Keep it Down!

Senior year comes around and a group of entitled high-school kids rents a two-bedroom, beach-front condo for the traditional “beach week”. Regrettably for their neighbor, 25 of the kids’ best friends plan to make the condo the week’s hangout and partyplace. The first night of revelry is wild for the seniors, both the high schoolers and the neighbors. The high schoolers over imbibe and there are serious episodes of “calling Ralph at the porcelain”. Neighbors bang on the shared wall several times to “keep it down”, thinking that they are only relating to the music and the student’s chattering. Joan, one of the students, is over poured on the second night and passes out. In the morning, she is still “out of it” and her friends begin to worry when she does not respond. They rush outside and beg the next-door neighbors to please help see what is wrong, at which time the neighbors summon an ambulance and Joan is rushed to the ED. Ultrasound reveals cardiomegaly and she is rushed to surgery. Given her condition and her friends’ description that Joan has been heavily abusing alcohol daily for over five years, the ED doc decides to perform a coronary artery by-pass. In preparing Joan for the by-pass, the thoracic surgeon inserts his finger in the transverse pericardial sinus. What is the location of this sinus in the images?

Location of transverse sinus is best indicated by which numbered line?