Address correspondence to Thomas C. Wheeler, MD Dept. of Ob-Gyn, Vanderbilt University, 21st & Garland Ave, Nashville, TN 37232-2516 Ph: 615-322-2114 Fax: 615-343-0595 and

Dept. of Radiology.

Synonyms: None.

Definition: Interruption of the aortic arch between the ascending to descending aorta.

Classification: The classification is based on the position of the interruption relative to the brachiocephalic vessels³ (fig. 4) A: distal to the left subclavian artery; B; distal to the left common carotid artery; C: distal to the brachiocephalic artery. Each type may be subclassified to indicate association with other cardiac anomalies.

Prevalence: 1:10,000 births,1.3% of children with known heart disease resulting in death, cardiac catheterization, or surgery in the first year of life². Type A: 42%, type B: 53%, type C: 4%⁴. M1:F1

Associated anomalies: DiGeorge syndrome (in Type B: 10-50%⁶), associated abnormalities of the aortic arch (aberrant or isolated left or right subclavian arteries), intracardiac anomalies (96%^8,9) including VSD, patent ductus arteriosus, left ventricular outflow obstruction (subaortic stenosis or bicuspid aortic valve), truncus arteriosus, CHARGE syndrome (see text).

Etiology: Usually multifactorial but may be associated with aneuploidies and teratogenic exposure (Bis-dichloroacetyl diamene, isotretinoin).

Pathogenesis: Several mechanisms have been suggested: 1) abnormal involution of the third and fourth aortic arches⁶, 2) decreased antegrade bloodflow in the ascending aorta due to the almost constant presence of ventricular septal defects and left ventricular outflow obstructions¹¹.

Pathology: At autopsy the great vessels are usually related in a normal fashon. The pulmonary trunk is larger than the ascending aorta, which is often hypoplastic. The right ventricle is hypertrophied and somewhat dilated, due to the commonly associated VSD. The parietal band of the crista supraventricularis is often absent. The aortic valve is bicuspid in nearly half of the autopsied specimens⁵. Multiple other cardiac anomalies are usually present.

Prognosis: Death usually occurs in the early neonatal period, but survival into childhood has occurred and the lesion has been successfully corrected surgically.

Diagnosis: In longitudinal view, the ascending aorta follows a straight course to its branches without the normal continuous curvature to the descending aorta.

Differential diagnosis: Aortic atresia with hypoplasia of the ascending aorta, aortic coarctation with tubular hypoplasia of the aorta.

Obstetric management: Careful scanning for associated anomalies and chromosomal studies are recommended. The option of pregnancy termination should be offered prior to fetal viability, especially in the presence of hydrops. In the absence of associated anomalies or congestive heart failure, there is no indication to alter standard obstetric management. Delivery should be performed in a tertiary care center with immediate access to a pediatric cardiology service.

MESH Aorta, Thoracic BDE 0076 MIM 107550 (when associated with facial palsy and retinal coloboma) ICD9 747.11 CDC 747.215

Introduction

Nonimmune hydrops has been associated with abnormalities of many organ systems including congenital heart disease and cardiac arrhythmias. The underlying pathophysiologic mechanism is related to increased volume and pressure overload of the fetal right atrium, leading to venous hypertension and systemic edema. Mortality rates for nonimmune hydrops vary from 50 to 95%¹.We report a case of nonimmune hydrops associated with aortic arch interruption in a 23 week fetus with trisomy 21. The diagnosis was confirmed after therapeutic abortion.

Case report

A 42-year-old G₅P₄ patient, whose pregnancy was uncomplicated until the 21^st week of gestation when a discrepancy between size and dates was noted, was referred for a level II scan. The examination demonstrated significant polyhydramnios. The biometry was consistent with 23 weeks, and an edematous fetus with pleural effusions was found. A complex cardiac anomaly was noted (fig. 1).

  Figure 1: Top (left & right): Axial views of the base of the heart. The relationship between the superior vena cava (SVC), the ascending aorta (asc Ao) and the ductus is seen. Notice the larger size of the ductus compared to the aorta. Middle left: This section, just cephalad to the two previous, demonstrates the common carotids and the SVC. Middle right: Longitudinal section. The SVC is seen entering the right atrium (RA). The ascending aorta is between the SVC and the ductus. It does not connect with the ductus, and bifurcates into the common carotids. Bottom left: Similar view to the previous one. The conection between the ductus and the right ventricle (RV) is demonstrated. The ascending aorta lacks its normal curve towards the back and the left of the fetus. Bottom right: Thickened neck tissue with small cystic hygroma. Note the posterior nuchal ligament in the cyst.

The heart had four chambers, with its apex on the left. Large ventricular and atrial septal defects were present. The systemic venous circulation could be traced to the right atrium, entering the right ventricle, then following through the ductus arteriosus into the descending aorta. On the left side, one vessel could be traced cephalad from the ascending aorta from which both common carotid arteries originated. There was no communication between the ascending and descending aorta.

A diagnosis of interrupted aortic arch type B was made and termination of the pregnancy was offered due to the poor prognosis associated with a hydropic fetus at 23 weeks gestation.

A 1050g female fetus with massive subcutaneous edema was delivered by prostin induction. The autopsy revealed an atretic segment of aorta between the left common carotid artery and the descending aorta (fig. 2). A dilated ductus arteriosus (fig. 3), a high membranous VSD, and a septum secundum ASD were confirmed. The lungs were hypoplastic with associated pleural effusions.

 

  Figure 2: Heart in situ. The arrows points to the absent aortic knob.

  Figure 3: Exposed ductus. The two vascular orifices (blue arrows) represent the two pulmonary arteries. The vessel at the end of the ductus (yellow arrow) is the left brachiocephalic artery. Note the absence of connection of the ascending aorta to the ductus.

Histological evaluation demonstrated a normal thymus, parathyroid glands, and no facial features characteristic of DiGeorge syndrome. The karyotype was 47XX+21.

Discussion

Definition

An aortic arch is interrupted when the artery does not allow a continuity of flow from ascending to descending aorta. Loss of continuity is usually complete; however, there may be a segment of tissue interposed between proximal and distal aspects⁵. The ductus arteriosus provides the only direct communication between the heart and the lower half of the body.

Classification

The classification of arch interruptions is based on the position of the interruption relative to the brachiocephalic vessels. It consists of three major types³ (fig. 4):

• • A: distal to the left subclavian artery.
  • B: distal to the left common carotid artery.
  • C: distal to the brachiocephalic artery.

 

Each type may be subclassified to indicate association with other cardiac anomalies. In Van Praagh"s review of 165 cases, the distribution of cases was 42% type A, 53% type B, and 4% type C⁴.

Figure 4: Classification of interrupted aortic arches. A: interruption distal to the left subclavian artery; B: interruption distal to the left common carotid artery; C: interruption distal to the brachiocephalic artery.

Prevalence

Aortic interruption occurs in 1:10,000 births, and represents 1.3% of children with known heart disease resulting in death, cardiac catheterization, or surgery in the first year of life².

Associated anomalies

DiGeorge syndrome. The III-IV pharyngeal pouch syndrome is notable for hypoparathyroidism and cellular immune deficiency. Series range from 10-50% of associated cases of DiGeorge syndrome with autopsied cases of Type B interrupted aortic arch⁶ .

Associated abnormalities of the aortic arch. Aberrant or isolated left or right subclavian arteries are common.

Intracardiac anomalies are almost always present. In two review series, only 10 out of 260 patients had an isolated interruption of the aortic arch, and all ten were asymptomatic during infancy^8,9. Most cases have some form of a VSD; a patent ductus arteriosus is nearly universal and necessary for survival; a left ventricular outflow obstruction may take the form of a muscular subaortic stenosis or a bicuspid aortic valve; and a persistent truncus arteriosus may coexist.

CHARGE syndrome is a disruption of the neural crest migration with consequent effect on tissues arising from the third and fourth branchial arches⁹. It includes coloboma, heart disease, choanal atresia, retardation of postnatal growth, genital hypoplasia and ear abnormalities.

Pathogenesis

Four mechanisms have been found to be responsible for aortic arch interruptions. An abnormal involution of the third and fourth aortic arches has been suggested due to the known contribution to the fetal aortic arch and its branches⁶.

Interrupted aortic arch may be secondary to a decreased antegrade bloodflow in the ascending aorta due to the almost constant presence of ventricular septal defects and left ventricular outflow obstructions¹¹.

Infants with trisomy 18 share many common features with those afflicted with interrupted aortic arch. This disorder has also been reported in association with partial trisomy 8q and monosomy 22¹².

Toxins have also been implied: Bis-dichloroacetyl diamene, a drug previously studied as an abortifacient, consistently induces abnormalities of the snout, thymus, and the aortic arch in lab animals, and has been used as a model to study DiGeorge syndrome¹³. Isotretinoin consistently causes facial, palate, and aortic arch defects in lab animals.

Pathology

At autopsy, the great vessels are usually related in a normal fashion. The pulmonary trunk is larger than the ascending aorta, which is often hypoplastic. The right ventricle is hypertrophied and somewhat dilated due to the commonly associated VSD. The parietal band of the crista supraventricularis is often absent. The aortic valve is bicuspid in nearly half of the autopsies⁵. Multiple other cardiac anomalies are usually present.

Prognosis

Death usually occurs in the early neonatal period, but survival into childhood has been described, and the lesion has been successfully corrected surgically.

Diagnosis

In longitudinal view, the ascending aorta follows a straight course to its branches without the normal continuous curvature to the descending aorta. The V sign is associated with the B type interruption¹⁵. The W sign is associated with an image created by the three brachiocephalic vessels of a type A interruption¹⁶. The pseudo-arch formed by the main pulmonary artery, ductus arteriosus, and descending aorta should be differentiated from the true aortic arch by its lack of brachiocephalic vessels.

Differential diagnosis

The differential diagnosis includes: aortic atresia with hypoplasia of the ascending aorta and aortic coarctation with tubular hypoplasia of the aorta.

The hypoplastic ascending aorta in aortic atresia can almost always be imaged. Diagnosis of interrupted aortic arch is characterized by conoventricular septal defect as well as a leftward deviation of the crista supraventricularis¹⁷. If a diagnosis of interrupted aortic arch is suspected in the presence of an intact ventricular septum, diagnoses such as proximal or distal aorticopulmonary window or anomalous origin of a pulmonary artery from the ascending aorta should be considered¹⁵.

Hemodynamic considerations

The blood flow through the aortic isthmus represents only 10% of the total fetal cardiac output, so it is possible that an interrupted aortic arch may not cause significant hemodynamic changes in utero¹⁸. With other associated anomalies, however, right ventricular overload may lead to systemic venous hypertension and fetal hydrops.

The neonatal course tends to parallel the fetal circulatory system. With complete interrupted aortic arch, the descending aortic bloodflow is dependent on shunting through the ductus arteriosus. A significant left-to-right shunt across the VSD will cause a delayed fall in pulmonary vascular resistance. Therefore, right-to-left shunting into the descending aorta through the patent ductus arteriosus provides the descending aortic blood flow and pressure. As the ductus constricts, blood flow to the lower body falls in commensurate fashion. As pulmonary vascular resistance falls, left-to-right shunting decreases and blood flow across the ductus further diminishes. When pulmonary vascular resistance falls, pulmonary blood flow increases and neonatal heart failure ensues. Infants given prostaglandin E₁ before 4 days of age will respond with increased blood flow though the ductus and increased pressures in the descending aorta. The narrowing of the pressure difference between the main pulmonary artery and the descending aorta correlates with an increase in urine flow and a decline in metabolic acidosis.

Once stabilization has been achieved, surgical treatment is required. In type B interruption with short atretic segment, the left subclavian artery can be used in an anastomosis with the descending aorta after the ductus has been divided¹⁹. Synthetic grafts have been used, but long-term results have not been encouraging. Banding of the pulmonary artery is also necessary when there is a large ventricular septal defect.

Obstetric management

When the initial diagnosis is made, careful scanning for associated anomalies and chromosomal studies are recommended. The option of pregnancy termination should be offered prior to fetal viability. The association of hydrops with interrupted aortic arch and other cardiac defects is an ominous combination. In the absence of congestive heart failure, there is no indication to alter standard obstetric management. Delivery, however, should be performed in a tertiary care center with immediate access to a pediatric cardiology service.

References

1. Kleinmen SC, Donnerstein R, Devore G, et al: Fetal echocardiography for evaluation of in utero congestive heart failure. N Engl J Med 1982; 306:568-75.

2. Collins-Nakai R I, Dick M, Parisi-Buckley L, et al: Interrupted aortic arch in infancy. J Pediatr 88: 959, 1976.

3. Celoria G C, Patton R B: Congenital absence of the aortic arch. Am Heart J 1959;58: 407-13.

4. Van Praagh R, Bernhard W F, Rosenthal A, et al: Interrupted aortic arch: surgical treatment. Am J Cardiol 1971;27:200-11.

5. Arey J C. Cardiovascular Pathology. W B Saunders, Philadelphia, 1981.

6. Conley M E, Beckwith J B, Mancer J, et al: The spectrum of DiGeorge syndrome. J Pediatr 94:883-90,1979.

7. Van Mierop L, Kutsche L: Interruption of the aortic arch and coarctation of the aorta: pathogenetic relations. Am J Cardiol 54:829-34,1984.

8. Higgins C, French J, Silverman J, et al: Interruption of the aortic arch: preoperative and post-operative, clinical, hemodynamic, and angiographic features. Am J Cardiol 39: 563-71,1977.

9. Dische W, Tsai M, Baltaze H: Solitary interruption of the arch of the aorta: clincopathologic review of eight cases. Am J Cardiol 27; 200-21,1971.

10. Lin A, Chin A, Devine W, et al: The pattern of cardiovascular malformation in the CHARGE association. Am J Dis Child 141:1010-1013,1987.

11. Rudolph A, Hoffman J: Rudolph"s Pediatrics, 18th Ed. Appleton and Lange, Norwalk, CT 1382-63, 1987.

12. Mascarello J, Bastion J, Jones M: Interstitial deletion of chromosome 22 in a patient with the DiGeorge malformation sequence. Am J Med Genet 32:112-14,1989.

13. Binder M: The teratogenic effects of a Bis(dichloroacetyl)diamine on hamster embryos. Am J Pathol 118: 170-93,1985.

14. Willhite C, Hill R, Irving D: lsotretinoin induced craniofacial malformations in humans and hamsters. J Craniofac Genet Dev Biol (suppl) 2: 193-209,1986.

15. Marasini M, Pongiglione G, Lituania M, et al: Aortic arch interruption: two-dimmensional echocardiographic recognition in utero. Pediatr Cadiol 6:147-49,1985.

16.Neye-Bock S, Fellows K: Aortic arch interruption in infancy: radio and angiographic features. AJR:135,1005-10,1980.

17. Riggs T, Berry T, Aziz K, et al: Two-dimensional echocardiographic features of interruption of the aortic arch. Am J Cardiol 50:1385-90,1982.

18. Rudolph A M: Congenital diseases of the heart: Clinical-physiologic considerations in diagnosis and management. Chicago, Year Book, 1974.

19. Nordan S, Scott 0: Heart Disease in Pediatrics, 3rd ed. Butterworth 242-43,1989.