Assessment of coronary artery patency after stent placement using magnetic resonance angiography

The ability to noninvasively assess the patency of coronary stents would represent a significant advance. We evaluated the safety and ability of two-dimensional coronary MR angiography In imaging stents and suggesting patency. Coronary MR angiography of 26 coronary stents (Palmaz-Schatz) was performed in 16 patients 39 to 73 years of age. Studies were performed between 2 and 4 months after stent placement. All patients were symptom free at the time of imaging. Coronary MR angiography was performed with a commercial 1.5-T MR imager using an electrocardio-graphically gated pulse sequence with breath-holding. Images were obtained in mid-diastole with and without fat suppression. Image artifacts caused by the metal in the stents were clearly visualized in all 26 stents (100% sensitivity for stent detection). Arterial flow signal was seen in the coronary artery or graft distal to the stent in 25 of 26 cases (96%). All patients, except for the one in which distal flow could not be seen, remained symptom free for >2 years. The distribution of stent locations was as follows: 10 in the right coronary artery (RCA), 10 in the left anterior descending coronary artery (LAD), 2 in the left circumflex coronary artery, and 4 in saphenous vein grafts (SVGs) to RCA. One patient had 2 RCA and 2 LAD stents, one had 3 RCA and 1 LAD stents, one had 3 SVG stents, and two had double RCA stents. Coronary MR angiography is safe for noninvasive imaging of coronary stents, and in the proper clinical setting, it can be used to help suggest patency.     

CT and MR imaging of nitinol stents with radiopaque distal markers

PURPOSE: To evaluate imaging characteristics and artifacts of a nitinol stent with distal tantalum markers with computed tomography (CT) angiography and magnetic resonance (MR) angiography. MATERIALS AND METHODS: A vascular phantom was built to simulate in-stent restenosis. A nitinol stent with tantalum markers (Luminexx stent) was evaluated with CT angiography in different orientations relative to the z-axis and with MR angiography in different positions relative to both B0 and the readout gradient. Stenosis measurements were compared with conventional digital subtraction angiography for both modalities. In-stent signal intensity obtained with different flip angles was assessed in two nitinol stents with distal markers (Luminexx stent and SMART stent) and one without markers (Memotherm-FLEXX stent). RESULTS: Stenosis detection was not possible with CT angiography when the stent was perpendicular to the z-axis because of streak-like artifacts induced by tantalum markers. Stenosis evaluation with multiplanar reformation was accurate when the stent was in parallel and oblique orientations relative to the table axis. With MR angiography, metallic artifacts were mostly related to the stent orientation with B0, whereas orientation of the readout gradient had little influence. The mean error (overestimation) for stenosis measurements varied between 0.1% and 7.4% for CT imaging in parallel and oblique positions and 3.6% and 9.5% for MR imaging. Higher flip angles did not improve signal intensity inside the three stents tested. CONCLUSION: CT and MR angiography can be used for evaluating the patency of stents with distal markers that are parallel or oblique relative to the table axis (iliac, carotid, or femoral stents). MR angiography is preferred if the stent is perpendicular to the table axis (renal stent).     

16层螺旋CT冠状动脉成像的临床应用

目的:探讨16层螺旋CT冠状动脉(简称冠脉)成像在冠心病诊断中的临床价值。方法:选取50例临床诊断或可疑冠心病患者行16层螺旋CT冠状动脉造影检查(MSCTCA),先行冠脉钙化积分平扫,然后行冠脉增强扫描,选取一组质量最佳的薄层图像行冠脉三维重建,分析MSCTCA对冠状动脉狭窄性病变的显示能力,并对冠脉支架显示及通畅性进行评价。结果:冠脉钙化积分与其狭窄程度呈正相关,中度以上狭窄的冠脉钙化积分值明显高于轻度狭窄,其间有统计学显著性差异(P<0.001)。MSCTCA对诊断有临床意义的冠脉中度以上狭窄的敏感度、特异度、诊断准确率、阳性预测值、阴性预测值分别约89.6%、93.9%、92.6%、86.7%、95.4%。MSCTCA对冠脉支架显示良好,检出5例9根支架,其中2根支架不通畅,出现支架内再狭窄。结论:16层螺旋CT冠脉成像安全、无创,对评价冠状动脉狭窄、支架开放及通畅性等方面有着较高的临床应用价值,可作为冠心病筛查的有效手段以及介入和手术治疗后的随访手段。     

Non-invasive evaluation of coronary artery stent patency with retrospectively ECG-gated 64-slice CT angiography

The aim of our study has been to evaluate the ability of 64-slice computed tomographic angiography (CTA) to assess coronary artery stent patency, relative to selective coronary angiography (SCA). Fifty-five consecutive patients (age range 45–80 years) with 97 previously implanted coronary artery stents underwent 64-slice CTA. The 55 patients comprised 40 subjects (group A) who were referred for follow-up SCA at a mean interval of 9.6 months after stent positioning, and 15 subjects (group B) in whom SCA was clinically indicated. Stent evaluation was performed independently by two blinded readers in terms of image quality and presence of in-stent restenosis (ISR; lumen obstruction of ≥50%). SCA was performed in 41/55 patients; 14 patients refused to undergo SCA after the 64-slice CTA exam. A total of 88 stents in 74 segments were analyzed. Twenty-one of the 74 stented segments were of poor image quality and were not considered for further analysis. Sixty-four-slice CTA detected 12/16 ISR (sensitivity: 75%) and ruled out ISR in 32/37 cases (specificity: 86%). Sixty-four-slice CTA is a valuable modality for follow-up of coronary artery stent patency only in selected patients. Appropriate candidates for follow-up 64-slice CTA should be established based on stent diameter, stent material and type as well as HR and heart rhythm. However, given the number of non-assessable segments, further work would appear necessary before 64-slice CTA can be considered a suitable procedure for broad clinical application in the evaluation of coronary artery stent patency.     

Iliofemoral arterial occlusive disease: contrast-enhanced MR angiography for preinterventional evaluation and follow-up after stent placement.

PURPOSE: To evaluate the efficacy of contrast material-enhanced magnetic resonance (MR) angiography for the diagnosis of peripheral arterial occlusion and follow-up after stent placement. MATERIALS AND METHODS: Sixty-seven patients (21 women, 46 men; mean age, 64.6 years) were examined. Digital subtraction angiography and contrast-enhanced MR angiography were performed in 28 patients for preinterventional evaluation of iliofemoral arterial occlusion and in 39 patients for follow-up after stent placement in the iliac or femoral arteries, which had been performed several months before. RESULTS: All 24 occlusions were correctly diagnosed with contrast-enhanced MR angiography. Of the 59 stenoses, 36 were greater than 50% and 23 were 50% or less. Sensitivity and specificity for the detection of stenoses greater than 50% were 100% and 83%, respectively. Patency of the different stents was determined correctly with contrast-enhanced MR angiography. Some stents caused signal intensity dropout, which made MR evaluation of stents difficult. Generally, these signal intensity artifacts were most severe in stainless steel stents and mild in some nitinol stents. CONCLUSION: Contrast-enhanced MR angiography is comparable to digital subtraction angiography for the detection of stenosis greater than 50% and occlusion in the iliofemoral arteries. Stent patency can be determined, but contrast-enhanced MR angiography is not suitable for stent evaluation owing to signal intensity dropout; however, it provides information about the vascular anatomic areas proximal and distal to the stent.     

The use of coronary stent in hepatic artery stenosis after orthotopic liver transplantation

PURPOSE: This retrospective study was undertaken to evaluate the effectiveness of coronary stent placement in hepatic artery stenosis after orthotopic liver transplantation (OLT). MATERIALS AND METHODS: Of 430 consecutive adult orthotopic liver transplant recipients between November 2003 and September 2005, 17 had hepatic artery stenosis (HAS). Fourteen of them underwent coronary stent placement in the HAS. The technical results, complications, hepatic artery patency and clinical outcome were reviewed. RESULTS: Technical and immediate success was 100%. After a mean follow-up of 159.4 days (range, 9-375 days), all patients obtained patent hepatic arteries except 2 patients occurred hepatic artery restenoses at 26 and 45 days after stent placement, respectively. Kaplan-Meier curve of patency showed cumulated stent patency at 3, 6, and 12 months of 78%, 58% and 45%, respectively. During the follow-up, 8 patients survived, 5 died of septic multiple-organ failure, 1 received retransplantation because of refractory biliary infection. Hepatic artery dissection induced by a guiding catheter occurred in one patient and was successfully treated with a coronary stent. CONCLUSION: Hepatic artery stenosis after OLT can be successfully treated with coronary stent placement with low complication rate and an acceptable 1-year hepatic artery patency rate.     

应用覆膜支架介入救治颈动脉破裂并假性动脉瘤

目的 探讨应用覆膜支架介入治疗颈动脉破裂并假性动脉瘤。方法4例肿瘤所致颈动脉破裂并假性动脉瘤形成的患者,均出现颈部或口腔危及生命的出血,采用Seldinger方法,选用自膨式聚四氟乙烯覆膜支架治疗。结果4例成功施行血管内介入治疗,其中颈总动脉中段1例,颈动脉球2例,颈总动脉远段1例。共置入覆膜支架6枚。术后假性动脉瘤腔被隔绝,颈动脉通畅,患者的临床症状明显改善,无神经功能障碍。1例患者11d后支架下缘颈总动脉与原瘤腔相通,再次置入覆膜支架,2个月的随访无再出血。1例患者经钢圈栓塞、放置覆膜支架及裸支架瘤腔隔绝,但术后6周先前的支架下缘出现假性动脉瘤,经置入覆膜支架后出血停止。结论自膨式聚四氟乙烯覆膜支架治疗颈动脉破裂并假性动脉瘤是患者安全、有效的方法,特别是在救治伴有出血的颈部假性动脉瘤,支架的长期效果有待于进一步随访观察。     

球囊扩张式冠脉支架治疗原位肝移植后肝动脉狭窄

目的探讨与分析球囊扩张式冠脉支架在治疗原位肝移植术后肝动脉狭窄中的作用和意义。方法回顾性分析我院2004年6月到2006年9月11例肝移植术后肝动脉狭窄患者的血管内支架治疗资料。结果11例患者共使用13枚球囊扩张式冠脉支架治疗,其中1例由于病变长度,需要2枚支架;1例出现再狭窄需要第2次支架植入。所有病例支架植入技术成功率为100%,随访中未出现与支架术相关的并发症。结论球囊扩张式冠脉支架在肝移植后肝动脉狭窄的治疗中应用安全有效,有极好的技术成功率和中期通畅率。     

Standard dose Gd-DTPA dynamic MR of renal arteries

Renal MR contrast enhancement depends on the timing of image acquisition. Limited human trials have demonstrated efficacy of renal artery stents on salvage of renal function. This study assessed the ability of dynamic gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) administration to demonstrate renal artery stenosis and renal stent patency compared to conventional angiography as the gold standard. Twenty subjects referred for renal angiography underwent 22 dynamic MR studies, including 7 with renal artery stenting (Palmaz P204 or P201, Johnson & Johnson, Sydney, Australia). All were examined with conventional angiography and after dynamic Gd-DTPA infusion. Coronal MR images of the kidneys were acquired using a GE Signa 1.5-T magnet (General Electric Medical Systems, Milwaukee, WI) (fast spoiled gradient echo [FSPGR]; TE = 4.2 msec, TR = 68–150 msec, flip angle = 75°) 0 to 600 seconds after iv bolus injection of 15 ml of Gd-DTPA during sequential breath-hold acquisitions, 13 to 32 seconds each. All 51 renal arteries (13 stenosed, 38 normal) were detected with dynamic MRI. Severity of renal artery stenosis was classified correctly with an accuracy of 98% (95% confidence interval [CI]: 85–100), yielding 98% specificity and 100% sensitivity. All nine renal stents were visualized with 100% accurate patency documentation. FSPGR MRI with bolus Gd-DTPA administration can provide adequate time and spatial resolution to demonstrate renal artery stenosis.     

多层螺旋CT冠状动脉成像的临床应用探讨

目的：探讨多层螺旋CT冠状动脉成像技术的应用和临床价值。材料和方法：对32例（包括3例冠状动脉搭桥术后和1例冠状动脉成形术及支架置入术后病人）进行了MSCT冠状动脉成像检查，并进行CT图像重建后处理，重建出各主要血管，对冠状动脉搭桥术后的病人重建出桥血管及含支架血管。分析MSCT对冠状动脉的显示能力，并分析是否有管壁钙化和软性斑块，评价管腔狭窄及其程度。对桥血管和支架的显示及通畅性进行评价。结果：MSCT冠状动脉成像对冠状动脉近中段显示清晰，显示率达90％以上；对冠状动脉钙化和软性斑块显示良好，对冠状动脉狭窄显示较佳。7根搭桥血管其中有1根可见约75％-90％的狭窄，其余均通畅，支架显示良好。结论：MSCT冠状动脉成像可作为冠状动脉粥样硬化疾患筛选手段，对血管搭桥术和支架放置并进行术后评价有很高的价值。     

颈动脉复杂性狭窄的血管内支架治疗

目的　报道５ 例颈动脉复杂性狭窄的血管内支架治疗结果,旨在评价血管内支架治疗颈动脉复杂性狭窄的可行性及临床疗效。方法　５ 例具有症状性颈动脉狭窄患者行血管内支架置入术治疗。颈动脉狭窄的病因包括动脉粥样硬化（ｎ ＝ ３） 和放射治疗后纤维化狭窄（ｎ ＝ ２） 。Ｄｏｐｐｌｅｒ 超声波检查提示颈动脉狭窄,并经血管造影证实。本组病例使用自展式Ｗａｌｌｓｔｅｎｔ 型支架。术后随访４ ～２２ 个月。结果　颈动脉造影显示全部患者颈动脉狭窄程度均大于７５ ％ ;狭窄位于颈总动脉（ＣＣＡ）３ 例,颈内动脉（ＩＣＡ）２ 例;病变长度２０ ～６０ｍｍ 。全部患者颈动脉内支架置入成功。１ 例术中出现短暂性脑缺血（ＴＩＡ） ,无其它并发症发生。随访期间无神经病学后遗症和支架内血栓形成。Ｄｏｐｐｌｅｒ 超声波检查未发现血管内支架早期及迟发性再狭窄。结论　应用血管内支架治疗颈动脉复杂性狭窄具有技术可行性和安全性,具有满意的中期开通率。     

Assessment of coronary artery bypass grafts: value of different breath-hold MR imaging techniques

OBJECTIVE: Our aim was to evaluate the patency of coronary artery bypass grafts and to detect graft stenosis using different breath-hold MR imaging techniques. SUBJECTS AND METHODS: Twenty-two patients with 59 grafts (14 internal mammary artery grafts and 45 saphenous vein grafts) and 76 distal anastomoses (singular and sequential grafts) were studied using a 1.5-T scanner. A two-dimensional T2-weighted breath-hold half-Fourier acquisition single-shot turbo spin echo (HASTE) sequence and a three-dimensional breath-hold contrast-enhanced MR angiography sequence (fast imaging with steady-state free precession) were performed. For MR angiography, a bolus of 20 ml of gadopentetate dimeglumine was used. Time delay for contrast injection was calculated by a test bolus. The gold standard was coronary angiography performed within 14 days of MR imaging. All images were evaluated independently by two radiologists. RESULTS: With the HASTE sequence, 95% of the patent grafts were recognized (42/44); specificity was 93% (14/15). MR angiography had both a sensitivity (41/44) and specificity (14/15) of 93%. Interobserver agreement for both sequences was good (Cohen's kappa = 87%; McNemar test, p = 56%). Forty-nine (83%) of 59 patent distal graft anastomoses were revealed with the HASTE sequence; 38 (64%) of 59 were seen on contrast-enhanced angiography. With HASTE imaging, only two of eight hemodynamically significant graft stenoses were detected. MR angiography revealed only four of eight significant graft stenoses. CONCLUSION: The HASTE sequence and three-dimensional MR angiography proved to be useful MR techniques when evaluating the patency of coronary artery bypass grafts. However, reliable detection of graft stenosis does not yet seem possible with these imaging techniques.     

Magnetic resonance angiography of stents

PURPOSE: To understand the behavior of stents during contrast-enhanced magnetic resonance angiography (MRA). MATERIALS AND METHODS: Seven different types of stents are explored in vitro with spin echo (SE) T2 sequence and MRA sequences using classification of the intra-prothesis signal. Six patients with 11 different proximal stents are studied by Gadolinium enhanced MRA with the same classification. RESULTS: Stent material is not the only determinant of behavior. In this way, one stainless steel stent produced less intra-luminal hyposignal than a nitinol device. Nevertheless, only a nitinol stent did not alter the intra-prothesis signal and allowed an appreciation of patency, despite a decrease of diameter and presence of edge artifacts. CONCLUSION: Even if stent compatibility is well known with MRI, even with Gadolinium, cannot be used alone to depict stenosis or diameter reduction. Even patency based on the presence of a constant signal, cannot be confirmed routinely with confidence: indeed, only a single stent does not modify intra-arterial signal.     

冠脉支架ZetaTM和DriverR的临床应用观察

 目的观察冠脉支架Multi-Llink RX ZetaTM和DriveR的特点、临床应用的安全性及其短期随访结果.方法分析经选择性冠状动脉造影(Coronary angiography,CAG)证实为管腔狭窄面积＞75%的冠心病(Coronary heart disease,CHD)患者87例,46例冠状动脉内置入Multi-Llink RX ZetaTM支架,共置入支架47只;41例冠状动脉内置入DriverR支架,共置入支架41只,观察支架术后疗效和6个月内临床心脏事件(Major adverse cardiac events,MACE)发生率以及再狭窄率.结果两组手术成功率均为100%.Multi-Llink RX ZetaTM支架组,血管扭曲病变及长病变占89.5%,6个月MACE发生率为2.2%,再狭窄率为12.6%;DriverR支架组,扭曲病变及长病变占87.8%,分叉病变占46.7%,其中,直接置入支架4个,6个月MACE发生率为2.4%,再狭窄率为12.2%.结论两组手术成功率高,治疗扭曲病变及长病变疗效好,MACE发生率和6个月再狭窄率均较低;Multi-Llink RX ZetaTM支架具有良好的跟踪性和高穿过性,DriverR支架具有可弯曲性好、支撑力好、侧孔大、易到位等优点,直接置入成功率高,对边支血管影响小,适用于分叉病变.     

Metallic artifacts of coronary and iliac arteries stents in MR angiography and contrast-enhanced CT.

Metallic artifacts of intravascular stents were assessed with MR angiography and contrast-enhanced spiral CT. Stainless steel showed less metal artifact than tantalum stent in CT. Metallic artifact in coronary and iliac arteries treated with tantalum stent was not remarkable in MR angiography. Contrast-enhanced CT might be preferable to assess patency of arteries treated with stainless steel stent. while MR angiography was useful in depicting intraluminal signal in tantalum stent.     

冠状动脉造影及支架置入术在冠心病诊断与治疗的临床应用

目的　评价冠状动脉造影及支架置入术在冠心病诊断与治疗的临床应用价值。方法　对 40例 47支冠状动脉病变内置入 5 6只支架 ,其中置入前降支 2 9只 ,右冠状动脉 1 8只 ,左回旋支 9只。结果　 40例全部置入成功 ,置入后经冠状动脉造影证实狭窄消失 ,即刻效果良好 ,由术前狭窄 ( 88.9± 8.1 ) %减至术后残余狭窄 ( 5 .6± 5 .1 ) %,支架置入成功率 1 0 0 %。术后低血压反应 2例 ,血肿 3例。结论　冠状动脉造影及支架置入术是冠心病诊断与治疗的一种安全可靠、效果良好的介入性诊断治疗方法 ,值得临床广泛应用。     

Endovascular stents in pulmonary valve and artery in swine: feasibility study of MR imaging-guided deployment and postinterventional assessment

PURPOSE: To assess the feasibility of using magnetic resonance (MR) imaging to guide stent deployment in the pulmonary valve and artery and evaluate, after stent deployment, the position and morphology of and blood flow through the stent. MATERIALS AND METHODS: Angiography and 1.5-T MR imaging were performed in a dual-imaging suite. Nitinol stents were placed in the pulmonary valve and main pulmonary artery in five pigs by using MR imaging guidance. For interactive MR imaging monitoring of catheter manipulation and stent delivery, balanced fast field-echo and T1-weighted turbo field-echo sequences were used. Visualization of the delivery system was based on T2* (with air as the contrast material) or T1 (with gadodiamide as the contrast material). After stent deployment, the position and morphology of and flow through the stent were verified with multiphase multisection balanced fast field-echo and velocity-encoded cine MR imaging. Findings at angiography and postmortem examination also helped verify stent placement. The paired Student t test was used for data analysis. RESULTS: The stent was successfully deployed in all animals. The stent was placed distal to the pulmonary valve in four animals and across the pulmonary valve in one animal. The position and morphology of the stent were clearly depicted on balanced fast field-echo images. In the animal with the stent placed across the pulmonary valve, the pulmonary regurgitant fraction was 37%; this was not seen in the animals with stents placed distal to the pulmonary valve. No complication (eg, stent migration, intramural injury, or vascular perforation) was noted during the intervention. Findings at angiography and postmortem examination confirmed the position of the stents. CONCLUSION: MR imaging has the potential to guide stent placement in the pulmonary valve or artery and to evaluate flow volume within the stent lumen after the intervention.     

电子束CT血管造影对冠状动脉内支架开通的评价

目的 :探讨电子束CT(EBT)血管造影在冠状动脉支架的定位及评价支架开通中的应用价值。方法 :5 6例患者分别于冠状动脉造影术后 1月～ 6年接受EBT检查。采用单层序列平扫及增强扫描、单层或多层血流序列扫描。三维重建采用最大密度投影法 (MIP)及曲面重建法 (CPR) ,三维结果均与手术结果对照 ,其中 8例有EBT检查后的造影结果。结果 :86支冠状动脉于造影中放置 12 0枚支架 ,EBT准确定位 118枚 (98.3% )。其中 4 0支显示通畅 ,通畅率 4 6 .5 % ;37支血管狭窄 ,狭窄率 4 3% ;9支冠状动脉支架内闭塞。结论 :①EBT血管造影及三维重建可准确定位冠状动脉内支架并判断支架开通 (通畅、狭窄、闭塞 )的情况 ;血流分析可提供支架远端血管的血流曲线及定量数据 ,是评价支架开通重要的定量补充诊断 ;②EBT可作为支架置入术后长期随访的无创检查方法 ,可部分减少冠状动脉造影有创复查的次数 ;③限度 :无法准确评价狭窄的程度     

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.     

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.