Vascular Rings

Vascular Rings, Slings, and Aortic Arch Anomalies

Clinical Presentation and Diagnostic Approach

Presentation by Laila Wazneh (Neonatal nurse practitioner at the Montreal Children's Hospital) and Dr Mahammed Alamer (Pediatric Cardiology Interventional fellow)

Case of a Right Sided Aortic Arch with aberrant origin of the left subclavian artery and left duct (or ligamentum arteriosum) forming a ring

Fetal echocardiography

Post-natal transthoracic echocardiography

Vascular Rings, Slings, and Aortic Arch Anomalies

Anomalies of the aortic arches arise from variable persistence or regression of the dorsal and ventral aortae and the six primitive aortic arches. Classically, the left fourth arch contributes to the aortic arch and the right fourth arch to the proximal right subclavian artery. By selectively “keeping” or “removing” segments in a developmental schema, one can reproduce the full spectrum of aortic arch variants observed postnatally.

Two broad categories:

Encircling anomalies (vascular rings): a complete ring is created when arch segments plus the ductus arteriosus/arterial ligament encircle the trachea and esophagus.
Non-encircling anomalies (slings): vascular structures compress the airway without forming a true circumferential ring.

A complete vascular ring capable of compression requires the arch system plus a ductal/ligamentous component closing the circle.

Clinical Presentation and Diagnostic Approach

A. Symptomatology and timing

Airway symptoms are driven by tracheobronchial compression and where it occurs:

Near the larynx (extrathoracic): predominantly inspiratory noise/difficulty.
Near the bronchi: predominantly expiratory symptoms/wheeze.
Tracheal compression: often mixed inspiratory–expiratory pattern with stridor.

Hemodynamic/flow physics apply: clinically relevant consequences typically appear when diameter is reduced >50% (~75% loss of cross-sectional area). At birth, ~95% are asymptomatic; major symptoms classically emerge around 3–4 weeks of age as the trachea stiffens and flows increase. Marked symptoms in this window suggest >90% compression and require urgent evaluation. Stridor is the most common trigger for the diagnostic pathway.

B. Diagnostic sequence

Consider trans-thoracic echocardiography if a neonate has stridor otherwise unexplained
Laryngoscopy to assess vocal cords first (≈67–75% of neonatal/infant stridor is laryngeal).
If larynx is normal → rigid bronchoscopy (under GA) to assess glottis, subglottis, and trachea; document site, pattern, and severity of compression.
Cross-sectional imaging—preferably contrast CT angiography—to define the arch configuration, branching, ductal/ligament connections, and relation to trachea/esophagus. MRI is an alternative where available. Echocardiography complements to confirm arch sidedness/branching and associated cardiac lesions.

Graphical representation of a primitive aortic ring giving rise to a right and a left arch, forming a complete vascular ring around the trachea and esophagus. From each side originate the common carotid and subclavian arteries. This vascular ring—often referred to as the aortic circle—is composed of segments derived from the primitive aortic arches and the ductus arteriosus. Abnormal persistence or regression of these segments determines the various aortic arch anomalies observed in clinical practice. They are traditionally classified into four main types (A, B, C, and D) depending on the location of the interrupted segment. Together, the aortic components and the ductus arteriosus create potential vascular rings capable of compressing the airway or esophagus.

III. Encircling Anomalies (Vascular Rings)

1) Double Aortic Arch (DAA):

Persistence of both right and left arches creates a complete ring around trachea and esophagus. Each arch typically gives rise to a carotid and subclavian artery. Most are right-dominant; left-dominant and balanced forms occur. Often severe airway/esophageal compression; many are symptomatic in early infancy. CT shows tracheal narrowing between the arches. Surgery: Via left thoracotomy in most cases:

Identify the nondominant arch and the ductus/ligament.
Divide the ductus/ligament and divide the nondominant arch, converting the anatomy to a non-encircling configuration and freeing trachea/esophagus.
In balanced arches, choose the segment to divide based on dominance, descending aorta position, and local compressive effect. Rarely, both arches can be borderline small—confirm complete relief intra-operatively.

2) “Equivalent” Double Arch (Atretic Segment)

A double arch in which a segment (often posteromedial) is atretic (non-patent) but persists as a fibrous cord, maintaining the ring. CT may show an aberrant left subclavian artery or a tract toward a diverticulum with no contrast lumen across the suspected segment. The surgery is through left thoracotomy, identify and divide the fibrous cord (the atretic arch segment) and the ligament/ductus to open the ring.

3) Right Aortic Arch (RAA) with Left Arterial Ligament

Mirror-image branching is typical (left brachiocephalic trunk first). A ring forms only if the left arterial ligament connects the pulmonary artery to the descending aorta/isthmus (not just to the brachiocephalic trunk). Surgery: Divide the left ligamentum arteriosum (and any contributing fibrous cord) to open the ring.

4) RAA with Aberrant Left Subclavian Artery (ALSA) from Kommerell’s Diverticulum (KD)

The right arch gives rise to an ALSA coursing retro-esophageal from a KD (remnant of left dorsal aorta). The left ligament completes the ring.

Compression & risk: Dividing the ligament relieves the ring, but the KD poses long-term risks (dilatation/aneurysm, rupture, dissection) and may cause dysphagia.

Surgery. Two goals: (1) Relief of the ring: divide the ligament. (2) Exclude the KD: detach ALSA from the diverticulum and reimplant onto the left common carotid (restoring a normal brachiocephalic trunk pattern). Close the KD base.
Long-term surveillance is advised given the non-normal aortic tissue.

IV. Surgical Outcomes and Expected Postoperative Course

Residual compression & tracheomalacia: After ring division (DAA, RAA+ligament), residual tracheal indentation is common—often >50% early—due to tracheomalacia from chronic compression. Expect persistent cough/noise for up to ~2 years as cartilage stiffens with growth. Monitor clinically; avoid routine re-imaging unless red flags (worsening distress, failure to thrive, recurrent infections).
Recurrent laryngeal nerve vulnerability: Division near the ductus/ligament risks recurrent laryngeal nerve traction or injury (especially with arch sidedness anomalies). Resultant paresis can cause aspiration; monitor voice/feeding post-op.
Hemorrhage and general risks Any aortic/branch reconstruction carries a bleeding risk; counsel families appropriately.
Long-term follow-up: After KD repair, plan periodic aortic surveillance into adulthood (dilatation/calcification risk of residual aorta or reimplanted segment).

V. Non-Encircling Anomalies / Slings

1) Brachiocephalic (Innominate) Artery Compression of the Trachea

Common incidental MRI/CT finding in toddlers; ≤50% diameter indentation is frequent and typically asymptomatic. With growth, the TABC moves anteriorly/away from the trachea. Operate only for severe, clearly symptomatic cases. Techniques:

Translocation of the brachiocephalik trunk to a more anterior aortic position, or
Aortopexy/innominate artery suspension to the sternum/ribs. A ~10 mm anterior shift often eliminates compression. Intra-op bronchoscopy confirms relief.

2) Left Pulmonary Artery (LPA) Sling

The LPA arises from the right pulmonary artery and passes posterior to the trachea (and often esophagus), compressing them—classically associated with congenital tracheal stenosis. Surgery:

Detach the LPA from the RPA, bring it anterior to the airway, and reimplant into the main pulmonary artery.
Because of the strong association with complete tracheal rings, a rigid bronchoscopy is mandatory; many require concomitant tracheal repair (see Section VI).

3) Aberrant Right Subclavian Artery (ARSA)

ARSA typically runs retro-esophageal and does not compress the trachea. Rarely causes dysphagia to solids. Surgical correction is exceptional and only after excluding more common causes (e.g., GERD). Infants on milk alone are usually unaffected.

VI. Rare or Complex Configurations

Crossed arches / retro-esophageal brachiocephalic variants: unusual trajectories that can sustain compression despite ductal division alone.
Retro-esophageal brachiocephalik trunk (very rare): management individualized—often duct/ligament division for compression relief; consider more complex revascularization only if persistent symptomatic compression or progressive dorsal aortic dilation threatens.

Postoperative Course and Follow-Up

Residual symptoms (noisy breathing, cough) are common after ring division due to tracheomalacia; reassure families that improvement is expected over months as cartilage stiffens. Avoid routine control CTs/bronchoscopies unless clinically indicated.
Voice/feeding checks detect recurrent laryngeal nerve dysfunction; treat aspiration proactively.
KD repairs: schedule periodic imaging into adulthood to surveil residual aorta and the reimplanted segment.

After repair, tracheomalacia dictates the pace of recovery; most children improve without additional intervention.
Long-term surveillance is prudent after KD exclusion and complex arch reconstructions.