The aim of this study was to evaluate whether the orientation of the heart, measured as an angle between the long axis of the heart and ascending aorta midline (heart-aorta-angle, HAA), associates with ascending aortic (AA) dilatation. Furthermore, the association between HAA and wall shear stress (WSS) was studied.HAA was retrospectively measured in 1000 consecutive coronary artery computed tomographic angiography (CCTA) images in patients with low-to-moderate pretest probability for coronary artery disease (CAD). To evaluate the effects of HAA on AA flow, 4D flow MRI was performed for 28 patients with AA dilatation (> 40 mm) and WSS was analyzed.The mean age of patients undergoing CCTA was 52.9 ± 9.8 years; 66.5% were women. Their median HAA was 128.7° and interquartile range 123.3-134.1°. HAA was significantly smaller in patients with dilated AA (median 126.7° [121.3-130.8°]) compared with the patients with normal AA (median 129.5° [124.3-135.3°], p < 0.001). HAA was smaller in males (p < 0.001) and in patients with diabetes (p = 0.016), hypertension (p = 0.001), CAD (p = 0.003), hypercholesterolemia (p < 0.001), and bicuspid aortic valve (p = 0.025) than without these factors. In a subpopulation without any of these underlying diseases (n = 233), HAA was still significantly smaller in the patients with dilated AA (median 127.9° [124.3-134.3°]) compared with patients with normal AA (median 131.9° [127.6-136.9°], p = 0.013). In 4D flow MRI, a smaller HAA correlated with increased total WSS in the outer curvature of the proximal AA (r = - 0.510, p = 0.006).A smaller HAA associates with AA dilatation and affects the blood flow in the proximal AA.• A smaller angle between the long axis of the heart and ascending aorta midline associated with ascending aortic dilatation. • A smaller heart-aorta-angle correlated with increased total wall shear stress in the outer curvature of the proximal ascending aorta.