Magnetic resonance monitoring of stent deployment: in vitro evaluation of different stent designs and stent delivery systems

RATIONALE AND OBJECTIVES: To evaluate MR imaging features of commercially available stents before, during, and after in vitro deployment as a step toward MR-guided stent deployment. METHODS: Fourteen stents were deployed in a phantom under MR monitoring at 1.5 T by using a gradient-echo sequence. Device visibility was rated on a four-point scale (excellent, fair, poor, not visible). RESULTS: The Memotherm stent and the rolling membrane (RM) Wallstent showed excellent stent visibility and at least fair scores for artifact-induced narrowing of the stent lumen. Three stents (Palmaz, AVE, Easy Wallstent) showed excellent visibility of the stent but no visible lumen. Five stents (Strecker, Accuflex, Hemobahn, Passager, Sinus) displayed fair visibility. The delivery catheters of four stent systems (Smart, Vascucoil, Symphony, ZA) displayed severe black hole artifacts. CONCLUSIONS: The imaging features of several stent systems might be suitable for MR-guided intervention. The Memotherm and the Wallstent RM combine good visibility of the stent and the lumen.     

Iliac artery stenting--clinical experience with the Palmaz stent, Wallstent, and Strecker stent.

A total of 82 iliac artery lesions (62 stenoses and 20 occlusions) were treated with 3 different types of endovascular metallic stents (12 lesions with the Palmaz stent, 36 with the Wallstent, and 34 with the Strecker stent). The complication rate was 12%. Occlusion of 2 Wallstents occurred 4 and 12 weeks after stent placement, respectively. Both stents were recanalized by local fibrinolysis. One Strecker stent occluded after 8 months. The observation period was 3 to 26 months (mean 9.7 months). The patency rate with secondary intervention (fibrinolysis) was 100% after 3 and 6 months, and 98% after 9 months. All 3 stent designs turned out to be effective in the treatment of complicated iliac artery occlusive disease.     

MR evaluation of stent patency: in vitro test of 22 metallic stents and the possibility of determining their patency by MR angiography

RATIONALE AND OBJECTIVES: To determine the extent to which visualization of intrastent anatomy in stents of different composition and design is possible by using contrast-enhanced MR angiography. METHODS: Twenty-two MR-compatible stents, most of which had a diameter of 8 mm, were positioned in a phantom filled with aqueous gadolinium solution. Coronal and axial spoiled three-dimensional gradient-echo sequences were performed. Images were acquired with stents positioned at varying angulations to the main magnetic field B0. Profiles orthogonal to the stent axis allowed measurement of artifact sizes independent of window width and center. RESULTS: Oriented along B0, the Cragg, Corvita, Passager, Wallstent, Strecker, Impag, Perflex, and ZA stents allowed visualization of more than 48% of the lumen. The Memotherm, Smart, and Jostent SelfX stents showed a prominent reduction of the inner lumen to below 41%. The lumina of the covered Jostent, Palmaz, Sinus, and Symphony stents were completely obscured. The Impag, Perflex, and Strecker tantalum stents showed growing artifact sizes and a lumen reduction of at least 40% with increasing angulation to B0. CONCLUSIONS. Evaluation of the inner stent lumen by applying contrast-enhanced, three-dimensional gradient-echo sequences is not possible for the majority of stents because of their large artifacts. These depend on the stent type and orientation to B0. Even stents made of nitinol and cobalt alloys only allow qualitative patency assessment but no quantification of stenosis.     

Physical properties of endovascular stents: an experimental comparison

PURPOSE: Different endovascular stent types (AVE Bridge, AVE Bridge X, Memotherm, Palmaz Large, Palmaz Medium, Palmaz-Schatz Long-Medium, Perflex, S.MA.R.T., Symphony, and Wall-stent) of 4 cm length and 8 mm diameter were subjected to standardized physical tests. MATERIALS AND METHODS: The metal mass of each stent was assessed by weighing. The balloon-expandable stents were pneumatically tested for hoop strength. In self-expanding stents, radial resistive force and chronic outward force were determined with use of a loop test. Stent delivery system pushability was assessed in a crossover model. Stent radiopacity was analyzed quantitatively. RESULTS: The hoop strength of the balloon-expandable stents ranged from 15.8 N/cm (Perflex) to 28.9 N/cm (AVE Bridge X). The stent weight increased with greater hoop strength (Perflex, 0.046 g/cm vs. AVE Bridge X, 0.061 g(cm). The self-expanding stents had a radial resistive force between 0.39 N/cm (Wallstent) and 1.7 N/cm (Smart). The flexible balloon-expandable stents showed pushability values between 0.13/N (AVE Bridge) and 0.20/N (Perflex). The self-expanding stents had flexibilities between 0.13/N (Memotherm) and 0.24/N (Symphony). Radiopacity assessed with use of a phantom simulating the iliac region ranged from 92 (Palmaz Large) to 115 (AVE Bridge) on a 256-point gray scale (0 = black, 256 = white). CONCLUSIONS: There is no stent with ideal physical properties. However, depending on the characteristics of the arterial lesion to be treated, the most appropriate stent can be chosen.     

In vivo evaluation of intravascular stents at three-dimensional MR angiography

The aim of this study was to assess in vivo patency of seven commonly used non-ferromagnetic plain stents as regards demonstration of the contained lumen at 3D gadolinium-enhanced MRA in a 0.5-T MR environment. Twenty-one patients with 22 stents (1 aortic, 18 iliac, 3 popliteal) were imaged with MRA. Stent-related artefacts were evaluated. Images were assessed for the presence and size of stent artefacts, luminal patency, and were correlated with stent metal mass, composition, configuration and angulation with respect to the magnetic field. Four different types of stent (Symphony, Wallstent, Memotherm, SMART) showed major artefacts preventing assessment of intradevice luminal patency or restenosis, in two stents (ZAV stent, Intracoil) minor artefacts allowed assessment of high-degree stenosis, and only one type of stent (Strecker) was perfectly imaged. Based on our limited experience, Gd-MRA appears well suited for the evaluation of only a minority of MR-compatible stents.     

Multislice CT angiography of the iliac arteries in the presence of various stents: in vitro evaluation of artifacts and lumen visibility.

RATIONALE AND OBJECTIVES: To evaluate the imaging characteristics of various iliac artery stents and stent-grafts in a multislice, computed tomography angiography (MSCTA) phantom study. METHODS: Twelve types of stents and three stent-grafts made of different materials (steel, nitinol, tantalum, cobalt-based alloy) were implanted in plastic tubes with an 8-mm inner diameter filled with iodinated contrast medium diluted to 200 HU. To evaluate the influence of scan parameters on artifacts, the Palmaz stent (as one example) was scanned with a four-slice scanner (Siemens VolumeZoom) with different detector collimations and pitches. All other stents were examined with a collimation of 4 x 1 mm and a table feed of 4 mm/rotation. Axial images and multiplanar reformations were evaluated regarding artifact size, lumen visibility, and intraluminal attenuation values. RESULTS: Higher pitch values caused more pronounced artifacts. Image quality and delineation of the stent struts improved with thinner detector collimation. The size of the stent-related artifacts and the visibility of the stent lumen depended on the underlying stent material and design. Pronounced artifacts, resulting in an insufficient delineation of the stent lumen, were caused by the Strecker tantalum stent and the Zenith stent. Moderate artifacts were caused by the Wallgraft, Passager, Palmaz P 395 and P 424, Bridge, Perflex, and ZA stents. Some artificial lumen narrowing but good lumen delineation was seen with the Strecker nitinol, Symphony, Memotherm, SMART, Corinthian, and Wallstent stents. CONCLUSIONS: Scanning parameters, stent material, and stent design influence lumen assessability and image quality in MSCTA. Detailed lumen assessment is impossible in the Strecker tantalum and Zenith stents and limited in the Wallgraft, Passager, Palmaz P 395 and PS 424, Bridge, Perflex, and ZA-stent stent-grafts but feasible in all other examined products.     

Changes in wall mechanics after endovascular stenting in the rabbit aorta: comparison of three stent designs

OBJECTIVE: The aim of this study was to evaluate changes in the wall mechanics of small-diameter arteries after endovascular placement of three different stents. SUBJECTS AND METHODS: Five self-expandable stents (Wallstent), five balloon-expandable noncovered Palmaz stents, and three balloon-expandable covered stents (Jostent) were placed in the infrarenal aorta of 13 New Zealand white rabbits. Systolic blood pressure changes, blood-flow velocity, systolic diameter, and diameter changes were measured and used to calculate the diameter compliance, the distensibility coefficient, and the pulsatility index. RESULTS: Compliance (10(-3) mm kPa(-1)) was 75.3 +/- 20.1 before stenting and reached 94.7 +/- 42.2 upstream, 38.8 +/- 14.2 at the stent level (p < 0.05), and 70.8 +/- 23.2 downstream from the stent. Distensibility (10(-3) kPa(-1)) was 24.3 +/- 6.3 before stenting and reached 27.8 +/- 10.3 upstream, 10.5 +/- 4.4 at the stent level (p < 0.001), and 21.9 +/- 8.6 downstream from the stent. Compliance and distensibility were significantly lower at the stent level than upstream and downstream (p < 0.05). Aortic diameter increased significantly at the stent level from 3.11 +/- 0.40 mm before to 3.76 +/- 0.42 mm after stenting. No significant difference was found among the three stent designs for all the studied data. CONCLUSION: Regardless of the three tested stent designs, endovascular stenting produces a significant decrease in arterial wall compliance of the rabbit aorta.     

Influence of blood-pool contrast media on MR imaging and flow measurements in the presence of pulmonary arterial stents in swine

PURPOSE: To compare the effects of various stents on magnetic resonance (MR) imaging flow volume measurements and to determine the value of a blood-pool MR imaging contrast medium in assessment of vascular stents. MATERIALS AND METHODS: In 11 pigs, six nitinol stents (Memotherm), four platinum stents (NuMed), and one elgiloy stent (Wallstent) were placed in the main pulmonary artery under x-ray fluoroscopic guidance. MR imaging was performed 3 months after stent placement before and after injection of NC100150 contrast medium. Blood flow volumes were assessed with velocity-encoded cine MR imaging through and next to the stent. The signal-to-noise ratio and width of susceptibility artifacts of the stents also were determined. Measurements were analyzed with the paired Student t test and Bland-Altman test, where appropriate. RESULTS: Blood flow volumes measured through the nitinol and platinum stents disclosed no significant difference between velocity-encoded cine MR imaging measurements through and next to the stent. On cine MR images, small susceptibility artifacts were observed around the nitinol and platinum stents. Signal-to-noise ratio in the stent lumen was reduced in nitinol and platinum stents when compared with that next to the stent. The elgiloy stent produced severe susceptibility artifacts, making measurement of flow volumes impossible. NC100150 injection caused no significant effect on flow volume measurements. It improved the signal-to-noise ratio of the pulmonary arterial lumen outside and, to a lesser extent, inside the stent. CONCLUSION: Assessment of morphology and flow volumes through nitinol and platinum stents is feasible with MR imaging. Blood-pool contrast media provide persistent signal enhancement in the pulmonary artery and, to a lesser extent, in the lumina of nitinol and platinum stents.     

Flow patterns from metallic vascular endoprostheses: in vitro results

The aim of this study was to determine flow characteristics and pressure gradients of different balloon- and self-expandable stents in an in vitro flow-model. Seven vascular stents (Bridge, Cragg, Memotherm, Palmaz PS 784, Sinus, Symphony, Wallstent), equal in length (60 mm) and diameter (10 mm), were deployed in a closed flow model. The inner diameter of the tube measured 9 mm. Flow at 1.5 and 6 l/min was applied. Flow patterns were visualized by anionic particles illuminated with two helium-neon lasers. Late laminary flow characteristics and pre- /post-stent pressure gradients were determined in either expanded stent, 25 and 50 % tube stenosis. Stent implantation induced a decrease of laminary flow when compared with an unstented tube with and without concentric 25 % stenosis (p < 0.01) at all flow rates and an increase of pressure gradients when compared with an unstented tube for a flow rate of 6 l/min and all stenoses (p < 0.01). At 1.5 l/min most stents revealed no significant change of pressure gradient, the highest gradient measured 4.0 mmHg. Sinus permitted maximum (expanded: 82.1 % and 76.9 % at 25 % stenosis at 1.5 l/min; p < 0.01) and Palmaz minimum of laminary flow at all flow rates and stenoses (70.2 and 52.4 % at 25 % stenosis at 1.5 l/min; p < 0.01). At 6 l/min, when completely expanded, Sinus is equal to Bridge and Memotherm; in 25 % stenosis Sinus is equal to Bridge, Memotherm, and additionally to Cragg and Wall. None of the endoprostheses revealed laminary flow at 50 % stenosis. Inadequate stent deployment bears the risk of creating less laminary flow and pressure gradients. Since flow disturbances and pressure gradients may influence neointimal hyperplasia, stent design and completeness of stent expansion are important factors regarding the appearance of thrombus formation and postinterventional restenosis. Received: 27 April 2000 Revised: 20 July 2000 Accepted: 26 July 2000     

Effects of nitinol Strecker stent placement on vascular response in normal and stenotic porcine iliac arteries

PURPOSE: This experimental study was conducted to evaluate neointimal thickness, lumen diameters, and histologic changes in normal and stenotic porcine iliac arteries following placement of self-expanding nitinol Strecker stents. MATERIALS AND METHODS: Neointimal trauma causing slight vascular stenosis was induced unilaterally within external iliac arteries of 12 swines by means of endothelial abrasion and high cholesterol diet. Nitinol Strecker stents were placed within the stenotic and the normal contralateral vascular segments. For histopathologic evaluation, the pigs were killed 12 or 24 weeks after stent placement and luminal diamters were evaluated angiographically. RESULTS: Excluding one occlusion, 15% narrowing of the lumen diameter was induced unilaterally (P = .002). Initial luminal gain after stent placement was greater for stenotic than for normal arteries. The amount of neointima thickness was not different between stenotic and normal vessels (P > .05). Comparing vascular diameters before stent placement and at follow-up, luminal loss due to neointima proliferation was 22% within normal arteries (P = .0002), while a luminal gain by 15% was found within the stenotic arteries (P = .008). Maturation of neointima and endothelial coverage were complete after 24 weeks. CONCLUSIONS: Even though nitinol Strecker stents induce excessive neointimal proliferation, stenotic arteries seem to profit from great early luminal gain resulting in 15% of vascular expansion at follow-up while slight stenosis is induced within normal iliac arteries.     

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.     

Iliac Artery Injury Following Placement of the Memotherm Arterial Stent

Iliac rupture and aneurysm formation at the site of stent placement has rarely been described in the literature. We report four cases, three of iliac rupture, including a delayed rupture, and an aneurysm, with the use of a single type of stent, the Memotherm stent. We believe the design of the stent significantly contributed to damage to the arterial wall and subsequently prevented closure of the arterial tear by balloon tamponade in the two cases where this was attempted. Two patients, one with rupture and one with an aneurysm, were successfully treated with a covered stent obviating surgery and two ruptures resulted in death. We recommend that all interventionists carrying out iliac angioplasty and/or stenting should have access to covered stents for such emergencies.     

A new stent designed for carotid artery application. An experimental study

PURPOSE: To evaluate a new stent developed for treating arterial stenoses located adjacent to the bifurcation of the carotid artery. MATERIAL AND METHODS: Eight 4-cm-long nitinol stents, each with a diameter of 6 mm in its distal half and 9 mm in its proximal half, were tested in 4 pigs. In each animal, the abdominal aorta was catheterized through the left common carotid artery, and 2 stents were inserted into the right and left iliac arteries, respectively, with the wider portion in the common iliac artery and the narrower portion in the corresponding external iliac artery. The pigs were killed after 24 hours, or 1, 4 or 8 weeks, following control angiography. The arteries were examined macroscopically and by scanning electron microscopy. RESULTS: All stents remained in the intended position, fitting the arterial wall, following successive expansion to their maximum diameter and after 4 weeks were completely covered by endothelium. The arteries remained patent, with preserved flow to the side branches through the stent mesh. A small thrombus was found in I artery CONCLUSION: In animal experiments, the new stent was safely inserted over the arterial bifurcation, remained in place and was covered by endothelium while flow through side branches was preserved.     

In vitro evaluation of stent patency and in-stent stenoses in 10 metallic stents using MR angiography

In vitro study to investigate the suitability of contrast enhanced magnetic resonance angiography (CEMRA) for determination of stent patency and grading of in-stent stenoses in 10 metallic stents. The Acculink carotid, DynaLink, Easy Wallstent, JostentSelfX XF, Luminexx, Omnilink, sinus-SuperFlex, SMART, Symphony and ZA stent were separately placed in a vascular phantom. Dedicated stenoses inside the stents generated a concentric lumen narrowing of 50%. CEMRA was performed for each stent. Signal loss inside the stents and artificial lumen narrowing were assessed objectively using the evaluation software of the MR imager. Moreover, three blinded observers determined visibility of stent patency and in-stent stenoses subjectively on a 3-point scale and graded in-stent stenoses. Loss of signal intensity within the stent lumen ranged between 90% (Wallstent) and 5% (ZA), artificial lumen narrowing between 56% (Symphony) and 22% (ZA). For the Symphony and Wallstent, visibility of patency and in-stent stenoses was impaired and the observers' grading exaggerated the degree of stenoses (by 23% and 33%, respectively). For the remainder of stents, patency and stenoses were visible and stenoses were graded accurately (less than 10% discrepancy from reference standard). In this in vitro study, eight of 10 stents presented with MRI characteristics which enabled determination of stent patency and accurate grading of clinically relevant in-stent stenoses.     

Arterial stent placement with use of the Wallstent: midterm results of clinical experience

Self-expandable stents of the Wallstent type were used in 26 iliac and 15 femoropopliteal artery lesions of 31 patients to treat stenoses or occlusions. The indications were confined to complex lesions, including residual stenoses and dissections after percutaneous procedures or previous surgery in the iliac artery lesions, and long-segment (mean, 13.5 cm) occlusions with inadequate response to percutaneous recanalization in the femoropopliteal artery lesions. In the iliac artery group, after stent placement, 96% of the lesions were patent at a mean follow-up of 16 months (range, 6-30 months). In the femoropopliteal artery group, of 11 patients available for follow-up, only six had patent stents at 7-26 months (mean, 20 months). Four of these six patients required one to three secondary interventions. Self-expanding endoprostheses are of great value in complex iliac artery lesions where simple balloon dilation is insufficient. Stent placement for long femoral artery lesions should be performed with utmost reserve, and the extent of stent placement should be as short as possible.     

Acute changes in aortic wall mechanical properties after stent placement in rabbits

PURPOSE: To evaluate mechanical property changes after endovascular stent placement in small-diameter arteries. MATERIALS AND METHODS: Self-expanding stents (Wallstent) were placed in the infrarenal aorta of five New Zealand White rabbits via a surgical right femoral approach. Blood pressure changes (deltaP) were monitored in the aorta. Blood flow velocity was measured with a 20-MHz, pulsed Doppler probe (n = 4) to calculate the pulsatility index. Aortic diameter (dA) and diameter changes (delta(d)) were measured with a 20-MHz probe in echo-tracking mode. Diameter compliance (Cd) and distensibility coefficient (DC) were calculated as Cd = 2(delta)d/(delta)P and DC = 2delta(d)/delta(P)/dA. RESULTS: Aortic diameter increased from 3.360 +/- 0.4033 mm to 4.020 +/- 0.3033 mm after stent placement at the stent level only. Compliance decreased from 77.644 +/- 24.306 mm kPa(-1) to 31.150 +/-8.245 x 10(-3) mm kPa(-1) at the stent level, and was then significantly lower than upstream (98.500 +/- 53.196 mm kPa(-1)) and down-stream (59.047 +/- 13.833 mm kPa(-1)). There was no significant change in pulsatility index. CONCLUSIONS: Endovascular stent placement produces a significant decrease in arterial wall compliance of the rabbit abdominal aorta.     

MR imaging-guided stent placement in iliac arterial stenoses: a feasibility study

PURPOSE: To assess the feasibility of magnetic resonance (MR) imaging-guided stent placement in iliac arterial stenoses. MATERIALS AND METHODS: Thirteen patients with 14 iliac arterial stenoses were examined prospectively. Angioplasty was performed through a femoral sheath by using a conventional 1.5-T MR imaging system. Stents and catheters were visualized on the basis of their artifacts. Nitinol stents were placed with gradient-echo MR imaging guidance. Angioplasty balloons were inflated with gadolinium-based contrast material. Results were evaluated clinically and with both digital subtraction angiography (DSA) and contrast material-enhanced MR angiography. RESULTS: Ten of 13 patients were treated with technical success by using MR imaging-guided intervention alone. Three patients were treated with additional fluoroscopic guidance, because complications (ie, panic attack, subintimal recanalization, and stent misplacement) occurred with MR guidance. The quality of the postinterventional contrast-enhanced MR angiograms of three of 12 lesions with stents was limited owing to stent-induced signal loss of the lumen. The mean stenosis degree after stent placement was significantly higher at contrast-enhanced MR angiography than at DSA (24.6% vs 6.2%). The mean MR imaging-guided procedure time was 74 minutes. CONCLUSION: MR imaging-guided stent placement in iliac arteries is feasible in select patients. The presented technique has limitations-that is, long procedure times, lack of real-time monitoring, and stent artifacts-that necessitate further modifications before it can be recommended for clinical use.     

Percutaneous Endovascular Treatment of Chronic Iliac Artery Occlusion

Purpose: To evaluate the clinical and radiological long-term results of recanalization of chronic occluded iliac arteries with balloon angioplasty and stent placement. Methods: Sixty-nine occluded iliac arteries (mean length 8.1 cm; range 4–16 cm) in 67 patients were treated by percutaneous transluminal angioplasty and stent placement. Evaluations included clinical assesment according to Fontaine stages, Doppler examinations with ankle–brachial index (ABI) and bilateral lower extremity arteriograms. Wallstent and Cragg vascular stents were inserted for iliac artery recanalization under local anesthesia. Follow-up lasted 1–83 months (mean 29.5 months). Results: Technical success rate was 97.1% (67 of 69). The mean ABI increased from 0.46 to 0.85 within 30 days after treatment and was 0.83 at the most recent follow-up. Mean hospitalization time was 2 days and major complications included arterial thrombosis (3%), arterial rupture (3%) and distal embolization (1%). During follow-up 6% stenosis and 9% thrombosis of the stents were observed. Clinical improvement occurred in 92% of patients. Primary and secondary patency rates were 75% and 95%, respectively. Conclusion: The long-term patency rates and clinical benefits suggest that percutaneous endovascular revascularization with metallic stents is a safe and effective treatment for patients with chronic iliac artery occlusion.     

Metallic stent placement for iliac artery occlusive disease

Since 1991, we have performed stent placement for 35 iliac artery lesions in 31 patients. The etiologic diseases were atherosclerotic in 34 patients and traumatic dissection in one. The indications of placement were total occlusion in 3, late restenosis after angioplasty in 5, dissection in 5, and residual stenosis due to inadequate angioplasty in 21. We also performed direct stent placement for one traumatic dissection. The stents used were Wallstents in 10, Palmaz stents in 14, Strecker stents in 9, and Memotherm stents in 2 lesions. Follow-up was performed clinically or angiographically with measurement of the ankle/arm pressure index. Stent placement was successful in all cases, and relief or improvement of symptoms was achieved. The follow-up period ranged from 6-85 months (mean, 37.3 months). Late stent stenosis or occlusion occurred in 6 cases, among which 4 occluded lesions were successfully recanalized by thrombolytic therapy with angioplasty or second stent placement. In total, the primary patency rates were 88% and 77% at two and four years, respectively, while the secondary patency rates were 94% and 94%. In conclusion, metallic stent placement may offer extended application of intravascular treatment for iliac artery occlusive disease, and good long-term patency rates can be expected.     

动脉粥样硬化性缺血性肾病的血管内介入方法选择和疗效探讨

目的评价动脉粥样硬化性肾动脉狭窄血管内介入治疗的方法和临床疗效。方法28例肾动脉狭窄采用导引导管法(A组19例)和导丝交换法(B组9例)，行经皮肾动脉内支架成形术，共植入支架31枚(Palmaz支架22枚，Wallstent4枚，Symphony支架5枚)。随访6个月～1年，观察血压、血肌酐、抗高血压药用药情况，并与术前比较。结果两组肾动脉内支架成形术技术成功率为100％，B组中有2例患者术中发生肾动脉远端分支栓塞，两组共有4支血管发生再狭窄。结论导引导管法肾动脉内支架是动脉粥样硬化性肾动脉狭窄介入治疗首选方法；维护肾功能是该治疗的首要目的。