantation; and the
`specific features of the available stents. In addition, we
`performed balloon dilations on various stents under flu-
`oroscopy to evaluate its geometric changes during ex-
`pansion. While all attempts were made to include as
`many stents as possible, we recognize that some stents
`may have been overlooked and not included in this study.
`General desirable features of stents include biocom-
`patibility. That is, the stent must be relatively resistant to
`thrombosis and must promote minimal neointimal
`growth. The stent must have a low profile with a smooth
`surface. The stent must be designed with a minimal
`surface area and must contain minimal impurities. It must
`also be immune to fatigue and corrosion. It must have
`good visibility under fluoroscopy for implantation and
`subsequent evaluation. It must also have reliable expan-
`sion with a high expansion ratio. For the pediatric pop-
`ulation, in addition to the above requirements, it must
`also have a small delivery system in order to minimize
`vascular trauma, usually at the femoral venous or arterial
`entrance site. The stent should be flexible enough to
`negotiate the turns within the cardiovascular system such
`as the right ventricular outflow tract. Most importantly, it
`must have the feature of further expandability over time
`as the child grows to adult size. The stent selected must
`
`© 2002 Wiley-Liss, Inc.
`
`have a potential maximal stent diameter that approxi-
`mates the normal-adult-size vessel in which that stent
`will be implanted.
`
`SELF-EXPANDING VS. BALLOON-EXPANDABLE
`STENTS
`
`All currently available stents can be divided into two
`broad categories as self-expanding stents and balloon-
`expandable stents. In general, self-expanding stents are
`constrained within a delivery sheath that is delivered to
`the site of stenosis. The sheath is withdrawn to expose
`the stent that self-expands to dilate the stenotic segment.
`Unfortunately, these stents are designed to expand to a
`specific diameter, no bigger or smaller. Therefore, if
`these stents are selected, it must be implanted into a
`vessel that does not have any growth potential. Hence, in
`most cases, these stents are not useful in growing chil-
`dren unless it is implanted into a vessel that has no
`further growth potential such as in a fully grown adoles-
`cent or a surgical shunt, baffle, or conduit. Most com-
`monly used self-expanding stents include the Wallstent
`(Schneider, Minneapolis, MN) [24 –37] and the SMART
`stent (Cordis Endovascular, Miami, FL; Fig. 1) [38 – 41].
`The advantages of the self-expanding stent in general are
`that they do not require a balloon for expansion and can
`be delivered through a lower-profile delivery system.
`They are very flexible and can traverse tortuous vessels.
`
`Cardiology Division, Children’s Hospital of San Diego, San Di-
`ego, California
`
`*Correspondence to: Dr. Frank Ing, Cardiology Division, Children’s
`Hospital of San Diego, San Diego, CA 92123.
`E-mail: fing@chsd.org
`
`Received 13 June 2002; Revision accepted 9 June 2002
`
`DOI 10.1002/ccd.10342
`Published online in Wiley InterScience (www.interscience.wiley.com).
`
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`

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`Stents
`
`375
`
`Fig. 1. A: Expanded Wallstents of various sizes. B: Expanded SMART stents of various sizes.
`Some stents have platinum markers at the stent edges for enhanced radiopacity (black arrows).
`
`They do not contain any stainless steel components and
`therefore are MRI-safe. However, the main disadvantage
`is that they cannot be further dilated to accommodate
`growth of the child. While the SMART stents have only
`an 8%–10% foreshortening (Fig. 2A), the Wallstents
`have significant foreshortening after expansion (Fig. 2B).
`Both have much lower radial strengths than balloon-
`expandable stents.
`
`BALLOON-EXPANDABLE STENTS
`
`The advantages of balloon-expandable stents include
`reliable expansion, the ability to be further expanded
`over time, and relatively good radial strength. In addi-
`
`tion, there is a relatively long history of its use in con-
`genital heart disease and much experience with this
`group of stents among pediatric interventional cardiolo-
`gists. However, the disadvantages are that they are rela-
`tively more stiff and require larger delivery systems
`compared to the self-expanding stents.
`In general, balloon-expandable stents can be catego-
`rized into four different sizes: small, medium, large,
`and extra large. Small stents are used almost exclusively
`in coronary arteries and vein grafts in adult patients
`following coronary artery bypasses. In general, these
`stents cannot be expanded larger than 3– 6 mm in diam-
`eter. Since pediatric cardiologists rarely get involved
`with stenotic coronary arteries, we will not be discussing
`
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`376
`
`Ing
`
`Fig. 2. A: A Wallstent self-expanding under fluoroscopy. Note the significant foreshortening. B:
`A SMART stent self-expanding under fluoroscopy. This design minimizes foreshortening.
`
`this group of stents. Medium stents can be expanded to a
`maximum diameter of 10 –12 mm. This group of stents is
`appropriate for implantation in segmental and subseg-
`mental branch pulmonary arteries, femoral and innomi-
`nate veins, pulmonary veins, and Blalock-Taussig shunts.
`Large stents can be expanded to a maximum diameter of
`18 mm. They are appropriate for main and proximal
`branch pulmonary arteries, lobar branch pulmonary ar-
`teries, the superior and inferior vena cava, proximal iliac
`vein, aorta, Fontan baffles, and surgical homografts and
`conduits. The extra-large stent can be expanded to a
`maximum diameter of 24 –25 mm and are appropriate for
`
`the aorta and large right ventricular baffles or homografts
`and Fontan baffles.
`
`MEDIUM STENTS
`
`Medium stents that are available for use include the
`Palmaz 4 series (Johnson and Johnson Interventional
`Systems, Warren, NJ) [39 – 43], the Corinthian series
`(Johnson and Johnson Interventional Systems) [44,45],
`the Bridge stent (Medtronic-AVE, Santa Rosa, CA)
`[46,47], and the NIR stent (Boston Scientific-Meditech,
`Natick, MA) [48 –52]. The Palmaz stent is constructed
`
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`377
`
`Fig. 3. The Palmaz stent is made of
`stainless steel and laser-cut slots (small
`white arrow), which becomes diamond-
`shaped cells (large white arrow) when ex-
`panded.
`
`Fig. 4. An expanded Corinthian stent.
`Note the smooth edges (small white ar-
`row) and the Omega hinge (large white
`arrow), which provides more flexibility.
`
`out of a 316 L stainless steel tube with laser-cut slots that
`form seven cells per row (Fig. 3). While the intended
`maximal diameter is only 6 mm, it can be overdilated up
`to about 10 mm in diameter. Available lengths range
`from 10 to 39 mm. They can be implanted through 6 –7
`sheaths. During our own laboratory testing, these stents
`demonstrated a foreshortening of 19%–23% when di-
`lated to 9 mm diameter and 33%– 40% at 10 mm diam-
`eter. General radial strength is good. The Corinthian stent
`is made of the same stainless steel as the Palmaz stent,
`but has an Omega hinge between the rows of cells (Fig.
`4). It has a seven-cell configuration and can be dilated to
`a maximum of 12 mm diameter. Available lengths range
`from 12 to 39 mm. Foreshortening is similar to the
`Palmaz 4 series. At 10 and 12 mm diameter, there is a
`38%– 41% and 55%– 60% foreshortening, respectively.
`These stents can be implanted through 6 –7 Fr sheaths.
`Radial strength is comparable to the Palmaz 4 series. The
`NIR stent is also made out of stainless steel and has a
`U-shaped hinge between rows of cells (Fig. 5). It comes
`in seven- and nine-cell configurations and is available in
`14 –19 mm lengths only. Maximal diameter is about 8
`mm. The nine-cell stent has only a 15%–16% foreshort-
`ening when dilated to 8 mm diameter. It requires a 6 –7
`Fr sheath for delivery and radial strength is good. The
`Bridge stent is made of stainless steel with laser-welded
`sinusoidal elements (Fig. 6). It can be dilated to about 14
`mm diameter and comes in 28 –100 mm lengths. They
`are available premounted on a balloon or unmounted.
`
`Fig. 5. An unexpanded NIR stent with U-shaped hinges (small
`white arrow). Hinges elongate during stent expansion to mini-
`mize foreshortening (large white arrow).
`
`They require a 7– 8 Fr sheath for delivery. This stent has
`the least amount of foreshortening compared to the other
`medium-sized stents. At 10 mm diameter, there is 3%–
`15% foreshortening at 12 mm about 15%–18%; at 14
`mm, there is about 22% foreshortening. Overall radial
`
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`378
`
`Ing
`
`Fig. 6. The Bridge stent is composed of rows of sinusoidal elements (A) with smooth edges (B)
`and are laser-fused (C).
`
`TABLE I. Comparison of Medium-Sized Stents
`
`Design
`
`Sizes
`
`Sheath
`Foreshortening
`
`Radial strength
`Advantages
`
`Disadvantages
`
`Palmaz 4 series
`
`316 L SS tube;
`laser-cut slots
`Maximum
`diameter, 10
`mm; 10–39
`mm length
`6–7 Fr
`9 mm, 19%–
`23%; 10 mm,
`33%–40%
`
`Good
`Much experience
`in pediatric
`cardiology
`
`Stiff; sharp
`edges
`
`Corinthian
`
`Omega hinge; 7-cell
`configuration
`Maximum, 12 mm;
`12–39 mm length
`
`6–7 Fr
`9 mm, 24%–26%;
`10 mm, 38%–
`41%; 12 mm,
`55%–60%
`Good
`Flexible; maximum
`to 12 mm
`diameter; rounded
`edges
`
`NIR stent
`
`Bridge AVE
`
`SS; U-hinge; 7- and 9-cell
`configuration
`Maximum, 8 mm; 14–19
`mm length
`
`SS laser-welded sinusoidal
`elements
`Maximum, 14 mm; 28–100
`mm length
`
`6–7 Fr
`9-cell configuration; 8 mm,
`15%–16%
`
`7–8 Fr (premounted, 10 mm)
`10 mm, 3%–15%; 12 mm,
`15%; 14 mm, 22%
`
`Good
`Less foreshortening; rounded
`edges
`
`Little experience in pediatric
`cardiology; smallest
`maximum diameter
`
`Good; (fair at 14 mm diameter)
`Flexible-trackability; rounded
`edges; maximum to 14 mm
`diameter; less foreshortening
`
`Little experience in pediatric
`cardiology
`
`strength is good, but weaker at 14 mm diameter. Table I
`summarizes the design, available sizes, sheath size
`needed for implantation, foreshortening, and general ra-
`dial strength of each medium-sized stent.
`
`Advantages and Disadvantages
`Advantages of the Palmaz stent are that there is much
`experience of this stent in pediatric cardiology. It was the
`first available stent used by pediatric cardiologists. How-
`ever, they are rather stiff stents and have sharp edges
`(Fig. 7), which increases the risk of balloon rupture
`during dilation. The Corinthian stent is much more flex-
`ible than the Palmaz stent and has rounded edges (Fig. 4).
`It can be dilated up to a maximum diameter of 12 mm. In
`general, the Palmaz 4 series has been replaced by the
`Corinthian stents. The NIR stent also has rounded edges
`and there is relatively less foreshortening compared to
`the first two stents. But it has a smallest maximal diam-
`eter and there is little experience with this stent among
`pediatric cardiologists. The Bridge stent is also very
`
`flexible and trackable through sheaths. It too has rounded
`edges. This stent has the largest maximal diameter
`among medium-sized stents at 14 mm and has the least
`amount of foreshortening; however, the radial strength
`tends to be less due to the larger cell size at the larger
`diameters. Again, there is little experience with this stent
`among pediatric cardiologists. Table I summarized the
`advantages and disadvantages of the medium stents. Fig-
`ures 8 and 9 compare the appearance of the various
`medium-sized stents before and after full expansion.
`
`LARGE STENTS
`
`The available large stents include the Palmaz 8 series
`(Johnson and Johnson Interventional Systems) [1–3], the
`Doublestrut LD stent (Sulzer-IntraTherapeutics, St. Paul,
`MN) [53,54], and the Cheatham-Platinum (CP) six-zig
`stent (Numed, Hopkinton, NY) [55].
`The Palmaz 8 series are designed similarly to the 4
`series except it has 10 cells in each row. Maximal dilat-
`
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`379
`
`needed when an 18 mm diameter BIB balloon is used.
`Overall, the radial strength is less than the Palmaz stent
`at larger diameters. Table II summarizes the design,
`available sizes, sheath size needed for implantation, fore-
`shortening, and general radial strength of each large-
`sized stent.
`
`Advantages and Disadvantages
`
`The Palmaz 8 series stent is probably the most used
`stent among pediatric cardiologists. Because of its long-
`standing history of use, this stent has become the gold
`standard for comparison even though it is not a perfect
`stent. Overall radial strength is good. However, there are
`many disadvantages, including stiffness, sharp edges,
`and significant foreshortening at larger diameters. The
`Doublestrut stent has rounded edges and is very flexible.
`Foreshortening is also significantly less than the Palmaz
`stent. The feature of variable foreshortening is due to its
`open-cell design. When dilated with a single 18 mm
`diameter balloon, not only is there an outward radial
`force applied to the expanding stent, but there is also a
`force exerted from the edge to the center of the stent,
`which acts to foreshorten the stent during expansion.
`However, when the stent is serially dilated starting with
`a 12 mm diameter balloon, the edge-to-center force is
`minimized. Cell geometry changes from three “dia-
`monds” to a single larger cell, hence to term “open-cell”
`(Fig. 12). Stent length is maintained by separation be-
`tween the rows of cells. The open-cell design also results
`in more flexibility (Fig. 13A). However, disadvantages
`include lower radial strength at larger diameters (⬎ 15
`mm). The open-cell design also results in less scaf-
`folding of the vessel wall. It is not uncommon to see
`encroachment of the endothelium into the vessel lu-
`men between the rows of the stent (Fig. 13B). While
`there is no demonstrable gradient due to this encroach-
`ment,
`it remains unclear whether this feature will
`result in significant restenosis in the future. Uneven
`dilation at the stent edge is also noted occasionally
`(Fig. 13C). Several studies in the literature have re-
`ported favorable results using this stent in congenital
`heart disease [53,54]. The CP stent is made of plati-
`num and is very radiopaque as well as MRI-safe. It has
`rounded edges and is less prone to balloon rupture
`during expansion. However, it is a rather stiff stent and
`has qualitatively lower radial strength than the Palmaz
`larger diameters (⬎ 14 mm). The biggest
`stent at
`drawback of this stent is that it is only available as a
`special order by prescription, which is probably the
`most limiting factor regarding its use in the catheter-
`ization laboratory. Table II summarizes the advantages
`and disadvantages of the large stents. Figure 14 com-
`pares the large-sized stents after full expansion.
`
`Fig. 7. Note the sharp edges (white arrows) of the Palmaz
`stent, which increases the risk of balloon rupture during its
`expansion.
`
`able diameter is 18 mm and comes in 12–30 mm in
`length. They can be implanted through 7–11 Fr sheaths
`depending on the balloon used. At 18 mm diameter, there
`is a 40% foreshortening. Overall radial strength is good.
`The Doublestrut LD stent
`is made of stainless steel
`laser-cut slots and has an open-cell system [53]. Maximal
`dilatable diameter is also about 18 mm and comes in
`16 –76 mm lengths. They too are implanted via 7–11 Fr
`sheaths. Foreshortening is variable. In vitro testing dem-
`onstrated there is a 26%–33% foreshortening when di-
`lated with a single 18 mm diameter balloon (Fig. 10A).
`However, there is no foreshortening when serially dilated
`with progressively larger-diameter balloons (Fig. 10B)
`[53]. Overall radial strength is less than the Palmaz stent
`at larger diameters (⬎ 15 mm). The CP six-zig stent is
`made of 0.013⬙ platinum wire (Fig. 11). Each row is
`made of six zigs and the rows are laser-welded together.
`Maximal dilatable diameter is about 18 mm and available
`lengths range from 16 to 45 mm. However, the manu-
`facturer (Numed) can special-make any length desired.
`This stent requires a 10 Fr sheath when mounted on a 12
`mm BIB balloon (Numed) catheter and a 12 Fr sheath is
`
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`380
`
`Ing
`
`Fig. 8. A comparison of various ex-
`panded medium-sized stents: A: A new
`Genesis stent dilated to 8 mm diameter.
`B: A Palmaz stent at 10 mm diameter. C:
`A Corinthian stent dilated to 10 mm di-
`ameter. D: A Corinthian stent dilated to
`12 mm diameter. Note the significant
`foreshortening at 12 mm diameter. E: A
`Bridge stent dilated to 14 mm diameter.
`Note the wide spacing of each cell, which
`provides less scaffolding.
`
`Fig. 9. A comparison of foreshortening of various medium-
`sized stents when fully expanded under fluoroscopy. A: A new
`Genesis stent dilated to 10 mm diameter results in 11% fore-
`shortening. B: A seven-cell NIR stent dilated to 8 mm diameter
`(31% foreshortening). C: A Palmaz stent dilated to 10 mm di-
`
`ameter (38% foreshortening). D: A Corinthian stent dilated to 10
`mm (38% foreshortening). E: A Bridge stent dilated to 12 mm
`diameter (22.1% foreshortening). F: The same stent further di-
`lated to 14 mm diameter (15.7% foreshortening).
`
`EXTRA-LARGE STENTS
`
`The available extra-large stents include the Palmaz XL
`series (Johnson and Johnson Interventional Systems) and
`the CP eight-zig stent (Numed).
`The Palmaz XL series is constructed similarly to the
`other Palmaz stents, but each row has 11 cells. Interest-
`ingly, the edges are rounded rather than square. Maximal
`expanded diameter is 25 mm and available lengths range
`from 30 to 50 mm. They are implanted through 11–13 Fr
`sheaths. At 25 mm diameter expansion, the foreshorten-
`ing is 23%. Radial strength is excellent. The CP eight-zig
`stent is similar to the six-zig stent, except for two addi-
`tional zigs per row of welded 0.013⬙ platinum wire.
`Maximal diameter is 24 mm and they come in 16 –50 mm
`lengths. They also go through 11–13 Fr sheaths. Fore-
`shortening at 24 mm diameter is about 22%–28%. Over-
`all radial strength is good. Table III summarizes the
`
`design, available sizes, sheath size needed for implanta-
`tion, foreshortening, and general radial strength of each
`extra-large-sized stent.
`
`Advantages and Disadvantages
`
`The features of the Palmaz XL series and the CP
`eight-zig stent are similar. Both have rounded edges to
`minimize risk of balloon rupture during implantation.
`Both are quite stiff and require large sheaths for de-
`livery. As with the smaller six-zig CP stent, the eight-
`zig stent is extremely radiopaque and MRI-safe, but
`they are also only available as special orders with a
`prescription from a physician. Table III summarizes
`the advantages and disadvantages of the extra-large
`stents. Figure 15 compares the extra-large-sized stents
`after full expansion.
`
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`Stents
`
`381
`
`Fig. 10. A: Expansion of a Doublestrut stent using a single 18 mm diameter balloon. The
`unexpanded length started at 27 mm, which decreased to 18–20 mm (26%–33% foreshortening)
`at full expansion. B: When the same stent was serially expanded, starting with a 12 mm diameter
`balloon, followed by a 14 mm, then a 16 mm, and finally an 18 mm diameter balloon, there was
`no foreshortening.
`
`NEW DEVELOPMENTS
`Two new series of stents scheduled for release this
`spring include the Genesis stent (Johnson and Johnson
`Interventional Systems) and the Mega LD and Max LD
`stent (Sulzer-IntraTherapeutics). These stents have been
`only partially tested in our catheterization laboratory and
`have not been implanted in patients at the time of this
`publication.
`The new Genesis series stent is similar to the Corin-
`thian stent except for the new sigmoidal hinge (Fig.
`16A). The sigmoidal hinge adds greater flexibility to the
`
`radial
`(Fig. 16B) without compromising its
`stent
`strength. Elongation of the sigmoidal hinge during ex-
`pansion prevents excessive foreshortening (Fig. 16C). It
`is important to note that the nomenclature for the Genesis
`series is quite confusing. Unlike the Palmaz series, the
`terms “medium” and “large stent” for the Genesis series
`do not refer to their potential expanded diameter size, but
`rather to a combination of their length and range of
`diameters. The medium stents are 12–24 mm in length
`and have an expansion range of 4 – 8 mm diameters,
`while the large stents are 19 –79 mm in length and have
`
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`382
`
`Ing
`
`Fig. 11. A six-zig CP stent dilated with an 18 mm BIB (balloon in balloon) balloon. The
`unexpanded stent started at 28 mm length, decreasing to 24.2 mm (13.6% foreshortening) at 12
`mm expansion by the inner balloon. After final expansion to 18 mm diameter by the outer
`balloon, the length decreased to 17.8 mm (36.4% foreshortening). Note the enhanced radiopac-
`ity due to the platinum content of the stent.
`
`TABLE II. Comparison of Large-Sized Stents
`
`Palmaz 8 series
`
`Doublestrut
`
`316 L SS tube; laser-cut slots
`
`SS; laser-cut; open-cell system
`
`Design
`
`Sizes
`
`Sheath
`Foreshortening
`
`Maximum diameter, 18 mm; 12–30
`mm length
`7–11 Fr
`At 18 mm diameter, 40%
`
`Radial strength
`
`Good
`
`Advantages
`
`Disadvantages
`
`Much experience; good radial
`strength
`Stiff; sharp edges; much
`foreshortening at larger diameters
`
`Maximum diameter, 18 mm; 16–
`76 mm length
`7–11 Fr
`Serial dilation, 18 mm, no
`foreshortening; Single dilation,
`18 mm, 26%–33%
`Less than Palmaz at larger
`diameters
`Rounded edges; flexible; little
`foreshortening
`Low radial strength at larger
`diameters; open-cell permits
`less scaffolding of vessel wall
`
`CP Six-Zig
`0.013⬙ platinum wire; zig configuration;
`laser-welded rows
`Maximum diameter, 18 mm; 16–45 mm
`length
`With BIB: 12 mm, 10 Fr; 18 mm, 12 Fr
`At 18 mm diameter, 20%–27%
`
`Less than Palmaz at larger diameters
`
`Rounded edges; very radiopaque; MRI-
`safe
`Stiff; by prescription only; low radial
`strength at larger diameter
`
`an expansion range of 5–9 mm. For the pediatric inter-
`ventionist who plans to use these in growing children, it
`is essential to remember that both the medium and
`large Genesis series have a maximal potential diameter
`of 12 mm and should be categorized as a medium-
`sized stent only. The large Genesis is not equivalent to
`the large Palmaz in potential maximum diameter. Both
`medium and large Genesis stents are available un-
`mounted or premounted on 4 –9 mm diameter balloons
`and can be implanted via 6 –7 Fr sheaths. Limited
`testing demonstrates foreshortening of about 11% at
`10 mm diameter. The Genesis Extra Diameter series
`has a potential maximal diameter of 18 mm and is
`
`available in lengths from 19 to 59 mm. They are
`available only in the unmounted form. It is expected
`that the Genesis medium and large stents will replace
`the Corinthian and the Palmaz 4 series while the
`Genesis Extra Diameter stents will replace the Palmaz
`8 series. We have not yet tested the minimal-sized
`sheaths required for the Palmaz Extra Diameter stents,
`but are told that when mounted on a 6 mm diameter
`Opta balloon (Johnson and Johnson Interventional
`Systems), it can go through a 6 Fr sheath. Data on stent
`foreshortening of all the Genesis series at maximal
`diameters are also unavailable at
`the time of this
`publication.
`
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`

`Stents
`
`383
`
`Fig. 12. Two expanded Doublestrut
`stents of the same size. A: This stent was
`serially expanded starting with a 12 mm,
`then 14, 16, and 18 mm diameter balloon.
`Note the change in geometry of the cells.
`The separation between cells prevents
`foreshortening. B: When the same stent
`was dilated with a single 18 mm diameter
`balloon, the cell geometry did not change
`and the stent foreshortened significantly.
`
`Fig. 13. A: The Doublestrut open-cell stent design permits flexible negotiation around the right
`ventricular outflow tract. B: The same design affords less scaffolding of the vessel wall,
`resulting in encroachment of the endothelium as well as uneven expansion (C) at larger
`diameters.
`
`Fig. 14. A comparison of various large-
`sized stents expanded to 18 mm diame-
`ter. A: Palmaz. B: Doublestrut after single
`dilation. C: Doublestrut after serial dila-
`tion. D: CP six-zig stent.
`
`The Mega LD stent has the same open-cell design as
`the Doublestrut LD stent, but it is designed to provide
`more radial strength at larger diameters (⬎ 14 mm di-
`ameter) compared to the Doublestrut stent. Benchwork
`testing by IntraTherapeutics indicated that
`the radial
`
`strength of the Mega LD is comparable to the Palmaz
`P308 stent, but this has not yet been verified in our
`laboratory. The Mega LD stent falls into the large-sized-
`stent category and can be dilated to 18 mm diameter. It is
`compatible with a 9 Fr sheath when mounted on a 12 mm
`
`Edwards Lifesciences Corporation, et al. Exhibit 1013, p. 10 of 13
`
`

`

`384
`
`Ing
`
`TABLE III. Comparison of Extra-Large Stents
`
`Design
`Sizes
`Sheath
`Foreshortening
`Radial strength
`Advantages
`Disadvantages
`
`Palmaz XL
`
`316 L SS tube; laser-cut slots
`Maximum diameter, 25 mm; 30–50 mm length
`11–13 Fr
`18 mm, 9%–10%; 20 mm, 12%–13%; 25 mm, 23%
`Good
`Smoother edges than other Palmaz
`Stiff; large sheaths
`
`CP Eight-zig
`0.013⬙ platinum wire; zig configuration; laser-welded rows
`Maximum diameter, 24 mm; 16–50 mm length
`11–13 Fr
`18 mm diameter, 8%–15%; 24 mm, 22%–28%
`Good
`Very radiopaque; MRI-safe; rounded edges
`Stiff; large sheaths; by prescription only; more foreshortening
`than XL at larger diameter
`
`Fig. 15. A comparison of extra-large-
`sized stents expanded to 24 mm diame-
`ter. A: Palmaz XL stent. B: CP eight-zig
`stent.
`
`Fig. 16. A: The new Genesis stent is de-
`signed with a sigmoid hinge resulting in
`greater flexibility (B). C: Note the sigmoid
`hinge elongates (white arrow) to maintain
`stent length during expansion.
`
`diameter balloon. It is available in lengths from 16 to 36
`mm. The Max LD stent falls into the extra-large-stent
`category and can be dilated to a maximum diameter of 25
`mm. Both stents feature the TransTaper cell technology
`for added radial strength without compromising flexibil-
`ity. At present, data on stent foreshortening, minimal
`diameter sheath requirements with larger-sized balloons,
`and radial strength at larger diameters are not yet avail-
`able.
`
`SUMMARY
`
`In summary, stents used for vascular stenoses in in-
`fants and children with congenital heart disease can be
`divided into three major categories based on the adult
`size of the vessel
`to be stented. They include the
`medium-, large-, and extra-large-sized stents. While still
`limited, there is more than one stent choice available in
`each of the three categories. Each available stent has its
`
`Edwards Lifesciences Corporation, et al. Exhibit 1013, p. 11 of 13
`
`

`

`own unique advantages and disadvantages. While there is
`not yet a perfect stent available for children with con-
`genital heart disease, new stents with improved features
`such as the Genesis stent or the Mega LD and Max LD
`stents are being developed. Finally, when selecting the
`appropriate stent, the interventionist needs to recognize
`and prioritize the specific features and needs of the par-
`ticular vessel to be stented, taking into consideration the
`size of the child and the technical aspects of the stent to
`be delivered to the target vessel.
`
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