(Circulation. 1995;91:339-350.)
© 1995 American Heart Association, Inc.
Articles |
Comparison of Clinical and Angiographic Outcomes After Saphenous Vein Graft Angioplasty Using Coronary Versus `Biliary' Tubular Slotted Stents
From the Department of Internal Medicine (Division of Cardiology) of the Washington Hospital Center, Washington, DC.
Correspondence to Martin B. Leon, MD, Director, Cardiovascular Research, Washington Hospital Center, Suite 4B-1, 110 Irving St NW, Washington, DC 20010.
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Abstract |
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 Top Abstract IntroductionMethods Results Discussion References |
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Background Saphenous vein graft (SVG) angioplasty using 15-mm articulated, tubular slotted stents results in low (0% to 20%) residual diameter stenoses and infrequent (<5%) major complications. A "biliary" stent design with greater radial compressive strength, enhanced visibility, and more variable sizing (diameter and length) has been approved for noncoronary indications. A comparison of outcomes after coronary versus biliary stent placement in SVG stenoses has not been performed. The purpose of this study was to compare the angiographic and clinical results after SVG angioplasty using these two balloon-expandable, tubular slotted stent designs.
Methods and Results During a 3-year period, 231 patients with 305
SVG lesions were treated using Palmaz-Schatz coronary (n=108) or
biliary (n=123) stents. Cineangiograms were reviewed using qualitative
morphological and quantitative angiographic methods. Time-dependent
clinical outcome (freedom from death, Q-wave myocardial infarction, or
the need for repeat coronary bypass surgery or SVG angioplasty) was
assessed using Kaplan-Meier life-table methods. Unstable angina
(P<.001) and recent myocardial infarction
(P=.001) were present more often in patients undergoing
biliary stent versus coronary stent placement. Biliary stent–treated
SVG lesions were more frequently de novo (P=.001), ostial in
location (P=.002), 
10 mm in length
(P=.009),
thrombus containing (P=.001), and ulcerated
(P<.001) than coronary stent–treated SVG lesions.
Angiographically, biliary stent–treated lesions had larger reference
vessel diameter (3.43±0.59 mm versus 3.10±0.64 mm,
P<.001), higher balloon-to-artery ratio (1.15±0.16 mm
versus 1.07±0.19, P=.0001), and lower residual diameter
stenosis (6±17% versus 14±11% in coronary stent–treated
patients;
P<.001). Procedural success rates were high (95%),
in-hospital major complications were uncommon (<3%), and follow-up
clinical outcomes were favorable (6-month event-free survival 
80%)
in both groups.
Conclusions Despite frequent short-term ischemic syndromes and unfavorable lesion characteristics, both biliary and coronary cohorts have similarly favorable short-term procedural results and long-term clinical outcomes. The increased strut thickness of the biliary stent confers greater fluoroscopic visibility and radial compressive strength in exchange for decreased stent flexibility and added technical demand in stent deployment. Extreme caution is recommended with biliary stent placement in the treatment of SVG lesions as clinical results are highly operator dependent.
Key Words: veins • angioplasty • stents • angiography
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Introduction |
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TopAbstractIntroductionMethods Results Discussion References |
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Conventional balloon angioplasty of complex saphenous vein graft (SVG) lesions is limited by frequent periprocedural complications (eg, plaque or thrombus distal embolization) and high rates of late clinical recurrence.1 2 3 4 5 6 7 8 Untoward early and late events are more common in older, degenerative, and complex, thrombus-containing SVGs.1 9 10 These findings have prompted some investigators to develop alternative treatment strategies (directional or extraction atherectomy and excimer laser angioplasty) in patients with high-risk SVG lesions,11 12 13 14 15 16 but the selective advantage of these new devices over standard balloon angioplasty in lower-risk SVG lesions remains unproven.17
Balloon-expandable, tubular slotted12 18 19 20 21 and self-expanding, wire mesh22 23 stents have been used successfully in patients with symptomatic SVG disease. Advantages of SVG stent placement over other new devices include its propensity to scaffold the friable SVG surface, potentially reducing the risk of distal particulate embolization, and its ability to achieve very low (5% to 10%) residual stenoses, which may reduce the risk of late restenosis.24 25 In addition, enhanced resistance to radial compression of the tubular slotted stent prevents external SVG compression or geometric plaque remodeling, which may contribute to late lumen loss after standard balloon and new-device angioplasty in some lesion locations.26 Until recently, treatment of SVG lesions using tubular slotted stents was limited to use of a 15-mm articulated coronary stent, which had been reserved for the treatment of discrete stenoses within SVGs with reference diameters ranging from 3.0 to 5.0 mm21 27 ; preliminary reports using the coronary stent suggested that high rates of procedural success and infrequent subacute thrombosis were obtainable.12 19 20 21 Another tubular slotted stent design, the "biliary" stent, has been approved for clinical use in noncoronary locations; the potential advantages of biliary versus coronary stents for the treatment of SVG disease include improved radiopacity and radial strength (due to increased strut thickness), variable length (10, 15, and 20 mm), and larger diameter (4 to 9 mm). The initial use of the biliary stent in large SVGs has been described,27 but a direct comparison of the performance characteristics and clinical and angiographic outcomes after SVG angioplasty using coronary versus biliary tubular slotted stents has been lacking. To address these issues, we reviewed our experience using two tubular slotted stent designs for the treatment of SVG stenoses.
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Methods |
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TopAbstractIntroductionMethods Results Discussion References |
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Patient Selection
From January 1990 to July 1993, 231 symptomatic patients with 305 SVG lesions were treated with tubular slotted stents at the Washington Hospital Center. Patients were considered for stent placement provided that there was no contraindication to acetylsalicyclic acid, dipyridamole, or long-term oral anticoagulation therapy with coumadin; angiographic evidence of thrombus; or significant inflow or outflow obstruction remote from the stent deployment site. Two tubular slotted stent designs were used in this study (Table 1
); their selection was based on the
estimated SVG reference size and time of stent deployment. From January
1990 until April 1992, the Palmaz-Schatz coronary stent (Johnson and
Johnson Interventional Systems) was available under an Investigational
Device Exemption from the Food and Drug Administration (FDA) for the
treatment of focal SVG stenoses (>50% diameter stenosis) with an
estimated reference diameter 3.0 mm.28 Allotted patient
recruitment for the coronary stent in SVG lesions was achieved in April
1992. Beginning in September 1992 and continuing to the present,
the biliary tubular slotted stent (Johnson and Johnson), approved by
the FDA Advisory Panel for treatment of biliary tract disease in
February 1991, has been used in patients with SVG stenoses (>50%
diameter stenosis) with an estimated reference diameter 4.0 mm. It is
of importance that anatomic entry criteria were expanded for biliary
stents to include more complex lesion morphologies, such as diffuse
stenoses requiring more than two stents, graft degeneration or
ulceration, and aorto-ostial stenoses. Informed consent was obtained
from all patients according to the guidelines of the Institutional
Review Board of the Washington Hospital Center.
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Stent Deployment
The implantation technique using the
coronary stent has been
described elsewhere.28 In general, a 0.014-in-high torque
floppy or extrasupport guidewire (Advanced Cardiovascular Systems) was
advanced across the stenosis; predilatation was performed using an
undersized 2.0- to 2.5-mm balloon; and a 3.0-, 3.5-, or 4.0-mm tubular
slotted stent delivery system was deployed. The dedicated Palmaz-Schatz
coronary stent delivery system incorporates a polyethylene balloon
deployment catheter, a premounted coronary stent, and a 5F overriding
sheath that is retracted after crossing the lesion site. Residual
stenoses (>10%) were treated with subsequent adjunct balloon
angioplasty using higher inflation pressures (sometimes requiring
noncompliant balloon materials) or larger balloon catheters in an
attempt to achieve a 0% visual residual diameter stenosis (Fig
1). In contrast to the relatively flexible coronary
stent, the increased profile and rigidity of the biliary stent favored
the use of larger (0.018 in) and stiffer guidewires as well as 9F
guiding catheters with shallow distal angulation (right Judkins, right
coronary bypass graft, multipurpose, or hockey stick configuration).
After predilatation using a 2.5- or 3.0-mm balloon catheter, a 4.0- to
6.0-mm (20-mm length) Schwarten LP (PSG), Sub-4 (Meditech), or Total
Cross (Schneider) balloon dilatation catheter was used to deliver a
manually crimped biliary stent of appropriate length (Table 1
)
across
the lesion. Adjunct balloon dilatation was performed using higher
inflation pressures and larger, noncompliant balloons to maximize
residual lumen diameter (Fig 2).
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Anticoagulation Protocol
All patients were started on
acetylsalicyclic acid,
dipyridamole, and a calcium channel antagonist 24 hours before stent
deployment (Fig 3). Intravenous heparin (>10 000 to
15 000 U) was given to maintain an in-laboratory activated clotting
time (ACT) >300 seconds. Immediately after the procedure, heparin was
interrupted, and the sheaths were removed when the ACT was <150
seconds. Continuous intravenous heparin was restarted 4 hours after
sheath removal and continued until a prothrombin time between 16 and 18
seconds was achieved using oral warfarin. Intravenous dextran-40 (100
mL/h) was begun >2 hours before the procedure and was maintained (50
mL/h) after the procedure until a therapeutic heparin dosage (partial
thromboplastin time 50 seconds) was achieved after sheath removal.
Acetylsalicyclic acid (indefinite), dipyridamole, and a calcium channel
antagonist (1-month duration), and warfarin (3 months based on SVG
appearance and patient tolerance) were continued thereafter.
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Patient Demographics
Baseline clinical demographics and
identification of in-hospital
complications were obtained using independent hospital chart audit.
Unstable angina was defined as a recent acceleration of angina
including pain at rest. Hypercholesterolemia was present in those
patients with a serum cholesterol level 240 mg/dL or a history of
elevated cholesterol requiring treatment. The occurrence of a recent
(<6 weeks) myocardial infarction was recorded. The age of the SVG was
estimated in months from the time of the most recent coronary bypass
operation. De novo SVG lesions included those that had not been
previously treated with balloon or new-device angioplasty.
Qualitative and Quantitative Angiography
All cineangiograms
were analyzed by reviewers unaware of early
and late clinical outcome. Standard qualitative morphological criteria
were used to assess lesion length ("shoulder to shoulder"),
ostial location (<3 mm from the origin of SVG), eccentricity,
angulation 45 degrees, presence of thrombus, and
ulceration.29 Degenerative SVGs were those with ectasia or
lumen irregularity comprising 50% of the SVG shaft length. The
development of postprocedural dissection (including the dissection
length and presence of contrast retention), abrupt closure, and
postprocedural thrombus was also recorded. Anterograde flow was
evaluated using the Thrombolysis in Myocardial Infarction (TIMI) flow
classification.30 Abrupt closure was defined as TIMI 0 or
1 flow at any time during the procedure. The development of TIMI 2 flow
that returned to TIMI 3 flow by the end of the procedure was classified
as a transient reduction in flow; distal embolization was defined as
sustained TIMI flow 
2 and/or complete occlusion of a distal branch at
any point during the procedure.
Selected end-diastolic cineframes were optically magnification (2.4:1) and digitized using a cine-video converter. Image calibration was performed using contrast-filled catheter. The external diameter of the catheter was used as the calibration standard. Reference and minimal lumen diameters (MLD) were determined before and after stent deployment from the single "worst view"31 using a validated, automated edge-detection algorithm (ARTREK, Quantitative Cardiac Systems).32 Short-term gain was defined as the improvement in MLD (final MLD minus pre-MLD).24 The mean balloon diameter of the largest balloon was used to calculate the balloon-to-artery ratio and the minimal diameter of largest balloon was used to determine percent elastic recoil ([balloon MLD minus final MLD]/reference diameter).33
In-Hospital Outcome
Deployment success (per lesion) was
obtained when the stent was
successfully positioned across the stenosis. Procedural success (per
patient) was defined as attainment of <50% final diameter stenosis in
all treated lesions and the absence of major clinical complications
(in-hospital death, Q-wave myocardial infarction, or emergency coronary
bypass surgery). Clinical success (per patient) was defined as <50%
final diameter stenosis in all treated lesions and no death, Q-wave
myocardial infarction, emergency coronary bypass surgery, or repeat
coronary angioplasty within 14 days of the procedure. Other
complications included non–Q-wave myocardial infarction (creatinine
phosphokinase–MB fraction of at least fivefold the upper normal
limit), subacute thrombosis, and vascular or bleeding complications
(arteriovenous fistula, pseudoaneurysm, retroperitoneal hematoma,
vascular repair, or any need for transfusion due to bleeding).
Follow-up Clinical Outcome
Patients undergoing successful SVG
stent deployment were
contacted by telephone or office visit 1, 3, 6, 9, and 12 months after
successful stent deployment. The occurrence of major late clinical
events (death, Q-wave myocardial infarction, or the clinical need for
late treatment site revascularization [coronary bypass surgery or
coronary angioplasty]) was recorded, and follow-up (6-month)
event-free survival curves were constructed.
Statistical Analysis
All analyses were performed on patients
(lesions) with
successful stent deployment. Continuous variables were reported as
mean±1 SD, and categorical variables were expressed as frequencies.
2 or Fisher's exact test was used for comparing
categorical variables between groups. Student's t test or
Mann-Whitney U test was used where appropriate to compare group
differences between continuous variables. Differing time periods for
the inclusion of patients treated with the two stent designs
necessitated the use of time-dependent models to compare the follow-up
outcomes between the two stent groups. A 6-month event-free survival
curve was constructed using Kaplan-Meier life-table analysis.
Mantel-Cox statistics were used to test equality of survival functions
between the two groups. Cox proportional hazards model was used to
assess device effect on event-free survival and target lesion
revascularization after stent placement. A value of P<.05
was considered statistically significant.
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Results |
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TopAbstractIntroductionMethods Results Discussion References |
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Stent Deployment
A total of 149 coronary stents were attempted in 110 patients with 146 SVG lesions (Fig 4
). Three lesions (2.1%) were
treated with multiple stents, and the remainder were treated with a
single coronary stent. Two failures (1.4%) occurred during deployment
of coronary stents; both of these failures were attributed to marked
SVG tortuosity proximal to the treatment site. A total of 188 biliary
stents were placed in 124 patients with 163 SVG lesions (Fig
4); these
biliary stents included 38 P 104 (10 mm), 14 P 154 (15 mm), and 136 PS
204 (20 mm) stent designs. Multiple (two or more) stents were placed in
28 (17.2%) lesions, and the remainder were treated with single biliary
stents. Two stent (1.2%) failures occurred during deployment of
biliary stents. The first failure was due to the inability of the stent
and balloon delivery catheter to negotiate the primary curvature of an
Amplatz Left I guiding catheter. The stent was ultimately withdrawn
without sequelae, and standard balloon angioplasty was performed. The
second failure occurred during an attempt to deploy a biliary stent
through a recently placed biliary stent in an effort to treat a
stenosis that developed distal to the stent site. The second stent and
balloon delivery system would not cross the proximal stent site, and
withdrawal of the stent and balloon system resulted in dislodgment of
the stent in the femoral artery; the stent was retrieved subsequently
by surgery without complications.
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Patient Demographics
The clinical characteristics of patients
undergoing successful
stent deployment are listed in Table 2. Unstable angina
(P<.001) and recent myocardial infarction
(P=.001) were present more often in patients undergoing
biliary than coronary stent placement. Patient age (66±8 years), male
gender (82%), presence of diabetes mellitus (26%),
hypercholesterolemia (66%) or systemic hypertension (59%), left
ventricular ejection fraction (0.41±0.13), and SVG age (99±49
months)
were not different in the two groups.
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Angiographic Findings
Biliary stent–treated SVG lesions
were more often de novo
(P=.001), ostial in location (P=.002), 10
mm in
length (P=.009), thrombus containing (P=.001),
or
ulcerated (P<.001) than coronary stent–treated SVG lesions
(Table 3). The incidence of degenerative SVGs (24%) was
similar between the two groups. The frequencies of lesion eccentricity
(61%), lesion angulation 45 degrees (6%), and total occlusion (1%)
were also similar in the two groups.
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There were no episodes of
in-laboratory abrupt closure after SVG stent
placement in either group, although a transient reduction in
anterograde flow (TIMI grade 2) was noted more often in lesions treated
with biliary stents (10% versus 2% in coronary stent–treated
patients; P=.003) (Table 3). Other
postprocedural
angiographic complications included distal embolization (n=7), thrombus
(n=2), focal (<10 mm) dissection with contrast retention
(n=1), and a
residual flap (n=1). Localized perforation occurred in one patient
after predilatation before stent deployment; subsequent stent placement
resulted in a resolution of the localized perforation. There were no
differences in these angiographic complications in the two treatment
groups.
SVGs treated with biliary stents were larger than those treated
with
coronary stents (3.43±0.59 mm versus 3.10±0.64 mm;
P<.001); preprocedural and final MLDs were also
significantly larger in biliary stent–treated patients (Table
4). The final percent diameter stenosis was lower in
biliary stent–treated SVG lesions than coronary stent–treated SVG
lesions (6±17 versus 14±11; P<.001). The
balloon-to-artery ratio was also higher in biliary stent–treated
lesions (1.15±0.16 versus 1.07±0.19 in coronary
stent–treated
lesions; P=.001). The magnitudes of short-term gain and
elastic recoil were similar in the two groups.
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Procedural Outcome
Stent deployment was successful in 305
(98.7%) of 309 attempted
lesions. Procedural success was obtained in 95.3% of patients treated
with SVG stents and clinical success was achieved in 93.6%; no
differences in procedural outcome were noted in the two groups (Fig
4).
Major complications occurred in 6 (2.6%) patients with successful
stent deployment, including three (1.3%) deaths, two (0.9%) Q-wave
myocardial infarctions, and one (0.4%) emergency coronary bypass
operation (Table 5). Of the three procedure-related
deaths, two patients died of acute myocardial infarction (distal
embolization after coronary stent deployment in one, and left internal
mammary artery occlusion after balloon angioplasty after coronary stent
placement into a SVG to the obtuse marginal branch in the other), and
the third patient developed multiorgan system failure after successful
biliary stent placement. Although no patient undergoing coronary stent
placement experienced acute or subacute thrombosis, two patients
undergoing biliary stent placement developed subacute thrombosis 4 and
5 days after stent placement. Subacute thrombosis was treated with
intragraft thrombolytics and repeat stent dilatation in one patient and
coronary bypass surgery in the other. The frequency of other
complications, including transient elevation of the creatinine
phosphokinase–MB fraction at least fivefold normal (13%) and
recurrent ischemia (12%), were similar in the two groups.
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Despite smaller sheaths in patients undergoing coronary stent placement (sheath size of 8F: 75% in coronary stents versus 11% in biliary stents; P<.001), the frequencies of pseudoaneurysm (5.3%), arteriovenous fistula (2.2%), and the need for vascular repair (8.4%) were similar in the two groups. Moreover, bleeding events requiring transfusion (at the access site or elsewhere) were also similar (25%) in the two groups.
Because duration of hospital stay after stent placement was largely determined by pretreatment clinical instability, periprocedural complications (especially vascular/bleeding events), and the time to achieve therapeutic oral anticoagulation level, the length of stay was similar in the biliary (8.5±4.9 days) and the coronary (8.4±4.8 days) stent groups.
Late Clinical Outcome
The follow-up period averaged
282±114 days for patients
undergoing coronary stent placement and 142±75 days for patients
undergoing biliary stent placement (P<.001) (Table
5). In
the 215 patients without early clinical events and clinical follow-up
3 months, late hierarchical events included 3 (1.4%) deaths, 3
(1.4%) patients who developed a Q-wave myocardial infarction, 15
(7.0%) patients who required coronary bypass surgery, and 25 (11.6%)
patients who required repeat coronary angioplasty for recurrent
symptoms due to in-stent restenosis. With Kaplan-Meier life-table
analysis, no differences in 6-month event-free survival were noted
in patients undergoing coronary versus biliary stent placement (Fig
5). In addition, with multivariate Cox proportional
hazards model, target lesion revascularization (relative risk, 0.41;
95% confidence interval, 0.16 to 1.07; P=.07) and
event-free survival (relative risk, 0.56; 95% confidence interval;
0.20 to 1.57; P=.26) rates, after adjusting for differences
in baseline clinical characteristics and angiographic findings, were
similar between the two groups. Furthermore, after adjusting for device
effect (coronary versus biliary stent), both the final stent MLD
(relative risk, 0.31; 95% confidence interval, 0.17 to 0.58;
P<.001) and stent percent diameter stenosis (relative risk,
1.30; 95% confidence interval, 1.00 to 1.69; P=.052) were
predictors for subsequent target lesion revascularization.
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Discussion |
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TopAbstractIntroductionMethods Results Discussion References |
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We report our consecutive, single-center experience in 234 patients undergoing SVG angioplasty using the Palmaz-Schatz coronary and biliary tubular slotted stent designs. High (95%) procedural success rates, infrequent (<3%) major complications, and favorable (77% to 80%) 6-month event-free survival rates were obtained using both coronary and biliary stent designs. These findings confirm previous reports demonstrating the value of stents in patients with SVG disease and support the expanded use of both stent designs in appropriate SVG lesion morphologies.
SVG Stent Implantation
Treatment options for patients who
develop recurrent symptoms
after coronary bypass surgery due to SVG disease are limited. Repeat
operation is associated with a higher mortality rate and less frequent
angina relief than the initial operation.34 35
Balloon
angioplasty of SVG stenoses has been the accepted alternative to
surgical revascularization, but standard balloon angioplasty has been
associated with frequent complications and high recurrence rates,
especially in older, degenerated, or complex thrombus-containing
SVGs.1 9 10 As a result, SVG angioplasty
using alternative
new devices has been used in carefully targeted lesion subsets to
improve procedural
outcomes.11 12 13 14 15 16
Thus far, only one
randomized study has been completed that demonstrated that directional
atherectomy may have little comparative advantage over balloon
angioplasty in reducing procedural complications or late angiographic
restenosis in focal low-risk SVG lesions.17
SVG angioplasty using Palmaz-Schatz coronary stents has also been used in patients with symptomatic SVG disease.12 18 19 20 21 High (96%) procedural success rates have been reported in single-center and multicenter studies using this approach, and complications have been uncommon.18 Late restenosis (>50% diameter stenosis) may occur in as few as 25% of patients after SVG angioplasty using the tubular slotted coronary stent,18 21 likely due to the very low (0% to 10%) residual diameter stenosis routinely obtained with this approach.24 Despite the potential benefits of SVG angioplasty using the coronary stent, its use was terminated in April 1992 after the completion of the Investigational Device Exemption Phase II protocol filed by Johnson and Johnson Interventional Systems. Pending Pre-Marketing Approval (PMA) by the FDA Advisory Panel for general use of the coronary stent in SVG stenoses, alternative methods for the management of patients with symptomatic SVG disease were sought, giving rise to the current clinical study using FDA-approved larger biliary stents.
Potential Use of Biliary Tubular Slotted Stents
Biliary
stents may offer several theoretical but unproven
advantages over the coronary stents for the treatment of SVG stenoses.
Larger stainless steel filaments (0.004 and 0.0055 in. versus 0.0025
in. in the coronary stent) render the biliary stent more radiopaque and
provide higher resistance to radial compressive force once expanded.
Biliary stents are also available in variable lengths (10 mm, 15 mm,
and 20 mm), which allows more precise stent selection based on the
extent of SVG involvement. Biliary stents are cut from a larger
diameter cylinder which permits a greater expansion range (4-9 mm) than
coronary stents (3-5 mm), thus facilitating treatment of SVG stenoses
with larger reference vessel diameters (>5 mm). On the other hand, the
thicker and larger biliary stent design also results in increased
rigidity and profile and the absence of a protective sheath delivery
system makes it technically more demanding for stent delivery to the
target sites.
After demonstration of the safety and efficacy of biliary stents in large SVGs,27 several clinical centers reported their preliminary results using biliary stents in patients undergoing SVG angioplasty.36 37 38 39 Although high procedural success rates (94% to 100%) were obtained in each of these single-center series, enthusiasm for this technique has been tempered by the confusing variability in the incidence of subacute thrombosis (0% to 19%), occurrence of non–Q-wave myocardial infarction (4% to 44%), and rate of vascular complications (5% to 14%).36 37 38 39 To date, no comparison has been made between the newer biliary stent design and the previous coronary stent in patients undergoing SVG angioplasty.
Present Study
In the present report, we sought to compare
using standardized
analytical methodology the clinical and angiographic outcomes of
consecutive patients undergoing nonrandomized SVG angioplasty with
either the coronary or biliary stents. The overall procedural success
rates were similarly high for both coronary stent–treated (95%) and
biliary stent–treated (96%) SVG lesions. It is noteworthy that
patients undergoing biliary stent placement had more acute ischemic
coronary syndromes (unstable angina [93%], recent myocardial
infarction [30%]) than patients undergoing coronary SVG stent use,
most likely due to our increasing confidence during the study period in
the safety and efficacy of tubular slotted stents for the treatment of
complex SVG disease. Accordingly, biliary stent–treated SVG lesions
were often longer (35%), ulcerated (31%), ostial (25%), and thrombus
containing (13%). On the other hand, the biliary stent cohort had
larger reference vessel diameters and a higher balloon-to-artery ratio,
which undoubtedly contributed to the lower residual diameter stenoses
obtained (6±17% versus 14±11%; P<.001) in the
biliary
stent–treated lesions. It is of importance that the SVG treatment
cohort for both coronary and biliary stents represented
older SVGs (mean age, 8.3 years), which have been associated with more
frequent complications and less favorable late clinical outcome after
conventional balloon angioplasty.9 10
Several
technical features require discussion and clarification.
Compared with the relatively flexible coronary stent delivery system,
the rigidity and increased profile of the biliary stent design mandated
the use of stiffer 0.018-in guidewires and guiding catheters that were
larger (9F), with shallow distal angulation and excellent support.
Biliary stents that are hand-crimped on one of several peripheral
dilatation balloons may dislodge unless the utmost care is taken; these
precautions included meticulous crimping technique, adequate
predilatation to facilitate stent passage across the lesion, and proper
manipulation of guiding catheters and guidewires. Although deployment
success rates have remained high with the biliary stent (>98%),
technical challenges are considerable, requiring experienced operators
with previous stent implantation experience. Stent deployment is
performed at nominal balloon inflations pressures to avoid balloon
rupture; in the event of a significant (>10%) residual stenosis,
additional balloon dilatation is performed using noncompliant balloon
catheters inflated to high pressures, if needed. Intravascular
ultrasound imaging has been a useful technique at our institution to
ensure that the stent is fully apposed to the SVG wall, symmetrical,
and full expanded.
Although major in-hospital complications were infrequent (2.6%) using tubular slotted stents in this series, elevations of creatinine phosphokinase–MB isoenzymes of at least fivefold normal occurred in 13% of patients. The occurrence of non–Q-wave myocardial infarction was similar in patients treated with biliary (11%) and coronary (15%) stents. Others have reported an 8.3% incidence of non–Q-wave myocardial infarction after SVG angioplasty with coronary stents.18 Higher frequencies (23% to 44%) have been suggested after biliary stent SVG angioplasty by some investigators,38 39 but these differences are most likely due to variations in biliary stent implantation technique, patient and anatomic selection factors, and inconsistent definitions used to report non–Q-wave myocardial infarction. The prognostic importance of these non–Q-wave myocardial infarctions after stent placement remains unclear. Prior studies have demonstrated that asymptomatic elevations of creatinine phosphokinase–MB fractions occur in >10% of patients after native vessel balloon angioplasty40 and directional atherectomy41 and after new-device angioplasty of SVG stenoses.42 Based on these studies, it appears that the prognosis of non–Q-wave myocardial infarction is favorable in the absence of associated angiographic complications,43 although close monitoring of patients with elevations creatinine phosphokinase–MB fractions after SVG angioplasty appears warranted.
Subacute thrombosis did not occur in any patients undergoing SVG angioplasty using coronary stents, although it developed in 2 (1.7%) patients undergoing SVG angioplasty using the biliary stent. Other series have reported higher (4% to 19%) incidences of subacute thrombosis after SVG angioplasty with biliary stents37 38 ; its occurrence may be related to more frequent use of overlapping stents, incomplete stent expansion, stent placement in the postinfarction period, noncompliance with anticoagulation regimen, and impaired distal runoff.38 In an effort to reduce the risk of subacute thrombosis, some investigators have proposed the use of ultrasound-guided stent implantation to more accurately determine lesion length, lesion composition, and reference SVG size and to monitor post-stent deployment expansion dimensions.
Despite the overall benefits of SVG angioplasty using coronary and biliary stents, the high incidence of vascular complications in these patients limits its overall effectiveness unless improved methods of groin site care are developed. Reported vascular complications in this series included pseudoaneurysm (5.3%), arteriovenous fistulae (2.2%), and need for surgical repair (8.4%); these findings are consistent with the 14% to 19% incidence of vascular complications reported after intracoronary stent placement in native vessels and SVGs18 19 44 45 and higher than the 2.5% to 4.7% incidence noted after other new angioplasty device procedures (eg, laser angioplasty, directional or rotational atherectomy).44 45 The increased risk of bleeding complications after stent placement has been attributed to the prolonged intense anticoagulation requirements in patient undergoing stent placement, sheath removal technique, and administration of concomitant thrombolytic agents.44 Current efforts to reduce these complications at our institution include less aggressive periprocedural anticoagulation (ACT >250 seconds), meticulous limitation of postprocedural anticoagulation with intravenous heparin, strict bedrest for 48 hours after stent placement, and contralateral arterial and venous sheath cannulation.
Follow-up clinical outcomes were also favorable in patients undergoing SVG angioplasty using coronary and biliary stents. With Kaplan-Meier life-table analysis, late clinical events occurred in 24% of coronary stent–treated patients and 20% of biliary stent–treated patients (P=.56). With multivariate Cox proportional hazards model, both the target lesion revascularization and event-free survival rates remained similar between the two groups after adjusting for differences in baseline clinical and angiographic findings. In addition, the final stent MLD and stent percent diameter stenosis, after adjusting for device effect, were noted to be predictors for 6-month target lesion revascularization. Thus, achieving a larger final poststent lumen diameter (lower percent diameter stenosis) independent of the stent type was strongly associated with decreased late clinical revascularization events. The favorable late clinical results in patients undergoing SVG angioplasty using tubular slotted stents will require confirmation with angiographic follow-up and more extended periods of clinical observation.
Study Limitations
Given the differences in patient
demographics, SVG reference
diameters, preprocedural morphology, and the time period of stent
placement, a case-matched comparison of patients undergoing SVG
angioplasty using coronary and biliary tubular slotted stents was not
practical. Thus, this study cannot identify which treatment modality
(coronary or biliary stent) is optimal for the treatment of SVG disease
and provides no definitive conclusions as to whether SVG angioplasty
with stents is preferable to standard balloon angioplasty; these issues
will require an analysis of ongoing, randomized clinical trials in
comparable subgroups. A second limitation of the present study
involves the lack of complete angiographic follow-up (<80% of those
eligible) for both coronary and biliary stent–treated SVG stenoses.
Incomplete determinations of follow-up angiographic end points was due
to the increased morbidity of patients with SVG pathology and the
absence of financial support, both of which reduced patient compliance
with requested "routine" follow-up angiography. Therefore, we
relied on careful clinical follow-up to determine the absolute and
comparative frequencies of late clinical outcomes. It is of importance
that the 6-month event-free survival, approaching 80% for both cohorts
in the present study, was similar to that of the multicenter
Palmaz-Schatz coronary stent experience in SVGs in which angiographic
restenosis (50% follow-up diameter stenosis) was <30% for all SVG
lesions and <20% in de novo SVG lesions.21
Clinical Implications
Given the limited treatment options in
patients with SVG, the
search for an alternative method of nonsurgical revascularization
appears warranted. Increasing evidence suggests that SVG angioplasty
with balloon-expandable or self-expanding stents is an effective
alternative treatment option in patients with SVG stenoses. In the
present study, the use of coronary and biliary tubular slotted
stent designs was associated with comparable procedural success rates,
infrequent complications, and similarly favorable 6-month clinical
outcomes. Nevertheless, with the added rigidity and technical demand
for biliary stent placement, extreme caution is recommended with
biliary stent implantation in SVGs, as clinical results are highly
dependent on operator technique, patient selection, and a close
familiarity with stent management issues.
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Acknowledgments |
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This study was supported by a grant from the Cardiology Research Foundation of the Washington Cardiology Center.
Received March 29, 1994; accepted August 31, 1994.
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References |
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