(Other synonyms: Atrioventricular canal defect, endocardial cushion defect)
Atrioventricular septal defect (AVSD) is a group of congenital heart malformations characterized by common atrioventricular junction coexisting with deficient atrioventricular septation. If there are separate atrioventricular valve orifices, despite the common junction, it is called
Prevalence of AVSD is estimated at 0.31/1000 live births (9). Digilio et al. reported a higher prevalence in subjects with
The diagnostic work-up should include clinical assessment to identify symptoms, echocardiogram, electrocardiogram, chest radiogram, spin-echo MR imaging, CT, diagnostic catheterisation and genetic testing.
Differential diagnosis should consider AVSD caused by Down syndrome and other chromosomal disorders.
Inheritance of AVSD is autosomal dominant.
AVSD1 (OMIM disease 606215) - susceptibility locus mapped to chromosome 1p31-p21
AVSD3 (OMIM disease 600309) -
AVSD4 (OMIM disease 614430) -
AVSD5 (OMIM disease 614474) -
Congenital heart defects, multiple types, 4 (CHTD4, OMIM disease 615779) -
AVSD2, partial, with heterotaxy syndrome (OMIM disease 606217) -
Noonan Syndrome 1 (NS1, OMIM disease 163950) -
Pathogenic variants may include missense, nonsense, splicing, small insertions, small deletions, gross deletions, gross insertions, small indels and regulatory substitutions.
To determine the gene defect responsible for the disease;
To confirm clinical diagnosis;
To assess the recurrence risk and perform genetic counselling for at-risk/affected individuals.
The test is listed in the Orphanet database and is offered by 10 accredited medical genetic laboratories in the EU, and in the GTR database, offered by 9 accredited medical genetic laboratories in the US.
Guidelines for clinical use of the test are described in Genetics Home Reference (
Clinically distinguishable syndromes can be analyzed by sequencing only those genes known to be associated with that specific disease using Sanger or Next Generation Sequencing (NGS); if the results are negative, or more generally if clinical signs are ambiguous for diagnosis, a multi-gene NGS panel is used to detect nucleotide variations in coding exons and flanking introns of the above genes. Potentially causative variants and region with low coverage are Sanger-sequenced. Sanger sequencing is also used for family segregation studies.
Multiplex Ligation Probe Amplification (MLPA) is used to detect duplications and deletions in
To perform molecular diagnosis, a single sample of biological material is normally sufficient. This may be 1 ml peripheral blood in a sterile tube with 0.5 ml K3EDTA or 1 ml saliva in a sterile tube with 0.5 ml ethanol 95%. Sampling rarely has to be repeated.
Gene-disease associations and the interpretation of genetic variants are rapidly developing fields. It is therefore possible that the genes mentioned in this note may change as new scientific data is acquired. It is also possible that genetic variants today defined as of “unknown or uncertain significance” may acquire clinical importance.
Identification of pathogenic variants in the above genes confirms the clinical diagnosis and is an indication for family studies.
A pathogenic variant is known to be causative for a given genetic disorder based on previous reports, or predicted to be causative based on loss of protein function or expected significant damage to proteins or protein/protein interactions. In this way it is possible to obtain a molecular diagnosis in new/other subjects, establish the risk of recurrence in family members and plan preventive and/or therapeutic measures.
Detection of a variant of unknown or uncertain significance (
The absence of variations in the genomic regions investigated does not exclude a clinical diagnosis but suggests the possibility of:
alterations that cannot be identified by sequencing, such as large rearrangements that cause loss (deletion) or gain (duplication) of extended gene fragments;
sequence variations in gene regions not investigated by this test, such as regulatory regions (5’ and 3’ UTR) and deep intronic regions;
variations in other genes not investigated by the present test.
Unexpected results may emerge from the test, for example information regarding consanguinity, absence of family correlation or other genetically-based diseases.
In autosomal dominant transmission, the probability that an affected carrier transmit the variant to his/her children is 50% in any pregnancy, irrespective of the sex of the child conceived.
The test is limited by current scientific knowledge regarding the genes and diseases.
NGS Analytical sensitivity >99.99%, with a minimum coverage of 10X; Analytical specificity 99.99%.
SANGER Analytical sensitivity >99.99%; Analytical specificity 99.99%.
MLPA Analytical sensitivity >99.99%; Analytical specificity 99.99%.
Clinical sensitivity: variations in the aforementioned genes are linked to AVSD, but may be individual variations (identified in one or few families) and total epidemiological data is therefore not available. Clinical sensitivity will be estimated on the basis of internal cases (11).
Clinical specificity: data not available
The genetic test is appropriate when:
the patient meets the diagnostic criteria for AVSD;
the sensitivity of the test is greater than or equal to that of tests described in the literature.
Clinical management | Utility |
---|---|
Confirmation of clinical diagnosis | Yes |
Differential diagnosis | Yes |
Couple risk assessment | Yes |
Availability of clinical trials can be checked on-line at |