Pathology

  • Perimembranous VSD
  • Infundibular RV obstruction

Hemodynamics

  • RV pressure is less than LV pressure
  • Shunt is always left to right
  • Significant shunt may cause LV volume overload

Clinical features

  • Significant left to right shunt may cause repeated chest infections
  • PSM of VSD and MSM of infundibular PS
  • Wide variable S2 split with soft P2 as in PS
  • No PES as PS is not valvular
  • RV left parasternal impulse
  • Differentiation from pure PS is by amyl nitrite inhalation which increases the pulmonary MSM in pure PS while decreases that in VSD with PS

ECG

  • RVH
  • BVH

Chest X-ray

  • RV enlarged
  • MPA not prominent
  • LV may be enlarged if significant left to right shunt

DD

  • Acyanotic TOF-
    • Cyanosis on exertion
    • No systolic thrill
    • No biventricular enlargement
    • Aortic override in echo

Management

Surgery in early childhood even if asymptomatic.