Introduction

  • Almost always associated with a VSD which is usually a large malaligned outlet VSD.  Hence often referred to as Tetralogy of Fallot with absent pulmonary valve (TOF with APV).
  • The pulmonary valve is rudimentary and usually both stenotic and regurgitant.
  • The pulmonary arteries are aneurysmally dilated.
  • Almost always associated with absence of PDA. In fact, this may be the cause of the syndrome.
  • Commonly associated with airway abnormalities which may cause respiratory failure. Abnormally branching pulmonary arteries compress bronchi.
  • Rarely, IVS may be intact.
  • TOF with APV constitutes 2.5% of TOF.
  • 75% of APV has 22q11 deletion. This is the commonest genetic association of APV.

Embryology

  • Agenesis or early closure of the ductus plays an important role in the pathogenesis.
  • APV syndrome is different from TOF in pathogenesis. Even though VSD and aortic override are present in APV also, obstruction is due to pulmonary annular hypoplasia, not infundibular narrowing.

Pathology

  • Pulmonary valve tissue is rudimentary.
  • Pulmonary annulus is hypoplastic.
  • Proximal pulmonary arteries are aneurysmally dilated. These may compress major bronchi.
  • Pulmonary segmental arterioles are replaced by tufts of vessels which compress bronchi.
  • Non-restrictive malaligned VSD
  • RVH
  • Coronary anomalies may occur- single origin, aberrant course.
  • MAPCAs may be present.

Clinical presentations

  • Hydrops fetalis occurs in 20%.
  • Neonatal presentation-
    • Cyanosis
    • Respiratory distress- sometimes needing mechanical ventilation
    • Harsh to-and-fro murmur, single S2, prominent right ventricular impulse, hepatomegaly due to RV failure.
    • Rhonchi due to bronchial narrowing.
    • VSD like- Presentation like a large VSD.

Diagnostic findings

  • ECG shows RVH and wide QRS.
  • Chest X-ray shows dilated pulmonary arteries with distal attenuation of pulmonary vasculature and cardiomegaly. Right aortic arch may be present.
  • Echo makes the diagnosis.
  • Cardiac catheterization may be needed for ruling out AP collaterals and for their preoperative coil embolization.
  • PA and RV pressures equalize in diastole due to PR. During systole there is a gradient between RV and PA suggesting PS.

Medical management

  • Respiratory distress may be lessened by placing the patient prone as this suspends the pulmonary artery off the airways.
  • Cyanosis is due to right to left shunt due to pulmonary stenosis, pulmonary regurgitation and abnormal distal pulmonary arteriolar bed.
  • Sometimes left to right shunt can occur leading to volume overload.

Surgery

  1. VSD closure.
  2. Transannular incision to relieve the annular obstruction.
  3. Repair of pulmonary arteries- approaches include
  • Anterior plication with or without translocation of MPA and RPA anterior to the aorta OR
  • Homograft insertion with excision of aneurysmal pulmonary arteries.

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