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389
Iliac Artery Stenosis or Obstruction After Unsuccessful Balloon Angioplasty: Treatment Self-Expandable
with a
Stent
: R. W. GUnther1 D. Vorwerk1 F. Antonucci2 B. Beyssen3 A. Essinger J. C. Gaux3 F. Joffre5 A. Raynaud3 H. Rousseau5
Ch. L. ZoIlikofer
Obstruction or stenosis of the iliac artery was treated by placement of a selfexpandable stent in 91 patients. A total of 100 lesions was treated. All patients had had poor results of balloon angioplasty including residual stenosis, iliac occlusion, and dissection. The stent used in all cases was a self-expandable stainless steel endoprosthesis mounted on a 7- or 9-French catheter and covered by an invaginated tubular rolling membrane. The diameter of the expanded stent varied from 7 to 12 mm. A total of 129 stents was placed. Technical success was 97%. Thromboses occurred immediately after placement in two patients and within the first month in six; these were mainly due to residual obstruction. Eighty-two (93%) of 88 patients with a follow-up longer than 3 months had no recurrent symptoms. Restenosis caused by intimab hyperplasia inside the stent occurred in 10 patients; these required repeated intervention in only four cases. In the remaining six patients, no further complications occurred. Our results show that self-expanding endoprostheses are of value for improving the results of inadequate percutaneous transluminal angioplasty. AJR
156:389-393,
February
1991
Percutaneous transluminal angioplasty (PTA) for the treatment of stenoses of the iliac artery has a high rate of success [i]. However, in some patients PTA [2, 3] is either technically unsuccessful or restenosis occurs [i ]. We studied the value of a self-expandable Wallstent type of endovascuban prosthesis for treatment of such lesions in our first i 00 consecutive patients.
Materials
and
Methods
Instrumentation
The Wallstent Received
March
7, 1990: accepted after revision
August 10, 1990. 1
of Technology, Aachen, Pauwelsstrasse, D-5i00 Aachen, Germany. Address reprint requests to A. w. GUnther. 2 Department of Radiology, Kantonsspital Win-
Department Paris, France. 3
from
characteristics
each other,
Department of Diagnostic Radiology, University
terthur, Winterthur,
braided
Switzerland. of Radiology,
H#{244}pitalBroussais,
4 Department of Diagnostic Radiology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
5 Department of Radiology, Rangueil, Toulouse, France.
H#{244}pital Universitaire
0361 -803X/91/1 562-0389 © American Roentgen Ray Society
prosthesis
(Medinvent
surgical-grade
spring
of the monofilaments
the prosthesis
Inc.
,
stainless
Lausanne, steel
and because
can be stretched
Switzerland)
monofilaments.
the braided
elastically
elements
is a tubular structure of the spring
Because
are free to pivot over
to an elongated
format
of small
diameter. When released, the stent recoils to its shorter, preset unrestrained diameter. The stents are selected so that the unrestrained diameter is between 1 and 2 mm larger than the target vessel. When implanted, the stent then can exert a residual radial pressure against the vessel wall, preventing collapse and holding the stent in place. The stent is premounted on a flexible delivery catheter, permitting access via tortuous and contralateral
vessels. The distal catheter prosthesis.
The maximal
segment
external
remains flexible despite the presence
diameters
of the delivery
of the mounted
devices were 7-French for stents of 7- to 1 0-mm unrestrained diameter and 9-French for 1 2- to 1 4-mm unrestrained diameters. The catheters are coaxial; the inner shaft is joined to the external shaft by an invaginated tubular rolling membrane, which covers and retains the stent stretched on the inner shaft. Hydraulic pressure of 3.5-4.0 atmospheres (350-400 kPa) applied to the anular space between the two layers of the rolling membrane facilitates rolling the membrane back off the stent. Peeling the membrane back like an inverted glove, therefore, allows the restrained prosthesis to open progressively. As long as the stent is deployed only partially, it can be
GUNTHER
390
retrieved vertent
hydraulic
by pulling further
out the delivery
deployment
pressure
of
the
system. stent
must be released.
In order
during
Pushing
this
to avoid maneuver,
the partially
madthe
open stent
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will not result in repositioning, but must be avoided because the open end will engage the vessel wall. Patients Eighty men and 1 1 women with a mean age of 55 years (range, 36-88 years) and a total of 100 iliac lesions were included in this study. Of the lesions, 50 were located in the common iliac artery; 37 in the external
iliac artery;
and 1 3 in both the common
and external
ET AL.
AJR:156,
PTA, and severe considered
after
coagulation successful
defects.
Stent
February
placement
was
1991
not
PTA.
Patients were considered for stent treatment only if their lesions did not respond well to angioplasty with respect to either immediate technical failure or poor results. Thus, patients with restenosis after previous angioplasty (n = 30) or occlusions (n = 25) were included. Thirteen patients were treated for flow-impairing dissections caused by previous angioplasty (Figs. 1 and 2). In 32 patients PTA was considered unsatisfactory, which was defined as a residual stenosis
greater than 30% and/or a residual
systolic pressure
mm Hg after administration of vasodilating drugs flow. Table 1 gives an overview of the reduction
gradient
of 20
and reduced blood in vessel diameter
iliac arteries, bridging the orifice of the internal iliac artery. According to Fontaine’s classification, ii patients had stage Ila claudication
before and after PTA and after placement of the stent. The mean length of all 100 lesions was 42 mm (range,
(walking
mm; Table 2). One third of all lesions were longer than 5 cm. Lesions longerthan 5 cm werefound in 1 3% (4/30)of patients with restenosis,
distance
200 m and more), and 79 had stage lIb (walking distance less than 200 m). Six patients had pain at rest (stage III), and four had cutaneous necrosis (stage IV). Risk factors such as smoking (n = 84), hypentriglyceridemia(n = 23), hypercholesterolemia
(n = 29), hypertension (n = 38), and diabetes (n = 9) were found. All patients gave their informed consent to participate. Contraindications to stent placement were acute thrombosis, vascular rupture after
10-i 80
72% (1 8/25) of patients with occlusion, 23% (3/1 3) of patients with dissection, and 25% (8/32) of patients with post-PTA recoil. A total of 129 stents was used in this study. Stents with implanted lengths of around 33 and 66 mm were available for implantation. Stents were selected to be longer than the target lesion, and the stented area
Fig. 1.-Complex artery.
lesion
of right external
iliac
A, Angiogram obtained after dilatation with 8mm
balloon
shows
residual
stenosis
in short close to orifice of internal iliac artery. Note aneurysmal dissection (arrow) caused by angioplasty performed 4 months earlier. B, Angiogram obtained after placement of an 8-mm stent shows normal vascular diameter and size of dissection (arrow) markedly decreased.
segment of proximal external iliac artery
A
B
A
B Fig. 2.-Acute
complication
treated
by stent
C
implantation.
A, Anglogram shows simple stenosis in a short segment of right external iliac artery that is amenable to balloon dilatation B, Anglogram obtained after dilatation with a 7-mm balloon shows marked dissection (arrows) compromising blood flow. C, Angiogram
obtained
after
immediate
placement
of a 8-mm
Wallstent
(arrows)
shows
restored
vascular
diameter.
alone.
February
AJR:156,
ILIAC
1991
TABLE 1: Grade (%) of Stenosis After Percutaneous Transluminal
or Obstruction Before Angioplasty (PTA)
ARTERY
and
STENOSIS
TABLE Severe
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Restenosis (n = 30) Before PTA After PTA After stent
82 (60-90) 46 (30-90) 9 (0-40)
TABLE 2: Length After Percutaneous
Maximum Mean
Dissection (n
=
Post-PTA (n
13)
1 00 83 (50-90) 62 (40-i 00 ) 46 (30-80) 4 (0-50) 10 (0-40)
=
Occlusion (n = 25)
Dissection (n = 1 3)
Recoil
84 (60-90) 51 (30-80) 17 (0-40)
Recoil
i .0 1 8.0
3.0 1 0.0
1 .0 1 0.0
11.0
3.5
5.9
3.9
3.4
1.0
was from approach
Acetylsalicylic acid was given 24 hr before the procedure and again on the day of the procedure. An intraoperative dose of 5000 IU of was given; this was supplemented by a further took longer than 1 hr. The protocol included
heparin administration tion
with
the study
warfarin
2000 IU if the postoperative
for 24 hr at a rate of i 000 lU/hr. Anticoagula3-6 months after treatment was used early
for
for a limited
number
of patients
(30 lesions
who had an occlusion treated or outflow occlusion of the ipsilateral superficial femoral
problems
in
in 27 patients)
such as an
artery.
Follow-up Before being discharged, all patients underwent a postoperative clinical examination and Doppler evaluation. IV digital subtraction angiography was performed selectively. The follow-up protocol called for angiographic and for clinical
examination of all patients and, if possible, angiographic
who were symptomatic studies at 1 (or 3), 6,
and 1 2 months. In cases in which the follow-up period exceeded i 2 months, additional angiographic studies were performed at 24 months and later. For the purpose of reporting, restenosis was defined as recurrent luminal narrowing within or adjacent to the stent exceeding 20% of the previously restored diameter regardless of whether
the patient
by an additional
stent
Hemanthros, hematuria (due to warfarin) Overall complication rate
Medication
procedure
complications
corrected
varied from 35 to 190 mm (mean, 61 mm). When a single lesion required two or more stents, the stents were placed with an overlap of approximately 1 0 mm, preferably from proximal to distal. In 76 lesions, one stent was implanted; in i 9 lesions, two stents were used; and in five lesions, three stents were used. The unrestrained
heparin
(n = 100 Lesions)
2 1 7 5
2 12
and
Post-PTA
stent diameters were 7, 8, 10, and 1 2 mm. Vessel access the ipsilateral side in 88 lesions and from the contralateral in i2.
3: Complications
Immediate thrombosis Perforation of the vessel before stenting Moderate complications Misplacement of a stent
32)
(cm) of Stenosis or Obstruction Before Transluminal Angioplasty (PTA)
Restenosis (n = 30) Minimum
Occlusion Q:1 = 25)
391
was symptomatic.
Results
Primary technical success was achieved in 97 of 1 00 besions. Complications occurred during treatment of i 2 lesions and were severe in three (Table 3). Two cases of acute thrombosis occurred. One happened
during an implantation that was performed peniopenatively as an adjunct procedure to a surgical crossover bypass. The thrombosis was caused by vascular clamping proximal to the implantation site. The other acute thrombosis occurred in a patient who had stage IV atherosclerotic disease, an iliac occlusion, and poor outflow conditions. Technical complications developed in one patient (two besions) with bilateral iliac disease after a successful stent implantation on one side. His contralatenal vessel was to be treated, but a perforation of the artery was found after balloon angioplasty; the patient was transferred for bilateral neconstnuctive surgery. Although misplacement occurred in seven (5%) of 129 stents implanted, it never had serious consequences. In four ofthese cases, a second stent was placed successfully during the same procedure to coven the lesion completely. In two cases, coverage by the stent remained incomplete, requiring neintervention: in one patient, an additional stent was implanted 2 months later; in the other, a proximal dissection was not sealed by the stent and was found thrombosed at follow-up. In all seven cases, misplacement was associated with lesions close to the aortic bifurcation or the origin of the internal iliac artery. The stent did not migrate in any case. No groin hematoma requiring surgical intervention or netropenitoneal hematoma was observed. In two patients, complications due to warfanin therapy occurred-one had spontaneous hemarthnosis of the knee, the second had macnohematuria because of a small vesical tumor. Six additional cases of neocclusion occurred within the first month after treatment. Prevalence of early thrombosis was almost the same, with 6% (4/70) in patients taking acetylsalicylic acid and 7% (2/30) in those taking anti-vitamin K. In three ofthose patients, a proximal dissection (n = 1 ) on plaque (n = 2) was covered incompletely by the stent, thereby causing an inflow obstruction. In one patient (stage IV disease, alcohol-induced hepatic insufficiency, acetylsalicylic acid medication), nethnombosis of the stent occurred 8 days after treatment. It was found after the patient had attempted suicide and probably was due to severe hypotension. Thromboses occurred in two other cases without any obvious reasons. Medication included acetylsalicylic acid in one and warfanin in the other. Consequently, early patency at 3month follow-up was seen in 90 of i 00 lesions. Clinical benefit was seen in 88 of 1 00 lesions. Clinical symptoms improved for patients with Fontaine’s stage I in 24, for stage II in 59, and for stage III in five lesions. No clinical change was seen in three patients without complications but with additional femorab lesions.
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392
GUNTHER
Eighty-two patients with 90 lesions were considered for follow-up studies longer than 3 months, which included clinical examination and Doppler evaluation for 26 lesions and clinical examination, angiographic studies and, if possible, Doppler imaging for 62 lesions. Two patients (two lesions) were lost to follow-up. Mean follow-up time was 1 3.5 months (range, 2-39 months). Ten lesions were followed up for 24 months or longer, 33 for 1 2-23 months, and 39 for 6-1 1 months. Six lesions were followed up for less than 6 months. In one patient, the stent was removed during bypass surgery for an aortic aneurysm 1 8 months after treatment[4]. One patient died 4 months after treatment. Clinically, no recurrence on worsening of symptoms was found for 82 (93%) of 88 lesions during the reported period of follow-up. All patients who became symptomatic again underwent angiognaphy. Symptomatic nestenosis was diagnosed between 4.5 and 26.0 (mean, 1 1 .5) months after treatment. Restenosis was found within the endoprostheses of seven (1 1%) of 62 lesions with angiognaphic follow-up, but reintervention was required in only three symptomatic patients; this was done either by athenectomy on balloon dilatation (Fig. 3). Restenosis touching the extremities of the stent occurred in three patients; one of these required neintenvention. In four cases, new lesions were detected that were unassociated with the stent in place. This means that recurrent symptoms were associated with nestenosis within on close to a stent in four of six cases. Angiographic nestenosis was related to the implant in 1 0 of 1 4 cases. Thus, the prevalence of clinically relevant nestenosis inside the stent was 5% (4/88), and the angiographic prevalence of nestenosis was 1 6#{176}Io (10/62).
Discussion
Early technical success and a long-term patency helped establish PTA [2, 3] of the iliac arteries as a widely accepted procedure [1 ]. A mean initial success rate of 92% and a 2year patency nate of 81 % were calculated by Becker and coworkers after analyzing the data from 2697 iliac procedures
ET AL.
AJA:156, February 1991
[1 ]. A positively biased selection of the patients undergoing PTA must, however, be assumed because a subset of iliac lesions is known to respond poorly to this treatment. A poor result after angioplasty may be characterized by flow-obstructing dissection or recoil of the stenosis typified by the collapsing bifurcation lesion at the iliac orifice [1]. Significant residual stenosis after PTA complemented by a high-grade residual pressure gradient across the lesion is associated with a higher rate of recurrence [5]. Beyond this, controversy exists on the usefulness of PTA of iliac occlusions. Percutaneous treatment of iliac occlusions, especially those longer than 2 cm, is infrequent. Early papers [6, 7] reported a high rate of complications. The group of complex iliac lesions also may include iliac restenoses after previous PTA, long and eccentric lesions [1 ], and extensively ulcerated plaques. An innovative technique such as placement of a stent must prove its clinical benefit by improving both the initial technical success and the long-term patency of this subgroup of complex lesions. Modern theories of the mechanism of balloon angioplasty favor fracture of plaque material and medial stretching [8]. Such controlled vascular injury, however, can cause severe changes in the intraluminal geometry, such as deep dissection, that increase the chances of early technical failure [1]. Implantation of a stent helps remodel the inner vascular surface by displacing an eccentric plaque or a dissecting membrane into the vessel wall. The implant is a foreign body, however, and thus poses additional problems, particularly thrombogenicity. In our patients, early technical failure generally was due to acute on subacute occlusion and occurred in nine of 100 lesions. This rate is somewhat high compared with the results of simple balloon angioplasty. However, a negatively biased selection of lesions not primarily amenable to percutaneous treatment must be taken into consideration. Impaired blood flow combined with presence of a foreign body certainly predisposes to thnombotic neocclusion, and in five of our patients, obstruction of either the inflow on the outflow was still present despite implantation of a stent. Most of these
Fig. 3.-Restenosis after placement of stent. A, Angiogram shows high-grade eccentric stenosis in both common iliac arteries close to bifurcation. B, Angiogram obtained 6 months after placement of stents shows symptomatic stenosis (solid arrow) in lower part of left endoprosthesis and another proximal restenosis on right side (open arrow). Lesions were treated successfully by balloon angioplasty and atherectomy.
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AJA:i56,
February
1991
ILIAC
ARTERY
cases occurred during an early stage of our study, and the rate of early neocclusion declined remarkably as the study progressed. Complete coverage of the lesion was difficult sometimes, such as in stenoses of the aortic bifurcation, in which a slight protrusion of the stent into the aortic lumen was sometimes required to accomplish adequate stenting. Proper selection of patients is important, and in cases of severe restricted outflow, special attention should be given to postprocedunal anticoagulant therapy. Progression of intraluminal hyperplasia within a stent can be monitored angiographically because of the clearly visible outline of the metallic endoprosthesis. Neointimal coverage of the stent surface corresponding to less than 20% of the stent’s diameter was a normal finding. Excision of stenotic material inside implants with an athenectomy catheter showed neointimal hyperplasia [9, 10] similar to that seen after simple balloon dilatation [1 1 ]. Excessive growth of neointimal tissue has been reported in some patients with femoral stents [12, 1 3], so induction of neointimal growth by the stent cannot be excluded. With iliac stents, the prevalence of nestenosis due to intimal hyperplasia was notably lower than that reported in femoral arteries or hemodialysis shunts [1 2-i 7]. Moreover, in most cases nestenosis was found only at angiognaphy and was clinically insignificant. The follow-up period now extends to 3.5 years and, in most patients treated, stented iliac areas are completely patent and no stent-related late complications have been identified. Comparison with other types of stents, however, is still difficult because no larger series with cornparable data have been published, and the composition of patient subgroups is heterogeneous. Additional follow-up data therefore are required for a definitive assessment. Although the preliminary clinical experience with self-expandable stents, on stents in general [1 3, 1 6, 17], as an adjunct to balloon angioplasty in the iliac arteries is promising, the importance of a reasonable cost-benefit ratio should not be neglected. Placement of a stent is still a costly procedure, making PTA more expensive. A significant reduction of the rate of nestenosis has not been proved. Balloon angioplasty, therefore, still remains the gold standard of percutaneous treatment. Consequently, insertion of a stent should be limited to the selected subset of lesions that we described. Too liberal an approach should be avoided, because it may compromise the use of this advanced new technique by decreasing the use of balloon angioplasty, which has striking advantages as a safe, successful, and inexpensive procedure for most iliac lesions.
STENOSIS
393
ACKNOWLEDGMENTS The
authors
assistance
and
thank
Udo
Danielle
BuhI,
Aachen,
Venderickx,
Lausanne,
for the preparation
for editorial
of photographs.
REFERENCES 1 . Becker GJ, Katzen 1989:1 70:921 -940
BT,
Dake
MD.
Noncoronary
angioplasty.
Radiology
2. Dotter CT, Judkins
MP. Transluminal angioplasty of atherosclerotic obstructions: description of a new technique and a preliminary report of its application. Circulation 1964:30: 654-670 3. GrUntzig A, Hopff M. Perkutane Rekanalisation chronischer arterieller VerschlUsse mit einem neuen Dilatationskatheter: Modifikation der DotterTechnik. Dtsch Med Wochenschr 1974;99:2502-2510 4. Rousseau H, Joffre F, Raillat C, Duboucher C, et al. Iliac artery endoprosthesis: radiologic and histologic findings after 2 years. AJR 1989:153:1075-1076 5. Leimgruber P, Aoubin G, Anderson H, et al. Influence of intimal dissection on restenosis after successful coronary angioplasty. Circulation 1985:72:530-535 6. Ring E, Freiman D, McLean G, Schwarz W. Percutaneous recanalization of iliac artery occlusions: an unacceptable complication rate. AJR 1982:139:587-589 7. Pilla T, Peterson G, Tantana S, et al. Percutaneous recanalization of iliac artery occlusions: an alternative to surgery in the high-risk patient. AJR 1984:143:313-316 8. Wolf G, LeVeen A, Ring E. Potential mechanisms of angioplasty. Cardiovasc Intervent Radiol 1984:7:11-17 9. Vorwerk D, Guenther AW. Removal of intimal hyperplasia in vascular endoprostheses managed by combined use of atherectomy and balloon dilatation. AJR 1990:154:617-619 1 0. Zollikofer CL, Antonucci F, Thalmann A, Pfyffer M, Stuckmann G, Marty A. Early clinical experience with arterial stent placement with the Wallstent. Radiology 1989:173(P):351 1 1 . Giraldo AA, Esposo OM, Meis JM. Intimal hyperplasia as a cause of restenosis after percutaneous transluminal coronary angioplasty. Arch PatholLab Med 1985:109:173-175 1 2. Triller J, Mahler F, Do D, Thalmann A. Die vaskulaere Endoprothese bei femoropoplitealer Verschlusskrankheit. Fortschr Roentgenstr 1989:150: 328-334 1 3. Guenther AW, Vorwerk D, Bohndorf K, et al. Iliac and femoral artery stenoses and occlusions: treatment with intravascular stents. Radiology 1989:172:725-730 1 4. Guenther AW, Vorwerk D, Bohndorf K et al. Venous stenoses in dialysis shunts: treatment with self-expanding metallic stents. Radiology
1989:170:401-405 1 5. Antonucci F, Zollikofer CL, Thalmann J. Early clinical experience with the shunts. Radiology 1989:1 73(P): 107 1 6. Palmaz JC, Richter GM, Noeldge G, rotic iliac artery stenosis: preliminary ogy 1988:168:727-731 17. Palmaz JC, Garcia 0, Schatz A, et intraluminal stents in iliac arteries: 1990:174:969-975
A, Stuckmann G, Aedka Wallstent in veins, grafts
F, Largiader and dialysis
et al. Intraluminal stent in atherosclereport of a multicenter study. Radio!al. Placement first 171
of balloon-expandable procedures. Radiology
389
Iliac Artery Stenosis or Obstruction After Unsuccessful Balloon Angioplasty: Treatment Self-Expandable
with a
Stent
: R. W. GUnther1 D. Vorwerk1 F. Antonucci2 B. Beyssen3 A. Essinger J. C. Gaux3 F. Joffre5 A. Raynaud3 H. Rousseau5
Ch. L. ZoIlikofer
Obstruction or stenosis of the iliac artery was treated by placement of a selfexpandable stent in 91 patients. A total of 100 lesions was treated. All patients had had poor results of balloon angioplasty including residual stenosis, iliac occlusion, and dissection. The stent used in all cases was a self-expandable stainless steel endoprosthesis mounted on a 7- or 9-French catheter and covered by an invaginated tubular rolling membrane. The diameter of the expanded stent varied from 7 to 12 mm. A total of 129 stents was placed. Technical success was 97%. Thromboses occurred immediately after placement in two patients and within the first month in six; these were mainly due to residual obstruction. Eighty-two (93%) of 88 patients with a follow-up longer than 3 months had no recurrent symptoms. Restenosis caused by intimab hyperplasia inside the stent occurred in 10 patients; these required repeated intervention in only four cases. In the remaining six patients, no further complications occurred. Our results show that self-expanding endoprostheses are of value for improving the results of inadequate percutaneous transluminal angioplasty. AJR
156:389-393,
February
1991
Percutaneous transluminal angioplasty (PTA) for the treatment of stenoses of the iliac artery has a high rate of success [i]. However, in some patients PTA [2, 3] is either technically unsuccessful or restenosis occurs [i ]. We studied the value of a self-expandable Wallstent type of endovascuban prosthesis for treatment of such lesions in our first i 00 consecutive patients.
Materials
and
Methods
Instrumentation
The Wallstent Received
March
7, 1990: accepted after revision
August 10, 1990. 1
of Technology, Aachen, Pauwelsstrasse, D-5i00 Aachen, Germany. Address reprint requests to A. w. GUnther. 2 Department of Radiology, Kantonsspital Win-
Department Paris, France. 3
from
characteristics
each other,
Department of Diagnostic Radiology, University
terthur, Winterthur,
braided
Switzerland. of Radiology,
H#{244}pitalBroussais,
4 Department of Diagnostic Radiology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
5 Department of Radiology, Rangueil, Toulouse, France.
H#{244}pital Universitaire
0361 -803X/91/1 562-0389 © American Roentgen Ray Society
prosthesis
(Medinvent
surgical-grade
spring
of the monofilaments
the prosthesis
Inc.
,
stainless
Lausanne, steel
and because
can be stretched
Switzerland)
monofilaments.
the braided
elastically
elements
is a tubular structure of the spring
Because
are free to pivot over
to an elongated
format
of small
diameter. When released, the stent recoils to its shorter, preset unrestrained diameter. The stents are selected so that the unrestrained diameter is between 1 and 2 mm larger than the target vessel. When implanted, the stent then can exert a residual radial pressure against the vessel wall, preventing collapse and holding the stent in place. The stent is premounted on a flexible delivery catheter, permitting access via tortuous and contralateral
vessels. The distal catheter prosthesis.
The maximal
segment
external
remains flexible despite the presence
diameters
of the delivery
of the mounted
devices were 7-French for stents of 7- to 1 0-mm unrestrained diameter and 9-French for 1 2- to 1 4-mm unrestrained diameters. The catheters are coaxial; the inner shaft is joined to the external shaft by an invaginated tubular rolling membrane, which covers and retains the stent stretched on the inner shaft. Hydraulic pressure of 3.5-4.0 atmospheres (350-400 kPa) applied to the anular space between the two layers of the rolling membrane facilitates rolling the membrane back off the stent. Peeling the membrane back like an inverted glove, therefore, allows the restrained prosthesis to open progressively. As long as the stent is deployed only partially, it can be
GUNTHER
390
retrieved vertent
hydraulic
by pulling further
out the delivery
deployment
pressure
of
the
system. stent
must be released.
In order
during
Pushing
this
to avoid maneuver,
the partially
madthe
open stent
Downloaded from www.ajronline.org by 190.3.239.78 on 10/15/15 from IP address 190.3.239.78. Copyright ARRS. For personal use only; all rights reserved
will not result in repositioning, but must be avoided because the open end will engage the vessel wall. Patients Eighty men and 1 1 women with a mean age of 55 years (range, 36-88 years) and a total of 100 iliac lesions were included in this study. Of the lesions, 50 were located in the common iliac artery; 37 in the external
iliac artery;
and 1 3 in both the common
and external
ET AL.
AJR:156,
PTA, and severe considered
after
coagulation successful
defects.
Stent
February
placement
was
1991
not
PTA.
Patients were considered for stent treatment only if their lesions did not respond well to angioplasty with respect to either immediate technical failure or poor results. Thus, patients with restenosis after previous angioplasty (n = 30) or occlusions (n = 25) were included. Thirteen patients were treated for flow-impairing dissections caused by previous angioplasty (Figs. 1 and 2). In 32 patients PTA was considered unsatisfactory, which was defined as a residual stenosis
greater than 30% and/or a residual
systolic pressure
mm Hg after administration of vasodilating drugs flow. Table 1 gives an overview of the reduction
gradient
of 20
and reduced blood in vessel diameter
iliac arteries, bridging the orifice of the internal iliac artery. According to Fontaine’s classification, ii patients had stage Ila claudication
before and after PTA and after placement of the stent. The mean length of all 100 lesions was 42 mm (range,
(walking
mm; Table 2). One third of all lesions were longer than 5 cm. Lesions longerthan 5 cm werefound in 1 3% (4/30)of patients with restenosis,
distance
200 m and more), and 79 had stage lIb (walking distance less than 200 m). Six patients had pain at rest (stage III), and four had cutaneous necrosis (stage IV). Risk factors such as smoking (n = 84), hypentriglyceridemia(n = 23), hypercholesterolemia
(n = 29), hypertension (n = 38), and diabetes (n = 9) were found. All patients gave their informed consent to participate. Contraindications to stent placement were acute thrombosis, vascular rupture after
10-i 80
72% (1 8/25) of patients with occlusion, 23% (3/1 3) of patients with dissection, and 25% (8/32) of patients with post-PTA recoil. A total of 129 stents was used in this study. Stents with implanted lengths of around 33 and 66 mm were available for implantation. Stents were selected to be longer than the target lesion, and the stented area
Fig. 1.-Complex artery.
lesion
of right external
iliac
A, Angiogram obtained after dilatation with 8mm
balloon
shows
residual
stenosis
in short close to orifice of internal iliac artery. Note aneurysmal dissection (arrow) caused by angioplasty performed 4 months earlier. B, Angiogram obtained after placement of an 8-mm stent shows normal vascular diameter and size of dissection (arrow) markedly decreased.
segment of proximal external iliac artery
A
B
A
B Fig. 2.-Acute
complication
treated
by stent
C
implantation.
A, Anglogram shows simple stenosis in a short segment of right external iliac artery that is amenable to balloon dilatation B, Anglogram obtained after dilatation with a 7-mm balloon shows marked dissection (arrows) compromising blood flow. C, Angiogram
obtained
after
immediate
placement
of a 8-mm
Wallstent
(arrows)
shows
restored
vascular
diameter.
alone.
February
AJR:156,
ILIAC
1991
TABLE 1: Grade (%) of Stenosis After Percutaneous Transluminal
or Obstruction Before Angioplasty (PTA)
ARTERY
and
STENOSIS
TABLE Severe
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Restenosis (n = 30) Before PTA After PTA After stent
82 (60-90) 46 (30-90) 9 (0-40)
TABLE 2: Length After Percutaneous
Maximum Mean
Dissection (n
=
Post-PTA (n
13)
1 00 83 (50-90) 62 (40-i 00 ) 46 (30-80) 4 (0-50) 10 (0-40)
=
Occlusion (n = 25)
Dissection (n = 1 3)
Recoil
84 (60-90) 51 (30-80) 17 (0-40)
Recoil
i .0 1 8.0
3.0 1 0.0
1 .0 1 0.0
11.0
3.5
5.9
3.9
3.4
1.0
was from approach
Acetylsalicylic acid was given 24 hr before the procedure and again on the day of the procedure. An intraoperative dose of 5000 IU of was given; this was supplemented by a further took longer than 1 hr. The protocol included
heparin administration tion
with
the study
warfarin
2000 IU if the postoperative
for 24 hr at a rate of i 000 lU/hr. Anticoagula3-6 months after treatment was used early
for
for a limited
number
of patients
(30 lesions
who had an occlusion treated or outflow occlusion of the ipsilateral superficial femoral
problems
in
in 27 patients)
such as an
artery.
Follow-up Before being discharged, all patients underwent a postoperative clinical examination and Doppler evaluation. IV digital subtraction angiography was performed selectively. The follow-up protocol called for angiographic and for clinical
examination of all patients and, if possible, angiographic
who were symptomatic studies at 1 (or 3), 6,
and 1 2 months. In cases in which the follow-up period exceeded i 2 months, additional angiographic studies were performed at 24 months and later. For the purpose of reporting, restenosis was defined as recurrent luminal narrowing within or adjacent to the stent exceeding 20% of the previously restored diameter regardless of whether
the patient
by an additional
stent
Hemanthros, hematuria (due to warfarin) Overall complication rate
Medication
procedure
complications
corrected
varied from 35 to 190 mm (mean, 61 mm). When a single lesion required two or more stents, the stents were placed with an overlap of approximately 1 0 mm, preferably from proximal to distal. In 76 lesions, one stent was implanted; in i 9 lesions, two stents were used; and in five lesions, three stents were used. The unrestrained
heparin
(n = 100 Lesions)
2 1 7 5
2 12
and
Post-PTA
stent diameters were 7, 8, 10, and 1 2 mm. Vessel access the ipsilateral side in 88 lesions and from the contralateral in i2.
3: Complications
Immediate thrombosis Perforation of the vessel before stenting Moderate complications Misplacement of a stent
32)
(cm) of Stenosis or Obstruction Before Transluminal Angioplasty (PTA)
Restenosis (n = 30) Minimum
Occlusion Q:1 = 25)
391
was symptomatic.
Results
Primary technical success was achieved in 97 of 1 00 besions. Complications occurred during treatment of i 2 lesions and were severe in three (Table 3). Two cases of acute thrombosis occurred. One happened
during an implantation that was performed peniopenatively as an adjunct procedure to a surgical crossover bypass. The thrombosis was caused by vascular clamping proximal to the implantation site. The other acute thrombosis occurred in a patient who had stage IV atherosclerotic disease, an iliac occlusion, and poor outflow conditions. Technical complications developed in one patient (two besions) with bilateral iliac disease after a successful stent implantation on one side. His contralatenal vessel was to be treated, but a perforation of the artery was found after balloon angioplasty; the patient was transferred for bilateral neconstnuctive surgery. Although misplacement occurred in seven (5%) of 129 stents implanted, it never had serious consequences. In four ofthese cases, a second stent was placed successfully during the same procedure to coven the lesion completely. In two cases, coverage by the stent remained incomplete, requiring neintervention: in one patient, an additional stent was implanted 2 months later; in the other, a proximal dissection was not sealed by the stent and was found thrombosed at follow-up. In all seven cases, misplacement was associated with lesions close to the aortic bifurcation or the origin of the internal iliac artery. The stent did not migrate in any case. No groin hematoma requiring surgical intervention or netropenitoneal hematoma was observed. In two patients, complications due to warfanin therapy occurred-one had spontaneous hemarthnosis of the knee, the second had macnohematuria because of a small vesical tumor. Six additional cases of neocclusion occurred within the first month after treatment. Prevalence of early thrombosis was almost the same, with 6% (4/70) in patients taking acetylsalicylic acid and 7% (2/30) in those taking anti-vitamin K. In three ofthose patients, a proximal dissection (n = 1 ) on plaque (n = 2) was covered incompletely by the stent, thereby causing an inflow obstruction. In one patient (stage IV disease, alcohol-induced hepatic insufficiency, acetylsalicylic acid medication), nethnombosis of the stent occurred 8 days after treatment. It was found after the patient had attempted suicide and probably was due to severe hypotension. Thromboses occurred in two other cases without any obvious reasons. Medication included acetylsalicylic acid in one and warfanin in the other. Consequently, early patency at 3month follow-up was seen in 90 of i 00 lesions. Clinical benefit was seen in 88 of 1 00 lesions. Clinical symptoms improved for patients with Fontaine’s stage I in 24, for stage II in 59, and for stage III in five lesions. No clinical change was seen in three patients without complications but with additional femorab lesions.
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392
GUNTHER
Eighty-two patients with 90 lesions were considered for follow-up studies longer than 3 months, which included clinical examination and Doppler evaluation for 26 lesions and clinical examination, angiographic studies and, if possible, Doppler imaging for 62 lesions. Two patients (two lesions) were lost to follow-up. Mean follow-up time was 1 3.5 months (range, 2-39 months). Ten lesions were followed up for 24 months or longer, 33 for 1 2-23 months, and 39 for 6-1 1 months. Six lesions were followed up for less than 6 months. In one patient, the stent was removed during bypass surgery for an aortic aneurysm 1 8 months after treatment[4]. One patient died 4 months after treatment. Clinically, no recurrence on worsening of symptoms was found for 82 (93%) of 88 lesions during the reported period of follow-up. All patients who became symptomatic again underwent angiognaphy. Symptomatic nestenosis was diagnosed between 4.5 and 26.0 (mean, 1 1 .5) months after treatment. Restenosis was found within the endoprostheses of seven (1 1%) of 62 lesions with angiognaphic follow-up, but reintervention was required in only three symptomatic patients; this was done either by athenectomy on balloon dilatation (Fig. 3). Restenosis touching the extremities of the stent occurred in three patients; one of these required neintenvention. In four cases, new lesions were detected that were unassociated with the stent in place. This means that recurrent symptoms were associated with nestenosis within on close to a stent in four of six cases. Angiographic nestenosis was related to the implant in 1 0 of 1 4 cases. Thus, the prevalence of clinically relevant nestenosis inside the stent was 5% (4/88), and the angiographic prevalence of nestenosis was 1 6#{176}Io (10/62).
Discussion
Early technical success and a long-term patency helped establish PTA [2, 3] of the iliac arteries as a widely accepted procedure [1 ]. A mean initial success rate of 92% and a 2year patency nate of 81 % were calculated by Becker and coworkers after analyzing the data from 2697 iliac procedures
ET AL.
AJA:156, February 1991
[1 ]. A positively biased selection of the patients undergoing PTA must, however, be assumed because a subset of iliac lesions is known to respond poorly to this treatment. A poor result after angioplasty may be characterized by flow-obstructing dissection or recoil of the stenosis typified by the collapsing bifurcation lesion at the iliac orifice [1]. Significant residual stenosis after PTA complemented by a high-grade residual pressure gradient across the lesion is associated with a higher rate of recurrence [5]. Beyond this, controversy exists on the usefulness of PTA of iliac occlusions. Percutaneous treatment of iliac occlusions, especially those longer than 2 cm, is infrequent. Early papers [6, 7] reported a high rate of complications. The group of complex iliac lesions also may include iliac restenoses after previous PTA, long and eccentric lesions [1 ], and extensively ulcerated plaques. An innovative technique such as placement of a stent must prove its clinical benefit by improving both the initial technical success and the long-term patency of this subgroup of complex lesions. Modern theories of the mechanism of balloon angioplasty favor fracture of plaque material and medial stretching [8]. Such controlled vascular injury, however, can cause severe changes in the intraluminal geometry, such as deep dissection, that increase the chances of early technical failure [1]. Implantation of a stent helps remodel the inner vascular surface by displacing an eccentric plaque or a dissecting membrane into the vessel wall. The implant is a foreign body, however, and thus poses additional problems, particularly thrombogenicity. In our patients, early technical failure generally was due to acute on subacute occlusion and occurred in nine of 100 lesions. This rate is somewhat high compared with the results of simple balloon angioplasty. However, a negatively biased selection of lesions not primarily amenable to percutaneous treatment must be taken into consideration. Impaired blood flow combined with presence of a foreign body certainly predisposes to thnombotic neocclusion, and in five of our patients, obstruction of either the inflow on the outflow was still present despite implantation of a stent. Most of these
Fig. 3.-Restenosis after placement of stent. A, Angiogram shows high-grade eccentric stenosis in both common iliac arteries close to bifurcation. B, Angiogram obtained 6 months after placement of stents shows symptomatic stenosis (solid arrow) in lower part of left endoprosthesis and another proximal restenosis on right side (open arrow). Lesions were treated successfully by balloon angioplasty and atherectomy.
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AJA:i56,
February
1991
ILIAC
ARTERY
cases occurred during an early stage of our study, and the rate of early neocclusion declined remarkably as the study progressed. Complete coverage of the lesion was difficult sometimes, such as in stenoses of the aortic bifurcation, in which a slight protrusion of the stent into the aortic lumen was sometimes required to accomplish adequate stenting. Proper selection of patients is important, and in cases of severe restricted outflow, special attention should be given to postprocedunal anticoagulant therapy. Progression of intraluminal hyperplasia within a stent can be monitored angiographically because of the clearly visible outline of the metallic endoprosthesis. Neointimal coverage of the stent surface corresponding to less than 20% of the stent’s diameter was a normal finding. Excision of stenotic material inside implants with an athenectomy catheter showed neointimal hyperplasia [9, 10] similar to that seen after simple balloon dilatation [1 1 ]. Excessive growth of neointimal tissue has been reported in some patients with femoral stents [12, 1 3], so induction of neointimal growth by the stent cannot be excluded. With iliac stents, the prevalence of nestenosis due to intimal hyperplasia was notably lower than that reported in femoral arteries or hemodialysis shunts [1 2-i 7]. Moreover, in most cases nestenosis was found only at angiognaphy and was clinically insignificant. The follow-up period now extends to 3.5 years and, in most patients treated, stented iliac areas are completely patent and no stent-related late complications have been identified. Comparison with other types of stents, however, is still difficult because no larger series with cornparable data have been published, and the composition of patient subgroups is heterogeneous. Additional follow-up data therefore are required for a definitive assessment. Although the preliminary clinical experience with self-expandable stents, on stents in general [1 3, 1 6, 17], as an adjunct to balloon angioplasty in the iliac arteries is promising, the importance of a reasonable cost-benefit ratio should not be neglected. Placement of a stent is still a costly procedure, making PTA more expensive. A significant reduction of the rate of nestenosis has not been proved. Balloon angioplasty, therefore, still remains the gold standard of percutaneous treatment. Consequently, insertion of a stent should be limited to the selected subset of lesions that we described. Too liberal an approach should be avoided, because it may compromise the use of this advanced new technique by decreasing the use of balloon angioplasty, which has striking advantages as a safe, successful, and inexpensive procedure for most iliac lesions.
STENOSIS
393
ACKNOWLEDGMENTS The
authors
assistance
and
thank
Udo
Danielle
BuhI,
Aachen,
Venderickx,
Lausanne,
for the preparation
for editorial
of photographs.
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