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1、定义,正常情况下冠状动脉及其主要分支走行于心外膜下组织的浅层，若某部分或几部分走行于心肌纤维中，被形似桥的心肌纤维所覆盖，该心肌纤维束称为心肌桥（myocardialbridge），这段血管则称为壁冠状动脉(intramural coronary)。,病因,是一种先天性冠状动脉异常，可能是由于原始冠状动脉小梁网内动脉未能外化造成男性多于女性，尤其多见于肥厚型心肌病,解剖与病理生理,多发生于左前降支(98.08%)，尤其是前降支中段（86.27%），也有在回旋支（1.92%），右冠的较少。MB一般长10mm30mm，厚约24mm,解剖与病理生理,按解剖按部位分：（1）浅表型肌桥，前降支沿着室间沟
2、前行，在达到心尖部之前被心肌在垂直方向覆盖一段而形成，厚度一般不超过2mm，较常见，约占75%。（2）纵深型肌桥，前降支从室间沟向右室侧迂曲走形，来源于右室心尖部的肌束横向覆盖或环绕冠状动脉，覆盖于其上的肌束更长且深，较少见，约25%。,解剖与病理生理,冠状动脉在收缩期的血流量只占全心周期的530，大部分血流在舒张期灌注，不导致心肌缺血心肌桥对血管的压迫可持续到舒张早、中期,从而减少冠状动脉的血流储备,当心率增快、舒张期缩短时,更易导致心肌灌注不足而出现心肌缺血,临床表现,大多数无症状部分病人可有心肌缺血的表现：不同类型与不同程度的心绞痛、心肌梗塞、致命性心律失常甚至猝死。冠状动脉MB静息心电
3、图检查多正常，运动实验可诱发非特异性的缺血征象，传导异常或心律失常。,诊断,冠脉造影(CAG)是目前诊断心肌桥的金标准。冠脉造影的特点为“挤奶效应”，即肌桥段冠状动脉在收缩期狭窄，在舒张期正常。（必须两个以上投照角度）另外还有CT冠状动脉造影（CTA）、血管内超声（IVUS）。,诊断：CAG,据肌桥收缩期狭窄程度分为三级：I、收缩期狭窄直径小于50，II、收缩期狭窄介于5070之间III、收缩期狭窄大于70，,治疗,内科治疗介入治疗 外科治疗,内科药物治疗,受体阻滞剂可降低心收缩力，减轻心肌桥对冠状动脉的压迫，降低心律，延长舒张期，从而改善心肌血供。（心率130次/分），同时此病人应避免大负荷
4、运动以防止心率过快，收缩期/舒张期时间之比提高，加重心肌桥对冠状动脉的血流影响,内科药物治疗,钙离子拮抗剂 可降低心收缩力，缓解冠状动脉痉挛，增加冠状动脉血流，特别是非二氢比啶类，如维拉帕米、合贝爽等，即可消除可能的痉挛，又能延长心动周期的舒张期时限，时心肌桥的主要有效药物,内科药物治疗,抗凝、抗血小板治疗 用于心肌桥伴冠状动脉粥样硬化性心脏病硝酸酯类药物可加重心肌桥导致的冠状动脉 收缩期狭窄，应避免使用,介入治疗,之前研究显示对于药物难以 控制或同时出现冠状动脉粥样硬化性固定狭窄 的患者，可选用支架植入术 支架选择上一般采用柔韧性强、支撑力大的支架。目前研究显示尽管心肌桥患者行支架置入术后近
5、期效果尚可，但可能伴有冠脉破裂、心肌穿孔的危险，远期支架内血栓或再狭窄率明显增高。目前心肌桥大多不主张支架植入治疗。,外科治疗,造影显示收缩期狭窄75%、临床上有严重心绞痛症状或运动诱发心动过速时心电图上有明显缺血性变化,药物治疗不能缓解者,可考虑手术治疗。可行心肌桥松解术或冠状动脉旁路移植术。,外科治疗,肌桥松解术：适用于浅肌桥。对于心肌桥较薄较短，与壁冠状动脉有间隙者应采用心肌桥切开松解术;心肌桥纤维切开可从根本上解除心肌的压迫,多数患者术后胸痛症状消失。但心肌桥松解术风险较大,因为冠状动脉在心肌桥内的行走不可预知,有时需切开心室壁较深,可能会引起术后室壁瘤形成或右室穿孔,术后瘢痕组织也可
6、加重局部压迫。,外科治疗,冠脉搭桥术：适用于深肌桥。肌桥较厚，或较长其下冠状动脉不易分离或有心室穿孔的危险，应行冠状动脉搭桥术。尤其对于合并动脉粥样硬化斑块的心肌桥患者CABG可能是较好的选择。,Interactive CardioVascular and Thoracic Surgery 2012,There is no definite guideline regarding the therapy of myocardial bridging.It is very clear that stenting of the tunnelled segment can relieve its s
7、tenosis and its relevant symptoms.However,the short-term and long-term results of stenting are not satisfactory.The high incidence of in-stent restenosis has been described。surgical myotomy is the optimal therapy.However,there are some cases with a very extensive and deep myocardial bridging that ca
8、nnot be myotomied thoroughly due to some serious complications such as an aneurysm or rupture of the heart.Therefore,If myotomy could not be done,coronary artery bypass grafting would be performed.,Outcome of Intracoronary Stenting After Failed Maximal Medical Therapy in Patients With Symptomatic My
9、ocardial Bridge-Catheterization and Cardiovascular Interventions 71:185190(2008),Results:Intracoronary stents were placed in all patients successfully.The incidence of recurrent severe angina and TVR were signicantly greater in the stent group while MI and death in two groups were similar at mean fo
10、llow-up of 15 months.Conclusions:Coronary stent placement for medically refractory symptomatic myocardial bridge failed to relieve severe angina and is associated with high clinical restenosis and hence should be avoided.,Stent Fracture Following Stenting of a Myocardial Bridge:Report of Two Cases-C
11、atheterization and Cardiovascular Interventions 71:191196(2008),Given persistent anginal symptoms 5 weeks later,angiography was repeated,revealing stent fracture with in-stent restenosis in the mid portion of the previously placed mid LAD Taxus stent One year after the LAD stenting she had recurrent
12、 exertional angina.Repeat CAG revealed a stent fracture in the mid segment associated with restenosis.,Surgical treatment of myocardial bridging:report of 31 cases-WU Qing-yu Chinese Medical Journal,2007,Vol.120 No.19,Methods From January 1997 to December 2006,31 consecutive patients Among them,15 u
13、nderwent myotomy and 16 underwent coronary artery bypass grafting(CABG).ResultsAll patients survived and recovered uneventfully.Follow-up time was 3-115 months(mean 31 months).All patients were symptom-free and currently in NYHA class III.ConclusionThe patients who are refractory to medication should actively undergo the surgical procedures such as myotomy and CABG.Myotomy should be advocated as the first choice because of its safety and satisfactory results.（if coronary artery in association with MB cant recover completely in diastole by angiography,CABG should be preferred to myotomy.）,
