Thoracic aortic dissection

Palmiere C, Burkhardt S, Staub C, Hallenbarter M, Pizzolato GP, Dettmeyer R, La Harpe R. Thoracic aortic dissection associated with cocaine abuse. Forensic Sci Int 2004 141 137 12. 

Pulsation of the aorta causes artifacts, especially in the aortic root and ascending aorta. ECG-triggered data acquisition helps to significantly reduce these artifacts and therefore plays an important role in the examination of unclear chest pain or thoracic aortic dissection (Fig. 23.1). Furthermore, this technique enables the evaluation of coronary arteries and can replace invasive clinical diagnostics in some cases. Flowever, detailed protocols of the thoracic aorta are normally based on protocols of coronary artery CT. Due to their specifications, they lead to longer acquisition times than those of standard protocols and do not properly visualize the abdominal aorta. This can be overcome by an ECG-gated acquisition of the thoracic aorta and a change to the standard protocol for the abdominal aorta. In order to achieve a sufficient contrast in the abdominal aorta, the time delay to modify the examination protocol should be minimized (Fig. 23.2). 

S. E., Shete, S. S., and Milewicz, D. M. (2003). Mapping a locus for familial thoracic aortic aneurysms and dissections (TAAD2) to 3p24-25. Circulation 107, 3184-3190. 

AAAs present in three different types or shapes. Fusiform aneurysms, the most typical, are mostly symmetrical bulges that occur around the entire circumference of the aorta. These are sometimes referred to as false aneurysms or pseudoaneurysms, because layers of the wall of the aorta are missing (as opposed to the presence of all three layers in a true aneurysm). An aortic dissection, on the other hand, is when blood penetrates the inner layer of the aortic wall, and flows between the layers, similar to delamination. This typically occurs in the thoracic region of the aorta, but can sometimes occur in the abdominal region. Figure 21.3 shows these various types of aneurysms. 

The thoracic aorta may be affected by several different diseases, such as aortic dissection, intramural hematoma, penetrating atherosclerotic ulcer, aneurysms and traumatic injury. Any of these diseases may well be displayed in the axial slices, as well with post-processing (Takahashi and Stanford 2005). Volume rendering in particular is helpful in displaying the anatomical situation of the thoracic aorta after stent graft placement (Fig. 15.7). 

Yoshida S, Akiba H, Tamakawa M, Yama N, Hareyama M, Morishita K, Abe T (2003) Thoracic involvement of type A aortic dissection and intramural hematoma diagnostic accuracy-comparison of emergency helical CT and surgical findings. Radiology 228 430-435... 

Clinical Applications 300 Aortic Aneurysm 300 Thoracic Aortic Aneurysm 300 Abdominal Aortic Aneurysm 302 Inflammatory Aortic Aneurysm 303 Aortic Dissection 304 Stanford A Dissection 305 Stanford B Dissection 305 Penetrating Aortic Ulcer 306 IMH 306 Aortitis 307 Injury of the Aorta 307 CTA in Endovascular Aortic Reconstruction 308... 

Most aortic dissections (ADs) occur in the thoracic aorta and extend into the abdominal aorta or even into the pelvis. An isolated dissection of the abdominal aorta is rare and should be distinguished from classic ADs. Penetrating atherosclerotic ulcers are considered as the origin of abdominal AD. 

The challenge for spinal artery CTA is to provide sufficient arterial enhancement but to scan before arrival of contrast medium in the venous system. An ROI of the bolus tracking system placed in the ascending aorta might be affected by inflow artifacts of the SVC and may result in a mistimed early scan. Therefore, placement of the ROI in the aortic arch or descending aorta is recommended. In the presence of aortic dissection, caution should be taken that the ROI is not too big or positioned in the false lumen or across the dissection membrane, respectively. In these cases, manual start of the scan should be considered. The Hounsfield unit threshold should be around 100 HU above baseline. Scan start is usually delayed by time for table movement (<3 s), which is usually right above the origin of the vertebral arteries. An additional scan delay of 3 s is recommended for scanners with equal to or more than 16 rows and rotation time equal or less than 0.4 s. Hounsfield unit values of attenuated blood in the thoracic aorta should never be lower than within the pulmonary trunk. 

Minato, N., Katayama, Y, Yunoki, J., Kawasaki, H., Satou, H. Hemostatic effectiveness of a new application method for fibrin glue, the rub-and-spray method , in emergency aortic surgery for acute aortic dissection. Ann. Thorac. Cardiovasc. Smg. 15(4), 265-271 (2009)... 

Kazui, T., Washiyama, N., Bashar, A.H., Terada, H., Suzuki, K., et al. Role of biologic glue repair of proximal aortic dissection in the development of early and midterm redissection of the aortic root. Ann. Thorac. Surg. 72, 509-514 (2001)... 

Among the non-ischaemic cardiovascular causes of thoracic pain that should be ruled out, some present a benign prognosis as pericarditis, while others, in turn, point to a much serious prognosis, such as an acute aortic syndrome (dissecting aneurysm or other aortic pathologies) and a pulmonary embolism. On the whole, these account for 5-10% of all cases of thoracic pain. 

Figure 7.4 (A) A patient with thoracic pain due to a dissecting aortic aneurysm. An ST-segment elevation in V1-V3 can be explained by the mirror pattern of an evident LVE (V6) due to hypertension. This ST-segment elevation has been erroneously interpreted as due to an acute coronary syndrome. As a consequence, fibrinolytic...

Fig. 25.3. Oblique sagital volume-rendered multi-detector row CT angiogram of segmented thoracic aorta in a patient with an acute dissection Stanford A. The reconstruction shows the involvement of the supra-aortic braches (arrows). The dissection membrane is depicted as sharply bounded line (arrowheads)...

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