A 68-year-old man with hypertension and a history of smoking was 1 week post-op from a right total knee replacement. He presented to the emergency room with acute onset of shortness of breath and right leg swelling. A helical computed tomography (CT) scan of his chest showed a small subsegmental pulmonary embolus (PE) and deep venous thrombosis (DVT) of the right femoral vein. He was incidentally noted to have a 6.7-cm aneurysm of his thoracic aorta that involved the visceral segment (Figure 31-1). Given its size and the involvement of the visceral segment, an open repair was recommended.
FIGURE 31-1
As is often the case, thoracic and thoracoabdominal aneurysms are often found incidentally. When the aneurysm is in close proximity to the visceral segment or arch vessels, an open repair is indicated. In cases where this is not an option due to comorbidities, either a hybrid procedure (debranching or extra-anatomic bypass) or non–FDA-approved custom branched or fenestrated endografts are potential options. CT angiography shows the thoracic aorta with diameter measurements indicated in two places.
Most thoracoabdominal aortic aneurysms (TAAA) are asymptomatic at the time of diagnosis; however, most will become symptomatic before rupture.
Much like abdominal aneurysms, they are diagnosed incidentally.
The most common initial symptom is vague pain in the back, flank, chest, or even abdomen.
The differential diagnosis is extensive in patients who present with these vague symptoms, and they may often be dismissed.
Compressive symptoms may also occur.
Left recurrent laryngeal nerve causing hoarseness.
The aneurysm may compress the trachea or esophagus causing cough, dysphagia, or other associated symptoms.
Like abdominal aortic aneurysms, embolization to the visceral, renal, and lower extremity arteries has been reported.
Unless there is an abdominal component to the TAAA there are no specific physical examination findings. If there is an abdominal portion, then a pulsatile mass may be present.
CT angiography is the mainstay of imaging modalities for evaluation of TAAAs.
Depending on the size and rate of growth, imaging for follow-up purposes is typically done at 6- to 12- month intervals.
While catheter-directed aortography historically was the modality of choice, helical CT angiography is the current modality of choice.
Currently angiography is used for special situations such as mapping the spinal cord circulation or concurrent occlusive disease in the head and neck vessels.
CT angiography allows for reconstructed views of the aorta (Figure 31-1) as well as examination of other organs in the chest, abdomen, and pelvis, which occasionally will reveal incidental pathology.
CT angiography, like conventional angiography, can also aid in operative planning by identifying large intercostal arteries as well as mural thrombus, inflammatory changes, and other anatomic features that would affect operative planning (Figures 31-1 and 31-2).
FIGURE 31-2
In this computed tomography (CT) angiography example, there is aneurysmal dilatation of the aorta involving the celiac artery and the superior mesenteric artery (SMA). Measurements of diameter are also indicated. This is another indication to perform an open repair. In this case if the SMA and celiac artery are in close proximity, they may be included in a single anastomosis. CT angiography such as this is crucial for planning the repair. Consideration of clamp sites, visceral segment revascularization options, and location of the intercostals can be determined with the aid of CT angiography.
TAAAs are dilatations in the thoracic and abdominal aortas.
Once the thoracic aorta is at least 1.5 times its normal size it is considered an aneurysm.
TAAAs account for 10% of thoracic aneurysms, with ascending thoracic aortic aneurysms being the most common (40%).
TAAAs have been categorized based on their extent in four types:
Type I starts just distal to the left subclavian artery and includes the entire descending thoracic aorta up to the renal arteries.
Type II starts at the left subclavian artery and ends at the aortic bifurcation.
Type III begins in the distal thoracic aorta and ends at the aortic bifurcation or lower.
Type IV starts at the level of the diaphragm (T12) and continues to the aortic bifurcation.
Most TAAAs are fusiform aneurysms, which are diffuse dilatations involving the entire circumference of the aorta.
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