Persistent Fifth Aortic Arch: A Rare Congenital Cardiovascular Anomaly and Its Clinical Implications

Abstract

Persistent Fifth Aortic Arch (PFAA) is a very rare congenital cardiovascular anomaly that is caused by the persistence of the fifth aortic arch during fetal development. PFAA was first reported by Van Praagh in 1969 and is still an underdiagnosed condition because it is a very rare condition with difficult detection. This anomaly is also commonly found with complex congenital heart diseases and hence, early and correct diagnosis is vital to achieve good management. Refinement of imaging technologies, such as echocardiography, CTA, and MRI, has facilitated improved detection of PFAA. As there are very few cases being reported, nevertheless, an incomplete picture is yet to be formulated about its embryogenesis, classification, and ideal management options. This review offers an extensive overview of the embryonic development, pathological classification, diagnostic strategy, and clinical management of PFAA. Through increased awareness and knowledge about this infrequent condition, we expect to be part of enhanced diagnosis, optimal treatment choice, and improved patient results.

Introduction

Congenital cardiovascular malformations occur in a large percentage of the population, some being well-described and others remaining extremely rare. Persistent Fifth Aortic Arch (PFAA) belongs to the latter group, with few case reports only since its initial description in 1969. The fifth aortic arch normally regresses in normal embryonic development, but persistence can result in several abnormal vascular connections that can cause important hemodynamic effects. Because of its rarity, PFAA is usually misdiagnosed or missed in clinical practice. The objective of this review is to describe the embryologic background, classification, imaging studies, and management options for PFAA with a clear outline of this infrequent anomaly.

Embryonic Development of the Aortic Arches

In embryogenesis, the morphogenesis of the aortic arches is complex yet highly organized. The aortic arch complex consists of six bilateral arches that develop from the aortic sac and play an important role in the formation of the great arteries. The first, second, and fifth arches generally degenerate, and the third, fourth, and sixth arches give rise to important structures like the carotid arteries, aortic arch, and pulmonary arteries.

The fifth aortic arch is typically regarded as an ephemeral structure that briefly appears in early embryonic life before it vanishes. In a few cases, its persistence causes PFAA, which presents in different forms of anatomy. Knowledge of the embryonic nature of this disorder is important in making a proper diagnosis and classification.

Pathological Classification of PFAA

PFAA is classified based on its anatomical configuration and association with other vascular structures. The most widely accepted classification includes:

1. Systemic-to-Systemic PFAA – Forms an additional connection between the aortic segments, contributing to altered blood flow patterns in the systemic circulation.

2. Systemic-to-Pulmonary PFAA – Acts as a vascular shunt between the systemic and pulmonary circulation, often found in association with congenital heart defects such as interrupted aortic arch or patent ductus arteriosus.

3. Double-Lumen Aortic Arch – The PFAA runs parallel to the normal fourth aortic arch, creating a double-lumen configuration.

4. PFAA with Aortic Coarctation – Characterized by a narrowing of the persistent arch, leading to obstruction and increased cardiovascular strain.

Due to the diverse presentations of PFAA, imaging and clinical correlation are essential for classification and appropriate management.

Imaging and Diagnostic Approaches

The diagnosis of PFAA requires a high index of suspicion, particularly in neonates and infants with unexplained cardiovascular abnormalities. Advanced imaging modalities play a crucial role in the identification and characterization of this anomaly:

1. Echocardiography:

   • Serves as the initial screening tool for congenital heart disease.

   • Color Doppler imaging may reveal abnormal vascular flow patterns suggestive of PFAA.

2. Computed Tomography Angiography (CTA):

   • Provides high-resolution, three-dimensional visualization of the aortic arch and associated anomalies.

   • Essential for preoperative planning and assessment of vascular anomalies.

3. Magnetic Resonance Imaging (MRI):

   • Offers detailed soft-tissue contrast without radiation exposure.

   • Useful for evaluating coexisting congenital cardiac abnormalities.

4. Cardiac Catheterization:

   • Performed in select cases for hemodynamic assessment and interventional planning.

   • Can confirm the presence of PFAA and determine its impact on circulation.

Accurate diagnosis relies on a combination of these imaging techniques, along with clinical correlation and genetic testing in cases with suspected syndromic associations.

Clinical Presentation and Associated Anomalies

The clinical manifestations of PFAA vary widely, depending on the specific anatomical variant and associated cardiovascular abnormalities. Some patients may remain asymptomatic, while others present with severe hemodynamic instability. Common presentations include:

• Cyanosis and respiratory distress in neonates

• Heart murmur detected during routine examination

• Upper limb hypertension due to coarctation-like lesions

• Congestive heart failure secondary to increased cardiac workload

• Differential cyanosis if PFAA functions as a shunt between systemic and pulmonary circulation

PFAA is frequently associated with other congenital heart defects, such as:

• Interrupted aortic arch

• Patent ductus arteriosus (PDA)

• Ventricular septal defects (VSD)

• Tetralogy of Fallot (TOF)

• Pulmonary artery anomalies

Recognizing these associations is crucial for comprehensive patient management.

Treatment Strategies and Clinical Management

Given the variability in anatomical presentation and severity, treatment for PFAA must be individualized. Management options include:

1. Surgical Intervention:

   • Indicated in cases with hemodynamic compromise or obstruction.

   • Procedures may involve excision of the persistent arch, aortic reconstruction, or repair of associated cardiac defects.

2. Catheter-Based Interventions:

   • Balloon angioplasty or stenting may be considered for cases with coarctation-like narrowing.

   • Less invasive approach compared to open-heart surgery, particularly for older children and adults.

3. Medical Management:

   • Supportive care, including diuretics and inotropic agents, for heart failure symptoms.

   • Antihypertensive therapy in cases of systemic hypertension due to vascular obstruction.

The choice of treatment depends on multiple factors, including age at diagnosis, severity of symptoms, and presence of concomitant anomalies. Early diagnosis and a multidisciplinary approach involving pediatric cardiologists, cardiothoracic surgeons, and radiologists are essential for optimal outcomes.

Future Directions and Research Perspectives

Despite advancements in imaging and surgical techniques, gaps remain in our understanding of PFAA. Future research should focus on:

• Genetic and molecular studies to identify underlying developmental mechanisms.

• Long-term outcomes of surgical and interventional treatments.

• Refinement of diagnostic imaging techniques for early and accurate detection.

• Exploration of novel therapies to minimize surgical morbidity.

Increasing awareness and documentation of PFAA cases through collaborative research efforts will contribute to improved patient care and management strategies.

Conclusion

Persistent Fifth Aortic Arch is an uncommon congenital abnormality that is highly diagnostic and management-intensive. Because of its rarity, it tends to be underdiagnosed or misdiagnosed, and as a result, treatment is delayed and complications can arise. Imaging technology improvements have improved diagnostic yields, allowing timely intervention. A knowledge of the embryologic basis, pathological classification, and clinical implication of PFAA is required to optimize outcomes in patients affected by it. With continuous research and developments in cardiovascular medicine, early detection and proper management of PFAA will further develop, eventually resulting in improved prognosis and quality of life for the patients.