What is a type B interrupted aortic arch?

Type B Interrupted Aortic Arch: Definition and Clinical Significance

Type B interrupted aortic arch is a rare congenital cardiac malformation characterized by complete loss of luminal continuity between the left common carotid artery and the left subclavian artery, representing the most common form of interrupted aortic arch (approximately 67% of cases). 1

Anatomical Classification

Type B interrupted aortic arch is defined by the specific location of the interruption:

• The interruption occurs between the left common carotid artery and the left subclavian artery 2, 1
• The ascending aorta terminates at the left carotid artery, with no anatomical connection to the descending aorta 3
• The descending aorta receives blood flow through a patent ductus arteriosus, which connects smoothly to the descending portion 3
• The left subclavian artery typically arises distal to the ductus arteriosus 3

This contrasts with Type A (interruption distal to the left subclavian artery, 30% of cases) and Type C (interruption between the innominate and left common carotid arteries, 3% of cases). 1

Epidemiology and Associated Conditions

All infants with type B interrupted aortic arch should be tested for 22q11.2 deletion syndrome (DiGeorge syndrome) regardless of the presence of extracardiac features, as this association is extremely strong. 2, 4

Key epidemiologic features include:

• Interrupted aortic arch represents approximately 1% of all congenital heart disease 1
• Occurs in approximately 3 per million live births 5
• More than 97% of cases have associated cardiac anomalies 1
• In one surgical series, 78% (21 of 27) of patients with type B interrupted aortic arch had DiGeorge syndrome 6

Associated Cardiac Malformations

The vast majority of patients have additional intracardiac defects:

• Ventricular septal defect is commonly present 6
• Subaortic stenosis caused by posterior displacement of the infundibular septum occurs frequently 3
• Tetralogy of Fallot with associated anomalies occurs in 10-15% of cases 4
• Other associations include double outlet right ventricle and truncus arteriosus 3

Clinical Presentation and Prognosis

Without treatment, the median age at death is 10 days, making this a neonatal surgical emergency. 1

Critical clinical features:

• The condition becomes life-threatening when the ductus arteriosus begins to close 1
• Peripheral pulse inequality may be the only characteristic finding on physical examination, though it can be absent or transient 3
• The ascending aorta appears small compared to the pulmonary trunk on imaging 3

Genetic Counseling Implications

Affected individuals with 22q11.2 deletion syndrome have a 50% chance of having a child with the same deletion in each pregnancy. 4

This autosomal dominant inheritance pattern necessitates:

• Genetic counseling for families 4
• Family planning discussions 4
• Consideration of prenatal testing in future pregnancies 4

Diagnostic Approach

Cross-sectional echocardiography from the suprasternal approach provides the only accurate method of non-invasive diagnosis. 3

Echocardiographic findings include:

• The ascending aorta terminates in the left carotid artery 3
• The ductus arteriosus continues smoothly into the descending aorta 3
• No vestige of an aortic arch connects the ascending and descending portions 3
• Cardiovascular magnetic resonance imaging may be used for follow-up assessment 4