Early Experience with the Palmaz Expandable Intraluminal Stent in Iliac Artery Stenosis Dolores F. Cikrit, MD, Gary J. Becket, MD, Michael C. Dalsing, MD, Karen O. Ehrman, MD, Stephen G. Lalka, MD, Alan P. Sawchuk, MD, Indianapolis, Indiana
Since 1987, we have used the Palmaz expandable intraluminal stent in 22 selected cases of lilac artery stenosis in 14 men and six women with a mean age of 63 years for claudication (9), graft salvage (5), rest pain (4), and tissue loss (2). Morphologic criteria included severe percutaneous balloon angioplasty-induced dissection (6), long or multiple stenoses or occlusions (5), post-percutaneous balloon angioplasty elastic recoil (4), location of stenosis (4), and restenosis following percutaneous balloon angioplasty (3). Twenty-two limbs were treated with 61 stents. The mean pressure gradient across the lesion fell from 31 __ 15 to 1.1 -+ 2.4 mmHg after stenting. The mean ankle/brachial systolic pressure index improved from 0.59 __ 0.31 to 0.83 __ 0.25 after stenting. The mean follow-up is 11.4 months, with a mean ankle/brachial index at their most recent follow-up of 0.88 _+ 0.19. Symptomatically, 11 extremities are normal and five limbs are improved. Three patients have died and two have required bypass grafts for lilac occlusive disease. In this early experience, the Palmaz intraluminal stent appears to be valuable for the management of post-percutaneous balloon angioplasty restenosis, elastic recoil, and percutaneous balloon angioplasty-induced dissection, although it is not without complications. (Ann Vasc Surg 1991 ;5:150-155). KEY WORDS: Palmaz expandable intraluminal stent; stent; lilac artery stenosis; percutaneous balloon angioplasty; elastic recoil.
Percutaneous balloon angioplasty (PTA) is an accepted means of treating selected cases of iliac artery stenosis [1-3]. It is most successful in the treatment of common iliac artery stenosis with short-term success rates ranging from 66% to 100% [4,5]. In two- to three-year follow-up, the success From the Departments of Surgery. and Radiology, Indiana University Medical Center, Indianapolis, lndiana. Presented at the Fifteenth Annual Meeting of Peripheral Vascular Surgical Society, June 2, 1990, Los Angeles, California. Reprint requests: Dolores F. Cikrit, MD, Department of Surgery, Indiana University Medical Center, 1001 West lOth Street, Indianapolis, Indiana 46202.
rate ranges from 70% to 92%, but in a five-year study of PTA the success rate was only 48% [3,6,7]. These less than optimal results are due to the limitations of PTA which include elastic recoil, restenosis in the early post-angioplasty period, acute occlusion secondary to PTA-induced dissection, and progression of atherosclerosis proximal or distal to the PTA site. Intraluminal stents have evolved as a complement to PTA. The concept of intraluminal stents originated in 1969 with Dotter, who used them in the popliteal artery in a canine model [8]. Stents failed to gain popularity until 1983 when the limitations of PTA became obvious and stents seemed a viable solution [9]. Since then intraluminal stents 150
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have been used experimentally in iliac, renal, coronary, femoral, and popliteal arteries, as well as in vena cava and arteriovenous dialysis shunts. Stents have evolved in two ways. One type involves the use of a self-expansion mechanism and was developed by Wallsten and Gianturco-Wallace [10,11]. The other type of stent is mechanically expanded by an angioplasty balloon. Such a stent, developed by Palmaz*, is the subject of this report [12]. Another type of balloon-expandable stent was developed by Strecker [13]. The Palmaz and Gianturco-Wallace stents are both rigid, while the Wallsten and Strecker stents are flexible. In 1987, we became involved in a Food and Drug Administration (FDA) approved multi-institution study of the Palmaz expandable intraluminal stent in the treatment of iliac artery stenosis. This is a report of our early experience with this treatment modality.
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Fig. 1. Upper illustration shows stainless Palmaz stent on balloon deployment catheter in stenotic vessel prior to expansion, Lower illustration shows stent expanded with balloon removed and stenosis resolved,
F r o m D e c e m b e r 1987 to February 1990, 14 men and six women patients have undergone stent placement for iliac artery stenosis at the indiana University Medical Center in Indianapolis. Patients ranged in age from 44 to 76 years with a mean age of 63 +8.4 years. Symptoms included worsening or disabling claudication in 11 patients, rest pain in seven patients, and tissue loss (either nonhealing ischemic ulcer or gangrenous lesion) in two patients. All patients had a smoking history. Thirteen patients had a history of hypertension and two were diabetics on oral hypoglycemics. Other associated diseases included cardiovascular disease (l 1), cerebral vascular disease (5), chronic pulmonary disease (5), and chronic renal failure (2). Some of the patients had had prior PTA (5) or bypass grafting (6). The bypass procedures included femorofemoral (3), femoropopliteal, or femorodistal bypass grafts (2), and, in one case, an aortoiliac endarterectomy. The five infrainguinal bypass grafts were in jeopardy due to hemodynamically-significant iliac disease. Morphologic criteria for stent placement in the 22 limbs included stenosis with PTA-induced dissection (6), elastic recoil after PTA (4), long or multiple areas of stenoses (4), an unfavorable stenosis location (4), restenosis following PTA (3), and complete occlusion (1). The mean ankle/brachial systolic pressure index (ABI) of limbs prior to treatment was 0.59 -+ 0.31. The mean pressure gradient across the stenotic segments was 31 -+ 15 mmHg with the lesion length averaging 3.2 - 2.8 cm. The percent stenosis ranged from 50 to 100% with a mean of 86%
and a mean stenotic diameter of 2.1 mm as measured by arteriographic determination. These stenotic lesions were calcified in nine instances. The status of the run-off vessels were widely patent in 12 limbs, and the superficial femoral artery was severely stenotic in four limbs and completely occluded in six limbs. The decision to offer the patient an intraluminal stent was made in conjunction with both a peripheral vascular surgeon and an interventional radiologist. The protocol for the placement of the Palmaz expandable intraluminal stent was approved by the Institutional Review Board at Indiana University Medical Center. All patients voluntarily consented to this experimental treatment method. The Palmaz balloon expandable intraluminal stents (BEIS) were provided by Johnson & Johnson Interventional Systems as an investigational balloon-assisted expansion stent. The stainless steel tube stent measures 3.1 mm in diameter by 30 mm in length with a wall thickness of 0.015 mm (Fig. 1). Prior to stent deployment, balloon angioplasty was performed with an appropriately sized balloon catheter as determined for each stenotic lesion. For deployment, the stent was mounted on an 8 mm • 3 cm PE Plus II balloon t. The stent/balloon assembly was advanced over a guidewire to the target site within a 9 French transfemoral 30 cm Teflon sheath. Once the assembly had reached the target site, the sheath was withdrawn and the stent was expanded into position by inflating the PTA balloon to the appropriate diameter. The expanded stent has a diameter of 8.12 mm (Fig. 1). The balloon was deflated and withdrawn with the stent remaining in position [14]. Multiple stents may be placed in an
* Manufactured by Johnson and Johnson Interventional Systems, Warren, NJ.
* Manufactured by C. R. Bard Inc., Billerica, MA.
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Fig. 2. Some patients require only one stent but often multiple stents are required as illustrated here. Ends of stents overlap slightly as noted near arrow.
iliac artery (Fig. 2). Stents can bridge branch orifices such as the internal iliac artery with these vessels still remaining patent. All but o n e stent placement was performed percutaneously through a femoral approach in the radiology suite after PTA. One was performed by femoral artery cutdown in the operating room.
RESULTS Twenty-two limbs in 20 patients were treated with 61 stents. Multiple stents were required in 14 patients. The maximal number of stents placed in any one iliac artery (combined common and external iliac) was seven (Fig. 2). Six patients required only one stent. Two patients required bilateral iliac stents. The location of the stents included the common iliac artery only in three patients, the external iliac artery only in eight, and both the common and external iliac arteries in 11 patients. At the time of stenting, the mean pressure gradient across the stenotic area decreased from 31 + 15 mmHg to 1.1 +- 2.4 mmHg. One day following stenting, the mean ABI improved from 0.59 _+ 0.31 pre-intervention to 0.83 + 0.25 post-intervention. At one month of follow-up, the mean ABI was 0.88 + 0.19. Despite the marked improvement in inflow as exemplified by the improved ABI, five patients still required additional PTA or surgery for infrainguinal disease for symptom relief. The mean long-term follow-up in the 16 surviving patients with functioning stents was 11.4 _+ 6.4
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months. At their most recent clinic visit, in the 17 limbs (16 patients) available for evaluation, 11 were symptomatically normal, two had a significant improvement in claudication symptoms, two had improved healing of ulcers, one limb with rest pain had improved to the point of claudication only, and one patient had persistence of symptoms which required an aortobifemoral bypass graft six months after stent placement. During the most recent clinic visit, the mean ABI was 0.88 _+ 0.19. Complications included one femoral arteriovenous fistula, one iliac artery perforation that necessitated an iliofemoral bypass graft, and two femoral thromboses which required thrombectomy. There was one periprocedural death which was secondary to a severe contrast reaction. In follow-up, two other patients died of myocardial infarction, one 23 days following stent placemeAt and the other three months following this intervention. One of these deaths was in a patient with bilateral stents. Follow-up pelvic films have demonstrated an absence of stent migration. Follow-up arteriograms have been done in seven patients as part of the six-month follow-up protocol. All arteriograms demonstrated the stent lumens to be widely patent. Three iliac arteriograms were normal while two arteriograms revealed a stenosis proximal to the stents and one arteriogram revealed a stenosis distal to the stents. In another arteriogram, a fusiform common iliac aneurysm appeared to be developing proximal to the stents. None of these areas of stenosis were significant enough to require intervention at six months. By 12 months, one patient required placement of an additional stent for progression of atherosclerotic disease in a nonstented portion of the vessel.
DISCUSSION Percutaneous balloon angioplasty has become an accepted means of treating selected cases of iliac stenosis. Johnston, in a study of nearly 1,000 PTA patients, reported an initial success rate of 89% based on combined objective findings and symptomatic results, which declined in five years to a success rate of only 48% [3]. The failures of PTA are usually the result of elastic recoil, acute occlusion secondary to PTA-induced dissection, restenosis in the early post-angioplasty period, and progression of atherosclerotic disease proximal or distal to the PTA site. Periprocedural restenosis usually results from elastic recoil. It most often occurs with eccentric lesions or in severely ulcerated lesions [15]. The inherent elasticity of the arterial wall causes some recoil, especially i n eccentric lesions where no angioplasty-induced fracture can occur in the
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plaque [14]. Elastic recoil was the indication for stent placement in tour of our patients, with resolution of symptoms in each case. Recoil was suggested by the reappearance of the lesion following deflation of the angioplasty balloon or by a residual pressure gradient across the lesion. Periprocedural restenosis may also result from PTA-induced dissection which may actually result in acute occlusion of the vessel. This has been noted to occur in 4-5% of coronary angioplasties and in nearly 5% of iliac angioplasties [16,17]. Six patients in our series received stents for severe PTA-induced dissection (Fig. 3). In this setting, several stents were often required to adequately tack the dissection to the vessel wall and reestablish a patent lumen (Fig. 2). It is imperative to maintain a guidewire across the dissection during the angioplasty procedure to secure access to the vessel's true lumen when stenting is considered for this problem [7]. These patients had lost blood flow to their legs as a result of the dissection and would probably have required surgery if the stents had not been available. Stents may be especially useful in controlling such PTA-induced dissections [14]. In approximately one-third of angioplasties performed in medium and small arteries early restenosis occurs, usually in a 6- to 12-month period of time. These PTA failures may involve the formation of thrombus on the irregularly cracked atheromatous surface after angioplasty. This may then be replaced by smooth muscle and fibrous tissue causing early restenosis from fibrocellular proliferation or atherosclerosis [14]. Stents were placed in three patients for restenosis occurring at least six months after PTA. The stent may decrease problems with restenosis by Ibrming a relatively smooth surface which prevents the events which result in restenosis [14]. Johnston, in his analysis of nearly 1,000 patients treated with PTA, showed that common iliac PTA had superior results compared to an external iliac PTA. Furthermore, the results were better when a single site was dilated rather than multiple areas. He also suggested that arterial stenoses were dilated more successfully than total occlusions [3]. Nine of our patients fell into diagnostic categories predicted to have a less successthl result. Four patients received stents because of the location of their stenosis, while four others received stents for the treatment of multiple or very long stenoses and one of a complete occlusion. Eight patients were significantly improved following stent placement while the patient with a complete occlusion required an iliofemoral bypass graft. This was necessitated by vessel perforation during deployment of his second stent. Gunther found stents to be most helpful in maintaining patency in iliac artery occlusions [15]. However, occlusions are probably the most technically
153
Fig. 3. (a) Immediately following PTA, left lilac artery developed a severe dissection that acutely occluded blood flow. Maintenance of wire through dissection allowed placement of intraluminal stents and tacking of dissection back to vessel wall lumen. Arrow shows area of dissection. (b) Following stent placement for treatment of dissection illustrated in (a), a widely patent lumen has been reestablished, avoiding an emergency operation.
difficult to treat with angioplasty and stenting since the true lumen may be difficult to find [18]. One-half of our patients required an additional PTA or operation despite stent placement. One operation was required because of failure of the stents to relieve the patient's symptoms adequately. Three surgical procedures were necessary because of stent complications and included one iliofemoral bypass graft for perforation and two femoral thrombectomies for occlusions. The remaining six procedures were performed to treat progressive disease. This included two PTAs of the superficial femoral artery and inffainguinal bypass grafts in four cases.
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Even as early as six months, post-stenting arteriograms revealed progression of atherosclerotic disease in nonstented iliac segments. This was simply a reflection of the natural history of aortoiliac occlusion. Complications occurred in 20% of our patients, a higher complication rate than the 5-10% reported for PTA alone [2,3]. Three complications (two femoral thromboses and one femoral arteriovenous fistula) may have been related to the large-sized sheath (9 French) that is used for stent deployment. One patient died in the periprocedural period of a severe contrast reaction, and even with simple PTA this may have occurred. The other two deaths, both the result of myocardial infarction, served to emphasize the severe vascular disease these patients have in both peripheral vascular and cardiovascular locations. Aside from complications associated with deployment, intraluminal stents are foreign bodies introduced in the arterial system. Infection, thrombosis, embolization, perforation, and aneurysm and pseudoaneurysm formation can all occur. Aneurysms, severe aortic occlusive disease, and hypercoagulable states represent the major contraindications to stent insertion [6]. Stents, although stainless steel in composition, are thrombogenic and may thrombose acutely as a result of poor run-off, hypercoagulable states, and poor inflow either from severe aortic occlusive disease or from an iliac stenosis proximal to the stents [14,15]. One patient, one year following initial stent placement, required an additional stent to correct a new stenosis that was developing proximal to his other stents to prevent potential thrombosis. The thrombogenic potential of stents may improve with time as the stent becomes covered by endothelial cells. In animal models, endothelial coverage of the stents appears to occur quite rapidly and may be related to the fact that the stent material actually covers less than 20% of the luminal surface when deployed appropriately. In long-term evaluations of the rabbit aorta, Palmaz demonstrated complete endothelial coverage in three weeks [12]. Sigwart [19] has suggested that endothelial coverage may be related to stent thickness since he demonstrated endothelial coverage in three weeks on stents that were only 0.09 mm thick, while Wright [11], using a stent that was 0.46 mm thick had only 30% endothelial coverage by one month. The Palmaz stent is 0.015 mm thick. Endothelialization has not yet been clearly demonstrated in humans, but if it does occur, it should decrease the thrombogenic potential of stents and improve their patency. Another long-term potential complication of stents may be the development of intimal hyperplasia. Gunther showed severe intimal hyperplasia in the superficial femoral artery in three patients fol-
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lowing the use of the Wallsten stent [15]. The Palmaz stent does not appear to induce fibromuscular hyperplasia in animal specimens although in atherosclerotic rabbit aorta the neointima covering the stents tripled in size in 24 weeks. Palmaz thinks that this does not indicate proliferation but rather an attempt to model the lumen by filling the depressions produced by the stent bars. Only slight hyperplasia has been noted in isolated cases using the Palmaz stent. No luminal narrowing was noted in these specimens [12]. In our arteriograms done six months after stenting, no luminal narrowing was noted in the area of the stents either.
CONCLUSION This early experience with the Palmaz expandable intraluminal stent suggests that stenting is valuable for the management of post-PTA restenosis, elastic recoil, and PTA-induced dissection. Like any procedure, it is not without complications or mortality, but this risk must be viewed in relation to the benefits gained. Finally, long-term follow-up is required for any analysis of this technique's worth.
REFERENCES 1. BOROZAN PG, SCHULER JJ, SPIGOS DG, et al. Longterm hemodynamic evaluation of lower extremity percutaneous transluminal angioplasty. J Vasc Surg 1985;2:785-793. 2. NEIMAN HL, BERGAN JJ, YAO JST, et al. Hemodynamic assessment of transluminal angioplasty for lower extremity ischemia. Radiology 1982;143:63%643. 3. JOHNSTON KW, RAE M, HOGG-JOHNSTON SA, et al. Five year results of a prospective study of percutaneous transluminal angioplasty. Ann Surg 1987;206:403-413. 4. GUNN IG, COWIE TN, FORREST H, et al. Haemodynamic assessment following iliac dilatation. Br J Surg 1981; 68:858-860. 5. MOTARJEME A, KEIFER JW, ZUSKA AJ. Percutaneous transluminal angioplasty of the iliac arteries: 66 experiences.
AJR 1980;135:937-944. 6. JOHNSTON KW, COLAPINTO RF, BAIRD RJ. Transluminal dilation--an alternative? Arch Surg 1982;117:16041610. 7. WALTMAN AC, GREENFIELD AJ, NOVELLINE RA, et al. Transluminal angioplasty of the iliac and femoropopliteal arteries. Current status. Arch Surg 1982;117:1218-1221. 8. DOTTER C. Transluminally placed coil-spring endoarterial tube grafts: long-term patency in canine popliteal artery. Invest Radiol 1969;4:329-332. 9. DOTTER CT, BUSCHMANN RW, MC KINNEY MK, et al. Transluminally expandable Nitinol coil stent grafting: preliminary report. Radiology 1983;147:259-260. 10. ROUSSEAU H, PUEL J, JOFFRE F, et al. Self-expanding endovascular prosthesis: an experimental study. Radiology
1987;164:70%714. 11. WRIGHT KC. WALLACE S, CHARNSANGAVE C, et al. Percutaneous endovascular stents: an experimental evaluation. Radiology 1985;156:69-72. 12. PALMAZ JC, WINDELER SA, GARCIA F, et al. Athero-
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sclerotic rabbit aortas: expandable intraluminal grafting.
Radiology 1986;160:723-726. 13. S T R E C K E R EP, B E R G G, S C H N E I D E R B, et al. A new vascular balloon-expandable prosthesis: experimental studies and first clinical results. J Intervent Radiol 1988:3:59-62. 14. P A L M A Z JC, R I C H T E R GM, N O E L D G E G, et al. Intraluminal stents in atherosclerotic lilac artery stenosis: preliminary report of a multicenter study. Radiology 1988:168:727731. 15. G U N T H E R RW, V O R W E R K D, B O H N D O R F K, et al. Iliac and femoral artery s t e n o s e s and occlusions; treatment with intravascular stents. Radiology 1989;172:725-730. 16. B E C K E R GJ, C I K R I T DF, B E N E N A T I JF, et al. Early
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experience with the Palmaz stent in h u m a n iliac angioplasty. lnd Med 1989:286-292. 17. B E C K E R G J, P A L M A Z JC, R E E S CR, et al. Palmaz balloon expandable intraluminal stents in the m a n a g e m e n t of angioplasty-induced dissections in h u m a n iliac arteries. J Vase Surg 1990; in pressl 18. R E E S CR, P A L M A Z JC, G A R C I A O, et al. Angioplasty and stenting of completely occluded iliac arteries. Radiology
1989:172:953-959. 19. S1GWART U, P U L L J, M I R K O V I T C H V, et al. lntravascular stents to prevent occlusion and restenosis after transluminal angioplasty. N Engl J Med 1987;316:701-706.
Since 1987, we have used the Palmaz expandable intraluminal stent in 22 selected cases of lilac artery stenosis in 14 men and six women with a mean age of 63 years for claudication (9), graft salvage (5), rest pain (4), and tissue loss (2). Morphologic criteria included severe percutaneous balloon angioplasty-induced dissection (6), long or multiple stenoses or occlusions (5), post-percutaneous balloon angioplasty elastic recoil (4), location of stenosis (4), and restenosis following percutaneous balloon angioplasty (3). Twenty-two limbs were treated with 61 stents. The mean pressure gradient across the lesion fell from 31 __ 15 to 1.1 -+ 2.4 mmHg after stenting. The mean ankle/brachial systolic pressure index improved from 0.59 __ 0.31 to 0.83 __ 0.25 after stenting. The mean follow-up is 11.4 months, with a mean ankle/brachial index at their most recent follow-up of 0.88 _+ 0.19. Symptomatically, 11 extremities are normal and five limbs are improved. Three patients have died and two have required bypass grafts for lilac occlusive disease. In this early experience, the Palmaz intraluminal stent appears to be valuable for the management of post-percutaneous balloon angioplasty restenosis, elastic recoil, and percutaneous balloon angioplasty-induced dissection, although it is not without complications. (Ann Vasc Surg 1991 ;5:150-155). KEY WORDS: Palmaz expandable intraluminal stent; stent; lilac artery stenosis; percutaneous balloon angioplasty; elastic recoil.
Percutaneous balloon angioplasty (PTA) is an accepted means of treating selected cases of iliac artery stenosis [1-3]. It is most successful in the treatment of common iliac artery stenosis with short-term success rates ranging from 66% to 100% [4,5]. In two- to three-year follow-up, the success From the Departments of Surgery. and Radiology, Indiana University Medical Center, Indianapolis, lndiana. Presented at the Fifteenth Annual Meeting of Peripheral Vascular Surgical Society, June 2, 1990, Los Angeles, California. Reprint requests: Dolores F. Cikrit, MD, Department of Surgery, Indiana University Medical Center, 1001 West lOth Street, Indianapolis, Indiana 46202.
rate ranges from 70% to 92%, but in a five-year study of PTA the success rate was only 48% [3,6,7]. These less than optimal results are due to the limitations of PTA which include elastic recoil, restenosis in the early post-angioplasty period, acute occlusion secondary to PTA-induced dissection, and progression of atherosclerosis proximal or distal to the PTA site. Intraluminal stents have evolved as a complement to PTA. The concept of intraluminal stents originated in 1969 with Dotter, who used them in the popliteal artery in a canine model [8]. Stents failed to gain popularity until 1983 when the limitations of PTA became obvious and stents seemed a viable solution [9]. Since then intraluminal stents 150
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have been used experimentally in iliac, renal, coronary, femoral, and popliteal arteries, as well as in vena cava and arteriovenous dialysis shunts. Stents have evolved in two ways. One type involves the use of a self-expansion mechanism and was developed by Wallsten and Gianturco-Wallace [10,11]. The other type of stent is mechanically expanded by an angioplasty balloon. Such a stent, developed by Palmaz*, is the subject of this report [12]. Another type of balloon-expandable stent was developed by Strecker [13]. The Palmaz and Gianturco-Wallace stents are both rigid, while the Wallsten and Strecker stents are flexible. In 1987, we became involved in a Food and Drug Administration (FDA) approved multi-institution study of the Palmaz expandable intraluminal stent in the treatment of iliac artery stenosis. This is a report of our early experience with this treatment modality.
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Fig. 1. Upper illustration shows stainless Palmaz stent on balloon deployment catheter in stenotic vessel prior to expansion, Lower illustration shows stent expanded with balloon removed and stenosis resolved,
F r o m D e c e m b e r 1987 to February 1990, 14 men and six women patients have undergone stent placement for iliac artery stenosis at the indiana University Medical Center in Indianapolis. Patients ranged in age from 44 to 76 years with a mean age of 63 +8.4 years. Symptoms included worsening or disabling claudication in 11 patients, rest pain in seven patients, and tissue loss (either nonhealing ischemic ulcer or gangrenous lesion) in two patients. All patients had a smoking history. Thirteen patients had a history of hypertension and two were diabetics on oral hypoglycemics. Other associated diseases included cardiovascular disease (l 1), cerebral vascular disease (5), chronic pulmonary disease (5), and chronic renal failure (2). Some of the patients had had prior PTA (5) or bypass grafting (6). The bypass procedures included femorofemoral (3), femoropopliteal, or femorodistal bypass grafts (2), and, in one case, an aortoiliac endarterectomy. The five infrainguinal bypass grafts were in jeopardy due to hemodynamically-significant iliac disease. Morphologic criteria for stent placement in the 22 limbs included stenosis with PTA-induced dissection (6), elastic recoil after PTA (4), long or multiple areas of stenoses (4), an unfavorable stenosis location (4), restenosis following PTA (3), and complete occlusion (1). The mean ankle/brachial systolic pressure index (ABI) of limbs prior to treatment was 0.59 -+ 0.31. The mean pressure gradient across the stenotic segments was 31 -+ 15 mmHg with the lesion length averaging 3.2 - 2.8 cm. The percent stenosis ranged from 50 to 100% with a mean of 86%
and a mean stenotic diameter of 2.1 mm as measured by arteriographic determination. These stenotic lesions were calcified in nine instances. The status of the run-off vessels were widely patent in 12 limbs, and the superficial femoral artery was severely stenotic in four limbs and completely occluded in six limbs. The decision to offer the patient an intraluminal stent was made in conjunction with both a peripheral vascular surgeon and an interventional radiologist. The protocol for the placement of the Palmaz expandable intraluminal stent was approved by the Institutional Review Board at Indiana University Medical Center. All patients voluntarily consented to this experimental treatment method. The Palmaz balloon expandable intraluminal stents (BEIS) were provided by Johnson & Johnson Interventional Systems as an investigational balloon-assisted expansion stent. The stainless steel tube stent measures 3.1 mm in diameter by 30 mm in length with a wall thickness of 0.015 mm (Fig. 1). Prior to stent deployment, balloon angioplasty was performed with an appropriately sized balloon catheter as determined for each stenotic lesion. For deployment, the stent was mounted on an 8 mm • 3 cm PE Plus II balloon t. The stent/balloon assembly was advanced over a guidewire to the target site within a 9 French transfemoral 30 cm Teflon sheath. Once the assembly had reached the target site, the sheath was withdrawn and the stent was expanded into position by inflating the PTA balloon to the appropriate diameter. The expanded stent has a diameter of 8.12 mm (Fig. 1). The balloon was deflated and withdrawn with the stent remaining in position [14]. Multiple stents may be placed in an
* Manufactured by Johnson and Johnson Interventional Systems, Warren, NJ.
* Manufactured by C. R. Bard Inc., Billerica, MA.
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Fig. 2. Some patients require only one stent but often multiple stents are required as illustrated here. Ends of stents overlap slightly as noted near arrow.
iliac artery (Fig. 2). Stents can bridge branch orifices such as the internal iliac artery with these vessels still remaining patent. All but o n e stent placement was performed percutaneously through a femoral approach in the radiology suite after PTA. One was performed by femoral artery cutdown in the operating room.
RESULTS Twenty-two limbs in 20 patients were treated with 61 stents. Multiple stents were required in 14 patients. The maximal number of stents placed in any one iliac artery (combined common and external iliac) was seven (Fig. 2). Six patients required only one stent. Two patients required bilateral iliac stents. The location of the stents included the common iliac artery only in three patients, the external iliac artery only in eight, and both the common and external iliac arteries in 11 patients. At the time of stenting, the mean pressure gradient across the stenotic area decreased from 31 + 15 mmHg to 1.1 +- 2.4 mmHg. One day following stenting, the mean ABI improved from 0.59 _+ 0.31 pre-intervention to 0.83 + 0.25 post-intervention. At one month of follow-up, the mean ABI was 0.88 + 0.19. Despite the marked improvement in inflow as exemplified by the improved ABI, five patients still required additional PTA or surgery for infrainguinal disease for symptom relief. The mean long-term follow-up in the 16 surviving patients with functioning stents was 11.4 _+ 6.4
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months. At their most recent clinic visit, in the 17 limbs (16 patients) available for evaluation, 11 were symptomatically normal, two had a significant improvement in claudication symptoms, two had improved healing of ulcers, one limb with rest pain had improved to the point of claudication only, and one patient had persistence of symptoms which required an aortobifemoral bypass graft six months after stent placement. During the most recent clinic visit, the mean ABI was 0.88 _+ 0.19. Complications included one femoral arteriovenous fistula, one iliac artery perforation that necessitated an iliofemoral bypass graft, and two femoral thromboses which required thrombectomy. There was one periprocedural death which was secondary to a severe contrast reaction. In follow-up, two other patients died of myocardial infarction, one 23 days following stent placemeAt and the other three months following this intervention. One of these deaths was in a patient with bilateral stents. Follow-up pelvic films have demonstrated an absence of stent migration. Follow-up arteriograms have been done in seven patients as part of the six-month follow-up protocol. All arteriograms demonstrated the stent lumens to be widely patent. Three iliac arteriograms were normal while two arteriograms revealed a stenosis proximal to the stents and one arteriogram revealed a stenosis distal to the stents. In another arteriogram, a fusiform common iliac aneurysm appeared to be developing proximal to the stents. None of these areas of stenosis were significant enough to require intervention at six months. By 12 months, one patient required placement of an additional stent for progression of atherosclerotic disease in a nonstented portion of the vessel.
DISCUSSION Percutaneous balloon angioplasty has become an accepted means of treating selected cases of iliac stenosis. Johnston, in a study of nearly 1,000 PTA patients, reported an initial success rate of 89% based on combined objective findings and symptomatic results, which declined in five years to a success rate of only 48% [3]. The failures of PTA are usually the result of elastic recoil, acute occlusion secondary to PTA-induced dissection, restenosis in the early post-angioplasty period, and progression of atherosclerotic disease proximal or distal to the PTA site. Periprocedural restenosis usually results from elastic recoil. It most often occurs with eccentric lesions or in severely ulcerated lesions [15]. The inherent elasticity of the arterial wall causes some recoil, especially i n eccentric lesions where no angioplasty-induced fracture can occur in the
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plaque [14]. Elastic recoil was the indication for stent placement in tour of our patients, with resolution of symptoms in each case. Recoil was suggested by the reappearance of the lesion following deflation of the angioplasty balloon or by a residual pressure gradient across the lesion. Periprocedural restenosis may also result from PTA-induced dissection which may actually result in acute occlusion of the vessel. This has been noted to occur in 4-5% of coronary angioplasties and in nearly 5% of iliac angioplasties [16,17]. Six patients in our series received stents for severe PTA-induced dissection (Fig. 3). In this setting, several stents were often required to adequately tack the dissection to the vessel wall and reestablish a patent lumen (Fig. 2). It is imperative to maintain a guidewire across the dissection during the angioplasty procedure to secure access to the vessel's true lumen when stenting is considered for this problem [7]. These patients had lost blood flow to their legs as a result of the dissection and would probably have required surgery if the stents had not been available. Stents may be especially useful in controlling such PTA-induced dissections [14]. In approximately one-third of angioplasties performed in medium and small arteries early restenosis occurs, usually in a 6- to 12-month period of time. These PTA failures may involve the formation of thrombus on the irregularly cracked atheromatous surface after angioplasty. This may then be replaced by smooth muscle and fibrous tissue causing early restenosis from fibrocellular proliferation or atherosclerosis [14]. Stents were placed in three patients for restenosis occurring at least six months after PTA. The stent may decrease problems with restenosis by Ibrming a relatively smooth surface which prevents the events which result in restenosis [14]. Johnston, in his analysis of nearly 1,000 patients treated with PTA, showed that common iliac PTA had superior results compared to an external iliac PTA. Furthermore, the results were better when a single site was dilated rather than multiple areas. He also suggested that arterial stenoses were dilated more successfully than total occlusions [3]. Nine of our patients fell into diagnostic categories predicted to have a less successthl result. Four patients received stents because of the location of their stenosis, while four others received stents for the treatment of multiple or very long stenoses and one of a complete occlusion. Eight patients were significantly improved following stent placement while the patient with a complete occlusion required an iliofemoral bypass graft. This was necessitated by vessel perforation during deployment of his second stent. Gunther found stents to be most helpful in maintaining patency in iliac artery occlusions [15]. However, occlusions are probably the most technically
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Fig. 3. (a) Immediately following PTA, left lilac artery developed a severe dissection that acutely occluded blood flow. Maintenance of wire through dissection allowed placement of intraluminal stents and tacking of dissection back to vessel wall lumen. Arrow shows area of dissection. (b) Following stent placement for treatment of dissection illustrated in (a), a widely patent lumen has been reestablished, avoiding an emergency operation.
difficult to treat with angioplasty and stenting since the true lumen may be difficult to find [18]. One-half of our patients required an additional PTA or operation despite stent placement. One operation was required because of failure of the stents to relieve the patient's symptoms adequately. Three surgical procedures were necessary because of stent complications and included one iliofemoral bypass graft for perforation and two femoral thrombectomies for occlusions. The remaining six procedures were performed to treat progressive disease. This included two PTAs of the superficial femoral artery and inffainguinal bypass grafts in four cases.
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Even as early as six months, post-stenting arteriograms revealed progression of atherosclerotic disease in nonstented iliac segments. This was simply a reflection of the natural history of aortoiliac occlusion. Complications occurred in 20% of our patients, a higher complication rate than the 5-10% reported for PTA alone [2,3]. Three complications (two femoral thromboses and one femoral arteriovenous fistula) may have been related to the large-sized sheath (9 French) that is used for stent deployment. One patient died in the periprocedural period of a severe contrast reaction, and even with simple PTA this may have occurred. The other two deaths, both the result of myocardial infarction, served to emphasize the severe vascular disease these patients have in both peripheral vascular and cardiovascular locations. Aside from complications associated with deployment, intraluminal stents are foreign bodies introduced in the arterial system. Infection, thrombosis, embolization, perforation, and aneurysm and pseudoaneurysm formation can all occur. Aneurysms, severe aortic occlusive disease, and hypercoagulable states represent the major contraindications to stent insertion [6]. Stents, although stainless steel in composition, are thrombogenic and may thrombose acutely as a result of poor run-off, hypercoagulable states, and poor inflow either from severe aortic occlusive disease or from an iliac stenosis proximal to the stents [14,15]. One patient, one year following initial stent placement, required an additional stent to correct a new stenosis that was developing proximal to his other stents to prevent potential thrombosis. The thrombogenic potential of stents may improve with time as the stent becomes covered by endothelial cells. In animal models, endothelial coverage of the stents appears to occur quite rapidly and may be related to the fact that the stent material actually covers less than 20% of the luminal surface when deployed appropriately. In long-term evaluations of the rabbit aorta, Palmaz demonstrated complete endothelial coverage in three weeks [12]. Sigwart [19] has suggested that endothelial coverage may be related to stent thickness since he demonstrated endothelial coverage in three weeks on stents that were only 0.09 mm thick, while Wright [11], using a stent that was 0.46 mm thick had only 30% endothelial coverage by one month. The Palmaz stent is 0.015 mm thick. Endothelialization has not yet been clearly demonstrated in humans, but if it does occur, it should decrease the thrombogenic potential of stents and improve their patency. Another long-term potential complication of stents may be the development of intimal hyperplasia. Gunther showed severe intimal hyperplasia in the superficial femoral artery in three patients fol-
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lowing the use of the Wallsten stent [15]. The Palmaz stent does not appear to induce fibromuscular hyperplasia in animal specimens although in atherosclerotic rabbit aorta the neointima covering the stents tripled in size in 24 weeks. Palmaz thinks that this does not indicate proliferation but rather an attempt to model the lumen by filling the depressions produced by the stent bars. Only slight hyperplasia has been noted in isolated cases using the Palmaz stent. No luminal narrowing was noted in these specimens [12]. In our arteriograms done six months after stenting, no luminal narrowing was noted in the area of the stents either.
CONCLUSION This early experience with the Palmaz expandable intraluminal stent suggests that stenting is valuable for the management of post-PTA restenosis, elastic recoil, and PTA-induced dissection. Like any procedure, it is not without complications or mortality, but this risk must be viewed in relation to the benefits gained. Finally, long-term follow-up is required for any analysis of this technique's worth.
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1987;164:70%714. 11. WRIGHT KC. WALLACE S, CHARNSANGAVE C, et al. Percutaneous endovascular stents: an experimental evaluation. Radiology 1985;156:69-72. 12. PALMAZ JC, WINDELER SA, GARCIA F, et al. Athero-
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sclerotic rabbit aortas: expandable intraluminal grafting.
Radiology 1986;160:723-726. 13. S T R E C K E R EP, B E R G G, S C H N E I D E R B, et al. A new vascular balloon-expandable prosthesis: experimental studies and first clinical results. J Intervent Radiol 1988:3:59-62. 14. P A L M A Z JC, R I C H T E R GM, N O E L D G E G, et al. Intraluminal stents in atherosclerotic lilac artery stenosis: preliminary report of a multicenter study. Radiology 1988:168:727731. 15. G U N T H E R RW, V O R W E R K D, B O H N D O R F K, et al. Iliac and femoral artery s t e n o s e s and occlusions; treatment with intravascular stents. Radiology 1989;172:725-730. 16. B E C K E R GJ, C I K R I T DF, B E N E N A T I JF, et al. Early
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experience with the Palmaz stent in h u m a n iliac angioplasty. lnd Med 1989:286-292. 17. B E C K E R G J, P A L M A Z JC, R E E S CR, et al. Palmaz balloon expandable intraluminal stents in the m a n a g e m e n t of angioplasty-induced dissections in h u m a n iliac arteries. J Vase Surg 1990; in pressl 18. R E E S CR, P A L M A Z JC, G A R C I A O, et al. Angioplasty and stenting of completely occluded iliac arteries. Radiology
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