1353362 - Added value of 4D-flow imaging in repaired aortic coarctation

A 53-year-old male with history of prior aortic coarctation repair 23 years ago presented for pre-operative evaluation of thoracic aortic aneurysm. No additional history was available regarding his prior surgery or interval clinical course.

Diagnostic Techniques and Their Most Important Findings:

Initial CT angiogram was ordered for pre-operative evaluation of the aneurysm dimension and showed a fusiform aneurysmal dilation in the proximal descending thoracic aorta measuring 6.8 x 5.9 cm (Figure 1) with an additional saccular aneurysm in the aortic arch just distal to the origin of the left subclavian artery measuring 2.1 x 1.1 cm. Subsequently, a magnetic resonance angiogram (MRA) with 4-dimensional (4D) flow was performed to better evaluate the aorta prior to surgery. The 4D flow analysis revealed presence of flow through a tiny fenestration between the inferior aspect of the proximal aortic arch and the superior aspect of the aneurysm (Figure 2). On further review, this site was most likely the original coarctation which was not well-appreciated initially at CTA. The majority of flow went through an interposition bypass graft now complicated by aneurysmal degeneration at both proximal and distal anastomoses (Figure 3). Following imaging, the patient underwent explant of prior bypass graft and resection of the aortic coarctation with new interposition graft between the aortic arch and the mid descending thoracic aorta with reimplantation of the left subclavian artery.

Learning Points from this Case:

Surgical repair of aortic coarctation repair is typically performed by either resection of the coarctation with end-to-end anastomosis or endovascular repair with stent positioning. Less common surgical options include resection with interposition graft, patch arthroplasty, and extra-anatomic bypass, usually considered in case of re-stenosis or associated aortic arch hypoplasia.  In our case, the coarctation was initially repaired with extra-anatomic bypass subsequently complicated by aneurysmal dilation right below the anastomosis between the graft and the thoracic aorta, that on CT obscured the presence of communication through the original coarctation site. 4D flow MRI allows non-invasive in-vivo measurements of 3D flow dynamics with full volumetric coverage of the cardiac or vascular region of interest. In patients with aortic coarctation repair 4D flow evaluation offers qualitative visual evaluation of the flow throughout the region of interest and, interestingly, increased peak velocity on 4D flow analysis has been associated with progressive narrowing at the coarctation site repair. In this case, MR 4D flow analysis was able to easily demonstrate presence of flow across the original coarctation site and allowed not only a precise and confident diagnosis that was not evident on prior CT evaluation but also a more comprehensive pre-operative evaluation and planning that was particularly helpful in this case where no details regarding the patient past medical surgery were available.