Circumflex Aortic Arch, a Rare Cause of Symptomatic Vascular Ring: Case Report and Review of Literature

Technical Summary: Circumflex Aortic Arch as a Cause of Symptomatic Vascular Ring

Problem Statement
Circumflex aortic arch (CAA) is a rare congenital vascular anomaly where the aortic arch crosses the midline posterior to the trachea and esophagus, descending on the contralateral side. While often asymptomatic, CAA can form a symptomatic vascular ring, typically completed by a ligamentum arteriosum connecting the crossing arch to the contralateral pulmonary artery. This configuration causes compression of the airway and/or esophagus, presenting clinically as stridor or dysphagia. A significant diagnostic challenge exists in differentiating CAA from other vascular ring anomalies, such as a double aortic arch with a hypoplastic segment. Furthermore, failure to identify and resect the compressing ligamentum arteriosum during surgical correction can lead to persistent symptoms and the need for revision surgery.

Methodology
The authors present a case report and literature review involving two pediatric patients diagnosed with CAA:

1. Case 1: A five-year-old male presenting with progressive stridor.
2. Case 2: A nine-year-old female presenting with dysphagia lusoria and progressive stridor.

The diagnostic workflow for both cases involved:

• Initial Screening: Plain chest radiography to exclude pulmonary causes and transthoracic echocardiography (TTE) to suspect a vascular ring.
• Definitive Imaging: Cardiac computerised tomography (CCT) with volume rendering (VR) and minimum intensity projection (Min-IP) reconstructions. These modalities were used to delineate the aortic arch anatomy, branching patterns, and the presence of a ligamentum arteriosum or diverticulum of Kommerell.
• Surgical Intervention: Both patients underwent surgical correction. Case 1 involved a left lateral thoracotomy with resection of the diverticulum and ligamentum arteriosum, followed by aortopexy. Case 2 involved a right lateral thoracotomy with division of the ligamentous structure tethering the diverticulum of Kommerell, followed by aortopexy.

Key Contributions and Results

• Diagnostic Precision: The study demonstrates that CCT is superior to TTE and plain radiography for preoperative planning. Specifically, VR images were critical in distinguishing CAA from a double aortic arch with a hypoplastic segment. In Case 1, the absence of the "four-vessel sign" (where a hypoplastic arch gives rise to arteries separately) and the presence of a brachiocephalic artery as the first branch confirmed the CAA diagnosis.
• Anatomical Identification: In both cases, CCT successfully identified the specific anatomy of the vascular ring:
  • Case 1 (Right CAA): A right-sided arch crossing to the left, with a blind-ended diverticulum tethered to the left pulmonary artery, indicating a left-sided ligamentum arteriosum.
  • Case 2 (Left CAA): A left-sided arch crossing to the right, featuring an aberrant right subclavian artery with a diverticulum of Kommerell tethered to the right pulmonary artery, indicating a right-sided ligamentum arteriosum.
• Surgical Outcomes: Both patients underwent division of the ligamentum and aortopexy. The authors note that aortic uncrossing (the standard repair) was not performed in Case 1 due to the patient's age and weight, highlighting aortopexy as a viable alternative for patients unsuitable for major aortic reconstruction.
• Literature Context: The review cites previous works (e.g., Langenfeld et al., 2025; Priya and Nagpal, 2020) confirming that CCT is the preferred modality for identifying these anomalies and emphasizing that overlooking the ligamentum arteriosum is a primary cause of postoperative symptom persistence.

Significance and Claims
The paper asserts that despite its rarity, CAA must be considered a potential cause of symptomatic vascular rings in patients presenting with respiratory or esophageal compression. The primary significance of this work lies in the emphasis on active preoperative surveillance for the ligamentum arteriosum using CCT. The authors claim that identifying the tethered appearance of the distal aortic arch toward the contralateral pulmonary artery is crucial for surgical planning.

The paper concludes that:

1. Preoperative CCT is essential for diagnosing complex aortic anomalies and identifying the specific site of vascular compression.
2. Radiologists must explicitly report suspicions of CAA and the presence of a ligamentum arteriosum to prevent incomplete surgical correction.
3. While aortic uncrossing is the definitive repair, aortopexy serves as a necessary alternative for high-risk patients to prevent the persistence of compression symptoms and the need for reoperation.

The authors acknowledge limitations, including the unavailability of operative images for the second case and source images for VR reconstruction, relying instead on reconstructed images for illustration.