OBJECTIVES: This study aimed to classify anatomical variations in aortic root rotation using preoperative three-dimensional transoesophageal echocardiography (3D-TEE), validate these findings with cardiac computed tomography (CT) in patients undergoing mitral valve surgery and evaluate the clinical impact on postoperative atrioventricular conduction disorders. METHODS: A total of 126 patients with normal electrocardiograms who underwent isolated mitral valve surgery were included. Anatomical variation was diagnosed using 3D-TEE, and aortic root rotation angle was measured using cardiac CT. New-onset postoperative atrioventricular block (AVB) and bundle branch block were analysed. RESULTS: Variations of aortic root rotation were classified by 3D-TEE into two categories: 'center rotation' (normal) (85.7%, n = 108/126), where the commissure of the left and non-coronary aortic leaflet was located at center of the anterior mitral leaflet, and 'lateral rotation' (14.3%, n = 18/126), rotated to the lateral trigone side. The aortic root rotation angle, where the interatrial septum was defined as a reference, measured by cardiac CT strongly correlated with 3D-TEE findings ('center rotation' vs 'lateral rotation': 51.6° vs 64.6°, P <
0.001). The incidence of new-onset conduction disorder, all presenting with first-degree AVB, was significantly higher in the 'lateral rotation' than in the 'center rotation' (38.9% [n = 7/18] vs 5.6% [n = 6/108], P <
0.001). Aortic root rotation angles were identified as significant risk factors for postoperative first-degree AVB (odds ratio, 1.05
95% confidential interval, 1.01-1.09
P = 0.027), with cutoff values of 58.7° predicting persistent new-onset AVB. CONCLUSIONS: Aortic root rotation angle measured by cardiac CT validated 3D-TEE diagnosis of 'lateral rotation' of the aortic root. 'Lateral rotation' and larger aortic root rotation angles were significant risk factors for postoperative first-degree AVB following mitral valve surgery.