Next Best Imaging for Suspected Aortic Arch Aneurysm

Rationale for CTA as First-Line Imaging

The American College of Radiology recommends CT angiography (CTA) of the chest as the next imaging modality for suspected aortic arch aneurysm, providing comprehensive evaluation with high sensitivity and specificity for thoracic aortic aneurysms, allowing for detailed assessment of aneurysm location, size, and relationship to branch vessels 1, 2
CTA uses thin-section acquisition timed to coincide with peak arterial enhancement, producing a volumetric dataset that can be interpreted using transverse reconstructions, multiplanar reformations, and 3D renderings, with advantages over other modalities including wide availability, speed of acquisition, and ability to detect complications such as thrombus and dissection 1, 2, 4
ECG-gated CTA acquisition is recommended to minimize cardiac motion artifact and allow for accurate orthogonal measurement of the thoracic aorta, with a strength of evidence supporting its use 3, 4

The American College of Radiology suggests MRA chest as an acceptable alternative when CTA is contraindicated, providing similar sensitivity and specificity to CTA while allowing for post-processing capabilities, although with limitations including longer acquisition times and potential contraindications 1, 5

TEE can be considered in unstable patients who cannot be transported for CTA or when rapid bedside assessment is needed, useful for evaluating the aortic root and associated valvular abnormalities, although with limited visualization of the anterior aortic arch 3, 4

The scan should include the entire aorta from the aortic sinus through the iliac bifurcation for thoracic aortic aneurysm evaluation, with measurement of the maximal aortic diameter performed perpendicular to the long axis of the aorta (outer-to-outer wall diameter) 3, 6
Non-contrast CT can still provide valuable information about aortic size and wall calcifications in patients who cannot tolerate iodinated contrast, though with reduced diagnostic accuracy 8

Relying solely on chest X-ray findings without confirmatory cross-sectional imaging can lead to missed diagnoses, with a recommendation to use CTA for accurate diagnosis and management planning 2
Non-ECG-gated studies may have variable image quality through the aortic root and coronary vessels due to cardiac motion, and streak artifacts from implanted devices can limit CTA evaluation 3