4.5h Interrupted Aortic Arch (q25.21, Preferred; Also Q25.2, Q25.4)

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Interrupted aortic arch (IAA) is a structural heart defect characterized anatomically by a discontinuity (interruption) along the aortic arch. Depending on the site of discontinuity, IAA is classified into three types (see Fig. 4.21). Type B is the most common (50–70%), type A is less common (30–45%) and type C is rare.

Fig. 4.21. Interrupted aortic arch

Type A: The discontinuity is distal to the left subclavian artery (approximately in the same region as coarctation of the aorta).
Type B (the most common form): The discontinuity is more proximal, between the left carotid and subclavian.
Type C: The discontinuity is more proximal still, between the brachiocephalic artery and the common carotid artery

Relevant ICD-10 codes

Q25.21 Interruption of aortic arch (preferred)
Q25.2 Atresia of aorta
Q25.4 Other congenital malformations of aorta (heterogeneous; might include interrupted aortic arch)

Diagnosis

Prenatal. IAA is easily missed on the obstetric anomaly scan, though it might be suspected based on discrepancy between the left and right ventricular sizes. Prenatally diagnosed cases should be confirmed postnatally.

Postnatal. Infants can present clinically in the early neonatal period, when the ductus closes, with signs and symptoms of congestive heart failure and systemic hypoperfusion (cardiogenic shock). Newborn screening via pulse oximetry can lead to earlier diagnosis.

Clinical and epidemiologic notes

As noted, an early presentation is heart failure and cardiogenic shock, with rapid clinical deterioration as the ductus closes. Because of right-to-left shunting at the ductus arteriosus, infants might initially show differential oxygen saturation or cyanosis. In type A, the difference in saturation is between the upper and lower limbs, with the lower limbs having lower saturation; in type B, there is a difference in saturation between the left and right arms, with the left arm having lower saturation.

Ventricular septal defect and other intracardiac defects are often present.

The three types of IAA differ in their association with genetic risk factors. For example, deletion 22q11 occurs in 50% or more of cases of type B IAA, and is rare in the other types. Other syndromes that can occur with IAA include CHARGE syndrome (Q30.01).

Environmental risk factors include use of the medication isotretinoin (specifically for type B IAA) and maternal pregestational diabetes.

Birth prevalence of IAA, all types, is approximately 1 in 15 000 births (approximately 0.7 per 10 000 births).

Inclusions

Q25.21 Interruption of aortic arch

Exclusions

Q25.43 Congenital aneurysm of aorta
Q25.44 Congenital dilation of aorta
Q25.45 Double aortic arch
Q25.46 Tortuous aortic arch
Q25.47 Right aortic arch
Q25.48 Anomalous origin of subclavian artery

Checklist for high-quality reporting

Checklist for high-quality reporting
Interrupted Aortic Arch (IAA) – Documentation Checklist
Describe in detail the clinical and echocardiographic findings: Anatomy – specify site of discontinuity, type of IAA as noted in echocardiographic report, and intracardiac anomalies, including the presence of ventricular septal defects. Procedure – specify whether the cardiac findings are from a prenatal or postnatal echocardiogram, or from other investigations (e.g. catheterization, MRI), surgery or autopsy. Look for and document extracardiac birth defects: IAA can occur with genetic syndromes such as deletion 22q11, which is associated with many external and internal anomalies. Report whether specialty consultation(s) was done: Report whether the diagnosis was made by a paediatric cardiologist, and whether the patient was seen by a geneticist. Reportanygenetictestingandresults(e.g. chromosomalstudies, genomicmicroarray, genomicsequencing).

Suggested data quality indicators

Suggested data quality indicators
Category	Suggested Practices and Quality Indicators
Description and documentation	Review sample of clinical descriptions for documentation of key elements: Anatomy: Note site of interruption and type (A, B or C), presence of ventricular septal defect, and other aortic or intracardiac anomalies. How cardiac findings were detected (e.g. echocardiography). Who made the diagnosis (e.g. paediatrician, paediatric cardiologist). Specialists who evaluated the child, in particular, a paediatric cardiologist or geneticist. Key evaluations done, especially genetic testing.
Coding	Code as Q25.21; track and minimize codes Q25.1 (atresia of the aorta) and Q25.4 (other congenital anomalies of the aorta) so that cases of IAA are not dispersed across different codes.
Clinical classification	Track proportion of congenital anomalies and syndromes occurring with IAA: If considerably < 50% for type B, or < 25% overall, consider under-ascertainment of co-occurring conditions, especially deletion 22q11.
Prevalence	Monitor prevalence: If low (< 0.3 per 10 000 births) it suggests under-ascertainment. Compare prevalence among the smallest site/time units: Statistically significant dissimilar results suggest a possible methodological problem in one or more site/time units.