Histological assessment of the shared vascular wall in anomalous aortic origin of coronary arteries with an interarterial course

Abstract Background In anomalous aortic origin of a coronary artery (AAOCA) an intramural segment is present if the proximal AAOCA courses through the aortic wall. This is defined as a shared tunica media of the aorta and AAOCA in the ‘intramural septum’. This definition is based on autopsy studies of selected AAOCA patients who suffered sudden cardiac death and is difficult to apprehend on imaging modalities. Therefore, the aim was to identify the histological features and variants of the interarterial vascular wall in living adult patients, and correlate this to CT-angiography (CTA). Methods This prospective multicenter study included consecutive adult AAOCA patients who underwent surgical unroofing between 2021 to 2024. The excised interatrial vascular wall tissue was embedded, sectioned, and immunohistochemically stained for physiological components, e.g. smooth muscle cells and connective tissue, and pathological components such as fibrosis. Microscopic examination and quantification was performed by two independent observers and findings were correlated with CTA. Results Fifteen patients (mean age 42.9±14.0 years, 60% female) and 1 postmortem specimen were included. Fourteen (93%) had a right-AAOCA and 1 (7%) a left-AAOCA, with a mean intramural length of 8.4±4.1mm. Histopathologically, disorganized elastic lamellae with fragmentation, presence of fibrosis and loss of nuclei were observed. No vasa vasorum or nervi vasorum were identified. Post-sectioning virtual 3D reconstructions enhanced the spatial insight in correlation of histological sections with CTA. Conclusion This first study of the intramural septum in adults with AAOCA reveals the histological structure of the shared vascular wall between the aorta and AAOCA. Marked vascular wall abnormalities such as lack of vasa and nervi vasorum, fragmentation of elastic lamellae and fibrotic changes were observed. These findings support a propensity to local vascular wall pathology in patients with AAOCA. 3D reconstruction supported the translation of histological data to clinical imaging techniques.Central Figure