冠状动脉内支架置入术在冠心病治疗中的应用

目的 :评价冠状动脉内支架置入术在冠心病治疗中的临床应用价值。方法 :对 186例 2 0 4支冠状动脉病变内置入 2 2 9只支架 ,其中置入左前降支 12 3只 ,右冠状动脉 73只 ,左回旋支 31只 ,左主干 2只。结果 :186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。其中 12例急性心肌梗死患者急诊置入支架后 10例病情迅速缓解 ,2例术后死亡 ,死因分别为再次心肌梗死和颅内出血。择期冠状动脉支架置入术无一例死亡。其他并发症为股动脉假性动脉瘤 2例 ,术后低血压反应 9例。结论 :冠状动脉内支架置入术是治疗冠心病的一种安全可靠、效果良好的介入性治疗方法 ,值得临床广泛应用。     

冠状动脉内支架置入术在冠心病治疗中的价值

目的 评价冠状动脉内支架置入术在冠心病治疗中的临床应用价值。方法 对157例206支冠状动脉病变内置入203只支架，其中置入左前降支103只，右冠状动脉57只，左回旋支42只，左主干1只。结果 157例全部置入成功。置入后经冠状动脉造影证实狭窄消失，效果良好。其中5例急性心肌梗死患者由于急诊置入支架后，病情迅速缓解。择期冠状动脉支架置入术全部置入成功，无一例发生严重并发症。结论 冠状动脉内支架置入术是治疗冠心病的一种安全可靠、效果良好的介入性治疗方法、有良好的应用价值。     

无预扩张直接冠状动脉内支架置入术

目的　探讨无预扩张直接冠状动脉内支架置入术的可行性及临床效果。方法　参照国外直接冠状动脉内支架置入术标准 ,对 2 7例冠心病患者进行无预扩张直接冠状动脉内支架置入术。结果　 2 7例患者共 2 8处病变 ,置入 2 8个支架 ,其中 A型病变 14例 ,B1 型病变 10例 ,B2 型病变 4例。置入支架前管腔狭窄程度为 78.2 %± 5 .6% ,支架置入后血管残存狭窄程度为 0 .9%± 1.4% ,支架置入成功率为 10 0 % ,无并发症发生。术后随访 1年 ,2例患者出现心绞痛 ,冠状动脉造影证实 1例患者出现支架内再狭窄。结论　正确选择适应证的情况下 ,无预扩张直接冠状动脉内支架置入术是一种安全有效的治疗方法 ,可获得较好的近、远期临床效果     

老年冠心病患者冠状动脉内支架置入术的疗效评价

目的　评价老年冠心病患者冠状动脉内支架置入术的临床疗效和安全性。方法　对比分析 49例老年 (86支血管 )和 6 1例老年前期 (98支血管 )冠心病患者冠状动脉内支架置入术的结果。结果　老年组冠状动脉病变严重、复杂病变较多 ,在复杂病变内置入支架比率高于老年前期组 ;手术即刻成功率和临床成功率均为 98.0 % ;术前病变平均狭窄率为 (94.5± 5 .6 ) % ,术后残余狭窄率为 (7.4± 8.2 ) % ;因球囊扩张不理想置入支架的为 45 .0 % ,因经皮冠状动脉腔内成形术 (PTCA)并发夹层或濒临闭塞而置入支架的比率高于老年前期组。出现严重并发症 1例(2 .0 % )。结论　老年冠心病患者冠状动脉内支架置入术成功率高 ,并发症发生率低。     

原发性冠状动脉夹层的造影特点及介入治疗

目的　了解原发性冠状动脉夹层 (SCAD)的发生情况及介入治疗的效果。方法　分析 22 16例冠状动脉造影以发现SCAD ;对适合经皮冠状动脉介入治疗术 (PCI)的SCAD患者行支架置入术 ,手术前后及手术中按要求使用阿司匹林、氯吡格雷、肝素或低分子肝素等药。结果　发现SCAD共 2 6例 ,男 19例 ,女 7例 ,平均年龄 (6 0 9± 11 6 )岁 (34～ 75岁 ) ,检出率为 1 17%。其中急性心肌梗死 15例 ,不稳定型心绞痛 11例。 2 6例患者共 2 8支血管发生SCAD。其中冠状动脉左主干 1例 ,左前降支 9例 ,回旋支 4例 ,右冠状动脉 14例。对适合PCI术的 18例患者 19支血管撕裂处行支架置入术。其中 14例 15处行经皮腔内冠状动脉成形术 (PTCA) 支架置入术 ,4例行直接支架置入术。撕裂处共置入支架 2 3枚。支架置入术后 ,1例冠状动脉原发性撕裂处残余狭窄小于 30 % ,另 1例残余狭窄小于 10 % ,其余 16例均无残余狭窄。经介入治疗后患者的临床症状均明显缓解。结论　SCAD并非罕见 ,存在冠状动脉粥样斑块者是SCAD相对高发的人群。支架置入术是治疗SCAD较为理想的方法。     

应用小C臂X光机行经皮冠状动脉腔内成形术(附134例报告)

目的探讨应用小Ｃ臂Ｘ光机（ＯＥＣ）行经皮冠状动脉腔内成形术（ＰＴＣＡ）和冠状动脉内支架植入术的可行性。方法１３４例冠心病患者造影显示冠状动脉狭窄程度均≥７５％,采用美国ＯＥＣ９６００型小Ｃ臂Ｘ光机行ＰＴＣＡ和冠状动脉内支架置入术。结果１３４例冠心病患者共２０４处病变成功地完成了ＰＴＣＡ,其中９２例置入了１０６枚冠脉内支架,６例因多支冠脉病变分别置入２～３枚支架,术后冠脉造影显示管腔扩张满意,无残余狭窄。全部病例术后心绞痛症状较术前明显减轻或消失。除１例在支架置入术后发生急性血栓形成和３例出现术后穿刺部血肿外,无其它并发症发生。结论对冠心病患者应用小Ｃ臂Ｘ光机行ＰＴＣＡ和冠脉内支架置入术可能是一种安全有效的治疗方法。     

Multi-Link冠状动脉内支架的临床应用和长期随访结果

目的 :评估 Multi- L ink冠状动脉内支架置入术的临床疗效。　　方法 :总结和分析行 Multi- L ink支架置入术的 96例冠心病患者 ,并做长期临床随访和冠状动脉造影复查。　　结果 :共置入 Multi- L ink支架 116只 ,平均每例 1.2 (1～ 4)只。急性心肌梗塞行直接冠状动脉内支架置入术 30只 ,初发原位病变 (De Novo) 34只 ,经皮冠状动脉腔内成形术 (PTCA )效果不满意 38只 ,非阻塞性内膜撕裂 9只和濒临闭塞(bailout) 2只 ,再狭窄病变 3只。手术成功率 99.0 %。住院期间死亡 1例 ,余无其他心脏事件发生。49.0 %患者于术后平均 17± 11个月复查冠状动脉造影 ,再狭窄率为 2 .1%。临床随访 2 7± 8个月 ,无临床心脏事件生存率为 91.6 %。　　结论 :Multi- L ink冠状动脉内支架置入术是一种安全和有效的治疗冠心病的方法。     

经皮桡动脉冠状动脉造影及冠状动脉成形术的临床应用

目的 :评价经皮桡动脉冠状动脉造影术与冠状动脉腔内成形术 (PTCA)的临床应用价值。方法 :有选择性的对 37例患者行经皮桡动脉途径冠状动脉造影及冠状动脉成形术 ,观察其疗效和血管并发症。结果 :1 桡动脉穿刺成功率为 93 8% (有 2例失败 )。 2 14例冠状动脉造影正常 ,17例冠状动脉造影显示 2 6处存在≥ 70 %的狭窄病变 ,适合行冠状动脉介入手术。 2 6处病变有 4处PTCA疗效满意 ,2 2处行PTCA +支架术 ,植入支架 31只。狭窄从 (81± 12 ) %降低至 (10 6± 7 4 ) % ,最小血管直径由 (0 86± 0 12 )mm增加至 (3 0 8± 0 32 )mm。 6例病人行冠状动脉旁路移植术。 3 所有患者术后即拔导管鞘 ,局部压迫 4h。术后并发症的发生率为 3 3% (1例术后的桡动脉闭塞 )。结论 :经桡动脉途径行冠状动脉造影及冠状动脉成形术安全可行 ,其具有穿刺部位出血少、住院时间短的特点 ,可选择性的应用于某些冠心病患者。     

Coroflex冠状动脉内支架的临床应用

目的　评估Coroflex冠状动脉内支架的临床应用效果。方法　回顾性分析 81例接受Coroflex冠状动脉内支架置入术患者的即刻疗效和临床随访结果。结果　 81例患者共置入Coroflex冠状动脉内支架 88枚。根据ACC AHA分型 ,A B1 型病变 38处 ,B2 C型病变 5 0处。原发病变 5 2处 ,单纯球囊扩张术疗效不满意病变 2 2处 ,内膜撕裂病变 14处。支架成功置入 82处 (93 2 % )。 3例严重钙化病变需辅以高压 (16～ 18atm)球囊才充分扩张 ,2例支架远端发生内膜撕裂 ,1例弥漫性病变支架置入术后TIMI血流 2级。 75例患者平均随访 (7 5± 3 0 )月 (3～ 13月 ) ,无心源性死亡和心肌梗死 ;17例 (2 2 7% )有心绞痛 (CCS分类Ⅰ级 )发生 ;7例行冠状动脉造影复查 ,2例显示支架内再狭窄 ,予再次血管重建术后缓解。结论　Coroflex冠状动脉内支架可安全有效地应用于冠心病的介入治疗。     

Driver冠状动脉内支架的临床应用

目的评估Driver冠状动脉内支架的临床应用效果。方法回顾性分析49例接受Driver冠状动脉内支架置入术患者的即刻疗效和临床随访结果。结果49例患者根据ACC/AHA分型,A-B1型病变25处,B2-C型病变29处。全部支架成功置入。1例术后TIMI血流2级。平均随访6～9月,无心源性死亡和心肌梗死,2例行冠状动脉造影复查,未显示支架内再狭窄。结论Driver冠状动脉内支架可安全有效地应用于冠心病的介入治疗。     

Complete Myocardial Revascularization by Single Session Triple Vessel Percutaneous Coronary Angioplasty and Provisional Stenting

Background: Although availability of stents has made percutaneous transluminal coronary angioplasty (PTCA) safer, single vessel angioplasty still represents 90% of procedures performed today. We report our initial experience with single session triple vessel angioplasty, using stents as needed to improve suboptimal balloon results. Patients: Fourteen patients (12 men, 85%), aged 67 ± 19 years were treated. All had triple vessel disease and angina. Mean left ventricular ejection fraction was 61%± 8%. Results: PTCA was attempted in all three coronaries or one of their major branches during the same procedure. Seventeen target lesions were in the left anterior descending coronary artery, 2 in a diagonal branch, 11 in the left circumflex, 2 in a marginal branch, 13 in the right coronary artery, 3 in the posterior descending, and 1 a saphenous vein graft. PTCA of 3.5 ± 0.7 sites/procedure was attempted. The success rate was 13 (93%) of 14 patients and 47 (96%) of 49 lesions. Thirty-four (69%) lesions were treated by implantation of one or several stents, and 10 (71%) of 14 patients received at least one stent. Hospital stay duration was 4 ± 2 days. One patient required repeat PTCA to treat subacute stent thrombosis 2 days after the procedure (creatine kinase [CK] peak < 2 times upper limit of normal). There were no in-hospital deaths, Q-wave infarction, or need for coronary artery bypass grafting (CABC). After a median follow-up period of 24 months (range 3–102), one (7%) patient had died of a noncardiac cause, three (21 %) had required repeat PTCA for restenosis in previously dilated lesions, and none had suffered a myocardial infarction. At follow-up, the median angina class was I (range I-II). Conclusion: For selected patients with three vessel disease, complete revascularization by single session PTCA and provisional stenting as needed is feasible, and is associated with a low rate of short- and long-term complications when successfully performed.     

Short stent implantation for routine use is feasible in a high proportion of coronary interventions and yields a low restenosis rate

Stent length predicts restenosis. The feasibility of using a short stent (<10 mm) routinely was investigated in 331 consecutive patients treated for 424 coronary artery lesions. A single short stent provided suitable coverage and achieved a residual stenosis <30%, with or without predilatation, in 252/424 lesions (59.4%). Longer stents were implanted in 58/424 lesions (13.7%), while only percutaneous transluminal coronary angioplasty was performed in 114/242 lesions (26.9%). Angiographic success and procedural success were achieved in 250/252 lesions (99.2%). Restenosis occurred in 36/231 lesions (15.6%) after short stenting, in 10/53 lesions (18.9%) after long stents, in 21/88 lesions (23.9%) after percutaneous transluminal coronary angioplasty, and in 67/372 lesions (18.0%) controlled angiographically. Only small vessel diameter predicted restenosis after short stenting. Thus, a single short stent implanted directly or after predilatation is sufficient to achieve an acceptable angiographic result in more than in nearly 60% of all treated lesions. Short stenting results in a low restenosis rate.     

Long-Term Restenosis After Multiple Stent Implantation: A Quantitative Angiographic Study

Elective high pressure stent implantation in focal coronary lesions has a high procedural success and low incidence of restenosis in comparison with balloon angioplasty. For the treatment of diffusely diseased coronary arteries, however, a high incidence of subacute thrombosis and late restenosis has been reported. The aim of this study was the prospective evaluation of procedural and long-term outcome after implantation of multiple stents. In a consecutive series of 48 patients, 48 lesions were treated with the implantation of 120 stents (2.5 ± 1.0 stents/lesion). Stent implantation was performed electively in 15%, for dissection in 56%, and for suboptimal balloon angioplasty result in 29% of patients. The lesion length before stenting, including balloon angioplasty induced dissections, was 28.5 ± 9.8 mm (range 20–62), the mean length of the stented segment was 40 ± 16 mm. The procedure was successful in 45 patients (95%). Procedural related complications included two urgent bypass operations (4%) and one transmural myocardial infarction (2%). Two subacute stent thrombosis events (4%) occurred, both in-hospital, 1 and 3 days after implantation. Follow-up was obtained in 43 eligible patients at 6.4 ± 1.3 months, revealing an overall restenosis rate of 30% (13 patients). Quantitative angiography (CAAS II, edge detection algorithm) showed a minimal lumen diameter of 0.93 ± 0.28 mm (diameter stenosis 62%± 13%) before treatment, 2.81 ± 0.26 mm (diameter stenosis –4 ± 13%) after stenting, and 1.79 ± 0.58 mm (diameter stenosis 30%± 20%) at follow-up. Predictors of restenosis were not identified. Thus, multiple stent implantation has high procedural success and the late restenosis of long lesions after multiple stents compares favorably with balloon angioplasty.     

Efficacy of Coronary Stenting Versus Balloon Angioplasty in Small Coronary Arteries

Objectives. The goal of this study was to compare the efficacy of elective stent implantation and balloon angioplasty for new lesions in small coronary arteries.Background. Palmaz-Schatz stents have been designed and approved by the Food and Drug Administration for use in coronary arteries with diameters ≥3.0 mm. The efficacy of elective stent placement in smaller vessels has not been determined.Methods. By quantitative coronary angiography, 331 patients in the Stent Restenosis Study (STRESS) I–II were determined to have a reference vessel <3.0 mm in diameter. Of these, 163 patients were randomly assigned to stenting (mean diameter 2.69 ± 0.21 mm), and 168 patients were assigned to angioplasty (mean diameter 2.64 ± 0.24 mm). The primary end point was restenosis, defined as ≥50% diameter stenosis at 6-month follow-up angiography. Clinical event rates at 1 year were assessed.Results. Baseline clinical and angiographic characteristics were similar in the two groups. Procedural success was achieved in 100% of patients assigned to stenting and in 92% of patients assigned to angioplasty (p < 0.001). Abrupt closure within 30 days occurred in 3.6% of patients in both groups. Compared with angioplasty, stenting conferred a significantly larger postprocedural lumen diameter (2.26 vs. 1.80 mm, p < 0.001) and a larger lumen at 6 months (1.54 vs. 1.27 mm, p < 0.001). Restenosis (≥50% diameter stenosis at follow-up) occurred in 34% of patients assigned to stenting and in 55% of patients assigned to angioplasty (p < 0.001). At 1 year, event-free survival was achieved in 78% of the stent group and in 67% of the angioplasty group (p = 0.019).Conclusions. These findings suggest that elective stent placement provides superior angiographic and clinical outcomes than balloon angioplasty in vessels slightly smaller than 3 mm.     

Elective Coronary Stenting as an Adjunct to Balloon Angioplasty in Stable Coronary Artery Disease: No Association with Incidence of Acute Complications. Results of the PTCA Registry of the German Community Hospitals

Background: Elective coronary stenting has hem shown to reduce the rate of recurrent stenoses after angioplasty but no firm data are available on its possible association with in-hospital ischemic complications . Methods: We analyzed the data of the registry of the German community hospitals covering approximately one quarter of all interventions in Germany. We included all angioplasty procedures performed in patients with stable coronary artery disease in 1996. Interventions with elective coronary stenting were compared to those with conventional balloon angioplasty. Interventions with bailout stenting were excluded . Results: Of 19,170 angioplasty procedures, 32.2% included elective coronary stenting. The immediate angiographic success rate (residual stenosis < 50%) was 90.6% of the procedures with stents versus 86.3% of those without stents (P < 0.001). The overall incidence of complications (death, myocardial infarction, bypass surgery, vessel closure, reintervention) was 3.9% and 3.8% (NS). Major events (death, myocardial infarction, bypass surgery) were more common in the stent-treated group (1.8% vs 1.4%, P = 0.027). In multivariate analysis, the following factors were significantly associated with complications: residual stenosis ≥ 50%, female gender, angioplasty of proximal left anterior descending coronary artery, morphological fype of lesion B2 or C, and multivessel disease. Angioplasty of restenoses after previous angioplasty was associated with significantly less risk than of de novo lesions. Stents were neutral with respect to the overall incidence of complications . Conclusions: Complications after elective coronary angioplasty remain largely unpredictable in individual patients despite the identification of several clinical and procedural risk factors. Elective coronary stenting is not associated with the immediate therapeutic risk of angioplasty in stable coronary artery disease .     

Deep Intubation of 6 French Guiding Catheters for Transradial Coronary Interventions

Deep intubation of coronary guides may improve the backup support required to deliver interventional materials through 6 French catheters. Eighteen patients (17 male, 1 female) with 20 lesions were selected for transradial angioplasty and stenting using the Cordis Long Brite Tip¨ guide. Patients with an evolving acute myocardial infarction and those with an abnormal Allen test were excluded. All patients were pretreated with aspirin, ticlopidine, and heparin. The mean age was 55 (range 34D81). The target vessel was the right coronary in 6 of 20 (30%), the circumflex artery in 6 of 20 (30%), left anterior descending in 4 of 20 (20%), vein grafts in 3 of 20 (15%), and ramus intermedius in one case (5%). Seventeen lesions were treated with stents, and 3 with PTCA alone. Three lesions received 2 stents. Procedural success (less than 20% residual stenosis) was obtained in 19/20 cases. No dissections were seen as a result of deep intubation. Dampening of pressure and ischemia occurred in only 2 patients. Deep intubation with this guide may be safely used to obtain support when performing 6 French angioplasty and stenting using the transradial approach.     

经皮冠状动脉腔内成形术后再狭窄与介入前病变形态学的关系

目的：探讨国人冠心病经皮冠状动脉腔内成形术（ＰＴＣＡ）后再狭窄与冠状动脉（冠脉）病变类型、部位和病变血管数的关系。　　方法：冠心病介入治疗３５２ 例,选择其中６５ 例（８６个病变）术后３～１６个月造影随访者,按随访结果分为再狭窄组（ｎ＝ ３８）,非再狭窄组（ｎ＝ ２７）,分析再狭窄与病变形态学的关系。　　结果：再狭窄与多个易患因子、多支病变、病变类型和前降支病变呈正相关,与支架置入呈负相关。再狭窄组Ｃ型、钙化病变多见,前降支病变内径丢失比回旋支、右冠脉病变大（Ｐ＜ ０．０５）,半年内一支血管病变再狭窄率（１０．２７％ ）低于二支（４１．１０％ ）和三支（４８．５０％ ）血管病变再狭窄率（Ｐ＜ ０．０００１）。　　结论：再狭窄与冠脉病变类型、部位和血管支数相关,Ｃ型及钙化、多支和前降支病变再狭窄率高     

Unprotected left main coronary artery stenting: immediate and medium-term outcomes of 24 procedures

OBJECTIVES: We have examined the immediate and long-term patient outcomes following angioplasty of unprotected left main coronary artery stenoses. BACKGROUND: Coronary disease of the unprotected left main artery is considered as an absolute contraindication for percutaneous intervention. Recently, several studies have reported good results with unprotected left main coronary artery stenting when surgical revascularization was contraindicated. METHODS: From October 2004 to June 2006, 24 patients with a contraindication to surgery and with unprotected left main coronary artery stenoses received stents. Patients were surveyed at one, six and 12 months with telephone interviews. RESULTS: The procedure's success rate was 100%. The percentage of stenosis and minimum lumen diameter (MLD) were respectively 63.4% (+/-15.4) and 1.1mm (+/-0.5) before procedure; 13.8% (+/-10.2) and 3.2mm (+/-0.5) after angioplasty. The size of stents averaged 3.79mm (+/-0.46) with an average 1.04 stents per patient. During follow up, two deaths occurred (8.3%). No intrastent restenosis was found. CONCLUSIONS: Stenting of unprotected left main coronary artery stenoses may be a safe and effective alternative to coronary artery bypass especially when surgical revascularization is contraindicated. However, further studies with larger patient populations are needed to assess the late outcome and to clarify the relevance of percutaneous intervention compared to surgery.     

Unprotected left main coronary artery stenting: immediate and medium-term outcomes of 140 elective procedures

OBJECTIVES: We sought to evaluate immediate and late outcomes after stenting for left main coronary artery (LMCA) stenosis. BACKGROUND: Conventional percutaneous transluminal coronary angioplasty (PTCA), for which coronary artery bypass grafting (CABG) has been the gold standard therapy for years, has yielded poor results in unprotected LMCA lesions. The development of coronary stents, together with their dramatic patency improvement provided by new antiplatelet regimens and their validation against restenosis, warrants a reappraisal of angioplasty in LMCA stenosis. METHODS: From January 1993 to September 1998, 140 consecutive unselected patients with unprotected LMCA stenosis underwent elective stenting. Group I included 47 high-CABG-risk patients, and group II included 93 low-CABG-risk patients. Ticlopidine without aspirin was routinely started at least 72 h before the procedure and continued for one month. Patients were reevaluated monthly. A follow-up angiography was requested after six months. RESULTS: The procedure success rate was 100%. One-month mortality was 9% (4/47) in group I and 0% in group II. A follow-up angiography was obtained in 82% of cases, and target lesion revascularization was required in 17.4%. One-year actuarial survival was 89% in the first 29 group I patients and 97.5% in the first 63 group II patients. CONCLUSIONS: Stenting of unprotected LMCA stenosis provided excellent immediate results, particularly in good CABG candidates. Medium-term results were good, with a restenosis rate of 23%, similar to that seen after stenting at other coronary sites. Stenting deserves to be considered a safe and effective alternative to CABG in institutions performing large numbers of PTCAs.     

血管内支架置入术治疗症状性椎动脉开口处狭窄临床效果及随访

目的探讨血管内支架置入术治疗症状性椎动脉开口处狭窄的手术疗效及安全性。方法回顾性纳入2010年11月—2013年1月中日友好医院神经内科收治的40例症状性椎动脉开口处狭窄且狭窄率≥70%的患者,所有患者接受血管内支架置入术治疗,其中置入金属裸支架15例,置入药物洗脱支架25例。分析患者手术技术成功率、围手术期并发症及症状缓解率,同时,在随访期内(13~36个月),观察支架血管供血区的卒中和死亡事件以及相关缺血症状并记录再狭窄率。结果对40例患者共置入42枚支架,技术成功率100.0%。椎动脉开口处术前狭窄率为75%~99%,平均(85±7)%;术后残余狭窄率为0~20%,平均(6±4)%。围手术期无并发症发生。随访期内19例临床症状完全消失,16例明显改善,症状缓解率87.5%。未发生支架血管供血区相关的卒中和死亡,4例发生后循环短暂性脑缺血发作;13例术后出现再狭窄,其中金属裸支架10例,药物洗脱支架3例,置入金属裸支架再狭窄发生率(10/15)与药物洗脱支架再狭窄发生率(3/25)差异有统计学意义(χ2=12.771,P=0.001)。结论血管内支架治疗症状性椎动脉开口处狭窄是一种安全有效的方法,虽然存在较高的再狭窄率,但能够有效改善后循环缺血症状。