Challenges in Diagnosis of Non-A Non-B Acute Aortic Dissection

Background: Non-A non-B (NANB) aortic dissections are uncommon and frequently unrecognized diseases. However, their proper identification is crucial given the unpredictable behavior of the dissected aorta with potential mortality and increased morbidity. We investigate the accuracy of radiological computed tomography angiography (CTA) reports in the diagnosis of acute NANB and the risk related to delayed recognition or misdiagnosis.

Methods: The pretreatment contrast CTA of all consecutive patients admitted with acute aortic dissection (AAD) in a University Hospital in London (UK) between January 2017 and May 2023 were reviewed to retrospectively verify the accuracy of CTA reports in the diagnosis of NANB AAD (B1-2_D The risk related to the delayed diagnosis (morbidity, mortality, and hospital readmissions) were evaluated as secondary outcomes. The study was conducted according to the Strengthening the Reporting of Observational Studies in Epidemiology guidelines.

Results: Overall, 588 aortic CTAs were reviewed for a total of n = 393 (66.8%) type A AADs, n = 171 (29%) type B AADs and n = 25 (4.3%) NANB AADs (n = 16, 64% men, mean age 60.56, standard deviation ± 14.6 years). While no case of misdiagnosis was identified in Type A or B AAD groups, in NANBs only about a third of cases (n = 9, 36%) were immediately indicated as "NANB" (n = 2, 8%) or "B with retrograde extension into the arch" (n = 7, 28%), n = 8 cases (32%) were described generically as "arch dissections" (n = 6, 24%) or "type A and B" AAD (n = 2, 8%). The remaining 32% of patients received a diagnosis that did not include mention of the arch, as n = 6 (24%) cases were reported to be "type A″ and n = 2 (8%) to be "type B″ AADs. Despite the heterogeneity of terms used to describe NANB AAD, no case of cardiac tamponade, new onset malperfusion nor neurological complications were reported, and no sudden death nor home-discharge and readmission while waiting for the proper diagnosis.

Conclusions: The heterogeneity of terms used to describe NANB aortic dissection highlights the need for increased awareness, adoption of in guideline based classification systems, and further education to better understand and correctly address this challenging entity, minimizing misdiagnosis in ambiguous or difficult cases.