Congenital heart disease
ATRIOVENTRICULAR SEPTAL DEFECT:
FROM FETUS TO ADULT
Heart 2006;92:1879–1885. doi: 10.1136/hrt.2006.093344
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Dr Brian Craig, Royal Belfast
Hospital for Sick Children,
Belfast, Northern Ireland,
BT12 6BE, UK; brian.craig@
atrioventricular valvar orifices despite a common junction, while in complete AVSD the valve
itself is also shared.
The estimated incidence of the condition in the era of two-dimensional echocardiography varies
from 0.24/1000w1live births to 0.31/1000w2live births. There is a strong association with Down’s
syndrome, with half of patients with AVSD in the population of Bohemia also complicated by
Down’s syndrome.w3Conversely in a Toronto study about one third of patients with Down’s
syndrome had a complete AVSD and 5% had an ostium primum ASD.w4In a prospective
screening study within the relatively static Northern Irish population the incidence of AVSD in
Down’s syndrome was 17% and the overall incidence of congenital heart disease in Down’s
syndrome was 42%.1
Three different genetic patterns are described in AVSD: the association with Down’s syndrome,
as an autosomal dominant trait, and isolated. Molecular studies of patients with congenital heart
disease and partial duplications of chromosome 21 have proposed DSCAM (Down’s syndrome cell
adhesion molecule) as a candidate gene causing congenital heart disease in Down’s syndrome.2
Cases with autosomal dominant inheritance, however, are not linked to chromosome 21.w5
Over the past four decades the management of the complete form of the condition has evolved
from palliative pulmonary artery banding in infancy with later repair to primary repair in early
infancy to prevent the development of pulmonary vascular obstructive disease. Decreasing
operative mortality has significantly altered the prognosis of these patients with and without
Down’s syndrome. The improved prognosis for patients with Down’s syndrome and AVSD has
implications for the management of patients diagnosed antenatally. The postnatal and longer
term outcomes are influenced by the presence of associated defects, such as ventricular
hypoplasia, and the management of these may be both difficult and controversial.
he term ‘‘atrioventricular septal defect’’ (AVSD) covers a spectrum of congenital heart
malformations characterised by a common atrioventricular junction coexisting with deficient
atrioventricular septation. In ostium primum atrial septal defect (ASD) there are separate
SPECTRUM OF ANATOMY
The essential morphological hallmark of an AVSD is the presence of a common atrioventricular
junction as compared to the separate right and left atrioventricular junction in the normal heart.
Other morphological features include defects of the muscular and membranous atrioventricular
septum and an ovoid shape of the common atrioventricular junction with unwedging of the left
ventricular outflow tract from the normal position between the tricuspid and mitral valve. There
is disproportion of outlet and inlet dimensions of the left ventricle, with the former greater than
the latter as compared to the normal heart where both dimensions are similar.
The valve leaflet morphology in AVSD bears little resemblance to the arrangement of the
leaflets of normal mitral and tricuspid valves. There are essentially five leaflets, two of which are
bridging leaflets across the crest of the interventricular septum (fig 1). In ostium primum ASD
there are separate right and left valve orifices due to a tongue of valvar tissue joining the bridging
leaflets, but the atrioventricular junction remains a common structure (fig 2). In complete AVSD
there is a space between the bridging leaflets and therefore the atrioventricular valvar orifice is
The potential for left to right shunting is related to the bridging leaflets being attached to the
atrial septum, to the ventricular septum, or floating within the AVSD (fig 3). In Rastelli’s
classification the superior bridging leaflet was mostly contained within the left ventricle in type A,
with increased extension into the right ventricle in types B and C.w6The potential for ventricular
shunting tended to increase from type A to type C. This classification has been superseded by a
simpler independent description of the two aspects of the anatomy which determine the
variability and clinical presentation.3The first is the individual leaflet arrangement within the
common atrioventricular junction. The second is the relationship of the bridging leaflets of the
common valve to the atrial and ventricular septal structures.
3 Anderson RH, Ho SY, Falcao S, et al. The diagnostic features of
atrioventricular septal defect with common atrioventricular junction. Cardiol
c Review of the morphological diagnostic features of AVSD.
4 Marino B, Vairo U, Corno A, et al. Atrioventricular canal in Down syndrome.
Prevalence of associated cardiac malformations compared with patients
without Down syndrome. Am J Dis Child 1990;144:1120–2.
c Down’s syndrome is associated with a simpler form of AVSD as
compared to patients with normal chromosomes. The exception is the
more common association of AVSD in Down’s syndrome with tetralogy
5 Ter Heide H, Thompson JDR, Wharton GA, et al. Poor sensitivity of routine
fetal anomaly scanning ultrasound screening for antenatal detection of
atrioventricular septal defect. Heart 204;90:916–7.
c In a series of 92 consecutive patients with AVSD, only 29% were
6 Delisle MF, Sandor GG, Tessier F, et al. Outcome of fetuses diagnosed with
atrioventricular septal defect. Obstet Gynecol 1999;94(pt1):763–7.
c Prenatal diagnosis of AVSD was associated with a 58% risk of
aneuploidy (mainly trisomy 21).
7 Huggon IC, Cook AC, Smeeton NC, et al. Atrioventricular septal defects
diagnosed in fetal life: associated cardiac and extra-cardiac abnormalities
and outcome. J Am Coll Cardiol 1000;36:593–601.
c AVSD diagnosed prenatally associated with heterotaxy syndromes in
32% of cases.
8 Berger TJ, Blackstone EH, Kirklin JW, et al. Survival and probability of cure
without and with operation in complete atrioventricular canal. Ann Thorac
c Early era of surgical repair of AVSD in infancy compared with natural
history without surgery.
9 Silverman NJ, Zuberbuhler JR, Anderson RH. Atrioventricular septal defects:
cross-sectional echocardiographic and morphologic comparisons. Int J Cardiol
c The accuracy of cross-sectional echocardiography in AVSD as
confirmed by angiography, surgery and/or autopsy.
10 Sulafa AK, Tamimi O, Najm HK, Godman MJ. Echocardiographic
differentiation of atrioventricular septal defects from inlet ventricular septal
defects and mitral valve clefts. Am J Cardiol 2005;95:607–10.
c Important echocardiographic distinction between AVSDs, inlet
ventricular septal defects and isolated mitral valve clefts.
11 Sittiwangkul R, Ma RY, McCrindle BW, et al. Echocardiographic assessment
of obstructive lesions in atrioventricular septal defects. J Am Coll Cardiol
c Ability of transthoracic echocardiography to identify obstructive left
heart lesions in AVSD is explored. Most common missed lesions were
double-orifice left atrioventricular valve and non-obstructive chordae in
the left ventricular outflow tract.
12 Cohen MS, Jacobs ML, Weinberg PM, et al. Morphometric analysis of
unbalanced common atrioventricular canal using two-dimensional
echocardiography. J Am Coll Cardiol 1996;28:1017–23.
c Echocardiographic morphometry of atrioventricular valve suggested to
qualitate unbalance in AVSD and to guide in selection for single
13 Smallhorn JF. Cross-sectional echocardiographic assessment of
atrioventricular septal defect: basic morphology and preoperative risk factors.
c Important overview of echocardiographic features of AVSD including
risk factors to be identified preoperatively.
14 Haworth SG. Pulmonary vascular bed in children with complete
atrioventricular septal defect: relation between structural and hemodynamic
abnormalities. Am J Cardiol 1986;57:833–9.
c Pulmonary vascular structural changes in AVSD increase with age in
parallel with pulmonary artery pressure and resistance.
15 Prifti E, Bonacchi M, Bernabei M, et al. Repair of complete atrioventricular
septal defects in patients weighing less than 5 kg. Ann Thorac Surg
c Survival following surgery for AVSD is similar above and below 5 kg
body weight. There is an increased incidence of late operation for left
atrioventricular valve repair in the latter group.
16 Najm HK, Coles JG, Endo M, et al. Complete atrioventricular septal defects:
results of repair, risk factors, and freedom from reoperation. Circulation
c Large series review of 363 patients following surgical repair of
complete AVSD reports early mortality of 10.5% and 10-year survival
17 El-Najdawi EK, Driscoll DJ, Puga FJ, et al. Operation for partial
atrioventricular septal defect: a forty-year review. J Thorac Cardiovasc Surg
c Long term outcome after surgical repair of ostium primum ASD in 334
patients; 40-year survival was 76%.
18 Bull C, Rigby ML, Shinebourne EA. Should management of complete
atrioventricular canal be influenced by coexistent Down’s syndrome. Lancet
c Combined early surgical mortality of 20% in patients with Down’s
syndrome and AVSD in 1985 compared to life expectancy of 80% at
15 years without surgery.
19 Rhodes J, Warner KG, Fulton DR, et al. Fate of mitral regurgitation following
repair of atrioventricular septal defect. Am J Cardiol 1997;80:1194–7.
c Deterioration in left atrioventricular valve regurgitation after surgery
for AVSD occurs primarily in the initial 30 postoperative months.
20 Bergin ML, Warnes CA, Tajik AJ, et al. Partial atrioventricular canal defect:
long-term follow-up after initial repair in patients . or =40 years old. J Am
Coll Cardiol 1995;25:1189–94.
c Early mortality of 6% in adults following primary repair of ostium
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