Placenta-First Risk Stratification in Pregnancy

AVSD : Atrioventricular septal defect results from failure of endocardial cushion development, leading to:

  • Ostium primum atrial septal defect
  • Inlet ventricular septal defect
  • A common atrioventricular valve instead of separate mitral and tricuspid valves

Single most important prognostic discriminator is:
Balanced vs unbalanced AVSD
Balanced AVSD

Anatomy

  • Common AV valve committed proportionately to both ventricles
  • Right and left ventricles adequate in size
  • Biventricular circulation feasible

Balanced complete AVSD is the classic cardiac lesion of Down syndrome.

Prognosis

  • In-utero: usually stable
  • Surgery: biventricular repair at 3–6 months
  • Survival: >95% in modern series
  • Re-intervention: 10–20% (mostly AV valve regurgitation)

Unbalanced AVSD

Anatomy

  • Common AV valve predominantly committed to one ventricle
  • One ventricle hypoplastic (usually LV)
  • Biventricular repair not feasible
  • Functionally single-ventricle physiology

Prognosis

  • In-utero: higher risk of AV valve regurgitation, hydrops
  • Postnatal course: single-ventricle palliation (Norwood/Glenn/Fontan)
  • Long-term survival: lower than balanced AVSD
  • Morbidity: high (arrhythmias, ventricular dysfunction, Fontan failure)

Partial AVSD

  • Primum ASD with cleft mitral valve
  • Less genetic association than complete AVSD
  • Often balanced physiology
  • Good surgical outcomes
  • Trisomy 21 still relevant but less frequent

Counseling

Balanced AVSD

  • High likelihood of chromosomal abnormality
  • Surgery highly successful
  • Expect normal lifespan after repair
  • Main long-term issue: AV valve function

Unbalanced AVSD

  • Often syndromic
  • Single-ventricle pathway
  • Higher mortality and morbidity
  • Genetic diagnosis strongly influences decision-making

Balanced AVSD is primarily a genetic counseling diagnosis with excellent surgical outcomes, whereas unbalanced AVSD is primarily a physiologic diagnosis with complex long-term morbidity.

Genetic associations
Strong associations

  • Trisomy 21 (Down syndrome)
    • ~40–50% of AVSDs
    • Balanced complete AVSD is the classic lesion
  • Heterotaxy syndromes
    • Especially left atrial isomerism
  • 22q11.2 deletion (less common but relevant)
  • Single-gene disorders
    • CRELD1 (familial AVSD)
    • Ellis–van Creveld syndrome
    • RASopathies (rare)

Prenatal testing recommendations

  • Invasive testing strongly recommended even if isolated
  • CMA preferred over karyotype
  • If heterotaxy or extracardiac anomalies: consider WES

Associated extracardiac findings
More common when syndromic:

  • Duodenal atresia (Down syndrome)
  • Absent nasal bone, short long bones
  • GI malrotation (heterotaxy)
  • Polysplenia / asplenia
  • Persistent left SVC

Natural history in utero

  • Usually hemodynamically well tolerated
  • AV valve regurgitation may worsen with gestation
  • Rare progression to imbalance
  • Fetal demise is uncommon unless:
    • Severe regurgitation
    • Associated aneuploidy with complications
    • Arrhythmia (heterotaxy)

Postnatal physiology
After birth:

  • Large left-to-right shunt
  • Pulmonary overcirculation
  • Congestive heart failure by 4–8 weeks
  • Failure to thrive if untreated

Surgical management
Timing

  • Definitive repair at 3–6 months of age
  • Earlier if:
    • Severe AV valve regurgitation
    • Pulmonary hypertension
    • Failure of medical therapy

Surgical principles

  • Closure of primum ASD and inlet VSD
  • Division and reconstruction of common AV valve
  • Creation of competent mitral and tricuspid valves

Balanced anatomy allows biventricular repair in >95% cases.

Surgical outcomes
Survival

  • Modern surgical survival: >95%
  • Long-term survival into adulthood is common

Reintervention risk

  • 10–20% may need:
    • AV valve repair (especially left AV valve)
    • Rare reoperation for LVOT obstruction

Effect of genetics

  • Down syndrome
    • Similar or better surgical survival
    • Slightly higher AV valve regurgitation risk
  • Heterotaxy: worse outcomes

Long-term prognosis

If isolated and balanced

  • Excellent functional outcome
  • Normal or near-normal exercise tolerance
  • Lifelong cardiology follow-up required

Neurodevelopment

  • Driven more by genetics than the heart lesion itself
  • Isolated AVSD with normal genetics: good outcomes
  • Trisomy 21: baseline cognitive profile applies

Pregnancy and adulthood

  • Many patients reach reproductive age
  • Pregnancy generally well tolerated after successful repair