Vascular rings and aberrant arteries
Many arch anomalies do not cause hemodynamic disturbances on their own, but create anatomical prerequisites for the compression of surrounding structures.
A right-sided aortic arch is formed by the persistence of the right pharyngeal arch. It is often accompanied by an aberrant origin of the left subclavian artery (LSA), which passes behind the esophagus. If the ligamentum arteriosum (ligamentum arteriosum) originates from the base of such an artery (or from an unresorbed arch remnant — the diverticulum of Kommerell), it attaches to the pulmonary artery and completes a true vascular ring. The ligamentum arteriosum tightens (tension effect), compressing the esophagus and trachea.
There are also anomalies without a true ring, but with a compression syndrome. For example, an aberrant brachiocephalic artery crossing the trachea anteriorly, or a retroesophageal right subclavian artery with a normal left arch — it originates from the descending aorta as the last branch and courses to the right arm behind the esophagus.
Aortic coarctation: clinical forms
Coarctation is a localized narrowing of the aorta. The condition is more common in males (80%), while in females it is frequently associated with Turner syndrome. Clinically, it manifests as arterial hypertension and a delayed, weak pulse in the femoral arteries.
There are two main types:
- Infantile (preductal) type. The narrowing is located proximal to the ductus arteriosus. Collateral vessels do not develop in utero. At birth, the ductus closes, blood supply to the distal aorta drops sharply, leading to heart failure. It is often associated with a bicuspid aortic valve and hypoplastic left heart syndrome.
- Adult (postductal) type. Located distal to the left subclavian artery. Collaterals manage to develop in utero, so patients may survive into adulthood, presenting with complaints of hypertension.
Imaging of anomalies
The radiologist's arsenal includes several key imaging modalities:
- Chest X-ray (CXR). Adult-type coarctation is characterized by rib notching — erosion of the inferior margins due to pressure from dilated collateral intercostal arteries. The first two ribs remain intact (their arteries arise proximal to the stenosis zone). A "figure-3" sign on the aortic contour is also characteristic. In infants with stridor due to vascular rings, the radiologist may note a right-sided aortic arch or tracheal compression.
- Barium esophagography. A double arch shows persistent bilateral and posterior esophageal compression. With a retroesophageal artery, an oblique posterior wall defect is seen.
- MRI. The method of choice. Cine phase-contrast MRI (Cine phase-contrast) allows not only visualization of the anatomy but also calculation of the pressure gradient. Static images show compression, while dynamic cine MRI during water swallowing confirms true compression.
- CT. Provides the highest image quality and allows visualization of a calcified ligamentum arteriosum. This is the primary modality for follow-up after stent-graft placement, as stents create significant artifacts on MRI.
Management approaches for coarctation
Without intervention, the prognosis is unfavorable — patients die from heart failure, aortic rupture, or endocarditis.
- Surgical treatment. Resection of the narrowed segment with an end-to-end anastomosis is optimal. If this is not feasible, subclavian flap aortoplasty is used (the flap grows with the child). A rare (1%) but formidable complication of surgery is paraplegia.
- Endovascular methods. Percutaneous transluminal angioplasty (PTA) is currently the primary treatment method for patients past infancy. Stenting is used when balloon dilation is ineffective (due to elastic recoil), but is not used in infants.
Briefly: answers to topical questions
Which congenital heart defects and genetic syndromes are associated with coarctation of the aorta?
Aortic coarctation in literature is associated with the following genetic syndromes and congenital heart defects.
Genetic syndromes:
- Turner syndrome (monosomy X) — in females, aortic coarctation is frequently associated with Turner syndrome.
Congenital heart defects and associated anomalies:
- Bicuspid aortic valve.
- Ventricular septal defect (VSD / VSD).
- Hypoplastic left heart syndrome.
- Left ventricular outflow tract obstruction (LVOT).
- Transposition of the great arteries (TGA).
- Common arterial trunk (common arterial trunk).
For the infantile, preductal type of coarctation, it is noted that in 50% of cases it is combined with other congenital heart defects, including a bicuspid aortic valve, VSD, and hypoplastic left heart syndrome.
What branches normally originate from the aortic arch?
Normally, three main arterial branches originate from the aortic arch.
- Brachiocephalic trunk (truncus brachiocephalicus / Innominate artery) — also referred to as the innominate artery.
- Left common carotid artery (a. carotis communis sinistra / Left common carotid artery).
- Left subclavian artery (a. subclavia sinistra / Left subclavian artery).
What anatomical variants of a double aortic arch exist?
The following anatomical variants of a double aortic arch exist, formed by the persistence of both fourth arterial arches:
- Right-dominant arch — occurs in 75% of cases, when the right (posterior) arch is larger than the left.
- Atretic variant — in approximately 30% of cases, the smaller arch is atretic (atretic), but maintains continuity with the descending aorta, forming a complete vascular ring.
Anatomically, two arches are distinguished:
- Left arch (anterior) — normally positioned, emerges from the pericardium and connects with the left-sided descending thoracic aorta after the origin of the left subclavian artery (LSA).
- Right arch (posterior) — connects with the descending thoracic aorta at the same level.
To remember rib notching in coarctation: "The first two are always intact!" The intercostal arteries of the 1st and 2nd ribs originate from the costocervical trunk ABOVE the stenosis, so they are not overloaded with volume and do not erode the bone.
Class and exam questions
What is Kommerell diverticulum?
This is an unresorbed remnant of the left fourth pharyngeal arch in a right-sided aortic arch. It gives rise to the ligamentum arteriosum, which can complete a pathological vascular ring.
What distinguishes pseudocoarctation from true coarctation?
In pseudocoarctation, the aorta is elongated and bulges, creating the figure-of-3 sign on radiographs. However, unlike true coarctation, there is no significant hemodynamic obstruction (stenosis).
Why is real-time MRI performed during water swallowing?
Water on T2-weighted images yields a high signal and distends the esophagus. This allows for dynamic visualization of the posterior impression from aberrant vessels and confirms true compression, which is not always visible on static images.
What else to study on this topic
- Hemodynamic aspects and pressure gradient calculation in MRI
- Detailed analysis of flow-time curves in phase-contrast imaging
- Association of aortic coarctation with bicuspid aortic valve and other CHD
- Aortic atresia and its hemodynamics (retrograde arch filling)
- Morphology of vascular rings in a left-sided aortic arch
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