Keywords
right-sided aortic arch - acute ischemic stroke - endovascular treatment
Introduction
A right-sided aortic arch (RAA) is a rare variant of the aortic arch found in approximately
0.01 to 0.1% of the general population.[1] We treated a patient with acute ischemic stroke due to basilar artery (BA) occlusion
with an RAA, which was first observed during endovascular treatment (EVT). A favorable
outcome was achieved by early change in the access route. Our experience may provide
useful information to guide others when performing neuro-EVT in patients with this
condition.
Case Report
A 70-year-old man presented with severe disturbance of consciousness and quadriparesis
and was admitted to our hospital. He had no history of a congenital heart disease
(CHD). His National Institutes of Health Stroke Scale (NIHSS) score was 26 points.
Diffusion-weighted magnetic resonance imaging revealed acute ischemia of the pons
([Fig. 1A]), and magnetic resonance angiography (MRA) suggested BA occlusion ([Fig. 1B]). No intravenous tissue plasminogen activator was administered because the stroke
had occurred over 13 hours before presentation.
Fig. 1 (A) Magnetic resonance imaging revealing acute ischemia of the pons (white arrow). (B) Magnetic resonance angiography revealing poor visualization of the basilar artery
(white arrowheads). (C) Aortic angiography revealing a right-sided aortic arch. (D) Right subclavian angiography via the right brachial approach revealing the vertebral
artery (white arrowheads). (E) Right vertebral angiography revealing basilar artery (BA) occlusion. (F) Right vertebral angiography revealed successful revascularization of the BA. (G) Image showing the retrieval stent and red clot.
Urgent EVT was performed via a femoral artery approach. Aortic angiography revealed
a RAA ([Fig. 1C]). Navigation of a 6-French ultra-long sheath to the dominant right vertebral artery
(VA) was unsuccessful. Approximately 20 minutes after the initial groin puncture,
successful navigation of another 6-French ultra-long sheath to the right VA was achieved
via the right brachial artery approach ([Fig. 1D]). Right VA angiography revealed a BA occlusion ([Fig. 1E]). After one pass of thrombectomy combined with the use of a retrieval stent (EMBOTRAP
II 5.0 mm × 33 mm Revascularization Device [Cerenovus, Irvine, CA]) and aspiration
catheter ([Penumbra, Alameda, CA, USA]), successful revascularization was achieved,
and a red clot was retrieved ([Fig. 1F, G]). The time from the initial groin puncture to revascularization was 57 minutes.
The patient's neurological symptoms improved rapidly, and 1 day postoperatively, his
NIHSS score was 8 points with disorientation, ataxia, mild dysarthria, and moderate
quadriparesis. MRA performed 1 day after the procedure confirmed successful revascularization,
and diffusion-weighted imaging showed only small ischemic changes. Anticoagulant therapy
(30 mg edoxaban daily) was commenced 24 hours after the procedure and was continued.
Post-treatment Holter electrocardiogram showed paroxysmal atrial fibrillation. The
patient was discharged on day 21, with no neurological deficit 3 months later.
Discussion
Several classifications of this variant have been identified, which are based on the
arrangement of the aortic arch vessels, relationships with the esophagus, or the presence
of CHD.[2]
[3]
[4] Edwards classification[5] of RAA describes three types—Type I: RAA with mirror image branching is the most
common type, which is strongly associated with CHD in up to 98% of cases, including
tetralogy of Fallot, truncus arteriosus, tricuspid atresia, and transposition of the
great arteries with pulmonary valve stenosis; Type II: RAA with aberrant left subclavian
artery is the second most common type, which is usually not associated with CHD; and
Type III: RAA with isolation of the left subclavian artery may cause congenital subclavian
steal syndrome and vertebrobasilar insufficiency. Furthermore, this type is associated
with CHD in over 50% of cases, most commonly tetralogy of Fallot. Our patient was
diagnosed with mirror image branching RAA with Kommerell's diverticulum (Type I) using
postoperative CT angiography ([Fig. 2A–C]).
Fig. 2 CT angiography revealed a right-sided aortic arch with mirror imaging branch. (A) Right anterior oblique view. (B) Front view. (C) Left anterior oblique view (white arrow is Kommerell's diverticulum).
To the best of our knowledge, this is the first case of EVT for acute large vessel
occlusion with an RAA. A RAA may make catheterization difficult because most of the
ready-made catheters used presently were designed for a left aortic arch. In our case,
navigation of the guiding sheath to the right VA via the femoral artery approach may
have been possible after a long period. However, EVT outcomes for acute ischemic stroke
are time-dependent. Mokin et al.[6] reported a significant increase in the prognosis of revascularization cases within
6 hours after onset in 100 cases of posterior circulation including basilar artery
occlusion. Mourand et al.[7] reported that the mean onset to revascularization time tended to be lower in patients
with poor outcomes than in those with favorable outcomes (411 ± 178 minutes vs. 663 ± 296 minutes,
p = 0.03) in 20 cases of basilar artery occlusions. Unexpected anatomical variant of
the aortic arch may increase procedural difficulty of neuro-EVT via the femoral artery
approach.[8] Even in cases of patients with a normal aorta, the meandering of tortuous vessels
tends to delay the femoral artery access procedure by 30 minutes or more, which is
also associated with unsuccessful revascularization.[9] Neuro-EVT is often performed via femoral artery approach. Due to the unexpected
unfamiliar RAA, we switched to an anatomically familiar brachial artery approach to
reduce the revascularization time. A right radial or brachial artery approach may
be effective in navigating the catheter to the right VA for all types of RAAs when
the angle formed by the VA and subclavian artery was 45 degrees or higher.[10] Performing an aortic angiography or MRA as a pretreatment image may lead to appropriate
device selection and appropriate initial puncture site, whether anatomical normal
or variant.
Conclusion
Flexible treatment strategies are warranted for cases of unexpected anatomical variant
in the fight against time for emergent cases, such as acute ischemic stroke.
