Most Common Congenital Heart Disease in Trisomy 21 (Down Syndrome)
Atrioventricular septal defect (AVSD) is the hallmark cardiac anomaly in Down syndrome and the most common congenital heart defect specifically associated with trisomy 21. 1
Epidemiology and Prevalence
AVSD occurs in approximately 15-30% of individuals with Down syndrome and represents the strongest cardiac association with trisomy 21. 1
Overall, 40-73% of individuals with Down syndrome have some form of congenital heart defect, making cardiac screening essential in all cases. 1
More than 75% of complete AVSDs occur in patients with Down syndrome, demonstrating the powerful bidirectional association between these conditions. 2
Important Clinical Context
While AVSD is the hallmark lesion, the distribution of cardiac defects can vary by population studied:
In predominantly Caucasian populations, AVSD is consistently reported as the most common defect. 2, 1, 3
One large Asian study from Singapore found ventricular septal defect (VSD) to be most common (39.2%), followed by patent ductus arteriosus (34.3%), with AVSD occurring in 15.6%. 4
A Turkish study confirmed AVSD as the leading defect (34.2% as isolated lesion, 49.2% when combined with other anomalies). 3
Despite geographic variation in overall CHD distribution, AVSD remains the cardiac lesion most specifically and strongly associated with trisomy 21. 2, 1
Critical Management Implications
Mandatory Screening
Early echocardiographic evaluation is mandatory for all infants diagnosed with trisomy 21, regardless of clinical symptoms. 1
This screening must occur even in asymptomatic infants, as physical examination alone is insufficient to exclude significant cardiac defects. 1
Timing of Intervention
Complete AVSD requires surgical repair typically before 6 months of age to prevent irreversible pulmonary vascular disease. 5, 3
Delaying repair beyond this window significantly increases the risk of developing pulmonary arterial hypertension, which carries excessive maternal and fetal mortality risk. 2, 1
High-Risk Complications
Patients with Down syndrome and AVSD are at particular risk for developing pulmonary arterial hypertension and require careful monitoring. 1
Pregnancy in patients with AVSD and severe pulmonary arterial hypertension (Eisenmenger syndrome) is contraindicated due to excessive maternal and fetal mortality. 2
Long-Term Follow-Up Requirements
All patients require lifelong follow-up at specialized adult congenital heart disease centers, regardless of whether they underwent surgical repair. 5
Serial imaging with echocardiography should be performed by staff trained in complex congenital heart defects. 1
Late complications include AV valve regurgitation or stenosis (5-10% requiring reoperation), left ventricular outflow tract obstruction (5%), and development of heart block. 1, 5