What are the most likely heart anomalies in individuals with trisomy 21 (Down syndrome)?

Most Common Heart Anomalies in Trisomy 21 (Down Syndrome)

Atrioventricular septal defect (AVSD) is the most characteristic cardiac anomaly in individuals with Down syndrome, though ventricular septal defect (VSD) may be the most frequently occurring defect depending on the population studied. 1

Primary Cardiac Defects

The distribution of congenital heart defects in trisomy 21 shows important patterns:

Most Common Defects

• Atrioventricular septal defect (AVSD) is widely recognized as the hallmark cardiac anomaly in Down syndrome, occurring in approximately 15-30% of affected individuals 1, 2

  • AVSD is so strongly associated with trisomy 21 that approximately 65% of all AVSD cases occur in individuals with Down syndrome 3
  • Type 3 (Inlet) VSDs are particularly associated with Down syndrome 4

• Ventricular septal defect (VSD) represents the most common defect in some populations, particularly Asian cohorts, occurring in 22-39% of cases 5, 2

  • One large Asian study found VSD in 39.2% of trisomy 21 patients, making it the most frequent cardiac lesion in that population 5

• Atrial septal defect (ASD), particularly secundum type, occurs in 23-28% of cases 5, 6, 2

• Patent ductus arteriosus (PDA) is found in 5-34% of individuals with Down syndrome 5, 6, 2

Less Common but Important Defects

• Tetralogy of Fallot occurs in approximately 3% of cases, with a notably high proportion (25%) of these patients also having AVSD 5, 2

• Coarctation of the aorta occurs in approximately 5% of cases 2

Clinical Implications and Pitfalls

Key Management Considerations

• Approximately 40-73% of individuals with Down syndrome have congenital heart defects, making cardiac screening essential in all cases 1, 6, 7

• Early echocardiographic evaluation is mandatory for all infants diagnosed with trisomy 21, regardless of clinical symptoms 1

• Genetic evaluation is recommended for all patients with CHD accompanied by extracardiac malformations or neurodevelopmental abnormalities 1

Important Caveats

• Population-based variation exists: Western/Caucasian populations show higher rates of AVSD as the predominant defect, while Asian populations demonstrate VSD as most common 5

• Multiple defects frequently coexist: A significant proportion of patients have more than one cardiac anomaly, requiring comprehensive echocardiographic assessment 5, 2

• Pulmonary hypertension risk: Patients with Down syndrome and AVSD are at particular risk for developing pulmonary arterial hypertension and require careful monitoring 1

Follow-Up Requirements

• All patients require periodic follow-up with a cardiologist experienced in adult congenital heart disease, typically annually, though frequency depends on residual abnormalities 1

• Serial imaging with 2-dimensional and Doppler 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

Reproductive Counseling

• Individuals with Down syndrome and AVSD have a 50% risk of transmitting trisomy 21 and other genetic defects to offspring, warranting reproductive counseling 1

• Pregnancy evaluation is essential before conception to ensure no significant residual hemodynamic lesions exist that might complicate pregnancy management 1