Persistent Fifth Aortic Arch With Multisystem Congenital Anomalies: A Two-Case Report

Technical Summary: Persistent Fifth Aortic Arch With Multisystem Congenital Anomalies

Problem Statement
Persistent fifth aortic arch (PFAA) is a rare congenital vascular anomaly characterized by a double-lumen transverse aortic arch, resulting from the failure of an embryologic vascular channel to regress during fetal development. While PFAA is known to coexist with intracardiac defects, concurrent multisystem congenital anomalies are rarely reported in the literature. A significant clinical challenge lies in distinguishing the systemic-to-systemic variant of PFAA—which is often hemodynamically insignificant when unobstructed—from other arch abnormalities such as coarctation or interrupted aortic arch that necessitate surgical intervention. The true incidence remains unknown, and the anomaly may be underrecognized due to its resemblance to other arch variants.

Methodology
This study presents a two-case report involving male infants diagnosed with systemic-to-systemic PFAA. The methodology relied on a multimodal diagnostic approach:

• Clinical Evaluation: Assessment of presenting symptoms (e.g., cardiac murmurs) and associated congenital anomalies (craniosynostosis, microcephaly, genitourinary defects).
• Echocardiography: Transthoracic echocardiography was utilized to evaluate segmental cardiac anatomy, ventricular function, and intracardiac shunts (ventricular septal defects and atrial septal defects).
• Cross-Sectional Imaging: Computed tomography angiography (CTA) and Doppler interrogation were employed to confirm the aortic arch configuration, assess flow dynamics, and rule out obstruction or coarctation.
• Follow-up: Both patients underwent longitudinal cardiology follow-up to monitor the stability of the anomaly and the management of associated defects.

Key Results

• Case 1: A 5-week-old infant with sagittal craniosynostosis and a small ventricular septal defect (VSD). Imaging confirmed a systemic-to-systemic PFAA with a double-barreled aortic arch. Doppler analysis revealed laminar, unobstructed flow through both channels. The VSD was hemodynamically insignificant, and no cardiac intervention was required.
• Case 2: An infant with microcephaly, cerebellar vermis hypoplasia, posterior corpus callosum hypoplasia, right hydronephrosis, and cryptorchidism. This patient presented with a fenestrated atrial septal defect (ASD) causing a moderate left-to-right shunt. Imaging confirmed a widely patent systemic-to-systemic PFAA without obstruction. The ASD required surgical closure, but the PFAA itself did not.
• General Findings: In both cases, the PFAA was identified as an incidental finding during the evaluation of other congenital abnormalities. The anomaly was non-obstructive, and neither patient required intervention specifically for the PFAA.

Key Contributions
This report contributes to the limited literature on PFAA by documenting two instances of systemic-to-systemic PFAA occurring in the context of complex multisystem congenital anomalies. Specifically, the paper:

1. Describes the co-occurrence of PFAA with extracardiac anomalies, including craniosynostosis and structural central nervous system and genitourinary defects.
2. Reinforces the diagnostic utility of combining echocardiography with cross-sectional imaging (CTA) to accurately characterize the "double-barreled" anatomy and differentiate it from obstructive arch lesions.
3. Provides clinical evidence that systemic-to-systemic PFAA can remain hemodynamically insignificant and asymptomatic, even in the presence of other significant congenital defects.

Significance and Claims
The authors claim that these cases underscore the necessity of thorough evaluation in infants presenting with multisystem congenital anomalies. The primary significance lies in the accurate diagnosis and anatomic characterization of PFAA, which allows clinicians to distinguish this benign variant from conditions requiring surgical repair. The paper asserts that while PFAA is rare and often associated with intracardiac defects, its presentation in the setting of multisystem anomalies warrants comprehensive imaging to avoid misclassification. The report concludes that careful imaging supports accurate diagnosis and appropriate longitudinal follow-up, noting that in these specific instances, the anomaly did not require intervention.