Discussion:
Chronic aortic dissection poses a risk of aortic diameter enlargement and rupture in the chronic phase. Therefore, imaging diagnosis with CT to monitor the aneurysmal diameter is strongly recommended. Reports on the prognosis of chronic aortic dissection have suggested that cases with an open false lumen have a poorer life prognosis than cases with a closed false lumen, indicating a potential link between blood flow within the false lumen and the enlargement or rupture of the aortic aneurysm in the chronic phase.1) Treatment with FET for total arch replacement has been reported to achieve good thrombosis of the false lumen in chronic aortic dissection. When performing total arch replacement, FET, compared to the conventional Elephant Trunk (ET) method for distal anastomosis, facilitates a more central anastomosis in the proximal portion of the arch, making peripheral anastomosis easier and reducing blood loss. Additionally, the insertion of a reinforced FET with a stent graft allows for the expectation of thrombotic occlusion and subsequent disappearance of the false lumen in the descending thoracic aorta during the chronic phase. However, complications such as dSINE may occur in the chronic phase as a result of FET. dSINE is the new entry of the stent graft’s distal end, leading to the generation of new blood flow from the true lumen to the false lumen, causing enlargement of the false lumen. After the FET procedure, dSINE occurred in 6.5% of patients in the chronic setting2). Excessive oversizing of the stent graft relative to the true lumen and the spring-back force of the stent graft contribute to SINE formation. Generally, dSINE is asymptomatic and incidentally discovered during regular follow-up CT scans. However, approximately 5% of cases present with symptomatic chest or back pain. 3)Typical CT images show the distal part of the stent graft inserted into the true lumen detaching from the intima of the aorta, protruding into the false lumen, and resuming blood flow into the false lumen or enlargement of the false lumen.
4D Flow MRI is a non-invasive imaging technique that expands 2D phase-contrast MRI in three dimensions. It allows for the direct measurement of blood flow, including flow from the true lumen to the false lumen, and wall shear stress (WSS) within the aorta in cases of aortic dissection. In this study, 4D Flow MRI was used for the first time to analyze blood flow in a case of dSINE. The analysis of aortic dissection with 4D MRI indicates that if accelerated blood flow and localized increases in WSS are observed in the remaining dissected area from the true lumen to the false lumen, factors contributing to remote enlargement are likely.4)
In the case of dSINE, as in cases of chronic open false lumen aortic dissection, accelerated blood flow from the true lumen to the false lumen was observed, suggesting further enlargement. Thus, TEVAR was chosen56), and good thrombosis of the false lumen was achieved. However, regular follow-up with CT imaging is necessary due to the risk of arterial expansion and re-dissection.