Role of intracoronary ultrasound after high-pressure stent implantation

Role of intracoronary stent implantation

ultrasound

James W. Choi, MD, Gil M. Vardi, MD, Sheridan and Charles J. Davidson, MD Cbkugo, IU

Background unknown inflation

is used

improved

with

during

defined

with

inflations performed.

ICUS

were

tial acute 24

7.6

f 2.2

(16%) mm2

(P < .OOOl). than The and

or equol

had

a symmetry

to 9.2 to ICUS

in optimizing ICUS

Even

acute

guidance (Am

gain,

is associated Heart

stents

reference

vessel event repeat

with

Forty-six

requiring

). Similarly,

were

diameter

were

rate

at 6 months

or larger

used

balloon

stent

in 33 was

in 40

after

which

reference

lumen

balloons

and

subsequent

stent

found

stent

from

in 95

If inad-

reevaluation (23%)

had

(99%)

ini-

struts

increased balloons

vessel

result

area.

to 68%

larger

obtained

of 8 target

35

atm

index

ICUS

unapposed

area

33%

whereas was

stents,

to have

minimum

improved

consisted

An optimal

Of these

patients,

Follow-up

which

stenosis),

of the

were

were (212

20.80

stents

are

15 1 stents

High-pressure

evaluated.

inflations,

patients.

9.3%,

residual

apposition

performed

in whom

estimation.

inflations.

(30%)

techniques inflation.

were

gain

additional

complete

dilations

acute

additional

area.

(~10%

dimensions

pressures

required lumen

high-pressure and

low

and

balloon

patients

it is balloon

from

of total

stents

greater patients.

revascularizations

intervention.

poststent

symmetry,

20.80,

higher

In patients

(P c .OOOl

cardiac

when

with

higher-pressure

reference requiring

(46%)

ratio

lumen

deployment

RN,

However,

high-pressure

if stent

1: 1 by visual

completion

and

initial

high-pressure

consecutive

sized

M. Goodreau,

outcomes.

after

to determine with

RN, Lynne

clinical

guidance

achieved

on 96

angiographic

symmetry

~0.80.

collected

symmetry,

dilations

of the

mm2

until

apposition,

ratio

ICUS,

adverse

Conclusions

were

angiographically

further

~80%

f 2.4

initial

closure

data

to improve

clinical was

high-pressure

A. Parker,

shown

result

were

continued

been

of this study

angiographic

balloons

Sixty-nine

were

major

1 abrupt

found,

the purpose

Prospective

Stent

that

After

overall

follow-up.

Thus

were

performed.

gains

additional

an optimal

of the stent,

were

has

p rovides

despite

as full apposition results

inflation

(ICUS)

placement.

high-pressure

was

ICUS

and

and

balloon

imaging

equate

stent imaging

MD, Michelle

balloon

ultrasound

and Results Stents

in all cases) was

high-pressure

introcoronary ICUS

Methods deployed. ICUS

Poststent

whether

N. Meyers,

after

apposition

rates

for

target

balloon

inflation

of introcoronary vessel

achieves stents

revascularization

an optimal

angiographic

in approximately and

maior

50% adverse

result, of patients.

cardiac

events

ICUS

assists

Moreover, at 6-month

J 2000;139:643-8.)

The use of stents as initial interventional treatment of coronary artery disease has been shown to be clinically superior to that of balloon percutaneous transluminal coronary angioplasty and to provide long-term benefits. l-6 Stents have been used successfully in de novo coronary lesions,@ chronic total occlusions,9 and saphenous vein bypass graft stenoses.rO Despite the superior results of stents, suboptimal deployment may lead to subacute thrombosis*tvla and/or restenosis caused by neointimal hyperplasia. Moreover, reductions in restenosis rates

From Northwestern Univen~ty Medical School. Presented in port at the Tronscatheter Cardiovascular Therapeutics Annual Sympo sium, Ott 1998, Washington, DC. Submitted March 30, 1999; accepted September 25, 1999. Reprint requests: Charles J. Davidson, MD, Northwestern University Medical School, 25 I E Huron #8-526, Chicago, It 606 1 I. E-mail: [email protected] Copyright 8 2000 by Mosby, Inc. 0002.8703/2000/$12.00 +0 4/l/103540 doi: 10.1067/mhi.2000.103540

have been demonstrated by increasing acute gains and decreasing elastic recoil of the treated vessel walI. l3 Previous work with intracoronary ultrasound (ICUS) has proven that visual or quantitative angiographic measurements of vessel dimensions for stent expansion and deployment appear to be inadequate.1422 Repeat inflations with larger balloons or higher-pressure inRations are often necessary to improve stent apposition and optimize luminal cross-sectional area (CSA).14,22-26 Furthermote, high-pressure dilation under ICUS guidance may improve luminal CSA and reduce stent restenosis. 11 Currently, high-pressure balloon dilation with the use of a balloon with a diameter equal to or slightly larger than the angio graphic reference segment is used routinely. Despite this accepted practice, it is unknown whether stent apposition, symmetry, and optimal expansion are routinely achieved after angiogtaphically guided high-pressure balloon dilation. It has been suggested that ICUS is not routinely necessary after high-pressure diIation.26 The purpose of this study was to determine if stent deployment

American

644

Choi

Table Age

(~1

Men Single stent 2 Stents 13 Stents No. of stents per patient Vessel distribution LAD RCA LCX SVG QCA reference diameter 2.00-2.49 mm 2X-2.99 mm 3.00-3.49 mm 3.50-3.99 mm 4.00449 mm 4.50-4.99 mm Stent size 3.0 mm 3.5 mm 4.0 mm 4.5 mm 5.0 mm Balloon diometer (mm) Inflation pressure (oh-n) No. of inflotions per stent

Heart Journal April 2ooO

et 01

64+ 10 72 (75%) 55 (75%) 27 (28%) 14(15%) 1.57 * 0.74 62 40 18 31

(41%) (26%) (12%) (21%)

8 46 63 18 10 3

(5%) (31%) (43%) (12%) (7%) (2%)

61 68 27 1 5 3.6 15.5f 3.2

(38%) (42%) (14%) (1%) (3%) f 0.4 1.6 zk 2.0

Data are mean f SD; number (%) of pattenk, stenk, vessels treated, or stent sizes. lAD, Left anterior descending artery; RCA. right coronary artery; LCX, left circumflex coronary artery; SVG, saphenous vein bypass graft.

techniques are improved by ICUS imaging despite an optimal angiographic result achieved with high-pressure balloon dilation.

Methods The study population consistedof 15 1 consecutive PalmazSchatz oohnson &Johnson Interventional Systems, Warren, NJ) stent implantationsin % patients. Lesionsin both native coronary atteries (n = 120) and saphenous vein bypass grafts (n = 3 1) wm ineluded. At the time of this study, aspirin and coumarin were routIne.ly used as the poststent anticoagukition regimen. Stent implantation procedure After balloon predilation, the PaImaz-Schatz stems were deployed with the stent delivery system previously described.* With the use of noncompliant balloons that were angiographicaIly sized 1: 1 to equal the reference segment lumen diameter, high-pressure inflations were performed to 112 atm (mean pnzssure of 14.9 f 1.6 atm) and until angiographic completion defined as
II. Index

ICUS

findings

of oil 96 patients

Reference lumen maximum diameter (mm) Reference lumen minimum diameter (mm) Reference lumen area (mmz) Stent CSA (mm2) Acute gain: stent/reference lumen area (%) No. of unapposed struts Symmetry index Balloon/reference lumen diameter

3.75 f 3.17 f 9.95 f 8.36 + 89.5 f 0.89 f 0.83 + 1.15f0.18

0.71 0.60 3.77 2.45 25 1.60 0.05

Dato are mean f SD.

distal to the stent and withdrawn with an automatic pullback device at 0.5 mm/s through the stent and proximal vessel. Images were simultaneously recorded on half-inch s-VHS videotape. During the procedure, the CSA of the stent was planimetered from the ultrasound images while minimum and maximum diameters were determined.” lf the initial ICUS image demonstrated optimal stent deployment, the procedure was terminated. If incomplete stent expansion, unapposed struts, or asymmetric expansion was noted on the ultrasound image, further balloon inflations were performed with either higher pressures or larger balloons. BaIIoons were upsized to equal the vessel diameter of the distal reference segment. If the balloon was already equal to the distal reference segment diameter, further dilations were performed at higher pressufes. ICUS and balloon inflations were repeated until complete apposition and symmetric stent expansion was achieved or no further improvement could be obtained. Definitions by ICUS Optimal stent deployment was determined by 3 ICUS criteria: (1) fuII apposition: complete expansion of the stent with no free space between the stent struts and the intimal surface, (2) symmetry: uniform expansion of the stent defined as the minimum-to-maximum lumen diameter ratio 20.80, (3) acute gain: optimization of the intrastent lumen CSA defined as an intrastent CSA-to-reference artery lumen CSA ratio L0.80.2z After the procedure, the ICUS images were reanalyzed offIine with the use of a computerized tracking software program (Tapemeasure, Indec, Inc, Mountainview, Calif) that calculated the CSA and measured the minimum and maximum diameters of various sites. The lumen area, defined as the blood-to-intima interface, was manually traced at 4 various locations: distal reference, distal stent, proximal stent, and proximal reference. The distal and proximal reference segments were measured at the maximum lumen CSA within 10 mm distal and proximal to the stent. Of the 2 measurements, the most normal-appearing image was used as the reference site. The distal stent dimensions were measured at the minimaI stent area between the distal articulation point and the mid-point of the stent, including both articulation points. Similarly, the proximal stent was measured at the minimal stent area between the mid-point of the stent and the proximal articulation, including both articulation points. The smaller of the intrastent CSA measurements was used in the analysis. The index image was defined as the fimt ICUS image obtained after angiographic success was achieved. The final ICUS image was defined as the image obtained at the completion of aII additional interventions.

American Heart Journal Volume 139. Number 4

Choi

Table III. Index balloon

and vessel

reference

measurements

in stents with and those Additional

-

without

intervention (n = 69)

intervention

No additional intervention (n = 82)

9.61 k3.4 3.52 f0.34 3.18 kO.48 1.12f0.15 3.68 f0.69 1.14f0.18 2.1 f0.9 14.2+ 1.9

Reference lumen area Balloon size (mm) Reference lumen diameter by QCA (mm) Balloon/reference by QCA Reference lumen diameter by ICUS (mm] Balloon/reference by ICUS No. of balloon inflations Maximum initial stent inflation pressures (atm)

additional

et 01 645

10.23 f4.1 3.59f0.45 3.26kO.55 1.12f0.14 3.82kO.73 1.15f0.17 2.4+ 1.4 14.2 +2.0

P value .32 .27 .35 .85 .23 .lO .15 .89

Data are meon + SD

Table

IV.

index

stent measurements

in stents with and those

withoirt

Additional

Stent CSA (mm*) Maximum stent diameter (mm) Minimum stent diameter (mm) Symmetry index Incomplete apposition No. of unapposed struts Acute gain (%)

Angiographic

measurements

Quantitative angiography also was performed off-line with a computerized semiautomated edge detection algorithm system (Artrek, ImageComm Inc, Santa Clara, Calif). The guide catheter was used for calibration. Follow-up

Patients were contacted by telephone or questioned during their office visit at 6 months. Major cardiac events defined as target vessel revascularization, coronary artery bypass surgery, cardiac death, and history of myocardial infarction defined as creatine kinase-MEi >3 times normal with electrocardiographic changes were recorded. Statistics

The data are expressed as mean value f SD. Continuous variables were compared by paired t test. Correlations were tested by &i-square test. Differences were considered significant at the level of P < .05.

Results Ninety-six consecutive patients received 15 1 PahnazSchatz stents with subsequent ICUS imaging. The study population consisted of 72 (75%) men with a mean age of 64 f 10 years. In all patients, stents were successfully deployed at the stenosis site. No ICUS-related complications, including prolonged or severe spasm,

qdditionol intervention (n = 69) 7.64k2.25 3.35 f0.47 2.76kO.45 0.82 f0.05 67%(46) 1.90 f

1.93

85+26

intervention No additional intervention (n = 82)

P value

8.97+ 2.47 3.59f0.50 3.03 kO.41 0.84f0.05 S%(5) 0.05 + 0.22 94f24

~0008 co3 c.0002 co5 <.OOOl <.OOOl c.02

were noted. Vessel size and distribution as weII as the stent characteristics are listed in Table I. ICUS findings at angiographic completion After angiographic completion, the index ICUS was analyzed as shown in Table II. The mean lumen diameter of the reference segment as measured by qualitative coronary angioplasty (QCA) was 3.22 f 0.52 mm vs 3.75 f 0.71 mm by KU.5 (P c .OOOl).In 82 (54%) stems, the index ICUS resuk met criteria for an optimal result and the procedure was terminated. In 69 (46%) stents, further balloon inllations were needed to achieve the criteria of optimal stent deployment (Table III). When comparing the 2 groups (Table IV), the group requiring additional intervention had (1) smaller CSA (7.64 f 2.25 mm2 vs 8.97 f 2.47 mm2, P c .OOOS),(2) smaller maximum and minimum diameters (maximum diameter

Index

3.35*0.47mmvs3.59*0.50mm,P<.003,lIlinimum diameter2.76~0.45mmvs3.03~0.41 mm,P<.OOO2), (3) increased number of unapposed struts (1.90 f 1.93 vs 0.05 f 0.22, P c .OOOl),and (4) less acute gain @tent area/reference lumen area 84.5% f 25.9% vs 93.7% f 23.6%, PC .02). intervention group In the 69 stents that required additionai intervention, larger balloons were used in 33 stems, of which 11 also

Additional

646 Choi

Amerlcon Heart Journal April 2030

et 01

$#&&i@&$w

additifm~l~in~rventian

(69

stents)’

I Index Complete strut apposition Symmetry ratio 20.80 Acute gain >O.Sg Stent CSA (mm2) No. of unopposed struts Maximum diameter (mm) Minimum diameter (mm) Acute gain (%) Symmetry index

ICUS

Final

23 (33%) 45 (65%) 34 (49%) 7.64 k 2.25 1.91 f 1.93 3.35 zk 0.47 2.76 f 0.45 85+26 0.82 + 0.05

ICUS

47 (68%) 54 (78%) 52 (75%) 9.25 f 2.42 0.26 f 0.53 3.67 f 0.5 1 3.05 + 0.46 102f28 0.83 f 0.07

P value coo0 1 c.06 coo0 1 <.ooo 1 <.OOOl c.000 1 <.OOOl <.ooo 1 Nat significant

Data ore meon It SD or n (%).

::$f!$$$@$(tid

f?eini:tkbirements

.

of addi@onal

intervention

group Additional

Stent CSA ( mm2) Maximum stent diameter (mm) Minimum stent diameter (mm) Symmetry index No. of unappased struts Acute gain (%)

vs index. stent measurements intervention (n * 69)

9.25 + 3.67 f 3.05 f 0.83 f 0.26 zt 102f28

2.42 0.5 1 0.46 0.07 0.53

of qo-additional-interntion

group

No additional intervention (n = 82)

P value

8.97 f 2.47 3.59 f 0.50 3.03 f 0.41 0.84 310.05 0.05 f 0.22 94f24

.48 .31 .72 .48 e.003 c.04

Dab are mean f SD.

required higher innation pressures. ‘IXrty-six stems did not require upsizing of balloons; however, of these, 29 required additional intlations with higher pressures. Balloon diameters were upsized by 0.5 mm in 20 (29%) and by 21 .Omm in 7 (10%) of the 69 stems requiring additional interventions. Of the stems requiting additional interventions with larger balloons, the mean increase in balloon size was 0.45 f 0.21 mm. Likewise, in the stems requiring addltional inflations with the same size balloon and an increase in balloon pressure, the mean increase in maximum ballmn inflation pressure was 1.9 f 1.7 attn. Furthermore, of the 69 stems that required additional interventions, 46 had incomplete apposition of the stent, 24 had a symmetry ratio <0.80, and 35 had acute gain
follow-up

One patient had abrupt stent closure after the procedure that required emergency intervention.. Within 6

month follow-up there were 2 cardiac deaths, 1 ventricular septal rupture, and 8 cases of target vessel revascularization, which consisted of 2 coronary artery bypass surgeries and 6 repeat interventions. No myocardial infarctions were noted. One patient was lost to followup. Therefore the total overall major adverse cardiac event rate at 6 months was 11 (11%) of 96.

Discussion Our study demonstrates that despite optimal angiographic results after poststent high-pressure balloon inflation, inadequate stent deployment is frequently noted with the use of ICUS criteria. This study further demonstrates that ICUS can be used to improve the acute gain and stent apposition during stent deployment. Several studies have shown that improvements in acute luminal diameter after the procedure translate to clinical reduction of restenosis.36 Previous work by Colombo et al** and others have demonstrated that repeat high-pressure dilation was necessary to achieve optimal stent expansion as guided by ICUS after initial stent deployment with nominal balloon pressures. On the basis of ICUS imaging, it was shown that with highpressure balloon inflations and selection of larger balloon size (equal to or larger than the reference segment lumen diameter), stent expansion, strut apposition, and symmetry can be improved.r*~**-26 High-pressure dilation thus has become routine during stent deployment.

American Heart Journal Volume 139, Number 4

In our series of 151 stents, only 54% had adequate stem expansion after initial high-pressure dilation as measured by ICUS imaging. All, however, had satisfactory angiographic results as determined by the operator before ICUS imaging. The number of suboptimal results after high-pressure dilation as noted by ICUS, despite optimal angiographlc appearance, was lower than in previous [email protected] difference probably is a result of the strategy of using initial high-pressure inflation in all cases. Despite this difference, stents still frequently required additional inflations. Even after initial high-pressure inflations, only 67% of the stents had complete strut apposition. This increased to 87% after repeat inflations (P c .OOl), whereas the number of unapposed struts decreased from 1.9 to 0.3 struts per stent (P < .OOOl).Furthermore, in the 69 stents that required additional intervention, only 33% of the stents had complete strut apposition after index intravascular ultrasound images. After repeat interventions, complete strut apposition increased to 68% (P < .OOO1). Because the presence of unapposed struts has been associated with subacute thrombosis,29 the improvement in stent apposition achieved with ICUS guidance is signikant. Maximizing luminal and intrastent CSA has been shown to lower restenosis rates8s so Furthermore, ICUS assistance has been used in improving lntrastent CSA.it One potential explanation for the improved results after ICUS is that the lumen size was initially underestimated by anglography. In our series, the mean lumen diameter by QCA was 3.22 f 0.52 mm, whereas the mean maximum lumen diameter by ICUS was 3.75 f 0.71 mm (P < .OOOl).As a result, balloon size was increased ln 48% of the stems that underwent additional dilations after ICUS. Moreover, a statistically significant increase in balloon size of 0.22 f 0.28 mm was noted. Therefore the more precise lumen size with ICUS appears to aid in maximizing stent CSA. Table III demonstrates that with the use of anglographic criteria, the characteristics of the additional intervention group were similar to those of the noadditional-intervention group. However, Table IV clearly shows that in the additional intervention group, ICUS measurements revealed significant underexpansion, nonapposition, and asymmetry compared with the noadditional-intervention group. Thus ICUS was able to identify abnormalities that were improved and documented on the final ICUS images (Table V). limitations

Although this study was prospective in its design, the use of ICUS was not randomized, and the operator was not blinded to the ICUS findings. However, it should be noted that data were analyzed after the procedure by an independent observer. Postprocedure antlcoagulation with coumarin may influence our major adverse

Choi

et al 647

cardiac event rate to be higher than would be expected with the currently accepted use of ticlopidine. Nonetheless, the use of coumarin should not have altered the measurements of stent deployment mechanics. Conclusions

Poststent high-pressure balloon dilation has improved stent deployment. Given the era of stenting with highpressure innations, the utility of ICUS in stent deployment has been questioned. However, as these data demonstrate, there is still a large percentage of stems that do not achieve optimal stent deployment as evaluated by ICUS, even after routine high-pressure dilation had produced an acceptable angiographic result. Therefore, despite high-pressure balloon dilation with an optimal angiographlc result, intravascular ultrasound lmaglng can provide incremental clinical information when attempting to optimize intracoronary stent placement.

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