Incidence

  • 1.5 to 3.5 per 1000 live births.
  • More in preterm babies.
  • More in females.

Anatomy of interventricular septum

  • Interventricular septum has two parts- muscular and membranous.
  • Membranous septum is divided by the septal leaflet of tricuspid into upper atrioventricular and lower ventricular parts.
  • Muscular septum has three parts- inlet, trabecular and outlet.

Classification

  • Modified Soto’s classification
    • Perimembranous- 80%
    • Muscular- 10%
    • Outlet- 5%
    • Inlet- 5%
  • Perimembranous is also called infracristal or subaortic.
  • Outlet is also called supracristal or subpulmonic.
  • Muscular VSD may be central, apical, marginal or multiple.
  • Causes of acquired VSD-
    • MI
    • IE
    • Trauma
    • Cardiac catheterization

Hemodynamics

  • Factors determining flow across VSD-
    • Size of VSD
    • SVR and PVR
    • Presence or absence of PS
  • Size of VSD-
    • Small-
      • No hemodynamic problem.
      • Size less than one-third the size of the aortic root.
      • Shunt is less than 1.5:1.
      • Also called Roger’s disease.
      • Risk of IE. This is rare before 2 years of age.
    • Moderate-
      • Size is one-third to two-third that of the aortic root.
      • RV systolic pressure is less than 3/4th of LV systolic pressure.
      • RV systolic pressure is 20 mmHg or more lower than LV systolic pressure.
      • Shunt is less than 2:1. Volume overload of LV.
      • PVR is normal.
    • Large-
      • Also called non-restrictive VSD.
      • Size is equal to that of the aortic root.
      • RV systolic pressure is equal to LV systolic pressure.
      • Shunt is more than 2:1. Volume overload of LV produces heart failure.
      • If infant survives HF (20% chance), early Eisenmengerisation occurs.
      • Some infants directly go into Eisenmengerisation without preceding HF due to persistence of fetal pulmonary vascular histology leading to absence of initial fall in PVR.
  • HF is more likely to occur in preterm due to early drop in PVR due to incomplete development of pulmonary vasculature.
  • Neonates are more prone for heart failure due to
    • Immature cardiac contractile apparatus
    • Immature sympathetic support to the heart
    • Physiological anemia
  • In the presence of non-restrictive VSD, PVR falls slowly. This is why HF does not usually develop in the first month.
  • Causes of improvement in an infant with VSD –
    • Decrease in size of VSD.
    • Development of pulmonary vascular disease.
    • Development of RVOT obstruction (Gasul phenomenon- occurs in 5% of large VSDs)
  • In Swiss cheese VSD, left to right shunt is usually small.

Clinical features

  • Look for features of trisomy 13, 18 or 21 and for Klippel-Feil syndrome.
  • Small VSD-
    • Murmur appears after first day of life.
    • PSM in 2LICS- suspect subpulmonic VSD.
    • Muscular small VSD may have earlsy systolic murmur due to closure in late systole.
    • Closes in 80% cases.
  • Moderate VSD and large VSD without pulmonary vascular disease-
    • LV enlargement.
    • Wide variable split S2.
    • LV S3.
    • PSM.
    • MDM at apex.
  • Large VSD with pulmonary vascular disease-
    • Cyanosis, clubbing
    • RV apex
    • Single S2
    • No PSM
    • PES
    • PR EDM may be present.
  • Mechanisms of VSD closure-
    • Muscular hypertrophy
    • Fibrosis
    • Tricuspid valve
    • Aortic cusp prolapse
    • Aneurysm
  • VSDs with less chance of closure-
    • Large VSDs ( 5 to 10% closure)
    • Outlet and inlet VSDs
    • Swiss cheese VSDs

ECG

  • Small VSD- normal
  • Moderate VSD and large VSD without pulmonary vascular disease- LVH or BVH, LAE.
  • Large VSD with pulmonary vascular disease- RVH.

Chest X-ray

  • Small VSD- normal.
  • Moderate VSD- LV type cardiomegaly, LAE, increased pulmonary vascular disease.
  • Large VSD- Regression of cardiomegaly, RV apex, engorged central pulmonary arteries with peripheral pruning.

Echocardiography

  • In any VSD case, during echo, the following points should be noted-
    • Location of VSD
    • Rule out additional VSDs (commonly missed as attention is captured by the first VSD)
    • Size of VSD
    • Direct of shunt across VSD
    • Gradient across VSD
    • RVSP from TR jet
    • PA MP from PR jet
    • LA and LV enlargement
    • If LV enlargement, LV function
    • Rule out RVOT obstruction

Cath study

  • Indications-
    • Type not clear from echo
    • Size not clear from echo
    • Shunt calculation
    • PVR calculation including reversibility
    • Additional VSDs need to be ruled out
    • Degree of AR not clear from echo
    • To rule out LSVC
  • Causes of oxygen step-up in RV (10%)
    • VSD
    • RSOV to RV
    • PDA with PR
    • Coronary AV fistula to RV
    • Aorta to RV fistula

Complications

  • HF
  • Eisenmengerisation
  • IE
  • AR- in 5%- especially in outlet VSD- usually RCC prolapses

Treatment-

  • Medical-
    • Oxygen may increase left to right shunt due to pulmonary vasodilation thus exacerbating heart failure.
  • Indications for VSD closure-
    • HF in infancy not responding to medical management
    • RV pressure more than 50% of LV pressure