Impact of ascending to descending aortic bypass for aortic coarctation on 3-dimensional hemodynamics.

n the management of aortic coarctation, endovascular techniques and surgical repair have been shown to have similar short-term morbidity. 1 However, further studies have shown that, in patients with coarctation that are complex or have previously undergone surgical repair, an ascending-descending aortic bypass surgery is effective in decreasing future interventions. 2 We present postoperative findings in a 67-year-old female patient after ascending-descending aortic bypass surgery for recurrent aortic coarctation. The patient has a history of aortic coarctation for which she underwent 2 separate surgical corrections via thoracotomies as a child (at 5 and 16 years of age). Her preoperative computed tomography scan (Figure 1A) revealed a stenotic segment with an aneurys-mal dilated area between the left common carotid artery to just distal of the left subclavian artery. Cardiac catheteriza-tion demonstrated a 40 mm Hg peak gradient across the ste-notic segment, and aneurysmal degeneration of the proximal descending thoracic aorta, as well. Because of the complex anatomy from the recurrent coarctation and associated aneu-rysm, repair via endovascular stenting was not favored. The 2 operative approaches considered included (1) resection with interposed graft reconstruction and (2) ascending to descending aortic bypass. Given the expected dense adhesions, and the concern for the inability to gain proximal control of the aorta from a thoracotomy, as well, in this particular patient, the bypass operation was chosen. A 16×30 mm Gelweave Dacron graft bypass was used between the ascending (AAo) and descending aorta (DAo). To assess the postinterventional aortic geometry and patency of the bypass graft, a computed tomography angio-gram was performed postsurgery. The large saccular aneu-rysm measured 3.9×5.7×3.9 cm, which was unchanged from presurgery. The Dacron graft extended from the right proximal AAo, wrapping rightward and posteriorly around the heart to anastomose with the descending thoracic aorta (Figure 1B). Although computed tomography data cannot provide information on the changes in aortic hemodynam-ics (intended reduction of systolic gradient at the site of the coarctation, bypass function, and aneurysmal flow patterns) by using the simplified Bernoulli equation dP max =4V max , 2 it is possible to estimate a presurgical peak velocity of 3.16 m/s at the stenotic site. 3 To better understand these complex postsurgical hemo-dynamics within the aorta, aneurysm, coarctation, and the AAo-to-DAo bypass graft, time-resolved 3-dimensional phase contrast (4D flow) MRI was performed (spatial reso-lution=3×2.13×3.5 mm, temporal resolution=38.4 ms, echo time=2.41 ms, velocity sensitivity=150 cm/s) to measure in vivo 3-dimensional blood flow velocities. The …