Interrupted Aortic Arch 

Updated: Mar 29, 2016
Author: Alvin J Chin, MD; Chief Editor: Syamasundar Rao Patnana, MD 

Overview

Background

Interrupted aortic arch (IAA) is a relatively rare genetic disorder that usually occurs in association with a nonrestrictive ventricular septal defect (VSD) and ductus arteriosus or, less commonly, with a large aortopulmonary window or truncus arteriosus.[1]  Although most cases occur in normally connected great arteries, interrupted aortic arch can coexist with any ventriculoarterial alignment and also with severe underdevelopment of one ventricle. The rare cases that involved interrupted aortic arch, aortic valve atresia, and VSD have been complex; two have presented with circle of Willis–dependent coronary blood flow,[2, 3] and two have presented with bilateral ductus in which coronary blood flow depended on the patency of the right ductus arteriosus.[4, 5]  

Interrupted aortic arch and complete common atrioventricular canal can be observed in the context of coloboma, heart disease, atresia choanae, retarded growth and development and/or CNS anomalies, genital hypoplasia, and ear anomalies and/or deafness (CHARGE) syndrome, which is usually caused by mutations in CHD7 on chromosome 8q12.1.[6, 7] Approximately 50% of patients with interrupted aortic arch have DiGeorge syndrome; in these cases, the interrupted aortic arch is usually type B, although cases of type A or type C have also been reported. There is considerable phenotypic overlap between CHARGE and DiGeorge syndromes.[8]

Surgical reconstruction of the arch is now relatively straightforward; hence, attention is increasingly focused on the preoperative identification and surgical management of the aortic valve and subaortic stenosis found in approximately one half of cases.[9] Interrupted aortic arch is the first cardiovascular pattern formation anomaly to be demonstrated to have a genetic basis in both mouse and human.

Embryology

Approximately one half of patients with interrupted aortic arch have a hemizygous deletion of a 1.5-3 Mb region of chromosome band 22q11.2,[10, 11] the most common deletion syndrome in humans. Among the 35-50 genes deleted, the T-box gene TBX1 appears to be responsible for most aspects of the DiGeorge phenotype.

In addition, 2 independent lines of evidence suggest that the etiology of many cases of interrupted aortic arch type A is different from the etiology of interrupted aortic arch type B (see below for definition of types). The variety of associated VSDs is different in the 2 types of interrupted aortic arch.[12] The prevalence of 22q11.2 hemizygosity is also different; approximately three fourths of patients with interrupted aortic arch type B have the deletion, whereas exceedingly few patients with interrupted aortic arch type A have the deletion.

Anatomy

Interrupted aortic arch has been classified into 3 types (A, B, and C) based on the site of aortic interruption. In type A interrupted left aortic arch, the arch interruption occurs distal to the origin of the left subclavian artery. In type B interrupted left aortic arch, the interruption occurs distal to the origin of the left common carotid artery. In type C interrupted left aortic arch, the interruption occurs proximal to the origin of the left common carotid artery.

In any of the 3 types, the right subclavian artery may arise normally or abnormally; the 2 most common abnormal sites are distal to the left subclavian artery (aberrant right subclavian artery) and from a right ductus arteriosus (isolated right subclavian artery).[13] Type B interruptions account for about two thirds of cases, type A occur in about one third of cases, and type C are present in less than 1% of cases.

Suprasternal echocardiographic identification of i Suprasternal echocardiographic identification of interrupted aortic arch Type B. Upper left: Frontal (coronal) view showing the takeoffs of the innominate artery (InnA) and left common carotid artery (LCCA). No connection is seen with the distal aorta. Upper right: Slightly more dorsal (posterior) frontal view showing the main pulmonary artery (MPA), large left-sided patent ductus arteriosus (PDA), and left-sided upper descending aorta (DescAo). The ascending aorta (AscAo) is not in discernible continuity with the descending aorta. Lower left: Left oblique view showing the LCCA takeoff and no discernible aortic arch. Lower right: sagittal view showing the origin of the left subclavian artery (LSCA) from the DescAo. Other Abbreviations: InnV= innominate vein; l=left; LPA=left pulmonary artery; p,l = posterior and leftward; s=superior; SVC=superior vena cava.
Section A depicts a subcostal frontal echocardiogr Section A depicts a subcostal frontal echocardiogram of interrupted aortic arch (IAA) type B with transposition of the great arteries. Section B shows a high parasternal echocardiogram showing that the innominate artery (Inn A) and left common carotid artery (LCCA) arise from the ascending aorta (a ao). In section C, the left subclavian artery (LSCA) arises from the descending aorta (desc ao), which is perfused by the ductus arteriosus.
This is the suprasternal sagittal ultrasonographic This is the suprasternal sagittal ultrasonographic view of the patient shown in Media file 2. Arch continuity has now been restored by a side-to-side anastomosis. Abbreviations are as follows: a ao = ascending aorta and desc ao = descending aorta.

Pathophysiology

During fetal development, left ventricular output supplies the arterial circulation proximal to the interruption whereas right ventricular output supplies arterial circulation distal to the interruption via the left ductus arteriosus. Postnatally, this arrangement continues, with the addition of the pulmonary blood flow to the load of the left ventricle. With naturally occurring ductal closure and/or fall in pulmonary vascular resistance after birth, the circulation to the lower part of the body is compromised, resulting in a shocklike state. 

Etiology

Abnormalities in any of the cell types involved in formation or patterning the pharyngeal arch arteries (ie, pharyngeal endoderm,[14]  pharyngeal mesoderm, endothelium, neural crest) can produce interrupted aortic arch. For example, Tbx1 has a cell-autonomous function in the pharyngeal mesoderm.[15]

More than 25 single-gene mouse knockouts display interrupted aortic arch as a principal phenotype. Mouse mutants displaying interrupted aortic arch are as follows:

  • Foxc1 [16, 17]

  • Foxc2

  • Tbx1 [18, 19, 20]

  • Fgf8 hypomorph

  • Sema3C [21, 22]

  • Nrp1

  • VEGF-A ( knockout of 164 isoform)

  • Cited 2

  • Crkl

  • ET-1 [23]

  • ETA

  • ECE-1

  • FLNA

  • Zic3

  • Dnahc5

  • MRTF-B

  • Sox4

  • AP2α

  • Hoxa1 [24]

  • Gbx2

  • Ltbp1L

  • TGFβ2

  • TGFβRII

  • Bmp4

  • RXR

  • RAR

Although most of these mouse mutants display interrupted aortic arch type B, at least 2 (Ltbp1L [25]  and the myocardin-related transcriptional coactivator Mrtf-B [26]  ) can also display interrupted aortic arch type C.

Additional double knockouts or tissue-specific single-gene knockouts with interrupted aortic arch include Chd7; Tbx1 compound heterozygotes,[27] Six1; Eya1 double nulls,[28]  second heart field-specific dominant-negative mastermind-like,[29]  neural crest-specific Dicer knockout,[30, 31]  neural crest – specific knockout of GATA6, [32]  neural crest – specific knockout of Hdac3, [33] Tbx1 domain-specific knockout of Bmp4,[34]  vascular smooth muscle – specific removal of integrin β 1,[35] α5; αv double null,[36]  and Fgf8 hypomorph; Fgf10 heterozygotes.[37]

Approximately 90% of patients with DiGeorge syndrome have deletions within 22q11, which includes TBX1. Rarely, individuals with DiGeorge syndrome have point mutations in TBX1. [38]  Patients with DiGeorge syndrome usually have interrupted aortic arch type B, but examples of type A and type C have been reported. Hemizygous deletion of chromosome 1q21.1[39]  can be associated with interrupted aortic arch type A.

Epidemiology

United States data

The incidence is approximately 2 cases per 100,000 live births.

Nearly all patients with interrupted aortic arch present in the first 2 weeks of life when the ductus arteriosus closes. Most patients present in the first day of life. Although the vast majority of the IAA cases present in neonates, presentation in childhood, early adulthood, and even in the elderly has been reported.[40, 41, 42, 43, 44, 45, 46] This may be related to persistence of the ductus arteriosus, alternative collateral circulation, and/or a balanced circulation. 

Prognosis

In most cases of interrupted aortic arch (IAA), with good surgical repair, the prognosis is excellent.

Mortality/Morbidity

Circulatory compromise manifested by metabolic acidosis begins when the ductus arteriosus constricts, thus decreasing flow to the circulation distal to the arch interruption. Prior to this, even severe aortic and subaortic hypoplasia is physiologically masked because of the presence of the VSD. Patients are at risk for severe low output syndrome (ie, cardiogenic shock) because of both the effect of profound metabolic acidosis on cardiac performance and the reduced distal systemic arterial circulation imposed by falling pulmonary vascular resistance.

Complications

Complications in patients with IAA:

  • Persistent subaortic and aortic stenosis[47]

  • Residual ventricular septal defect

  • Narrowing at the site of arch surgery

 

Presentation

History and Physical Examination

Symptoms of interrupted aortic arch (IAA) in the neonate include tachypnea, poor feeding, and lethargy.

Recognizing interrupted aortic arch is difficult prior to reduction in the caliber of the ductus arteriosus. The hallmark thereafter is a mottled or grey appearance to the lower body, representing poor perfusion to that portion of the circulation located distal to the arch interruption. Also consider the following physical examination findings:

  • A difference in systolic blood pressure between the right arm and the lower extremities may or may not be present. Frequently, a lack of discrepancy in blood pressure is due to the profound reduction in cardiac performance. If the right subclavian artery is aberrant, no disparity occurs between the systolic blood pressure in the right arm and that in the lower extremities because the right subclavian origin is distal to the arch interruption.

  • Although a difference in oxygen saturation between the right arm and the lower body may occur in cases without an aberrant right subclavian artery, this can be quite subtle in cases of high pulmonary blood flow. In normally connected great arteries, the oxygen saturation is higher in the right arm than in the lower body. In interrupted aortic arch with transposition of the great arteries, the reverse occurs.

Although all of the above signs may represent interrupted aortic arch, aortic thrombosis may also present with such findings.[48]

In addition, note the following:

  • The first heart sound is normal; the second heart sound is usually single.

  • A grade 2 or grade 3 systolic ejection murmur is usually present at the base, representing increased pulmonary blood flow. The mid diastolic rumble of flow-related mitral stenosis is uncommonly heard in neonates.

  • A holosystolic murmur of ventricular septal defect (VSD) may be heard in infants beyond the first few days of life, following a fall in pulmonary vascular resistance.

  • The liver is usually normal in size, but in neonates, this is principally a reflection of intravascular volume status.

  • Facial dysmorphism is frequently present because approximately 50% of patients with interrupted aortic arch have DiGeorge syndrome.

 

DDx

 

Workup

Laboratory Studies

The most helpful blood test in interrupted aortic arch (IAA) is the arterial blood gas (ABG) study to confirm the presence of metabolic acidosis.

A serum calcium measurement is occasionally informative because many patients with interrupted aortic arch have DiGeorge syndrome, including the hypoparathyroidism phenotype.

Fluorescent in situ hybridization (FISH) can reveal the typical 22q11.2 deletion[49] seen in 85-90% of patients with DiGeorge syndrome.

Imaging Studies

Two-dimensional echocardiography and Doppler analysis

Two-dimensional echocardiography is diagnostic for interrupted aortic arch (IAA). In addition, it can usually provide at least indirect evidence for the presence or absence of aberrant right subclavian artery. Occasionally, the presence of an isolated right subclavian artery can be detected. A suprasternal frontal sweep followed by left oblique and sagittal cuts is recommended.

Color-flow Doppler analysis may assist in the ultrasonographic tracing of such vessels by rapidly distinguishing them from venous structures. Furthermore, in the patient whose ductus arteriosus has markedly reduced in size, 2-dimensional and Doppler analysis can be used to monitor the effect of exogenous prostaglandin E1 on this structure.

The size and anatomic type of the ventricular septal defect (VSD) can also be identified. In the setting of a large VSD, additional small VSDs can be missed, just as with cardiac catheterization. The most important contribution of 2-dimensional echocardiography to the preoperative characterization of patients with interrupted aortic arch is the display of the aortic outflow region. The presence of thymus can be ascertained as well.

Echocardiography also demonstrates the site of arch interruption, the size and anatomic type of the ventricular septal defect, the morphology of the aortic valve, and the anatomic severity of subaortic hypoplasia.[50] Aortic valve and subaortic abnormalities are present in 50-80% of patients with interrupted aortic arch.

Chest radiography

Chest radiography findings vary. The cardiothymic silhouette may be normal or enlarged Patients with DiGeorge syndrome may have an absent thymus.

Pulmonary vascularity may be normal or increased.

Electrocardiography

Common electrocardiography (ECG) findings include right ventricular hypertrophy and ST-T wave abnormalities. Occasionally, QT prolongation is evident because of DiGeorge syndrome–related hypocalcemia.

Procedures

Cardiac catheterization

Cardiac catheterization reveals the site of arch interruption, the size and anatomic type of ventricular septal defect, and the anatomic severity of subaortic hypoplasia. Cardiac catheterization also reveals whether the right subclavian artery is aberrant.

 

Treatment

Medical Care

Evaluation of interrupted aortic arch (IAA) as an inpatient in an intensive care setting for diagnostic testing and surgical intervention is advised.

Intravenous prostaglandin E1 (alprostadil) (0.1 mcg/kg/min) is indicated promptly preoperatively to maintain patency of the ductus arteriosus. (No special medications are required postoperatively.)

The need for an arterial line and assisted ventilation can be judged best from the initial arterial blood gas (ABG) measurement.

Consultations

Consultations with the following specialists are importantant in the evaluation and management of patients with interrupted aortic arch:

  • Cardiothoracic surgeon

  • Cardiologist

  • Geneticist

Transfer

Transfer may be required for further diagnostic evaluation and surgical intervention.

Diet and activity

No special diet is required.

No exercise restrictions are necessary in later childhood if coexistent subaortic (and/or aortic) hypoplasia has been sufficiently relieved in earlier childhood.

 

Surgical Care

The arch interruption itself is usually treated with side-to-side anastomosis, rather than with conduit interposition. If the subaortic region is of good size, the ventricular septal defect is usually closed with a patch at the same occasion.

Whereas the aortic arch interruption is usually treated with side-to-side or end-to-end anastomosis, some surgeons have used the subclavian artery to create an arch-shaped aorta and reported good results.[51] Such options should be explored in future studies.

When a malalignment-type ventricular septal defect is present, the infundibular septum is not only misplaced but is also frequently hypoplastic. Hence, significant subaortic narrowing is frequently difficult to ameliorate with mere resection of infundibular septal muscle.

Two alternative approaches have been adopted: the Ross-Konno procedure and the Norwood-Rastelli procedure. Note the following:

  • In the Ross-Konno procedure, the aortic outflow region is directly enlarged (Konno) and the aortic valve is replaced with a pulmonary valve autograft (Ross).[52] The coronary arterial ostia must be relocated to the autograft, and some sort of right ventricle–to–main pulmonary artery conduit is interposed (Ross). One relative contraindication to the Ross-Konno procedure is an unfavorable coronary artery pattern because this may well limit the efficacy of the Konno procedure.

  • In the Norwood-Rastelli procedure, an interventricular baffle allows left ventricular blood to reach not only the aortic outflow but also the pulmonary annulus (Rastelli), and the main pulmonary artery is transected.[53] The proximal portion is anastomosed to the ascending aorta (Norwood) while the distal portion is connected to the right ventricle via a conduit (Rastelli).

One study reported the successful use of a regional cerebral perfusion technique to correct interrupted aortic arch.[54]

Following surgical reconstruction, echocardiographic and Doppler evaluation of the adequacy of the repair should be performed.

Diet

See the list below:

  • No special diet is required.

Activity

See the list below:

  • No exercise restrictions are necessary in later childhood if coexistent subaortic (and/or aortic) hypoplasia has been sufficiently relieved in earlier childhood.

 

Medication

Prostaglandins

Class Summary

Alprostadil (PGE1) is used for treatment of ductal dependent cyanotic congenital heart disease, which is due to decreased pulmonary blood flow.

Alprostadil IV (Prostin VR)

Used to maintain patency of the ductus arteriosus in neonates with ductal-dependent congenital heart disease until surgery can be performed. Has direct vasodilatation action on the ductus arteriosus and vascular smooth muscle.