Synonym

  • Also called hypoplastic right heart syndrome.

Embryology

  • May be due to fetal endocarditis during late gestation.

Pathology

  • Pulmonary atresia-
    • 75%- valvular/membranous
    • 25%- infundibular/muscular
  • Right ventricle-
    • RV components-
      • Tripartite- 58% (inlet, apex and outlet)
      • Bipartite- 34% (only inlet and outlet)
      • Unipartite- 8% (only inlet)
      • Note that in unipartite and bipartite types, all three components of RV are actually present, but there is muscle overgrowth in some components.
    • RV size-
      • Usually small.
      • Dilated RV in 10%- due to tricuspid regurgitation, in some cases due to Ebstein’s anomaly.
  • Tricuspid valve-
    • Corresponds to RV size
    • Usually hypoplastic
    • Sometimes (10%) dilated, leading to severe TR. In some cases, this is due to Ebstein’s anomaly.
  • Pulmonary artery-
    • Usually confluent.
    • Usually normal or mildly hypoplastic. Moderate or severe hypoplasia in 6%.
  • ASD-
    • Usually large enough for unobstructed blood flow from right atrium to left atrium
  • Ductus-
    • Pulmonary circulation is maintained by a patent ductus. If it closes, death will occur.
    • There are no aortopulmonary collaterals (MAPCAs support pulmonary circulation in pulmonary atresia with VSD and hence there is only mild cyanosis)
    • Obtuse angle between ductus and proximal aorta (normal)- late onset pulmonary atresia; acute angle- early onset.
  • Coronary anomalies
    • Communications between right ventricle and coronary arteries. RV- thick walled myocardial spaces- distended capillaries- coronary artery.
    • The term sinusoids is pathologically incorrect. Ventriculo-coronary arterial connections or VCC is correct.
    • Mainly located at RV apex.
    • More likely in small right ventricles, especially in monopartite.
    • Cause is non-regression of embryonic channels due to high RV pressure.
    • VCC causes myocardial ischemia due to coronary steal- causes RV and LV ischemia.
    • Even if no VCC is present, high RV luminal pressure decreases coronary flow to RV causing RV ischemia leading to RV fibrosis.
    • Types of coronary circulation (judged by coronary opacification during right ventricular angiography)-
      • No opacification- 58%
      • Mild opacification- 15%
      • Major opacification, but antegrade coronary flow from aorta preserved- 17%
      • Major opacification with coronary atresia or significant stenosis- 8%
    • RV dependent coronary circulation-
      • Atresia or severe stenosis of proximal coronary artery- RV decompression (during repair) would cause myocardial ischemia due to inadequate pressure to drive coronary flow.
      • No coronary stenosis, but coronary is ectatic- RV decompression would cause coronary steal through the dilated vessel into the RV.

Classification-

  • Greenwold classification-
    • Type I- small right ventricle
    • Type II- large right ventricle with tricuspid regurgitation
  • Bull and de Leval classification-
    • Group I- tripartite RV
    • Group II- bipartite RV
    • Group III- unipartite RV
  • Milliken classification (surgically oriented)-
    • Mild, moderate or severe hypoplasia of tricuspid annulus, RV cavity and RVOT.

Hemodynamics

  • Fetus-
    • Foramen ovale is large to accommodate increased flow.
    • Ductus carries blood from aorta to pulmonary artery (reverse of normal).
    • Ductus carries only 10% of cardiac output (normal 60%).
  • After birth-
    • RV pressure is high (suprasystemic).
    • No TR.
    • Blood that enters RV goes out through coronaries- circular shunt (as this drains back to RA).
    • RA is enlarged.
    • RA pressure is more than LA pressure- flow across non-restrictive ASD.
    • LA and LV are dilated.
    • Blood enters pulmonary circulation via ductus in newborn.
    • Ductus closes at normal time- profound cyanosis- death.
    • With significant TR, RV dilates and RV pressure is subsystemic.

Clinical features

  • Cyanosis noted at birth. Cyanosis worsens in first or second day. Tachypnoea and metabolic acidosis culminating in death.
  • No precordial activity, no murmurs (sometimes closing ductus murmur).
  • Type II- RV activity, PSM of TR.

Natural history

  • Severe TR- hydrops fetalis.
  • 50% are dead by 2 weeks.
  • 85% are dead by 6 months.

ECG

  • Adult precordial pattern in neonate (no RV, LV prominence)- also seen in tricuspid atresia.
  • QRS axis is +30⁰ to +90⁰ – helps to distinguish from tricuspid atresia where there is left axis deviation.

Chest X-ray

  • Pulmonary arteries appear normal or mildly hypoplastic.
  • Cardiomegaly only in type II.
  • Decreased pulmonary blood flow.
  • Aortic arch is always left sided. (Right aortic arch is present in 25 – 50% of PA with VSD)
  • DDs of massive cardiomegaly with decreased pulmonary blood flow-
    • Ebstein’s anomaly
    • PA with IVS type II
    • Uhl’s anomaly

Echocardiography

  • Thick membrane at pulmonary valve level with no flow across it.
  • RV is hypoplastic. RV endocardium shows deep invaginations which may or may not communicate with coronaries.
  • RA is dilated
  • There is right to left shunt across ASD
  • There is a ductus with left to right shunt
  • Type II has to be carefully distinguished from Ebstein’s anomaly (functional pulmonary atresia).
  • Surgical importance-
    • RV components
    • Tricuspid valve Z-score

Cardiac catheterization

  • Always needed to look for
    • RV morphology
    • VCC and coronary stenosis/atresia and
    • PA anatomy.
  • RA pressure is higher than LA pressure.
  • Same oxygen saturations in venacavae, RA and RV.
  • Same oxygen saturations, though lower than normal, in LA, LV and aorta.

Management

  • Start PGE1 0.1 μg/kg/min.
  • Then do cath study. Then plan further strategy based on RV type and sinusoids
  • Tripartite RV and bipartite RV-
    • Neonate- BT shunt + RV-PA connection (transannular RVOT patch/closed valvotomy/percutaneous laser)
    • 6 to 18 months-
      • TV Z-score > -2 and arterial oxygen saturation > 70% with BT shunt occlusion
        • Yes- Two ventricular repair (RVOT reconstruction + closure of BT shunt)
        • No- One and a half ventricular repair (BDG + RVOT reconstruction)
  • Monopartite RV and any type RV with RV dependent coronary circulation-
    • BT shunt- BDG or Hemi-Fontan- Fontan
  • Coronary atresia- Cardiac transplantation
  • Type II- Cardiac transplantation or Starnes’ procedure (convert to tricuspid atresia, then BT – BDG- TCPC)