Selection of landmarks
The ascending thoracic aorta is defined by international guidelines as “the tubular portion of the ascending aorta beginning at the sinotubular junction and extending to the brachiocephalic artery origin”6,14. Study landmarks were selected based on these guidelines. We considered selecting the aortic valve annulus as our proximal landmark but decided that the sinotubular junction would be a more consistently reproducible landmark due to the technical difficulty involved in orienting the aortic valve cusps to identify the annulus.