Can an aortic dissection be seen on a CT (Computed Tomography) angio (angiography) chest?

CT Angiography is the Gold Standard for Diagnosing Aortic Dissection

Yes, aortic dissection can be definitively diagnosed on CT angiography of the chest with excellent sensitivity and specificity exceeding 95%.

Diagnostic Capabilities of CT Angiography

CT angiography (CTA) has become the first-line imaging modality for suspected aortic dissection due to its:

• Superior spatial and temporal resolution 1
• Homogeneous intraluminal contrast enhancement 1
• Ability to provide multiplanar reformatting for accurate measurements 1
• Near-isotropic voxel capability allowing for 3D reconstructions 1

The American College of Radiology guidelines report that CTA has sensitivity and specificity exceeding 95% for diagnosing aortic dissection 2. This is supported by data from the International Registry of Acute Aortic Dissection (IRAD) showing CTA as the initially used diagnostic modality in 61% of patients with aortic dissection 1.

Key Imaging Findings of Aortic Dissection on CTA

CTA can identify several critical features of aortic dissection:

• Presence and extent of the dissection flap 1
• True and false lumens 1
• Regions of potential malperfusion 1
• Branch vessel involvement 1
• Signs of rupture or contrast leak 1
• Extension of dissection into abdominal aorta and branch vessels 1

Optimal CT Protocol for Aortic Dissection

For suspected aortic dissection, the recommended protocol includes:

1. Non-contrast study - To detect subtle changes of intramural hematoma 1
2. Contrast-enhanced arterial phase - To delineate the dissection flap 1
3. Delayed phase - For additional assessment 1
4. Coverage from thoracic inlet to pelvis - To assess full extent of dissection 1

Pitfalls to Avoid

Several potential pitfalls exist when interpreting CT for aortic dissection:

• Motion artifacts from cardiac movement can mimic dissection flaps, especially in the ascending aorta 1, 3
• Improper timing of contrast administration 3
• Streak artifacts from high-attenuation material 3
• Normal anatomic structures that can mimic dissection 3

ECG-gating is particularly useful for reducing motion artifacts in the ascending aorta 1.

Alternative Imaging Modalities

While CTA is the gold standard, other modalities include:

• MRI - Approaching 100% sensitivity and specificity, best for stable patients with contrast allergy or renal dysfunction 2
• Transesophageal echocardiography (TEE) - 99% sensitivity and 89% specificity, suitable for unstable patients who cannot undergo CT 2, 4
• Transthoracic echocardiography (TTE) - Lower sensitivity (59-80%) 2

Clinical Implications

Prompt diagnosis of aortic dissection is critical for patient survival. When aortic dissection is suspected:

• Obtain CTA chest with IV contrast as the first-line test 2
• Consider extending to abdomen and pelvis as dissections frequently extend below the diaphragm 1
• Ensure proper interpretation and immediate communication of findings to treating physicians 1

For patients with renal dysfunction, the benefits of contrast-enhanced CT usually outweigh the risks given the life-threatening nature of aortic dissection 5.

Remember that non-contrast CT alone has limited sensitivity for aortic dissection but may show suggestive findings such as displaced calcified intimal flaps, intraluminal high-densities, or aneurysmal aortic dilation 5.