Right aortic arch with vascular ring in one monozygotic twin
A. Sondakh, MD,aW. Daenen, MD,aM. Gewillig, MD, PhD,bK. Devriendt, MD, PhD,cand B. Meyns, MD, PhD,a
defect, and truncus arteriosus.1RAA does not necessarily cause
symptoms, but if the clinical manifestations of tracheal and/or
esophageal compression are present, then the diagnosis of vascular
ring is virtually certain.
Monozygotic twins offer an ideal situation to study the relative
contribution of genetics and environment in the development of
the cardiovascular system.2We report on monozygotic twins dis-
cordant for RAA with vascular ring.
ight aortic arch (RAA) has been found in approxi-
mately 0.1% of patients. Mostly, RAA is accompanied
by cardiovascular congenital anomalies, such as tetral-
ogy of Fallot, pulmonary atresia with ventricular septal
TWIN 1. As the second child of monochorionic monoamniotic
twins, twin 1 was delivered by caesarean section at 31 weeks’
gestation because of the deceleration of twin 2. The postnatal
period was complicated by pneumothorax and anoxemia. The
diagnosis of RAA and ventricle septum defects (5 and 2.7 mm in
diameter) was determined by echocardiography when the patient
was 2 weeks old.
She had persistent respiratory symptoms of hyperinflation with
airway obstruction. Bronchoscopy showed compression of the
distal trachea and left main bronchus.
Barium swallow highlighted an area of extrinsic compression
in the mid esophagus posteriorly. The presence of a vascular ring
was confirmed by cardiac catheterization (Figures 1 and 2). During
surgery, at the age of 9 months, both the retroesophageal ligamen-
tum arteriosum and the atretic distal left arch were divided.
Symptoms improved after surgery. She was discharged on day
4 but was readmitted on day 6 because of a period of apnea due to
secondary bronchotracheomalacia. At 7 months’ follow-up, she
remains symptom free, except for discrete wheezing.
Further clinical examination did not reveal any associated
anomalies. The karyotype was a normal 46 XX, and any microde-
letion in chromosome 22q11 was excluded by means of fluores-
cence in situ hybridization.
TWIN 2. In twin 2, the delivery and postpartum period were
uneventful. Echocardiography was normal.
In 1945, Gross3reported the first surgical repair of double aortic
arch. The most common lesion in published series were RAA and
left ductus arteriosus (49% of patients).4The predominance of
RAA may be facilitated by flow-related factors in the developing
embryo and fetus. Rudolph and colleagues5described in 1972 that
the hydrodynamic conditions in the normally developing outflow
region of the heart favor the laminar flow of right ventricular
output through the left-sided arterial duct and into the left arch.
This encourages the predominance of the left arch. With decreased
pulmonary outflow in the developing heart, right-to-left ductal
flow is absent or diminished, and this allows for a more stochastic
distribution of right and left predominance. Lesions with abnormal
right ventricular outflow are frequently accompanied by RAA,
whether there are deletions of chromosome 22q11 or not. This
suggests that deletion is not necessary for the development of RAA
in this context.6
Twins are known to have an increased incidence of congenital
cardiac malformation, but even in monochorionic twins, only 1
From the Departments of Cardiac Surgery,aPaediatric Cardiology,band
Human Genetics,cUniversity Hospital Leuven, Leuven, Belgium.
Received for publication Jan 7, 2005; accepted for publication Jan 11, 2005.
Address for reprints: B. Meyns, MD, PhD, Department of Cardiac Surgery,
Gasthuisberg University Hospital, Herestraat 49, 3000 Leuven, Belgium
J Thorac Cardiovasc Surg 2005;130:883-4
Copyright © 2005 by The American Association for Thoracic Surgery
Figure 1. Right aortic arch. The diverticulum of Kommerell at the
descending aorta indicates the presence of a left-sided ligamen-
The Journal of Thoracic and Cardiovascular Surgery●Volume 130, Number 3883
twin is affected in more than 90% of cases. The incidence of Download full-text
spontaneous monozygotic twinning is approximately 4 in 1000
live births. Two thirds comprise monochorionic diamniotic twins.
Possibly, the monozygotic twinning process itself increases the
incidence of congenital heart disease, with postzygotic unequal
division of the inner cell mass being responsible for discordant
cardiovascular anatomy. Congenital heart defects occur more com-
monly in monochorionic than in dichorionic monozygotic twins.
Monochorionic placentation and its complications may provide a
less favorable environment for the developing fetus. The circula-
tory imbalance in twin-twin transfusion syndrome augments this
increased incidence of congenital heart disease in recipient twins.
The influence of the twinning process may thus cause discordant
cardiovascular anomalies, including disturbance of laterality and
placental vascular anastomoses.2
The fact that only 1 of the monozygotic twins had cardiac
defects indicates that other nongenetic factors influence cardiac
development. Also, the fact that the genotype does not account for
all the phenotypic differences implies that we are unlikely to find
a genetic explanation for all variations of cardiovascular mispat-
There is no controversy about the necessity for surgical man-
agement of symptomatic congenital vascular ring.7After surgery,
secondary tracheomalacia is mostly present after the prolonged
period of airway compression, and symptoms may not resolve
completely. Delayed diagnosis of a vascular ring can result in
unnecessary investigations and prolonged periods of ineffective
1. McElhinney DB, Tworetzky W, Hanley FL, Rudolph AM. Congenital
obstructive lesions of the right aortic arch. Ann Thorac Surg. 1999;67:
2. Karatza AA, Wolfenden JL, Taylor MJO, Wee L, Fisk NM, Gardiner
HM. Influence of twin-twin transfusion syndrome on fetal cardiovas-
cular structure and function: prospective case-control study of 136
monochorionic twin pregnancies. Heart. 2002;88:271-7.
3. Gross RE. Surgical relief for tracheal obstruction from a vascular ring.
N Engl J Med. 1945;233:586-90.
4. Kocis KC, Midgley FM, Ruckman RN. Aortic arch complex anomalies:
20-year experience with symptoms, diagnosis, associated cardiac de-
fects, and surgical repair. Pediatr Cardiol. 1997;18:127-32.
5. Rudolph AM, Heymann MA, Spitznas U. Hemodynamic considerations
in the development of narrowing of the aorta. Am J Cardiol. 1972;30:
6. McElhinney DB, Hoydu AK, Gaynor JW, Spray TL, Goldmuntz E,
Weinberg PM. Patterns of right aortic arch and mirror-image branching
of the brachiocephalic vessels without associated anomalies. Pediatr
7. Chun K, Colombani PM, Dudgeon DL, Haller JA Jr. Diagnosis and
management of congenital vascular rings: a 22-year experience. Ann
Thorac Surg. 1992;53:597-602.
Figure 2. A combination bronchogram/esophagogram during
catheterization shows extrinsic compression in the mid esopha-
gus and mild hypoplasia of the proximal part of the left main
884The Journal of Thoracic and Cardiovascular Surgery●September 2005