Aortic branch artery pseudoaneurysms accompanying aortic dissection. Part II. Distinction from penetrating atherosclerotic ulcers

PURPOSE: Small collections of contrast material are frequently seen within the otherwise thrombosed false lumen of an aortic dissection (AD). These collections can be divided into those without apparent communication with the aortic lumen (ie, pseudoaneurysms) and those with obvious communications (ie, ulcers). The present study was performed to test the hypotheses that pseudoaneurysms and ulcers differ in their distribution around the aorta and that the distribution of pseudoaneurysms is similar to that of small aortic branch arteries. MATERIALS AND METHODS: Computed tomography (CT) scans in 187 patients with AD and thrombosed false lumens showed 335 intramural contrast medium collections, including 128 pseudoaneurysms and 207 ulcers. CT scans in 40 control individuals without AD were reviewed to localize small aortic branch arteries. The angular distributions around the circumference of the aorta of pseudoaneurysms and ulcers and the branch artery origins were tabulated and compared. The frequency of detection of small branch arteries arising from the contrast material collections was noted. RESULTS: The angular distribution of pseudoaneurysms did not differ significantly from that of branch artery origins but did differ from that of ulcers. Pseudoaneurysms were found along the posterior, medial, and anterior walls of the aorta in the chest, sparing the lateral wall abutting the pleura. Ulcers tended to spare the arc containing branch artery origins. The composite distribution of ulcers and pseudoaneurysms appears uniform around the circumference of the aorta except at the T10-T12 levels. CONCLUSIONS: Branch artery pseudoaneurysms spare the pleural surface of the aorta and have nearly the same distribution around the circumference of the aorta as the origins of small aortic branch arteries. In contrast, ulcers tend to spare branch artery origins. The characteristic appearance and distribution of pseudoaneurysms on CT can help differentiate them from ulcers.     

多层螺旋CT对主动脉夹层动脉瘤的诊断价值

目的探讨多层螺旋CT对主动脉动脉瘤的诊断价值。方法对25例主动脉瘤患者于临床症状出现后进行多层螺旋CT平扫加增强扫描并利用原始数据在AW4．3工作站进行MPR及VR后处理。结果横轴位图像上可观察到真假腔形态、大小、剥脱的内膜片、破口位置及内膜和主动脉壁钙化,MPR重建图像能观察主动脉弓受累情况,确定内膜剥离范围,显示内膜与各分支血管之间的关系,按DeBakey分型,本组患者表现为Ⅰ型4例,Ⅱ型2例,Ⅲ型19例。结论多层螺旋CT能直观、立体显示真、假腔的形态、大小,破口位置及其与大分支血管的关系,因而它应是诊断夹层动脉瘤的首选检查方法。     

MR evaluation of chronic aortic dissection

Thirty patients with suspected or known chronic aortic dissection were imaged with magnetic resonance (MR), CT, and angiography. Five of these patients had previously undergone surgical repair of the ascending aorta for a type A dissection. Magnetic resonance demonstrated an intimal flap and a double lumen in 25 cases. In four cases with a thrombosed false lumen, proved angiographically, an intimal flap and double channel were not seen. In two of four aortic dissections with a thrombosed false lumen, CT made the diagnosis by showing displaced intimal calcifications not visualized on MR. In one case the aortic dissection was made on CT and angiography but was not supported by MR which showed an aortic aneurysm, subsequently confirmed at surgery. Magnetic resonance, CT, and aortography differentiated between type A (nine patients) or B (20 patients) dissection in all cases and demonstrated extension into the abdominal aorta. Extension into the iliac arteries was seen on MR in three patients but missed in nine patients. Magnetic resonance differentiated the true and false lumen in all but one case. Thrombosis of the false channel was identified in four cases by a decrease in signal intensity on the second echo image. Cardiac gating and longitudinal contiguous sections seemed to be more suitable for appreciation of the relationships with arch vessels. Transverse contiguous slices allowed determination of the origin of celiac, mesenteric, and renal arteries from either the true or the false lumen. This study confirms that MR is an accurate and noninvasive method for the evaluation and follow-up of chronic aortic dissection, obviating the need for iodinated contrast media.     

不典型主动脉夹层的多层螺旋CT诊断价值

目的:回顾性分析不典型主动脉夹层(atypical aortic dissection,AAD)的CT表现,探讨螺旋CT诊断AAD的价值。方法:25例AAD患者,全部行平扫及增强扫描,并结合多平面重组、曲面重组等方法显示AAD及穿透溃疡,根据Stan-ford分类法分型。结果:25例AAD,A型7例,B型18例。主要CT表现:主动脉壁呈新月型或环形增厚,无内膜破裂形成的双腔主动脉征象,增强扫描假腔无强化。内膜钙化向内移位7例,穿透性溃疡征3例。并发心包、纵隔及胸腔积液和积血共10例。经内科保守治疗后,6例完全吸收,3例部分不典型吸收,2例无明显变化。结论:螺旋CT清楚显示夹层的部位、范围及并发症,可作为主动脉夹层的首选检查及随访方法。     

CT diagnosis of acute aortic dissection; clinical importance of acute aortic dissection with non-opacified false lumen

Sixteen (47.5%) of 35 patients with acute aortic dissection showed a non-opacified crescent in the aorta on an initial contrast CT. Seven of these 16 patients underwent cineangiography soon after the initial CT, and in all 7 patients, neither an intimal tear nor an intimal flap was obtained. All but one of above 16 patients were followed by CT. Mean duration of follow-up was 9.6 months. In 10 of 15 patients with non-opacified false lumen, the false lumen remained non-opacified until the last examination. Moreover, in 6 of these 10 patients, the false lumen shrunk, and in the other 3, it disappeared completely on follow-up CT. On the other hand, in remaining 5 of these 15 patients who were initially diagnosed to have non-opacified false lumen, the false lumen became opacified and enlarged in size on follow-up CT performed in the first 14 weeks. Moreover, in 4 of these 5 patients, the false lumen became opacified in the only first 6 weeks. No matter how intensive care should be paid at least for the first 6 weeks, it seems that patients with aortic dissection which have non-opacified false lumen had good prognosis in comparison to patients with ordinary aortic dissections which have opacified false lumen. We believe aortic dissection with non-opacified false lumen may consist of two type of aortic dissection, one has no intimal tear, the other has some intimal tears and a thrombosed false lumen. In conclusion, CT is the most useful modality in diagnosing acute aortic dissection. The reasons are the incidence of acute aortic dissection with non-opacified false lumen was high, patients with non-opacified false lumen had good prognosis, and it was difficult to diagnose aortic dissection with non-opacified false lumen by conventional cineangiography and/or DSA.     

Endovascular treatment of aortic type B dissection and penetrating ulcer using commercially available stent-grafts.

OBJECTIVE: The purpose of our study was to investigate the clinical experience and efficiency of translumenl endovascular stent-graft insertion using commercially available vascular endoprotheses. We studied seven patients with descending aortic dissection (type B) and four patients with penetrating aortic ulcer over a median follow-up period of 254 days during the years 1997-2000, using cross-sectional CT to evaluate the extent of the dissection, the distance between the entry tear and the left subclavian artery, and the diameter of the true lumen and the false lumen. CONCLUSION: Endovascular treatment of acute and chronic aortic type B dissections and penetrating ulcer is a minimally invasive method with a low complication rate that could be considered a feasible alternative to surgical repair. Depending on the length of the dissection, we recommend the placement of two overlapping stent-grafts in the thoracic aorta to stabilize the affected thoracic aorta over a longer distance. This might provide a reliable sealing of the entry tear and should prevent further communication between the true lumen and the false lumen.     

多层螺旋CT血管成像在主动脉壁间血肿的临床应用

目的探讨主动脉壁间血肿（IMH）MSCT表现和诊断价值。方法10例经多层螺旋CT诊断及临床证实的IMH,男6例,女4例。使用16层螺旋CT检查,应用多平面重建、最大密度投影和容积成像等后处理方法显示壁间血肿及穿透性溃疡。结果10例IMH中,A型2例,B型8例,其中2例局限于胸主动脉,6例累及胸腹主动脉（止于肾动脉上方2例,髂总动脉分叉上方2例,2例累及双侧髂总动脉）。MSCT表现为主动脉腔内新月形或环形充盈缺损,内壁较光整,钙化内膜片内移及局灶性尖角样穿透溃疡形成,主动脉腔内无明确内膜片显示。结论多层螺旋CT能为主动脉壁间血肿的诊断、鉴别诊断和治疗提供准确的信息。     

The normal distribution of thoracoabdominal aorta small branch artery ostia

The purpose of this study was to determine the normal distribution of aortic branch artery ostia. CT scans of 100 subjects were retrospectively reviewed. The angular distributions of the aorta with respect to the center of the T3 to L4 vertebral bodies, and of branch artery origins with respect to the center of the aorta were measured. At each vertebral body level the distribution of intercostal/lumbar arteries and other branch arteries were calculated. The proximal descending aorta is posteriorly placed becoming a midline structure, at the thoracolumbar junction, and remains anterior to the vertebral bodies within the abdomen. The intercostal and lumbar artery ostia have a distinct distribution. At each vertebral level from T3 caudally, one intercostal artery originates from the posterior wall of the aorta throughout the thoracic aorta, while the other intercostal artery originates from the medial wall of the descending thoracic aorta high in the chest, posteromedially from the mid-thoracic aorta, and from the posterior wall of the aorta low in the chest. Mediastinal branches of the thoracic aorta originate from the medial and anterior wall. Lumbar branches originate only from the posterior wall of the abdominal aorta. Aortic branch artery origins arise with a bimodal distribution and have a characteristic location. Mediastinal branches of the thoracic aorta originate from the medial and anterior wall. Knowing the location of aortic branch artery ostia may help distinguish branch artery pseudoaneurysms from penetrating ulcers.     

Thrombosis of the false lumen in acute aortic dissection. CT diagnosis

Three cases are reported of acute aortic dissection with complete thrombosis of the false channel, which is a very uncommon event in De Bakey's I and II type aortic dissections. The 3 patients entered hospital because of severe thoracic pain without any ECG sign of myocardial infarction. Emergency CT showed evidence of pericardial effusion suggesting hemopericardium, enlargement of the ascending aorta and a peripheral semilunar filling defect which caused a slight deformation of the true channel. On precontrast scans, only one case showed inward displacement of peripheral intimal calcifications and high-density aortic wall. No typical signs of aortic dissection were reported, except in the first patient--where a double contrast filled lumen, separated by an intimal flap was seen. CT findings are individually discussed. It is emphasized that in all patients more than one CT sign was present at a time. The correct evaluation of these signs together with the clinical data could lead to the right diagnosis of aortic dissection in spite of the lack of a filled false channel.     

Vascular diseases of the thorax: evaluation with multidetector CT

The list of vascular diseases in the thorax has been narrowed to three, which are considered essential information for radiologists interpreting CT scans of the thorax: (1) aortic dissection and its variants, intramural hematoma and penetrating atherosclerotic ulcer; (2) acute pulmonary embolism; and (3) coronary artery disease. The spatial resolution of multidetector CT is such that CT has become the imaging modality of choice for aortic dissection and pulmonary embolism. This move away from angiography has transpired over the last decade; perhaps the next decade will see the same occur for evaluation of coronary artery disease.     

64层螺旋CT对主动脉夹层的应用价值

目的:探讨64层螺旋CT诊断主动脉夹层的临床价值。方法:39例拟诊为主动脉病变的患者作为本组研究对象,对所有患者行CT平扫及增强扫描。CT平扫图像上观察内膜钙化的移位、主动脉直径扩大、心包和/或纵隔积血、胸腔积液/血。并对A型和B型主动脉夹层的平扫征象进行统计学比较。CT增强图像上观察低密度的内膜瓣、破口(入口和再入口)、真假腔及主要动脉分支受累情况。结果:21例主动脉夹层中,CT平扫观察到钙化的内膜瓣移位9例(42.9%),主动脉直径增宽8例(38.1%),心包和/或纵隔积血8例(38.1%),胸腔积液/血5例(19.0%)。CT增强扫描对主动脉夹层内膜瓣的显示率达100%(21/21),对真、假腔的显示率为100%(21/21),对破口的显示率为85.7%(18/21)。8例(38.1%)弓上血管受累,5例(19.0%)内脏血管受累。结论:64层螺旋CT对主动脉夹层有较高的诊断价值,能较好的显示夹层的真假腔、内膜瓣及破口,并且可以显示主要动脉受累情况,为外科的手术治疗提供重要信息。     

Radiologic evaluation of penetrating aortic atherosclerotic ulcer

Patients with penetrating atherosclerotic ulcers of the aorta present with back or chest pain that mimics classic aortic dissection. The pathologic findings, however, are distinctly different from those of aortic dissection in that an atherosclerotic lesion with ulceration penetrates into the internal elastic lamina, allowing hematoma formation within the media of the aortic wall. This may lead to false aneurysm or, rarely, transmural rupture of the aorta. Imaging findings of penetrating aortic atherosclerotic ulcers are also different from those of classic aortic dissection. We have found computed tomography to be especially useful in differentiating between these entities and present several illustrative cases.     

主动脉壁内血肿的多层面螺旋CT诊断

目的:评价多层面螺旋CT诊断主动脉壁内血肿的价值.材料和方法:对23例怀疑主动脉病变的患者进行多层面螺旋CT扫描并诊断为主动脉壁内血肿.两名有经验的心血管放射医师按照CT标准做出诊断.使用16排多层面螺旋CT获得1.25mm层厚(1mm重建间隔)图像,应用多平面重建、曲面重建、最大密度投影和容积重建等方法显示壁内血肿及穿透溃疡.结果:23例主动脉壁内血肿中,1例A型,22例B型;B型壁内血肿中,仅累及降主动脉的8例,胸腹主动脉受累11例,局限于腹主动脉3例;11壁内血肿伴主动脉穿透溃疡,其中2例行带膜内支架治疗.结论:多层面螺旋CT能为主动脉壁内血肿的诊断、鉴别诊断和治疗提供重要信息.     

Postoperative evaluation of composite aortic grafts: comparison of angiography and CT

Postoperative angiography and computerised tomography were performed in 10 patients 8 to 57 months after surgical repair (nine composite, one distal graft) of aneurysms of the thoracic aorta (six dissecting, four true aneurysms). Angiography and angio-CT showed chronic dissection of the distal aorta in five of six patients with dissecting aneurysms and detected a pseudoaneurysm originating from the distal suture line in another patient. CT may serve as an initial procedure for postoperative examinations after surgery of aortic aneurysms to demonstrate the state of the false lumen and the formation of pseudoaneurysms. The coronary arteries and aortic valve function have to be evaluated by angiography.     

Treatment of chronic type B aortic dissection with endovascular stent-graft placement

A 74-year-old man with chronic aortic dissection was treated with an endovascular stent graft, fabricated from expanded polytetrafluoroethylene and a Z-stent. It was placed in the true lumen to close an entry tear. Closure was obtained immediately and thrombosis of the false lumen at the descending thoracic aorta was observed on computed tomography (CT) obtained 1 week later. No procedure-related complications developed. The patient is doing well with no adverse events including aortic rupture or aortic branch ischemia.     

CT follow-up of medically treated type-B aortic dissection: a case report

The fate of the false lument of a type-B aortic dissection was studied using computed tomography (CT) in a 64-year-old woman with hypertension. The CT follow-up showed the disappearance of the false lumen in the thoracic aorta, shrinkage and thrombosis of the false channel in the proximal abdominal aorta (in these sections no major vesel arose from the false lumen), and persistence of the false lumen in the distal abdominal aorta, where the right common iliac artery arose from the false lumen. Such different findings at the various levels of dissection have not been described previously, and confirm the presumption that the fate of dissection depends on the blood flow in the false channel. Correspondence to: M. Heman     

Differentiation between dissection and a true aneurysm of the descending thoracic aorta using magnetic resonance tomography

The case reviewed here demonstrates that magnetic resonance imaging in contrast to CT and i.v. DSA can differentiate between aortic dissection with partially thrombosed false lumen and a true aneurysm using the spin-echo and the gradient-echo technique. The gradient-echo technique was able to depict the moving intimal flap as well as the higher blood flow velocity in the true lumen.     

Treatment of a Persistent False Lumen with Aneurysm Formation Following Surgical Repair of Type A Dissection

We describe the case of a 68-year-old man who developed aneurysmal dilatation of the proximal descending thoracic aorta 8 years after repair of a type A dissection. The aneurysm was due to an anastomotic leak at the distal end of the previous repair in the ascending aorta with antegrade perfusion of the false lumen. Surgical repair of the anastomotic leak partially obliterated the false lumen and computed tomography scan demonstrated thrombosis in a large proportion of the false lumen aneurysm. Follow-up with surveillance scans showed persistent filling of this aneurysm due to retrograde flow of blood within the false lumen. Coil embolization of the false lumen within the thoracic aorta was performed which successfully thrombosed the aneurysm with a reduction in diameter. Late aneurysm formation may complicate type A dissection repairs during follow-up due to a persistent false lumen, especially if there is an anastomotic leak. This case report describes a strategy to deal with this difficult clinical problem.     

16层螺旋CT血管成像技术在主动脉夹层中的临床价值

目的:探讨16层CT血管成像在主动脉夹层的诊断和临床治疗中的应用价值。方法:27例主动脉夹层患者均行16层CT胸腹联合平扫和增强扫描,采用多平面重组(MPR)、最大密度投影(MIP)、容积再现(VR)及表面遮盖显示(SSD)等后处理方法,重点观察和评价主动脉夹层的真假腔、内膜片、内膜破口以及重要分支血管的受累情况。结果:原始横轴位图像对病变信息的存储最为可靠;不同的重组方式所得图像有不同的显示特点;27例均很好地显示了主动脉全程及其分支,显示真、假腔27例(100%)、显示内膜片(100%)、内膜破口24例(88.9%)、假腔内血栓形成9例(30%)。结论:16层螺旋CT血管成像可以全面显示主动脉夹层的病变和解剖细节,在主动脉夹层的诊断和临床治疗中有重要的临床应用价值。     

特殊类型主动脉夹层的电子束CT表现及诊断

目的探讨表现特殊的主动脉夹层的电子束CT(EBCT)影像特征及诊断.材料和方法20例表现特殊的主动脉夹层,其中不典型夹层13例,三腔以上夹层动脉瘤3例,合并升主动脉壁内血肿的Stanford B型夹层2例,动脉瘤样夹层1例,外伤性主动脉夹层1例.结果主动脉不典型夹层为主动脉壁新月形或环形的低密度血肿包绕,常可见穿透性溃疡或钙化内移等征象;三腔以上夹层动脉瘤有2～3个内膜片,3～4个腔,瘤体管径较大;合并升主动脉壁内血肿的B型夹层见升主动脉管壁低密度新月形或环形增厚,降主动脉则见内膜片及真假两腔形成;动脉瘤样主动脉夹层见降主动脉局限性瘤样扩张,破口大,内膜片不易发现.1例外伤性夹层于主动脉弓峡部及降部起始见破裂内膜片.结论特殊类型的主动脉夹层表现各具特征,EBCT可清晰显示,是极适用于胸部急症的快速、无创的检查方法.