Increased Pulmonary-Aortic Interspace in Fetal Right Aortic Arch: A Matched Case-Control Study

Area of Science:

• Medical Imaging
• Fetal Cardiology
• Prenatal Diagnosis

Background:

• Prenatal detection of right aortic arch (RAA) has improved with the three-vessel view (3VV) in second-trimester anomaly scans.
• The 3VV comprises the pulmonary artery (PA), aorta (Ao), and superior vena cava (SVC).

Purpose of the Study:

• To evaluate the diagnostic value of measuring the distance between the PA and Ao within the 3VV for detecting fetal RAA.
• To assess the utility of the PAAo/AoSVC ratio in diagnosing isolated RAA.

Main Methods:

• A case-control study included 54 fetuses with isolated RAA and 162 matched controls.
• Measurements of PA-Ao and Ao-SVC distances were performed on 3VV images.
• The pulmonary-aortic interspace (PAAo) and the PAAo/AoSVC ratio were calculated.

Main Results:

• The mean PAAo distance was significantly larger in RAA cases (3.1 mm) than controls (1.8 mm) (p < 0.001).
• The mean PAAo/AoSVC ratio was significantly higher in RAA cases (2.9) compared to controls (1.4) (p < 0.001).
• A PAAo/AoSVC ratio cutoff of 1.9 demonstrated over 87% sensitivity and specificity for RAA diagnosis.

Conclusions:

• The pulmonary-aortic interspace and PAAo/AoSVC ratio are significantly increased in fetuses with RAA.
• An elevated PAAo/AoSVC ratio (≥1.9) is a valuable indicator for diagnosing RAA when increased pulmonary-aortic interspace is observed.