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1、概述,急性主动脉综合征（acute aortic syndrome，AAS）包括一组有相似临床症状的异质性疾病：主动脉夹层（aortic dissection，AD）、主动脉壁内血肿（intramural aortic hematoma，IMH）、穿透性粥样硬化性主动脉溃疡（penetrating atherosclerotic aortic ulcer，PAU）和不稳定性主动脉瘤（unstable aortic aneurysm） 。,特点,高死亡率（highest mortality） 由于AAS的高死亡率，尤其是AD,如在症状出现的头24小时内能准确诊断并立即进行适当治疗将会得到有利的结
2、果。,病理学基础,AD的基础病理学改变是主动脉中层胶原纤维及弹性纤维受累的中层退行性病变。这种退行性病变的原因尚不明确，高血压和年龄可能是最重要的2个因素。先天性因素如Marfan综合征经常影响血管平滑肌细胞的分化造成弹性组织的解离增加，中膜的囊性坏死，最终也导致夹层形成、内膜破裂等。,病理学基础,IMH系指主动脉中层的滋养血管破裂导致血肿进入外膜中层并扩展至外膜。IMH实际上是主动脉中层的内涵性血肿，其与典型的AD区别为主动脉内膜完整，没有撕裂的内膜片，主动脉管腔和血肿之间没有直接的血流交通。有一种假说认为IMH是AD形成的前奏。,病理学基础,PAU是主动脉粥样硬化病变的溃疡穿透内弹力层并在
3、动脉中层形成血肿。高血压及广泛的动脉粥样硬化和钙化是其危险因素。,相互关系,AD与IMH的关系：主动脉壁间血肿可单独存在，但亦可为AD的前期病变，随诊过程中发展为AD；急性壁间血肿或（和）AD可并发主动脉破裂应予注意。 PAU与AD、IMH的关系：PAU始于粥样硬化斑块的溃破，穿透内膜/内弹力，进而可形成中膜壁间血肿，常继发假性动脉瘤，甚至透壁破裂，尤其急性病例。,分型,AD国际上目前有两种分型方法较常用，即Stanford分型和Debakey分型。IMH和PAU目前无正式的分类标准，但可按照AD的分型方法进行划分类型。,分型,Debakey分型：Debakey型为累及升主动脉和降主动脉（30
4、%44%），Debakey型仅累及升主动脉（10%20%），Debakey型仅累及降主动脉（40%50%）。 Stanford分型：A型累及升主动脉，又称近端病变；B型为远端起源于左锁骨下动脉，仅累及降主动脉，又称远端病变。 A型相当于Debakey和Debakey型，B型相当于Debakey型,TYPES of IMH,According to recommendations of the Task Force on aortic dissection, European Society of Cardiology, there are two types of IMH: Type I sh
5、ows a smooth inner aortic lumen, the diameter usually being less than 3.5 cm, and the wall thickness is bigger than 0.5 cm .,TYPES OF IMH,The Type II IMH occurs in aortic atherosclerosis. A rough inner aortic surface with severe aortic sclerosis is frequently noticed. The aorta is dilated to more th
6、an 3.5 cm and calcification is usually found. Mean wall thickness is 1.3 cm ranging from 0.6 to 4 cm . Mohr-Kahaly S .J Am Coll Cardiol. 1994;23:658664.,分型价值,病变部位累及升主动脉时发生血管意外的可能性大，在治疗方面，累及升主动脉的主张早期手术治疗。未累及升主动脉的首先考虑内科治疗。故明确病变部位，正确进行分型有助于指导临床治疗。,临床表现及病程,典型AD多发生在6070岁年龄组，男性发病率较女性高（男女约31）。临床表现：突发的胸前刺痛、
7、后背部钝痛，有时向下肢放射，严重者可出现休克。当AD累及或压迫主动脉主要分支时可出现相应脏器缺血的症状，相关血管部位的脉搏减弱或消失。A型65%患者发生继发性主动脉瓣环断裂，可引起程度不等的主动脉返流 。,疼痛的部位与的位置相关：升主动脉的夹层常表现为前胸部疼痛；降主动脉夹层则多表现为后胸部、背部或腹部疼痛。,临床表现及病程,IMH好发于压力最大的部位如升主动脉的右侧壁和峡部近端。在临床上，IMH的症状与典型AD难以区分，多表现为胸痛，背痛，半数患者可以出现左侧胸腔积液，当病变部位累及升主动脉时还可出现心包积液。与AD不同的是，IMH的男女发病比例基本相似。 其临床病程多变，血肿可以完全吸收，
8、还可以发展为梭形动脉瘤、囊性动脉瘤、假性动脉瘤，约33%由于内膜断裂进展为典型AD 。 赵绍宏.主动脉壁内血肿的多层螺旋CT诊断. 中国医学影像学杂志，2005，13：415417.,临床表现及病程,PAU多发生60岁的老年男性，多数伴有高血压及广泛的动脉粥样硬化和钙化。PAU多发生在降主动脉，其早期症状为胸痛和背痛，与典型AD类似，47%出现纵隔积液。PAU的自然病程为溃疡穿透内弹力层再中层形成血肿，可引起主动脉扩张和动脉瘤形成，更严重的可形成AD、主动脉破裂或主动脉假性动脉瘤。,影像诊断方法,影像学方法为确诊AAS的最重要手段，主要包括CT扫描，主动脉造影，MRI，经食管超声心动图（TEE
9、）等 。 目前影像学在诊断AAS方面，不仅要求定性，而且要求定量，明确病变的严重程度，要明确是否存在AAS？还要求对破裂的入口和出口定位，夹层形成的大小、范围、分型，是否有进行急诊手术的指征（心包、纵隔、胸膜腔内出血）。,现在随着具有功能强大的球管和探测器技术、时间和空间分辨率俱佳的在全球的广泛应用，对有可疑表现患者适时进行检查，的诊断准确率几乎是。 The 64-slice MDCT has become widely used and can provide iso-volumetric, 3-dimensional information without loss of spatial
10、resolution during a single breath-hold. Because of a diagnostic accuracy approaching 100%, MDCT has become the first-line imaging study for valuating patients with suspicious AD. Chiles C, Carr JJ. Vascular diseases of the thorax:evaluation with multidetector CT. Radiol Clin NorthAm 2005;43:54369.,M
11、DCT,Multidetector-row computed tomography (MDCT) can be used to diagnose various acute and chronic abnormalities of the aorta, including aortic aneurysms, aortic dissection, intramural hematoma, penetrating atherosclerotic ulcer, traumatic aortic transection, and congenital malformations.,64-slice C
12、T with z-Sharp technology,Spartial resolution: 0.4mm0.4mm0.4mm Temporal resolution: 0.33s/r 165ms collimation 64 x 0.625 mm; rotation time 0.33sec; 120 kV; 750 mAs,Acute aortic syndromes imaging strategy,Precontrast series to assess for intramural hematoma Thick./Rec.-3mm/3mm CTA series CTA chest-ab
13、domen-pelvis Thick./Rec.-1mm/0.7mm scanning range: thoracic inlet femoral a.bifurcation! Gated chest +(abd.-pelv. Non-gated CTA),The advantages of ECG-gated aortic CT and differential point between intimomedial flap and aortic pulsa-tion artifact. (A) Artifact-free ascending aortic root (arrowheads)
14、 and normal coaptation of aortic valves (arrows) are noted on coronal MPR image of mid-diastolic phase. (B) Aortic (arrowheads) and pulmonary arterial motion artifact (arrows) are noted on non-ECG gated axial CT image at the level of right main pulmonary artery. Simul-taneous visualization of cresce
15、nt-shaped low attenuation in both ascending aorta and pulmonary artery suggests motion artifact rather than aortic dissection.,CT 检查方法,对比剂注射流率为3-5ml/s，总量75-100ml. 对比剂注射后20-25s开始扫描或将感兴趣区置于升主动脉触发启动扫描。 A bolus-tracking technique (CARE bolus, Siemens) in the ascending aorta was used for timing.,图像后处理技术,
16、Various postprocessing techniques such as multiplanar reformation (MPR), maximum intensity projection (MIP), and volume rendering (VR) help to facilitate understanding of complex aortic pathology and to expedite communication with surgeons and attending physicians.,AD的CT表现：,非增强CT仅可显示主动脉管腔扩张，内膜钙化向腔内移
17、位。 增强CT主动脉管腔显示含有真腔和假腔的双层主动脉，真腔管径多较小，附壁血栓少见，增强扫描早期密度较高，有分支血管，血流速度正常；假腔管径一般较大，附壁血栓多见，增强扫描早期密度稍低，血流速度较慢。真假腔之间可见剥离的内膜瓣，常为宽23 mm线样低密度影。增强CT可以较好的显示夹层，判断假腔内血栓的存在及分支血管受累情况，对AD诊断的准确性可高达87%94%。,View,Displaced intimal calcification in a patient with Stanford type B dissection and calcification at the top of mu
18、ral thrombus in an asymptomatic patient. Displaced intimal calcification (arrowheads) is noted on pre-enhanced (A) and contrast-enhanced (B) axial CT image at the level of left atrium.,Calcifications lying on intima(arrowheads) and top of mural thrombus (arrow) are noted on preenhanced (C) and contr
19、ast-enhanced (D) axial CT image at the level of left atrium.,In a study of Nienaber et al the sensitivity of the thorax CT was nearly 100% . According to studies, the majority (50% to 85%) is located in the descending aorta (type B) and are usually associated with hypertension . the multi-detector c
20、omputed tomography (MDCT) has an important role in the diagnosis of the IMH.,IMH的CT表现,非增强CT:IMH主动脉壁间充满血栓/出血导致动脉壁增厚（4 mm）为其基本征象，可累及动脉全周或部分（呈新月形），一般纵行扩展，其形状可随时间动态改变，不伴内膜撕裂和假腔形成。非增强CT显示为沿主动脉壁的新月形或环状增厚的高密度影 。 增强CT显示主动脉壁内血肿阴影没有强化，无撕裂的内膜瓣影，从而可排除其与主动脉之间的交通。但是仅通过增强CT检查难以与血栓化假腔撕裂、溃疡穿孔伴腔内附壁血栓相鉴别。IMH随访时可见主动脉壁内
21、血肿厚度呈动态变化。,Contrast-enhanced CT reveals an intramural haematoma (IMH) of the ascending aorta located mainly in the anterolateral wall (arrow). The haematoma is appeared as a thickening of the aortic wall.,PAU 的CT表现：,非增强CT显示不清。 增强CT可显示主动脉壁上突出的溃疡龛影，常伴主动脉管壁增厚及管壁的增强显影。病变区周围可伴有壁内血肿形成，当溃疡范围较大时，可使主动脉管壁呈动脉瘤样扩张改变。多方位重建可有助于诊断。PAU可以并发IMH，溃疡龛影是区分两者的要点。,