An innocent pulmonary flow murmur may be heard in many normal children and young adults. The history in our patient is unremarkable. The murmur heard at the upper left sternal edge occurs early in systole, at the time of rapid right ventricular ejection. This is characteristic of energetic ventricular contraction propelling blood into the pulmonic trunk and the right and left pulmonary arteries. The murmur is not associated with other abnormal findings, such as an ejection sound or pathologic splitting of the second sound.
Location and radiation
The murmur is best heard at the upper left sternal edge, or pulmonary area. Note the position of the pulmonary valve in relation to chest wall landmarks. Turbulent systolic flow in the pulmonary trunk, particularly at its bifurcation into right and left pulmonary arteries generates the murmur that is best heart at the second left intercostal space.
Volume curve
This is a graphic example of an innocent murmur. By simultaneously viewing the ventricular volume curve, we can see that two-thirds of the blood ejected leaves the ventricle in the first one-third of systole, therefore, the innocent flow murmur due to turbulent flow across the pulmonary outflow tract occurs in early systole.