SciCombinator

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Concept: Aortic arch

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Rationale: Vascular smooth muscle cell (VSMC) differentiation from neural crest cells (NCCs) is critical for cardiovascular development, but the mechanisms remain largely unknown. Objective: TGF-β function in VSMC differentiation from NCCs is controversial. We therefore determined the role and the mechanism of a TGF-β downstream signaling intermediate Smad2 in NCC differentiation to VSMCs. Methods and Results: By using Cre/loxP system, we generated NCC tissue-specific Smad2 knockout mouse model and found that Smad2 deletion resulted in defective NCC differentiation to VSMCs in aortic arch arteries during embryonic development and caused vessel wall abnormality in adult carotid arteries where the VSMCs are derived from NCCs. The abnormalities included missing one layer of VSMCs in the media of the arteries with distorted and thinner elastic lamina, leading to a thinner vessel wall as compared to the wild type vessel. Mechanistically, Smad2 interacted with MRTFB to regulate VSMC marker gene expression. Smad2 was required for TGF-β-induced MRTFB nuclear translocation whereas MRTFB enhanced Smad2 binding to VSMC marker promoter. Moreover, we found that Smad2, but not Smad3, was a progenitor-specific transcription factor mediating TGF-β-induced VSMC differentiation from NCCs. Smad2 appeared to be also involved in determining the physiological differences between NCC- and mesoderm-derived VSMCs. Conclusions: Smad2 is an important factor in regulating progenitor-specific VSMC development and physiological differences between NCC- and mesoderm-derived VSMCs.

Concepts: DNA, Gene, Genetics, Gene expression, Developmental biology, Common carotid artery, Smooth muscle, Aortic arch

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Both hybrid and chimney techniques are used for reconstruction of supra-arch branches during thoracic endovascular aorta repair (TEVAR). Our objective was to summarize our experience with reconstruction of the left common carotid artery (LCCA) or left subclavian artery (LSA) and evaluate the indications for these 2 strategies.

Concepts: Common carotid artery, Internal jugular vein, Brachiocephalic artery, Arteries of the thorax, Subclavian vein, Arteries of the head and neck, Subclavian artery, Aortic arch

3

Stroke is a life threatening event that is expected to more than double over the next 40 years. Atrial fibrillation (AF) has been reported as a strong independent risk factor for stroke. We have previously shown that a hemodynamic perturbation by AF or reduced cardiac output and cycle length may have a significant impact on clot trajectory and thus embolic stroke propensity through the left common carotid artery using an idealized aortic arch model. Here, we show the dependence of flow patterns and hence stroke propensity on geometry of patient-specific aortas. We performed computational fluid dynamics (CFD) simulations to determine the variations of AF-induced stroke propensity over various image-based patient-dependent aorta models. The results demonstrated that curvature pattern of aorta can play a determinant role in AF-induced stroke propensity alteration. Specifically, it was shown that the hemodynamic perturbation by AF considered led to substantial increase in stroke propensity (i.e., 2.5~3.8 fold elevation) for lower curvature angle <90° while the changes in stroke propensity by AF are negligible for higher curvature angle >90°. The present simulations suggest that aortic arch curvature is an important risk factor for embolic stroke which should be tested in future clinical trials.

Concepts: Heart, Stroke, Atrial fibrillation, Common carotid artery, Arteries of the thorax, Computational fluid dynamics, Subclavian artery, Aortic arch

1

Congenital variants and anomalies of the aortic arch are important to recognize as they may be associated with vascular rings, congenital heart disease, and chromosomal abnormalities, and can have important implications for prognosis and management. The purpose of this article is to review cross-sectional imaging techniques used in the evaluation of the aortic arch, describe the embryology and anatomy of the aortic arch system, discuss aortic arch variants and anomalies, and review other malformations of the aortic arch, including interrupted aortic arch, hypoplastic aortic arch, and aortic coarctation. Aortic arch variants and anomalies will be reviewed in the context of a theoretical double aortic arch system. Arch anomalies can be associated with symptoms, such as dysphagia lusoria in the setting of left aortic arch with aberrant right subclavian artery. Arch variants that form a vascular ring, such as double aortic arch, can result in respiratory distress due to tracheal compression. Certain arch anomalies are strongly associated with congenital heart disease, including right aortic arch with mirror image branching. Other malformations of the aortic arch have important associations, such as type B interrupted aortic arch, which is associated with a locus 22q11.2 microdeletion. Noninvasive imaging at CT angiography and MR angiography allows for comprehensive evaluation of the aortic arch and branch vessels in relation to surrounding structures. Familiarity with the spectrum and imaging appearances of aortic arch variants, anomalies, and malformations is essential for accurate diagnosis and classification and to guide management. (©)RSNA, 2016.

Concepts: Common carotid artery, Brachiocephalic artery, Arteries of the thorax, Subclavian vein, Vertebral artery, Subclavian artery, Aberrant subclavian artery, Aortic arch

0

Recent guidelines support more aggressive surgery for aneurysms of the ascending aorta and root in patients with bicuspid aortic valve. However, the fate of the arch after surgery of the root and ascending aorta is unknown. We set out to assess outcomes following root and ascending aortic surgery and subsequent growth of the arch.

Concepts: Aortic dissection, Aorta, Ascending aorta, Descending aorta, Arteries of the thorax, Aortic valve, Aortic arch, Bicuspid aortic valve

0

We present the case of an 86-year-old male with an aortic arch saccular aneurysm who underwent zone 1 thoracic endovascular aortic repair (TEVAR) with debranching from the right subclavian artery to the left carotid and left subclavian arteries. The patient developed a type Ia endoleak 1 month later. Postoperative contrast computed tomography (CT) showed a hematoma around the aneurysm, concerning for impending rupture. He thus underwent emergency endograft removal and replacement with a one-branched graft using selective cerebral perfusion via the left subclavian artery perfusion. The left subclavian artery was used for systemic and cerebral perfusion without need for cannulation of the cervical arteries. The patient was successfully discharged 6 months after surgery.

Concepts: Common carotid artery, Brachiocephalic artery, Arteries of the thorax, Subclavian vein, Vertebral artery, Subclavian artery, Aberrant subclavian artery, Aortic arch

0

An 81-year-old woman was referred to our centre for emergency surgery with a suspected diagnosis of acute aortic dissection. Laboratory tests showed marked elevation of serum creatinine and blood urea nitrogen. Enhanced computed tomography (CT) demonstrated Type A aortic dissection with a thrombosed false lumen in the ascending aorta. The primary entry tear was located 2 cm distal to the left subclavian artery. Malperfusion of bilateral renal arteries was also evident due to compression by the false lumen. Considering her poor preoperative condition, thoracic endovascular repair of the entry was performed. The primary entry tear was covered using a covered Zenith TX-D stent graft, and a supplemental non-covered Zenith TX-D stent was deployed from the distal edge of the stent graft to the infrarenal aorta. After 5 days of dialysis and additional renal angioplasty for the stenotic left renal artery, her renal function recovered to normal. Her postoperative course was uneventful. Enhanced CT 1 month after surgery showed obliteration of the false lumen of the ascending aorta and patent renal arteries bilaterally.

Concepts: Heart, Blood urea nitrogen, Common carotid artery, Aortic dissection, Brachiocephalic artery, Arteries of the thorax, Subclavian artery, Aortic arch

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A rare case of adult PHACE syndrome with a distal aortic arch aneurysm was treated surgically. The patient had several anomalies including uneven cerebral blood flow, a small left common carotid artery and a narrowed transverse aorta. Under deep hypothermic circulatory arrest, aortic replacement with reconstruction of the left subclavian artery was performed uneventfully. Cystic degeneration of the tunica media was observed in the aneurysm wall.

Concepts: Heart, Common carotid artery, Internal jugular vein, Brachiocephalic artery, Arteries of the thorax, Arteries of the head and neck, Subclavian artery, Aortic arch

0

We evaluated radiological findings and clinical significance of right aortic arch with mirror-image branching (RAMI) in adults using data from computed tomography (CT) examinations.

Concepts: Aortic arch

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Acute aortic dissection of Kommerell’s diverticulum in the right aortic arch is extremely rare. There are several different procedures for the disease. With advances in endovascular treatment, hybrid surgical and endovascular management may provide a treatment of choice for this kind of disease.

Concepts: Aortic dissection, Aorta, Descending aorta, Aortic arch