Mechanisms of improvement of heart failure in VSD

Mechanisms of improvement of heart failure in VSD

Mechanisms of improvement of heart failure in VSD: If a child with ventricular septal defect (VSD) and heart failure improves, what are the possibilities?

1. Spontaneous decrease in size of VSD: This is best natural course and needs no further treatment.
2. Development of right ventricular outflow tract (RVOT) obstruction: This is the next best possibility which could have occurred when the heart failure has decreased. This can progress to a Tetralogy of Fallot like physiology with right to left shunting across the VSD and is known as Gasul variant or Gasul phenomenon [1].  Still it can be remedied by surgical treatment. VSD closure and resection of RVOT are needed.
3. Development of pulmonary vascular disease: This is the worst scenario which could have occurred when the heart failure has decreased in a case of VSD. Here the options are limited as it progresses to Eisenmenger physiology as no curative therapy can be offered.

How do you clinically differentiate these situations?

Look for features of RVOT obstruction and pulmonary hypertension.
When the defect is decreasing in size, pansystolic murmur becomes more prominent, but second sound is normal. The murmur ultimately disappears when the VSD closes.

If RVOT obstruction develops, pulmonary component of second sound (P2) becomes softer. VSD murmur gets replaced by RVOT murmur.
If pulmonary hypertension develops, P2 becomes loud and VSD murmur decreases and disappears. Cyanosis develops later due to right to left shunt.
In all these situations, heart failure improves because pulmonary blood flow decreases.

References

1. Gasul BM, Dillon RF, Vrla V, Hait G. Ventricular septal defects; their natural transformation into the cyanotic or noncyanotic type of tetralogy of Fallot. J Am Med Assoc. 1957 Jun 22;164(8):847-53.