Physiology

  • 40% have pulmonary arterial oxygen saturation greater than systemic, 40% have systemic arterial oxygen saturation greater than pulmonary and the rest have equal saturations is systemic and pulmonary arteries.
  • With subpulmonary VSD, pulmonary oxygen saturation is always more than systemic.
  • With subaortic VSD, in 60% cases systemic arterial oxygen saturation is greater than pulmonary while in 40% pulmonary arterial oxygen saturation is greater than systemic.
  • With doubly committed VSD, pulmonary arterial oxygen saturation is more than systemic.
  • If systemic arterial oxygen saturation is more pulmonary, the VSD cannot be subpulmonary.
  • If pulmonary arterial saturation is more than systemic, VSD location cannot be predicted.
  • RV has systemic pressure.
  • If PS is present, PA pressure is reduced.
  • If PS is mild, pulmonary vascular disease can occur.
  • With restrictive VSD or intact ventricular septum, LV pressure is suprasystemic.
  • With subaortic stenosis, RV pressure is suprasystemic.

    Clinical manifestations

  • Four groups-
    • Like TOF- subaortic VSD + PS
    • Like TGA- subpulmonary VSD (with or without PS)
    • Like VSD- subaortic VSD without PS
    • Like Eisenmenger- subaortic VSD with pulmonary vascular obstructive disease
  • Group 1– like TOF- subaortic VSD + PS
    • Cyanosis, squatting.
    • PS MSM, single S2.
  • Group 2– like TGA- subpulmonary VSD (with or without PS)
    • Resemble TGA with VSD.
    • In early infancy, cyanosis with heart failure occurs.
    • Pulmonary plethora and frequent respiratory infections.
    • RV impulse, PSM at upper left sternal border and single loud S2.
  • Group 3– like VSD- subaortic VSD without PS
    • Heart failure.
    • PSM of VSD.
    • Apical MDM and S3.
  • Group 4– like Eisenmenger- subaortic VSD with pulmonary vascular obstructive disease
    • Older group 3 patients.
    • Cyanosis, decreased pulmonary blood flow, absent PSM, loud single S2.