LLSB: Early Systolic Murmur

Early systolic murmurs begin with the first sound and peak in the first third of systole. Early murmors have the greatest intensity in the early part of the cycle. Common causes are a small ventricular septal defect (VSD), or the innocent murmurs of childhood. The latter murmur is normal if the following are present:

The early systolic murmur of a small VSD stops before midsystole, because as ejection continues and the ventricular size decreases, the small defect is sealed shut causing the murmur to soften or cease. This murmur is characteristic of the type of children's VSD which may disappear with age.

The sound you heard is an early systolic murmur. It was recorded at the LLSB of a 20 year-old female with a small muscular VSD.