Chapter30 Aorta

786

Section V: Cardiac Radiology

*

A

B

C

Figure 30.46.  Acute Traumatic Aortic Injury (ATAI). Frontal chest radiograph ( A ) in a 42-year-old woman demonstrates mild superior medi- astinal widening, most notably affecting the aortic contour(*). Coronal CT image ( B ) demonstrates disruption of the aorta ( arrowheads ) along the aortic isthmus with adjacent periaortic hematoma ( arrow ). Sagittal reformat ( C ) demonstrates aortic isthmic irregularity with a focal anterior bulge near the expected attachment of the ligamentum arteriosum ( arrowhead ) with surrounding periaortic hematoma ( arrow ) consistent with ATAI. This must not be confused for the physiologic ductus bump that can also be seen at this location.

with extravasation only contained by adjacent soft tissues (Figs. 30.46 and 30.47). These higher-grade injuries carry extremely high morbidity and mortality and are treated with open surgical repair or, increasingly, with endovascular stent grafting. Of particular note, a slight, smooth convex bulge in the aortic contour at the attachment of the ligamentum arte- riosum called the “ductus bump” (Fig. 30.48) is physiologic and should not be confused for a traumatic pseudoaneu- rysm. The distinction is often easy, with a sharp, shouldered appearance, visible intimomedial fragment or mural irregu- larity in severe trauma; in less obvious cases, the presence of other findings, for instance adjacent mediastinal hematoma or fractures to the sternum and/or anterior ribs should raise concern for possible vascular injury. Improved spatial resolution in CTA has allowed detection of milder aortic injuries, and management of these injuries varies by institution and physician preference. Though no large-scale studies are available, limited-case series suggest that these milder injuries are unlikely to progress to clini- cal significance and, in most cases, can likely be managed nonoperatively.

Postoperative Aorta It is important to be familiar with the normal postoperative imaging appearance of the aorta to understand appropriate imaging evaluation and avoid misdiagnosis. Evaluation of the postoperative aorta is typically performed with helical CTA, although MRI/MRA can also be used. MR may be limited by accessibility, long image acquisition time, and metallic arti- facts from surgical material. For patients post aortic root or ascending aortic repair, ECG gating should be used to mini- mize motion artifact. Aortic root and ascending aortic pathologies such as type A dissection and ascending aortic aneurysm are usually repaired by resecting the native aorta and placing an interposition syn- thetic or tissue graft, with or without concurrent aortic valve replacement. Graft containing an attached prosthetic valve is termed a composite graft (Fig. 30.49). Synthetic grafts are composed of polyethylene and appear slightly hyperattenuating to the aorta on noncontrast CT but hypoattenuating to the aorta on CTA. Tissue grafts will have the same attenuation as

P

P

*

*

*

A

B

C

Figure 30.47.  Acute Traumatic Aortic Injury/Traumatic Pseudoaneurysm. Axial CTA image at the level of the aortic isthmus ( A ) and parasag- ittal reformat ( B ) demonstrates a complete transection of the aorta ( white arrow , A ) contained by a large pseudoaneurysm ( P, B ) and surrounding mediastinal hematoma (*, A , B ). Emergent catheter angiography mirrors the findings of the CTA with a pseudoaneurysm ( P ) at the aortic isthmus.