Department Obstetrics Gynecology, Rambam Medical Center, Haifa, 31096 Israel

Definition: Vascular rings are aortic arch or pulmonary artery malformations that exhibit an abnormal relation with the esophagus and trachea.

Prevalence: The anomaly is rare, and there are no figures in the literature. Review of data reveals that there were only 39 operations of a vascular ring during a 23-year period at the Johns Hopkins Hospital, 37 operations in 46 years at the Mayo Clinic and 44 operations in 13 years at the Emory University School of Medicine in Atlanta, Georgia. According to the authors' experience, the anomaly is observed in 1 in 1000 fetuses in early gestation. There are no other reports in the literature on the prenatal diagnosis of a fetal vascular ring.

Etiology: During embryonic life, the multiple paired brachial arches and paired dorsal aortas generally fuse and resorb in a predictable sequence, resulting in the usual left aortic arch and left descending aorta. Failure of resorption results in the formation of vascular rings around the trachea and esophagus with varying degrees of compression of these structures.

The most common forms of vascular rings are:

1. Double aortic arch
2. Right aortic arch and ligamentum arteriosum
3. Anomalous innominate artery arising further than usual to the left on the arch
4. Anomalous left carotid artery arising further than usual to the right and passing anterior to the trachea
5. Anomalous left pulmonary artery

Case reports

There were 16 fetuses in which a diagnosis of a vascular ring was done at 14-17 weeks gestation. Fortunately, so far only one of them was symptomatic. This child had tracheomalacia and stridor due to a double right aortic arch.

Case 1. Low risk pregnancy week 16; transverse section of the upper mediastinum: a wide vascular (with "branches") para tracheal structure( fig.1). No other abnormalities. Our diagnosis of vascular ring (in this case secondary to double aortic arch and coarctation of the rt arch: arrow ., T-trachea) was confirmed in the  3 D CT-angio (one with the trachea the second without) of the newborn (fig. 2 ); who suffered from congenital stridor secondary to tracheomalacia -secondary to the vascular ring.

A transverse  upper mediastinal section : there is a wide vascular  structure with  “branches” which encircles the trachea- T  , there is  a local narrowing of the ring – white arrow.

3D reconstruction of the CT angiography of the double  aortic arch  and coarctation  of the newborn (upper image: without the  trachea lower  with the trachea).

A transverse section in the upper mediastinum: a  narrow  vascular ring without “ branches” (white arrows) which encircle the trachea

Sonographic findings: The diagnosis of a vascular ring relies on visualization of a blood vessel, which surrounds the trachea. The image is obtained in the "deep short axis view" of the tracheal area. Vascular rings are associated with a right aortic arch in many cases. The normal course of the left aortic arch is upward, making a U-turn on the left side of the chest and continuing downward. The right aortic arch is longer and its upper course is over the fetal spine toward the right chest, making a U-turn encircling the trachea, and continuing downward toward the left side of the chest (fig 4).

Prognosis: According to the data from 150,000 deliveries in our region, the estimated risk for a symptomatic vascular ring is 1 in 7500 children. Based on our sonographic findings, it seems that nearly 90% of children with a vascular ring are asymptomatic and therefore unknown. Most symptomatic patients have respiratory symptoms that consist of stridor, cough, wheezing or combination of these symptoms. About one-third of patients also have dysphagia or evidence of poor feeding.

Associated anomalies: In our fetuses, we did find other structural anomalies. However, according to the literature there is an incidence of 7-28% of associated anomalies, mainly, heart defects.

Recurrence risk: There is one report on two sisters with a vascular ring.

Implication for targeted examinations: Diagnosis is accomplished via barium esophagogram, CT, MRI and echocardiogram of the vascular branching patterns.

Management: In symptomatic cases, the treatment is usually thoracotomy and excision, ligation or reimplantation of the aberrant vessel.

References

1.      Friedman WF. Congenital heart disease in infancy and childhood. In Braumwald E ed, Heart Disease, A Textbook of Cardiovascular Medicine 5th edn. WB Saunders Company 1997:877-962.

2.      Chunk K, Colombani PM, Dudgen DL, Haller JA, Jr. Diagnosis and management of congenital vascular rings: a 22-year experience. Ann Thorac Surg 1992;53:602-3

3.      van-Son JA, Julsrud PR, Hagler DJ, et al. Surgical treatment of vascular rings: the Mayo Clinic experience. Mayo Clin Proc 1993;68:1056-63.

4.      Anand R, Dooley KJ, Williams WH, Vincent RN. Follow up of surgical correction of vascular anomalies causing tracheobronchial compression. Pediatr Cardiol 1994;15:58-61.

5.      Ledwith MV, Duff DF. A review of vascular rings 1980-1992. Ir Med J 1994;87:178-9.

6.      Bronshtein M, Lorber A, Berant M, et al. Sonographic diagnosis of fetal vascular rings in early pregnancy. Am J Cardiol 1998;81:101-3.