ORIGINAL COMMUNICATION The Rotational Position of the Aortic Root Related to its Underlying Ventricular Support DOROTHY AMOFA, 1 SHUMPEI MORI , 2 HIROYUKI TOH, 2 HIEU T. TA, 3 MAIRA DU PLESSIS, 1 NELSON DAVIS, 1 YU IZAWA, 2 DIANE E. SPICER, 4 ROBERT H. ANDERSON , 5 AND JUSTIN T. TRETTER 3,6 * 1 Department of Anatomical Sciences, St. George’s University School of Medicine, St. George’s, Grenada, West Indies 2 Division of Cardiovascular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan 3 The Heart Institute, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio 4 Department of Pediatric Cardiology, University of Florida, Gainesville, Florida 5 Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK 6 Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio We aimed to assess the relationship of the rotational position of the aortic root to its underlying ventricular support, and to the position of the inferior margin of the mem- branous septum, which serves as a surrogate of the atrioventricular conduction axis. We analyzed 40 normal heart specimens (19 children, 21 adults). The inferior mar- gin of the membranous septum was measured relative to the virtual basal ring. The rotational position of the aortic root was determined by assessing the relationship of the aortic leaflet of the mitral valve to the interleaflet triangle between the non- and left coronary leaflets. The extent of supporting fibrous versus myocardial tissues was measured. We also performed a similar investigation of 30 adult computed tomo- graphic data sets. The median age was 0.25 years (44% male) for children, and 64 years (33% male) for adults. The aortic root was positioned centrally in 22 speci- mens (55%), rotated counterclockwise in 6 (15%), and clockwise in 12 (30%). In the setting of counterclockwise rotation, 53.4% (median) of the supporting circum- ference was myocardial, as opposed to 41.4% (median) in those with centrally posi- tioned roots, and 31.9% (median) in those with clockwise rotation (P < 0.0001). The position of the inferior margin of the membranous septum was not associated with the rotational position. Analysis of the 30 adult computed tomographic data sets (median age 66.5 years, 57% male) confirmed the positive relationship between clockwise rotation of the aortic root and an increase in the extent of fibrous as opposed to myocardial support. The rotational position of the aortic root correlates with variation in the extent of its fibrous as opposed to myocardial ventricular sup- port, but not with the position of the inferior margin of the membranous septum rela- tive to the virtual basal ring. Clin. Anat. 32:1107–1117, 2019. © 2019 Wiley Periodicals, Inc. Key words: aortic root; aortic valve; cardiac conduction system; computed tomography; left ventricle; membranous septum; transcutaneous aortic valve implantation; transcutaneous aortic valve replacement *Correspondence to: Justin T. Tretter, Heart Institute, Cincinnati Children’s Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229. E-mail: justin.tretter@cchmc.org Received 28 March 2019; Revised 17 July 2019; Accepted 22 July 2019 Published online 10 September 2019 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/ca.23462 © 2019 Wiley Periodicals, Inc. Clinical Anatomy 32:1107–1117 (2019)