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.