国产硅酮覆膜支架血液相容性的实验研究

目的评价国产硅酮覆膜支架在犬髂动脉内的血液相容性。方法实验犬9只。18条正常髂动脉,先行大球囊经皮腔内血管成形术(PTA)术后置人支架,继而置人硅酮覆膜支架10枚和镍钛合金编织型裸支架8枚(对照组)。术后第1、4、12周,两组分别抽取一定数量支架段血管行DSA观察通畅率和支架内再狭窄程度;其后处死动物,取出支架段血管,作苏木精-伊红染色及组织学检查,并对两组支架急性血栓形成情况、支架的内膜覆盖和新生内膜增生程度等作出评价。结果术后第1、4、12周DSA所见：①裸支架组各段时间造影均显示通畅,12周时支架段血管狭窄平均为36．7％;②硅酮膜支架组有2支血管闭塞(通畅率为80％),12周时支架段血管狭窄平均为72．3％。结论本组实验用国产硅酮膜支架的血液相容性不优于裸支架。     

Assessment of a Polyester-Covered Nitinol Stent in the Canine Aorta and Iliac Arteries

Purpose: To evaluate the patency and healing characteristics of a woven polyester fabric-covered stent in the canine model. Methods: Twenty-four self-expanding covered stents were placed in the infrarenal aorta and bilateral common iliac arteries of eight dogs and evaluated at 1 (n = 2), 3 (n = 2), and 6 (n = 4) months. Stent assessment was done using angiography prior to euthanasia, and light and scanning electron microscopy. Results: Angiographically, just prior to euthanasia, 8 of 8 aortic and 14 of 16 iliac endovascular covered stents were patent. Histologically, the stented regions showed complete endothelialization 6 months after graft implantation. A neointima had formed inside the stented vessel regions resulting in complete encasement of the fabric-covered stent by 3 months after graft implantation. Medial compression with smooth muscle cell atrophy was present in all stented regions. Explanted stent wires, examined by scanning electron microscopy, showed pitting but no cracks or breakage. Conclusion: The covered stent demonstrated predictable healing and is effective in preventing stenosis in vessels 10.0 mm or greater in diameter but does not completely preclude stenosis in vessels 6.0 mm or less in diameter.     

An Experimental Study of Endovascular Stenting with Special Reference to the Effects on the Aortic Vasa Vasorum

Purpose: To evaluate the effects of bare stents and covered stents on the aortic wall, especially the vasa vasorum. Methods: Eight bare stents and nine covered stents were placed in the infrarenal aorta of nine dogs. The dogs were euthanized at 4–45 weeks after stent placement. The vasa vasorum was evaluated by microstereoscopy with vascular casting, and the histopathology of the aortic wall was examined by light microscopy. Results: In the unstented normal aorta, vasa vasorum nourished the adventitia and the outer media, and the intima and inner media were avascular. In the stented segment, vascular dilatation and proliferation of vasa vasorum, medial atrophy, and intimal hyperplasia were observed, more prominent for covered stents than for bare stents. Conclusion: Intravascular stent placement caused not only medial atrophy and intimal hyperplasia but also proliferation of the vasa vasorum, probably due to hypoxia in the aortic wall. Received: 0/00/00/Accepted: 0/00/00     

Single and tandem stents in sheep iliac arteries: Is there a difference in patency?

Purpose: To compare patency and neointima formation of single and tandem arterial stents. Methods: In each of six sheep, two Memotherm nitinol stents (tandem stents) were inserted into the external iliac artery on one side and a single stent into the artery on the opposite side. The size of the iliac lumen was assessed in the proximal, middle, and distal segments of the stents by intravascular ultrasound (IVUS) before, immediately after, and 1 month after implantation when the sheep were killed. Neointimal thickness was determined in the proximal, middle, and distal segments of each stent by light microscopy. Results: All stents remained patent. There was no significant difference in lumen and neointimal thickness between single and tandem stents. Cranial tandem stents showed a significantly wider lumen and smaller neointimal thickness than caudal tandem stents. In the proximal and distal segments, the lumen of the stents was significantly smaller and the neointimal thickness greater than in the middle segment; differences in neointimal thickness were significant only between the proximal and the middle segment. Conclusion: In an experimental setting, tandem stents did not interfere with one another with regard to patency and neointima formation when compared with a single contralateral stent. Neointimal thickening after stent insertion seems to be inversely related to the original arterial diameter.     

Determination of stent stenosis: An in vivo experimental comparison of intravascular ultrasound and angiography with histology

Purpose: To compare intravascular ultrasound (IVUS) and angiography with histology in determining the degree of stent stenosis in an in vivo experiment. Methods: In 16 sheep, a total of 64 stents were implanted into the external iliac arteries. Two stents were inserted on either side. Patency was followed by angiography and IVUS. Four types of stent were used: two Dacron-covered (Cragg Endopro and heparinized Cragg Endopro) and two non-covered (Cragg and Memotherm stents). Eight animals were killed after 1 month, eight others after 6 months. Histological sections were prepared from the stented vessels. Measurements of the patent and total stent diameters determined by IVUS, angiography, and histology were compared. Results: Correlation between IVUS and angiography was 0.75, between IVUS and histology 0.77, and between angiography and histology 0.85. A mean stent stenosis of 17 ± 11% (range 0–51%) was found on angiography, of 10 ± 11% (0–46%) on IVUS, and of 20 ± 11% (4%–49%) on histology. In comparison with histology, IVUS underestimated the degree of stenosis by 10 ± 8%, and angiography underestimated it by 3 ± 6%. Resolution of IVUS was calculated to be about 0.35 mm and that of angiography to be about 0.15 mm. Conclusion: Under experimental conditions, IVUS was not superior to angiography in determining the degree of stent stenosis in long-segment stenoses of iliac artery stents, when measurements were correlated with histology. Angiography is sufficient for following the patency of iliac artery stents.     

Primary stenting for complex atherosclerotic plaques in aortic and iliac stenoses

Purpose: To evaluate the efficacy of primary stenting for complex atherosclerotic plaques in aortic and iliac stenoses that are not amenable to balloon angioplasty alone. Methods: Nineteen patients with complex atherosclerotic plaques were treated with a Palmaz stent (n= 19), Wallstent (n= 1), Strecker stent (n= 1), or Memotherm stent (n= 1). A total of 22 stenoses presenting with complex plaque morphology including ulcerated plaques, ulcerated plaques with focal aneurysms, plaques with heavy calcification, severely eccentric plaques, plaques with overhanging edge, and plaques with spontaneous dissection were stented. The lesions were in the aorta (n= 1), common iliac artery (n= 19), or external iliac artery (n= 2). Results: Immediate angiography after stent placement revealed restoration of patency of the stented segment. Focal aneurysms and ulcerated areas were occluded in the follow-up angiographies obtained 4–12 weeks after the procedure. In one case with poor distal runoff and multiple complex lesions of the iliac artery, subacute occlusion occurred. Clinical and angiographic follow-up (3–46 months) revealed patency of all other stented segments. Conclusion: Primary stenting is an effective and reliable approach for complex plaques in stenoses. Patency of the arterial segment with a smooth lumen can be created without the risk of acute complications such as distal embolization, dissection, or occlusion.     

Hemodynamics and wall mechanics after stent placement in swine iliac arteries: comparative results from six stent designs.

PURPOSE: To compare the hemodynamics and wall mechanics of swine iliac arteries after placement of six types of stent. MATERIALS AND METHODS: Stents were placed in the iliac artery of 18 pigs (three pigs each underwent placement with one of six types of stent); 16 untreated pigs served as control animals. Iliac arterial hemodynamics and wall mechanics were measured 4 days after placement. RESULTS: Four stents (Palmaz-Schatz, Cordis, Warren, NJ; and Strecker, Cragg, and Symphony, Boston Scientific/Vascular, Natick, Mass) caused decreased pulsatile flow rate in the treated and contralateral iliac arteries; one (Memotherm; Bard, Covington, Ga) caused increased flow pulsatility; and one (Wallstent; Schneider, Plymouth, Minn) had no effect. No compliance mismatching was noted for the Cragg, Symphony, and Memotherm stents, whereas a decrease in compliance was noted for the Palmaz-Schatz, Strecker, and Wallstent designs. The Palmaz-Schatz and Strecker stents caused increased arterial wall rigidity, the Symphony and Wallstent designs had no effect, and the Memotherm and Cragg stents caused decreased wall rigidity. Stents made of stiff metal yielded different early results than did stents made of the less rigid nitinol. CONCLUSION: Soon after implantation, the six stent designs elicited varying changes in blood flow, arterial compliance, and arterial wall mechanics. Contralateral arterial flow also was affected.     

Nonbiodegradable Expanded Polytetrafluoroethylene-Covered Stent Implantation in Porcine Peripheral Arteries: Histologic Evaluation of Vascular Wall Response Compared with Uncoated Stents

Purpose: To test the vascular wall response to an expanded polytetrafluoroethylene-covered stent, compared with conventional stenting, up to 6 months after deployment in the vascular district of a swine model. Methods: Fourteen minipigs underwent implantation of expanded polytetrafluoroethylene-covered stents (CS) and bare stents (BS) in five peripheral arteries. Animals were killed at different time points (from 1 to 180 days). Histopathologic assessment by morphologic and morphometric analysis and by scanning electron microscopy (SEM) were used to assess the incorporation characteristics and re-endothelialization extent of the two types of stents. Results: A total of 70 stents (14 CS and 14 BS in the renal arteries; 28 CS in the iliac arteries, and 14 CS in the aorta) were implanted. Microscopic examination confirmed the absence of occlusive thrombi in both the CS and BS groups. Microthrombi were observed in 10 of 13 CS (77% of cases) and in four of four BS (100% of cases, p < 0.05). Inflammation was mild in 69% of segments in which a CS was implanted and in 74% of segments in which a BS was implanted (p= NS), while a severe inflammatory reaction was observed in 6% of CS segments and in 8% of BS segments (p= NS). No differences were detected at the long-term analysis between neointimal thickness in CS compared with BS segments (0.46 ± 0.18 mm vs 0.42 ± 0.26 mm at 90 days and 0.36 ± 0.08 mm vs 0.35 ± 0.04 mm at 180 days; p= NS, respectively). At SEM analysis, re-endothelization was evident 15 days after the implant in both CS and BS starting from the stent edges. Conclusion: CS implantation did not elicit a more severe thrombotic deposition compared with that of BS. A similar inflammatory reaction of the arterial wall was present in the two stent groups 3 and 6 months following the implant. In addition, CS implantation did not stimulate excessive neointimal formation when compared with BS.     

Magnetic resonance angiography of nonferromagnetic lliac artery stents and stent-grafts: A comparative study in sheep

Purpose: To compare nonferromagnetic iliac artery prostheses in their suitability for patency monitoring with magnetic resonance angiography (MRA) using conventional angiography as a reference. Methods: In experiment 1, three Memotherm stents were inserted into the iliac arteries of each of six sheep: two “tandem” stents on one side and a single stent on the other side. In experiment 2, four prostheses (normal and low-porosity Corvita stent-grafts, Memotherm, ZA-stent) were inserted in each of 11 sheep. Patency was monitored before and 1, 3, and 6 months after insertion with 3D phase-contrast and two 2D time-of-flight sequences (TOF-1: TR/TE = 18/6.9, TOF-2: 13/2.5) with and without contrast at 1.5 T. On 206 coronal MIP images (72 pre-, 134 post-stenting), three readers analyzed 824 iliac segments (206 × 4) for patency and artifacts. Results: There was no difference in the number of artifacts between tandem and single iliac Memotherm stents. The ZA-stent induced significantly fewer artifacts than the other prostheses (p < 0.00001). With MRA, patency of the ZA-stent was correctly diagnosed in 88% of cases, which was almost comparable to nonstented iliac segments (95%), patency of the Memotherm stent in 59%, and of the Corvita stent-grafts in 57% and 55%. The TOF-2 sequence with contrast yielded the best images. Conclusion: MRA compatibility of nonferromagnetic prostheses depends strongly on the design of the device. MRA may be used to monitor the patency of iliac ZA-stents, whereas iliac Memotherm stents and Corvita stent-grafts appear to be less suited for follow-up with MRA.     

Covered Stents in the Treatment of Peripheral Arterial Aneurysms: Procedural Results and Midterm Follow-Up

Purpose: To evaluate initial and midterm results of percutaneous treatment of peripheral aneurysms using covered stents. Methods: Between June 1994 and December 1997 we used covered stents (EndoPro System or Passager) on 19 patients with peripheral aneurysms (7 iliac, 5 subclavian, 3 femoral, 3 popliteal, 1 carotid). Results: Successful aneurysm exclusion was achieved in 18 of 19 patients (95%). In the short term (<30 days), one patient died of puncture site hemorrhage complicated by myocardial infarction; two femoral stents were surgically removed because of leakage. At subsequent follow-up (mean 20 months) two further unrelated deaths occurred. At 1 year (intention-to-treat) the stent was patent in 13 of 19 patients (68%) and the aneurysm was excluded in 17 of 19 (89%). Conclusion: Treatment of peripheral aneurysms with covered stents has a high rate of immediate procedural success. Continued exclusion of the aneurysms is achieved in a large proportion of patients but there is a relatively high rate of stent thrombosis.     

Venous recanalization by metallic stents after failure of balloon angioplasty or surgery: Four-year experience

Purpose: This retrospective study describes our updated experience in treating venous stenoses and occlusions with metallic endovascular stents. Methods: Gianturco, Palmaz, and Wallstent stents were placed in 55 patients over a 4-year period. Stent sites included the subclavian veins (9), innominate veins (3), superior vena cava (4), inferior vena cava (3), iliac veins (29), femoral veins (5), and portal veins (6). The most common indications for stent placement were malignant stenoses and chronic pelvic venous occlusions. Venoplasty and/or urokinase were used as ancillary therapy. Patients were anticoagulated for 3–6 months. Follow-up included clinical assessment and duplex ultrasound. Results: Lifetable analysis shows 59%, 63%, and 72% primary, primary assisted, and secondary 1-year patency rates, respectively. The 4-year primary patency rates were the same. Duration of patency depended on the venous site. Death was a complication of stent placement in 2 patients and 12 patients died within 6 months after stent placement from primary disease progression. Although early failures were more common in stents placed across occlusions than stenoses, 1-year secondary patency rates were comparable. Primary patency rates were only slightly lower in patients with malignant obstruction than in patients with benign disease. Conclusion: Endovascular stent placement provides a nonsurgical alternative for reestablishment of venous flow and symptomatic relief in patients with benign as well as malignant venous obstruction. Received: 0/00/00/Accepted: 0/00/00     

Differences in Endothelial Injury After Balloon Angioplasty, Insertion of Balloon-Expanded Stents or Release of Self-Expanding Stents: An Electron Microscopic Experimental Study

Purpose: To evaluate which of six different commonly available stents inserted into an artery without percutaneous transluminal angioplasty (PTA) causes the least endothelial damage. To compare the degree of endothelial injury after insertion of such a stent with injury caused by PTA. Methods: Twelve healthy pigs were used in the experiments. In the first part of the study six different types of stents were inserted into the common iliac arteries. In the second part of the study self-expanding stents with large spaces between the wires were used. PTA was performed in the contralateral iliac artery. The pigs were killed immediately after the procedure and resected specimens examined after fixation, using scanning electron microscopy. Results: All procedures but two were accomplished successfully. More endothelium was preserved after insertion of self-expanding stents with large spaces between the wires, compared with stents with small spaces and balloon-expanded stents. After insertion of self-expanding stents with large spaces, 50.1% ± 16.4% of the endothelium remained intact, compared with only 5.6% ± 7.7% after PTA. The difference was statistically significant (p < 0.001). Conclusion: Self-expanding stents with large spaces between the wires, inserted without PTA, cause less damage to the endothelium than other stents and significantly less damage than PTA.     

Evaluation of three polytetrafluoroethylene stent-grafts in a model of neointimal hyperplasia

PURPOSE: The authors tested three different porosities of expanded polytetrafluoroethylene (ePTFE)-covered stents and bare stents by using an animal model of restenosis. MATERIALS AND METHODS: Both iliac arteries in 18 female pigs were injured by overdilating 20-mm-long angioplasty balloons. A 40-mm-long bare stent or one of three 44-mm-long ePTFE-covered stents was deployed at the injury site. To determine restenosis, neointimal area measurements were made with intravascular ultrasonography. Histologic analyses were performed at an independent laboratory to determine neointimal attachment. RESULTS: Neointimal area was greatest at the middle of the bare stent, where balloon injury was centered. When the middle location of the covered stents was evaluated, the neointimal area of both the medium- and high-porosity covered stents was smaller than that of the matched control stents (P = .0018 and P = .0118, respectively). The neointimal area of the low-porosity covered stents was similar to that of the bare stents. Histologic study showed dehiscence of the neointima of the low-porosity covered stents. CONCLUSIONS: The microstructure of the low-porosity covered stents did not provide a suitable surface for neointimal attachment and did not reduce neointimal growth compared to that with the control stents. The microstructure of the medium- and high-porosity covered stents yielded less neointimal growth than both the control stents and the low-porosity covered stents without evidence of neointimal dehiscence. The authors believe that covered stents made with ePTFE with either medium or high porosity could limit restenosis in humans compared to that with bare stents.     

Suitability of incorporated vascular stents for surgical patch-plasty: An experimental study

Purpose: Evaluate the feasibility of expanding arterial and venous stents incorporated into the vessel wall by surgical patch-plasty in an experimental study. Methods: An 8-mm Wallstent was percutaneously implanted into the carotid artery of 11 sheep and into the ipsilateral jugular vein in three of them. Three months after implantation, a patch-plasty was performed on the incorporated stents using a 0.4-mm-thick synthetic patch made of polytetrafluoroethylene (PTFE). Stent patency was monitored by color-coded duplex ultrasound and angiography for 6 months after operation. Results: No suture dehiscence or aneurysm formation were observed. Nine of 11 arterial and 2 of 3 venous stents remained fully patent during follow-up. In arteries, complications encountered were a complete stent thrombosis early after surgery, as well as a floating thrombus in the stent, found at final angiography after 6 months. In veins, one partial stent thrombosis was observed. Microradiographic and histological examinations revealed marked intimal hyperplasia in both arterial and venous stents. Intimal hyperplasia was significantly more pronounced in patched than in stented arterial segments (p<0.005). Conclusion: Patch-plasty surgery of previously incorporated vascular stents is technically feasible. Midterm patency rates were acceptable.     

Elastic Deformation Properties of Implanted Endobronchial Wire Stents in Benign and Malignant Bronchial Disease: A Radiographic In Vivo Evaluation

Purpose: To evaluate the long-term mechanical behavior in vivo of expandable endobronchial wire stents, we imaged three different prostheses in the treatment of tracheobronchial disease. Methods: Six patients with bronchial stenoses (three benign, three malignant) underwent insertion of metallic stents. Two self-expandable Wallstents, two balloon-expandable tantalum Strecker stents and two self-expandable nitinol Accuflex stents were used. Measurements of deformation properties were performed during voluntary cough by means of fluoroscopy, at 1 month and 7–10 months after implantation. The procedures were videotaped, their images digitized and the narrowing of stent diameters calculated at intervals of 20 msec. Results: After stent implantation all patients improved with respect to ventilatory function. Radial stent narrowing during cough reached 53% (Wallstent), 59% (tantalum Strecker stent), and 52% (nitinol Accuflex stent) of the relaxed post-implantation diameter. Stent compression was more marked in benign compared with malignant stenoses. In the long term permanent deformation occurred with the tantalum Strecker stents; the other stents were unchanged. Conclusion: Endobronchial wire stents can be helpful in the treatment of major airway collapse and obstructing bronchial lesions. However, evidence of material fatigue as a possible effect of exposure to recurrent mechanical stress on the flexible mesh tube may limit their long-term use. This seems to be predominantly important in benign bronchial collapse.     

Popliteal Artery Stenting Using Flexible Tantalum Stents

Purpose: To evaluate the safety and efficacy of stent therapy for the treatment of residual stenoses after percutaneous transluminal angioplasty (PTA) of popliteal stenoses and occlusions. Methods: In a prospective single-center study, flexible tantalum stents were implanted in 32 popliteal arteries for the treatment of residual stenosis greater than 50% after PTA of stenoses (n = 17) or occlusions (n = 15) in the P1 (n = 16), the P2 (n = 13), or both P1 and P2 segment (n = 3). Follow-up patency was assessed by clinical examination, ankle-brachial index, and color Doppler sonography or angiography. Results: Early stent thrombosis (10 days): 1 of 32 arteries (3%). 1-year and 2-year primary patency rate (PPR): 81% ± 7.1% and 74% ± 9.1%, respectively. 1-year PPRs for subgroups: stented stenoses versus stented occlusions: 88% ± 7.8% vs 73% ± 12.0%, p = 0.12; good lower limb runoff versus poor: 84.0% ± 8.7% vs 76.0% ± 12.4; p = 0.09; P1 versus P2: 77.3% ± 9.8% vs 85.7% ± 9.4%, p = 0.38. Recurrent PTA lesions treated with stents showed higher restenosis rate than de novo lesions. Conclusion: The results of stent therapy of residual popliteal stenosis after PTA are encouraging and warrant further investigation.     

Vein Graft-Coated Vascular Stents: A Feasibility Study in a Canine Model

Purpose: To evaluate different vein grafts for luminal coating of endovascular stents in normal canine arteries. Methods: Twenty-four tantalum Strecker stents were coated with either autologous (n= 10), denatured heterologous (n= 11), or denatured homologous vein grafts (n= 3). The carotid artery (n= 11) and the iliac artery (n= 13) were stented using a transfemoral approach. Angiograms were performed at days 0, 7, and 21, and months 3, 6, and 9. All grafts underwent histological examination. Results: Eight of 10 autologous vein grafts showed patency during the whole observation period of 9 months, without histological signs of inflammation. Denatured heterologous vein grafts revealed acute (n= 3), subacute (n= 5), or delayed (n= 3) vessel occlusion. Hyaloid transformation of the vein graft and lympho-plasmacellular formations were seen. Denatured homologous vein grafts showed acute vessel occlusion. Although significant inflammatory tissue response was seen, no host-versus-graft reaction was present. Conclusion: Autologous vein graft-coated stents showed good biocompatibility in canine arteries. Preparation was cumbersome and required surgical venae-sectio. Denatured vein grafts, however, were limited by inflammatory reactions.     

Retrospective Comparison of the Patency of Wallstents and Palmaz Long-Medium Stents Used for TIPS

Purpose: To compare patency rates of transjugular intrahepatic portosystemic shunts (TIPS) after placement of long-medium Palmaz stents or Wallstents. Methods: We performed a retrospective review of TIPS performed at our institution between December 1997 and December 1998. During this time period we placed long-medium Palmaz stents for TIPS procedures in 17 patients and Wallstents in 20 patients as the initial stent. Patency was determined on follow-up by ultrasound, angiography, or pathologic examination in the event of transplant. Results: Primary patency in the Palmaz stent group was 70.6% (12/17 patients) (follow-up 1–399 days, mean 127 days). Both primary assisted and secondary patency in the Palmaz group was 100% (17/17 patients) (follow up 1–399 days, mean 154 days). Primary patency in the Wallstent group was 50% (10/20 patients) (follow up 1–370 days, mean 65 days). Primary assisted patency in the Wallstent group was 80% (16/20 patients) (follow up 1–601 days, mean 141 days). Secondary patency in the Wallstent group was 100% (20/20 patients) (follow up 2–601 days, mean 142 days). Kaplan-Meier analysis of the two groups of patients yielded a primary patency of 266 days (standard error 45 days) for TIPS with the Palmaz stent and 139 days (standard error 45 days) for the Wallstent (p = .04). The 3, 6, and 12-month primary patency rates were .84, .63, and .42 respectively for the Palmaz stents and .36, .36, and .18 respectively for the Wallstent. There was no significant difference in primary assisted or secondary patency between the two stent groups. The mean tract curvature in the patients with Palmaz stents was 23.5° (SD 18.2°, range 0–69.0°) compared with 57° (SD 34.5°, range 7.0–144.0°) in patients with Wallstents (p = .01). Conclusions: Our nonprospective, nonrandomized study suggests that TIPS created with the long-medium Palmaz stent have a higher primary patency than those created with the Wallstent in tracts that are relatively straight.     

Angioplasty-induced dissections in human iliac arteries: management with Palmaz balloon-expandable intraluminal stents

Intravascular stent placement may be an effective treatment for percutaneous transluminal angioplasty (PTA)-induced dissection. Among the first 228 patients treated with Palmaz balloon-expandable intraluminal stents (BEISs) for iliac artery stenosis, stents were used to treat PTA-induced dissection in at least 12 iliac arteries in 11 patients. All 12 vessels were shown by angiography to be severely dissected. Stents were placed at the time of PTA in six vessels and as a separate procedure in the other six. An average of three stents per vessel were employed. All arteries showed marked improvement at angiography. Angiographic follow-up was obtained for eight vessels in seven patients at a mean follow-up time of 12.9 months. All had patent stent lumens with neointima formation, although one stented lumen had narrowed, and another clinical failure occurred despite a patent stented vessel and an ankle-arm index (AAI) of 1.35. With a mean clinical follow-up of 9.5 months, the mean AAI for the stented extremities in the nine remaining patients is 0.91 +/- 0.15. Palmaz BEISs are effective in the management of PTA-induced human iliac artery dissection.     

Short-term effects of a new intravascular nitinol stent in canine arteries

RATIONALE AND OBJECTIVES: To evaluate the short-term effects of a new nitinol stent on canine arteries. METHODS: Eighteen nitinol mesh stents were placed in abdominal aortas, common iliac arteries, and renal arteries of six dogs. Angiography was performed to evaluate the patency rates and structural changes of arteries at 1 day, 3 weeks, 4 weeks, and 10 weeks after stent insertion. Gross and light microscopic examinations were performed after angiography. RESULTS: On angiography, the patency rate was 100%, and no thrombosis was observed. All side branches from stented segments were patent. The mean neointimal thickness over and between stent wires was 94 and 167 microns. No difference was found between the aorta and the small vessels. Histologically, the neointima was covered with endothelium and was composed of subintimal fibrosis with mild inflammation. CONCLUSIONS: The new type of nitinol mesh stent showed a high patency rate, with no thrombosis and relatively thin neointimal proliferation.