From the Guidelines
To rule out dissection, order a CT scan as the initial diagnostic imaging, given its wide availability, accuracy, and speed, as well as the extent of anatomic detail it provides, as recommended by the 2022 ACC/AHA guideline for the diagnosis and management of aortic disease 1. When suspecting aortic dissection, it is crucial to prioritize imaging modalities that offer high accuracy and speed. The 2022 ACC/AHA guideline suggests that CT is the preferred initial diagnostic imaging due to its wide availability and the detailed anatomic information it provides 1.
- Key points to consider when ordering imaging for suspected aortic dissection include:
- CT scans are highly accurate for diagnosing aortic dissection and are recommended as the first-line imaging modality 1.
- Alternative imaging modalities such as TEE and MRI are reasonable but may not be as readily available or as quick as CT scans 1.
- A plain chest x-ray is not sufficient for diagnosing aortic dissection but may raise suspicion or suggest alternative diagnoses based on certain radiographic findings 1.
- The integration of a low aortic dissection risk score and a low D-dimer level may aid in excluding the diagnosis of aortic dissection, particularly in patients with a low pre-test probability 1. While considering these points, the primary recommendation remains to use CT as the initial diagnostic tool due to its advantages in terms of availability, accuracy, and speed, as emphasized by the 2022 ACC/AHA guideline 1.
From the Research
Imaging Options to Rule Out Dissection
To rule out dissection, particularly in the context of aortic dissection, several imaging options can be considered, each with its own advantages and considerations:
- Computed Tomography Angiography (CTA) is a commonly used method for diagnosing aortic dissection due to its high accuracy and speed 2.
- Triple rule-out CTA, which evaluates the coronary arteries, pulmonary arteries, and aorta in a single scan, has been shown to be highly accurate for detecting coronary artery disease but may not be as effective for diagnosing pulmonary embolism or aortic dissection due to low prevalence rates in the studied populations 2.
- Spectral CTA using gadolinium-based contrast agents offers a feasible alternative for patients with contraindications to iodine-based contrast agents, providing valuable diagnostic information for aortic pathologies 3.
- Time-resolved CTA has been explored for its potential in providing dynamic information about the aorta, which could be beneficial in the follow-up of endovascular aneurysm repair and aortic dissection, with a radiation dose comparable to standard biphasic CTA protocols 4.
- Combined CTA of the aorta and craniocervical artery has been proposed as a new imaging protocol for assessing acute type A aortic dissection, offering incremental information on craniocervical pathology and anatomy that can be useful for surgical repair 5.
- Low-dose protocols for CTA of the thoracic aorta using 80 kV and iterative reconstruction algorithms, with different concentrations of contrast media, have been evaluated, showing that such protocols are feasible without compromising image quality, thus reducing the effective radiation dose 6.
Considerations for Choosing an Imaging Protocol
When choosing an imaging protocol to rule out dissection, several factors should be considered:
- The patient's clinical presentation and suspected diagnosis
- The availability of imaging technologies and expertise
- The patient's history of contrast agent allergies or renal impairment
- The need for detailed anatomical information to guide surgical or endovascular interventions
- The balance between image quality, radiation exposure, and contrast agent volume 2, 3, 4, 5, 6.