Image analysis
Image analysis was conducted according to a standardized protocol. CTA analysis was conducted by manually demarcating an aortic centerline extending from the level of the aortic valve anulus through the origin of the left subclavian artery. Curved planar reformatted images were generated using the aortic centerline as the reference point (Figure 1). The sinotubular junction (STJ) and the origin of the innominate artery (IA) were then identified and labeled (Figure 2). The STJ was defined as the earliest point that the ascending aorta becomes tube-like. The origin of the IA was defined as the most proximal point at which the wall of the IA touches the ascending aorta (rather than at the middle of the IA lumen). The path length, distance, and tortuosity between the STJ and IA were recorded. The pulmonary artery bifurcation was identified in transverse plane and measured at the widest point of both the left and right branches of the PA (Figure 2). Cross-sectional area, average diameter, maximum diameter, and minimum diameter were measured at the levels of the STJ, IA, and PA bifurcation.