Recommendations for accurate CT diagnosis of suspected acute aortic syndrome (AAS)—on behalf of the British Society of Cardiovascular Imaging (BSCI)/British Society of Cardiovascular CT (BSCCT)

Abstract

Accurate and timely assessment of suspected acute aortic syndrome is crucial in this life-threatening condition. Imaging with CT plays a central role in the diagnosis to allow expedited management. Diagnosis can be made using locally available expertise with optimized scanning parameters, making full use of recent advances in CT technology. Each imaging centre must optimize their protocols to allow accurate diagnosis, to optimize radiation dose and in particular to reduce the risk of false-positive diagnosis that may simulate disease. This document outlines the principles for the acquisition of motion-free imaging of the aorta in this context.

Discriminatory Value of the Ascending Aorta Diameter in Suspected Acute Type A Aortic Dissection

“…The following variables were electronically abstracted from structured databases drawn from the electronic health record: age, sex, ethnicity, height, weight, past medical history (hypertension, diabetes, aortic stenosis), predisposing syndromes associated with TAAD (Marfan's, Turner's, fibromuscular dysplasia) and family history of aortic dissection or aneurysm. CT images were obtained using either 16‐ or 64‐slice technology on a variety of platforms, most being performed without electrocardiogram synchronized image capture (cardiac‐gating), as is commonplace under emergent diagnostic circumstances . Digitized CT images (iSite PACS, Koninklijke Philips NV) from the initial diagnostic study were analyzed by two emergency physicians (DGM and JAD) to obtain manual measurements of the AscAo diameter using the precontrast series.…”

“…A key limitation of our data is the variability in AscAo size that occurs throughout the cardiac cycle, given that cardiac‐gated CT image capture was rarely employed in this study, as is typical under emergent diagnostic circumstances . Studies have reported average changes in AscAo diameters of 2 mm or 3% between end‐diastole and end‐systole, and guidelines thus recommend the use of CT detector‐arrays with > 64 rows in conjunction with cardiac gating for imaging capture .…”

“…A key limitation of our data is the variability in AscAo size that occurs throughout the cardiac cycle, given that cardiac‐gated CT image capture was rarely employed in this study, as is typical under emergent diagnostic circumstances . Studies have reported average changes in AscAo diameters of 2 mm or 3% between end‐diastole and end‐systole, and guidelines thus recommend the use of CT detector‐arrays with > 64 rows in conjunction with cardiac gating for imaging capture . Using echocardiography or CT, the minimal AscAo diameter is typically obtained at end‐diastole and the maximal AscAo diameter is typically observed during systole, although professional guidelines recommend measurement at end‐diastole, largely by precedent .…”

Multidetector Computed Tomography in Traumatic and Nontraumatic Aortic Emergencies: Emphasis on Acute Aortic Syndromes

“…However, details of further discussion on various protocols and advantages and disadvantages of each are beyond the scope of the current review and may be found elsewhere. 10…”

Transthoracic Ultrasound Imaging of the Descending Thoracic Aorta: Could We, Should We, and Would We?

“…Its inability to image the entire length of the aorta reliably means that it does not have the diagnostic certainty to be a standalone test, especially when the clinical stakes are high and the consequence of missing the diagnosis is catastrophic. 11 The idea of using ultrasound as a gatekeeper to CT scan is plausible, although its cost-effectiveness is doubtful as patients will be subjected to multiple testing and the proportion of patients with non-conclusive ultrasound reports is not negligible. However, just because we should not use TTE in some clinical scenarios does not mean that we would not use it at all.…”